Innovative designs, based on nature, may make wind energy even more environmentall-friendly to wildlife as discussed in this article from Discovery News.
Tuesday, July 05, 2011
Wind Energy Follow-up
Innovative designs, based on nature, may make wind energy even more environmentall-friendly to wildlife as discussed in this article from Discovery News.
Friday, July 01, 2011
Wind Energy May Not Be As Bad for Birds; Bats on the Other Hand...
State study details turbine bat and bird deaths
The Associated Press
Updated: 06/29/2011 05:27:39 PM EDT
PITTSBURGH—Wind turbines in Pennsylvania kill an estimated 10,500 bats and 1,680 birds each year, according to a report from the Pennsylvania Game Commission.
That's an average of 25 bats and four birds at each of the state's 420 turbines.
The Daily American of Somerset reported that approximately 30 participating developers agreed to conduct one year of pre-construction and two years of post-construction monitoring of birds and bats at each site using Game Commission data-collection and study guidelines.
The report found no eagle deaths and three endangered bird deaths. The birds (all found in September 2009) included two blackpoll warblers and one yellow-bellied flycatcher. All three were considered to be migrants. Two endangered Seminole bats carcasses were also found during the study, and were also believed to be migrating.
State wildlife biologists aren't sure how the deaths will impact the long-term health of bat and bird populations.
"We don't really have a good population estimate on bats, so 25 bats per turbine per year seems like a lot, and if you do the math with all of the turbines we have—and how many are proposed—it's a huge number," said Tracey Librandi Mumma, a supervisory wildlife biologist for the commission. "But whether that number will impact the population is something we're wrestling with right now."
Experts said the impacts could vary greatly by species.
With some endangered species the loss of a single bird could be detrimental, while with common species the loss of several hundred birds wouldn't have a major impact, Paul Fischbeck, a professor of engineering and public policy at Carnegie Mellon University, said Wednesday.
Michael Gannon, a professor of biology at the Pennsylvania State University of Altoona and a recognized bat expert, had reservations about the report.
"One of my chief concerns is that they're keeping their (raw) data very secret. Does the data support their conclusions? If you can't review something it's not science," Gannon told the Daily American.
The report noted that some wind sites in Pennsylvania were not part of the cooperative study. Florida Light & Power Energy's subsidiary, NextEra Energy Resources, has five active projects and is the largest non-cooperating developer.
The report said that 31 of the 86 projects have a high risk of bat mortality, and 15 have a high risk of bird mortality. The Nature Conservancy estimates that between 750 and 2,900 additional wind turbines may be built in Pennsylvania by 2030.
Fischbeck added that just focusing on deaths caused by wind turbines doesn't tell the whole story. Another recent scientific study found that cats caused more deaths in a suburban area than any other predator.
A U.S. Department of Agriculture report estimated that about 550 million birds are killed each year in collisions with buildings, 130 million in collisions with power lines, 100 million by cats, 80 million by cars, and 67 million by pesticides. Wind turbines kill about 28,500, or far less than 1 percent, the report said.
Scientists look for surviving Eskimo curlew birdsBy Yereth Rosen ANCHORAGE, Alaska Thu Jun 23, 2011 6:34pm EDT
ANCHORAGE, Alaska (Reuters) - Federal scientists are on the lookout for the Eskimo curlew, as they work to determine if the elusive shorebird last seen two decades ago still exists.
The said it is seeking any information about the Eskimo curlew, a tundra-nesting bird once abundant over the skies of North and South America, which was nearly hunted into oblivion by the mid-20th century.
The agency, which made its announcement in the Federal Register on Wednesday, will review whether the bird should continue to be classified as endangered or formally designated as extinct.
The last sighting confirmed by the Fish and Wildlife Service was in Nebraska in 1987, said Bruce Woods, a spokesman for the agency.
An unconfirmed sighting -- of an adult and a chick -- was recorded in 1983 in Alaska's Arctic National Wildlife Refuge, Woods said.
The Eskimo curlew population once numbered hundreds of thousands, according to the Fish and Wildlife Service. It is the smallest of four species of Western Hemisphere curlews, and is known for its long migration route from Arctic tundra breeding grounds to wintering lands in South America.
But the birds died off in drastic numbers due to overhunting, the loss of prairie habitat that was converted from grasslands to agriculture and the extinction of a type of grasshopper that made up much of their diet.
Most were gone by the beginning of the 20th century, according to the Fish and Wildlife Service.
Despite its scarcity, the Eskimo curlew is well-known to bird lovers.
It was the subject of a classic short novel, "Last of the Curlews," that chronicled the life of a lonely Eskimo curlew waiting on the tundra for a mate and, finding none, flying solo on the long fall migration. The 1954 book was adapted into a children's movie in 1972.
The wildlife inquiry, to be conducted by the service's Alaska scientists, is the first such formal review of the Eskimo curlew under the Endangered Species Act, Woods said. The bird was listed as endangered prior to passage of the act. such reviews are typically completed within 12 months.
Brendan Cummings, senior attorney with the nonprofit Center for Biological Diversity, said he hopes the bird continues to be listed as endangered and not written off as extinct.
Continued listing will cost little and could help protect far-north habitat home to other birds and wildlife, he said.
"While I have my doubts, I think it would be premature to close the coffin lid on the species," Cummings said.
(Editing by Alex Dobuzinskis and Greg McCune)
Photo: Eskimo Curlew specimen, Cincinnati Museum of Natural History, photo by Casey Tucker/Wild Auk Photography.
Tuesday, March 22, 2011
Cats, Birds, & Catbirds...
It’s sometimes difficult to think of our friends as lethal killers. Nobody expects that their faithful companion—who sits by you in the evenings while you read or watch television, or follows you around the kitchen while you prepare dinner, or comforts you when you’ve had a rough day—harbors a murderous lust that can only be deemed a predatory instinct. Yet a predatory instinct is exactly what friends like Fluffy or Whiskers (pet cats) possess.A new study by researchers with the Smithsonian Migratory Bird Center illustrates the impacts that outdoor cats can have on the survival of Gray Catbird young.
There is perhaps no topic in bird conservation as contentious and controversial as that of outdoor house cats and birds. This is especially evidenced by an incident that occurred in Texas that drew national media attention, and polarized bird lovers and cat lovers across the U.S.
In November of 2006 Jim Stevenson, director of the Galveston Ornithological Society and author of the “Wildlife of Galveston,” was out birding at a favorite spot near the San Luis Pass channel bridge spanning in Galveston in November of 2006. He found a group of federally endangered Piping Plovers roosting among the grassy beach dunes below the bridge. As he watched the birds, a feral cat, from a nearby cat colony, began stalking the plovers. To protect the birds, he attempted to capture the cat and failed. The next day, Stevenson returned with a rifle and shot the cat that had been stalking the plovers the day before (Barcott 2007). It was a shot that set off a powder keg of debate and legal proceedings.
A bridge toll operator had been feeding and maintaining the feral cat colony that lived below the bridge. He considered the 15-20 cats to be his pets (Williams 2008). He became outraged when Stevenson killed the cat he had nicknamed Mama Cat (Murphy 2007) and called the police. Stevenson was arrested and charged with animal cruelty, which carried a penalty of up to two years in jail and a $10,000 fine (Barcott 2007, Murphy 2007). The case went to trial and eventually charges against Stevenson were dropped because of a deadlocked jury (Williams 2008).
Shortly after his trial, Stevenson had to flee Texas for a period of time because of death threats and a reported attempt on his life (Meyers 2007). Unfortunately, this case illustrates how emotion-fueled this issue is and both sides mean well for the animals that they love.
How Many Cats? How Many Dead Birds?
The introduction of domesticated cats into North America was innocent enough. It’s thought they were brought from Europe in the early 1800’s to help control rodents in eastern seaboard cities (George 1974). However, while their intended targets were rodents cats are opportunistic and will prey upon whatever they can catch. Almost a century after their introduction North America’s cat population had grown substantially as did their impact on non-target species, like birds.
In his 1915 book, “Wild Bird Guests,” Ernest Harold Baynes began compiling some early estimates of how many outdoor cats existed in the U.S., and how many birds they killed annually. Baynes reported that Frank Chapman, a prominent ornithologist of the time, calculated that a single cat could kill as many as fifty birds in a single season, and that the estimated 25 million cats of New England could kill 500,000 birds annually. Similarly, Baynes reported that another ornithologist had estimated 70,000 farm cats in Massachusetts were killing 700,000 birds every year in that state (Baynes 1915).
In 1972 the American Humane Association estimated 31 million cats existed throughout the U.S. (Ogan and Jurek 1997). By 1990 there were an estimated 60 million cats owned by households in the U.S, according to U.S. Census data (Coleman et al. 1996). These numbers do not include feral or semi-feral cats that are not considered pets. Recent estimates by the American Bird Conservancy put the number of pet cats in the U.S. closer to 90 million. A 1997 report by the Progressive Animal Welfare Society (PAWS) estimated that 50 million cats lived outdoors, as feral animals, in urban alleys, abandoned buildings, and parks across the U.S. Conservatively, anywhere from 40 to 80 million cats may roam the outdoors and perhaps many more when we consider feral cat colonies.
A survey of landowners in southeast Michigan estimated that approximately 15-56% of landowners had outdoor cats and the total number of cats ranged from ~800 to ~3100 and killed between ~16,000 and ~47,000 birds (Lepczyk et al. 2003). Sadly, the researchers suggest this may be an underestimate of both the number of outdoor cats and the number of birds killed in the region. While rural landowners typically had more outdoor cats, urban areas had higher cat densities (cats per hectare (ha)). Additionally, over 20 species of birds were reported as prey items, with sparrows and Blue Jays being the most frequently reported prey items (Lepczyk et al. 2003).
A 1996 study from Wisconsin suggests that the 1.4 to 2 million estimated free-ranging outdoor cats in that state may kill anywhere from 8 to 219 millions birds every year. If we assume that other states have approximately the same number of free-ranging outdoor cats that kill the same estimated number of birds, a rough calculation would find that there are approximately 70 to 100 million outdoor cats in the U.S. that kill anywhere from 400 million to 11 billion birds annually. Another estimate suggests there are at least 120 million free-roaming cats that kill an estimated 500 million to 3 billion birds annually (Dauphiné 2008). If either estimate is accurate, then the annual avian mortality caused by outdoor cats is potentially comparable or greater to mortality resulting from collisions. It’s also scary to think that birds make up only an estimated 20% of the prey items of outdoor cats. Small mammals make up an additional 70%, with the remaining 10% being other animals including reptiles and amphibians (Coleman et al. 1996).
Ecological interactions between birds and cats
As bird-lovers, we might be concerned that providing bird-feeders in our backyard might increase the number of birds that are preyed upon by cats, especially given that a 1994 study based on Project FeederWatch data suggests that cats account for 29% of the predation of birds at feeders (Dunn and Tessaglia 1994). A survey study in Michigan found that the number and density of bird feeders in a landscape was not correlated with the number of birds killed by outdoor cats (Lepczyk et al 2003). This means that it doesn’t matter if you have one feeder or dozens of feeders in your backyard, cats will potentially kill the same number of birds in your yard.
A study in Georgia found that 28 outdoor cats visited a yard over the course of a two year period. 26 of those cats were considered to be feral cats. Two were domesticated cats that were allowed to roam outdoors. The number of cats preying upon birds in the yard was enough to result in a decreased abundance of birds in the yard (Dauphiné and Cooper 2008). As bird lovers we have to be aware that creating habitat for birds in our backyards may expose birds to higher levels of predation from cats, if there are a lot of outdoor cats roaming our neighborhoods. Being aware of this is important because it allows us to take measures to help reduce predation pressures from cats.
While direct predation on birds is what we think about when we think about bird-cat ecological interactions, we must remember that cats can affect birds in other ways as well. For example, as an efficient predator, cats are a potential competitor for predatory birds; competing for rodent prey.
One study found that six cats were capable of removing 4200 mice from a 35 acre study plot in just eight months (Pearson 1964).
The predation behavior of three cats was observed over the course of five years to measure what kind of impact they could make in the potential prey items of raptors in a 20 acre area. Between 1967 and 1971 the three cats caught almost 484 prey items with 42% of those prey items being Prairie Voles (Microtus ochrogaster). Young cottontail rabbits (Sylvilagus floridanus) made up the greatest volume (40%) of prey items (George 1974). Both species are major prey items of a variety of raptor species including Red-tailed Hawks (Preston and Beane 1993), American Kestrel (Smallwood and Bird 2002), and especially the winter diet of Northern Harriers (Macwhirter and Bildstein 1996).
Beyond predation or competition outdoor cats may also cause stress on birds that might affect their survivability and their ability to reproduce (Dauphiné 2008).
Trap and Release Programs
One of the biggest problems with outdoor cats is that they are capable of being prolific breeders, and because outdoor cats are often subsidized by well-meaning humans who feed them (Patronek 1998), the off-spring of outdoor cats possess a greater likelihood of surviving to adulthood than many natural predators might have. As a result, outdoor cat populations can become disproportionately large and have a greater impact on native wildlife populations. While it may not sound pleasant, unfortunately the most effective solution is trapping and euthanizing outdoor cats (Andersen et al. 2004).
Some well-meaning cat-lovers have promoted an alternative remedy to this problem, in lieu of euthanasia, by promoting “Trap, Test, Vaccinate, Neuter, and Release” (TTVNR) programs. The idea behind these programs is that by trapping outdoor cats, testing them for diseases, and neutering them before releasing them back into the outdoors, it reduces the capability of outdoor cats to increase their populations which lessens the number of cats preying on birds and other animals.
While the idea sounds good in theory, it is extremely flawed. Outdoor cats, regardless of whether they have been neutered or not, still prey upon birds. Secondly, TTVNR cats often are managed in cat colonies by individuals or groups of volunteers from animal welfare organizations. These cat colonies increase the density of predatory cats in a given area, where they have the potential of having a greater impact on local wildlife populations.
In the summer the beaches of Cape May, New Jersey host federally threatened Piping Plovers, a small migratory shorebird related to American Killdeer. The beaches are also home to a TTVNR cat colony very near to the plover nesting beaches (AP 2007). The cats pose a threat to the threatened plovers; preying upon the adult plovers while on their nests, their eggs, and the young plovers that are born flightless. In order to protect the Piping Plovers Cape May’s City Council implemented a plan to move feral cat colonies at least 1000 feet away from beaches that host Piping Plover nest colonies. This was decided only after federal agencies threatened to withhold necessary funds that would enable Cape May to replenish its beaches. The 1000 foot buffer was a compromise between what cat lovers wanted and what US Fish and Wildlife Service (USFWS) officials had a promoted—a one mile buffer (AP 2008). While the 1000 foot buffer may have fulfilled Cape May’s commitment to the USFWS to receive the necessary federal funding for its beaches, it may do little to protect Piping Plover nest sites as cats can easily cover the 1000 foot distance while hunting.
Cape May is not alone with regard to conflicts between outdoor cat colonies, their advocates, bird nesting colonies, and the people who watch and protect birds. Feral cat colonies have been established on Long Island’s South Shore beach alongside Piping Plover nest colonies (Kilgannon 2006). Florida in particular has potentially some of the largest feral cat colonies, because cats are regularly abandoned by people who stay in Florida in the winter but travel north in the spring and summer. Florida also has some of the most emotionally charged battles over endangered species and feral cat colonies (Gorman 2003).
In some cases feral cat colonies may pose a threat to human health in a different way. The Port Authority of New York and New Jersey has had to take action to round up feral cats at J.F.K. International Airport due to the potential threat the cats pose to planes on runways. The action to capture the feral cats was mandated by the Federation Aviation Authority, which regulates how wildlife and other animals are managed around airports. The action has met with opposition from the Humane Society and other animal activist groups (Lee 2008).
In an attempt to curb TTVNR efforts many groups are stepping forward to make the problems with these programs known. The Association of Wildlife Veterinarians and the National Association of State Public Health Veterinarians, through written statements, have publicly opposed TTVNR programs (Burton and Doblar 2004). The American Bird Conservancy launched the Cats Indoors! in 1997 in an effort to keep both cats and birds safe by teaching cat and bird lovers alike about the importance of keeping cats indoors. These programs, while important, have yet to be shown to truly effective at reducing the problem of outdoor cat colonies and their impacts on birds.
Safety of Outdoor Cats
Beyond the threat that outdoor cats pose to birds and other wildlife they may also be a threat to themselves and to people.
Outdoor cats are susceptible to any number of environmental stressors like inclement weather conditions and cold temperatures.
Outdoor cats are also vulnerable to larger predators, even in urban settings that might seem relatively sheltered from wildlife. Recent studies by researchers at Ohio State University have found that feral cats composed at least 1% of the diet of urban coyotes in Chicago, but that coyotes in urban settings may also kill outdoor cats as a way of removing potential competitors for prey items (Gehrt 2007). In southern California the presence of coyotes in habitat fragments had a positive influence on bird populations in the fragments. Coyotes preyed upon cats in the fragments, which helped keep cat populations in check. As a result, scrub-breeding birds in habitat fragments with coyotes had greater bird diversity. 21% of coyote scat samples collected during the study contained the remains of cats that had been preyed upon by the coyotes. Additionally, 25% of radio-collared cats in the study were preyed upon (Crooks and Soulé 1999).
One important finding of the southern California study found that cat owners around the habitat fragments were surveyed and reported that 42% had lost a cat to coyote predation. Additionally, when coyotes were thought to be present in an area 46% of cat owners restricted their cats’ outdoor activities (Crooks and Soulé 1999).
Disease can also be a major source of mortality and injury for outdoor cats, and these diseases pose a threat to people as well.
A study of animal bites in El Paso, Texas in 1995 found that a majority of cat bites (89%) resulted from provoking cats, and women and adults in general were more likely to be bitten. The disturbing finding of the study, however, was that 92% of cat bites were from cats that had not been vaccinated against rabies (Patrick and O’Rourke 1998). In 2002, a major advocate of outdoor cat colonies was bitten while feeding the feral cats in the colony on Singer Island in Florida. The cat was rabid, and as a result the cats in the colony were destroyed by the county for public health reasons (Gorman 2003).
Feline Leukemia is another disease that outdoor cats are susceptible of contracting. According to the Cornell Feline Health Center (2006) 2-3% of all cats in the U.S. are infected with the Feline Leukemia virus, but that infection rates rise significantly to 13% or greater in cats that are in high risk of infection. Outdoor cats, especially those in feral cat colonies, are especially susceptible to risk of infection because they are exposed to other cats of unknown infection status and because they have a higher risk of being bitten by an infected cat. Feline Leukemia is a common source of cancer in cats, but can also weaken their immune system sufficiently enough to make them susceptible to a variety of other diseases. Fortunately, tests have shown that cats may not be able to pass the disease to humans, however the other diseases that they may be susceptible to, from a weakened immune system, may be transmitted to people.
One disease in particular that deserves more attention due to its potential impacts on humans is Toxoplasmosis. Toxoplasmosis is a disease caused by a parasitic microorganism named Toxoplasma gondii.
According to the Center for Disease Control (CDC) (2008) 60 million American are infected with Toxoplasmosis. Once infected with the microorganism you’re infected for life. Fortunately, most healthy people don’t realize they are infected because T. gondii establishes a balance between itself and the host’s immune system. However, pregnant women, children, the elderly and others with compromised immune systems are more susceptible to the effects of T. gondii.
In most healthy individuals, an infection by T. gondii may produce flu-like symptoms until the parasite is established in the immune system of its host (Zimmer 2006). However in pregnant women, the microorganism can result in miscarriage, a stillborn child, and the birth of children with abnormally enlarged or smaller heads (CDC 2008).
In some cases T. gondii infection can result in lesions of the eyes, though typically only occurs in T. gondii uses a body’s dendritic cells to quickly travel throughout a body. Dendritic cells are commonly found in the spleen and lymph nodes and help regulate a body’s immune system. When T. gondii infects a body it hijacks dendritic cells and directs these cells to move throughout the body, which enables the microorganism to travel into places it would not normally be able to including our brains (Zimmer 2006).
Some scientists suspect there may be a connection between schizophrenia and Toxoplasmosis infection in humans, though this hasn’t been well established yet. Researchers at Johns Hopkins University found that soldiers diagnosed with schizophrenia were twice as likely to have blood samples exhibiting Toxoplasma infection than soldiers not diagnosed with schizophrenia (Zimmer 2006).
Right now you might be asking yourself what does human schizophrenia and Toxoplasmosis have to do with feral cats. Well, cats are a carrier and distributor of the T. gondii microorganism.
TO BE CONTINUED…
Literature Cited
Andersen, M.C., B.J. Martin, and G.W. Roemer. 2004. Use of matrix population models to estimate the efficacy of euthanasia versus trap-neuter-return for management of free-roaming cats. Journal of the American Veterinarian Medical Association. 225:1871-1876.
Barcott, B. 2007. Kill the cat that kills the bird? New York Times (12.2.07)
Baynes, E.H. 1915. Wild bird guests: how to entertain them. E.P. Dutton & Company. New York.
Burton, D.L. and K.A. Doblar. 2004. Morbidity and mortality of urban wildlife in
the midwestern United States. Pages 171-181 in Shaw et al., (eds.), Proceedings 4th International Urban Wildlife Symposium.
Coleman, J., S. Temple and S. Craven. 1996. A conservation dilemma—The Free-ranging Domestic Cat. The Probe. 127:1-2, 5.
Cornell Feline Health Center. 2006. Feline Leukemia Virus. Prepared by the American Association of Feline Practitioners and the Cornell Feline Health Center, Cornell University, College of Veterinary Medicine, Ithaca, New York 14853-6401.
www.vet.cornell.edu/fhc/brochures/felv.html
Crooks, K.R. and M.E. Soulé. 1999. Mesopredator release and avifaunal extinction in a fragmented system. Nature. 400: 563-566.
Dauphiné, N. 2008. Impacts of domestic cats on birds in North America (Abstract). Proceedings of the 4th International Partners in Flight Conference.
Dauphiné, N. and R.J. Cooper. 2008. Conservation meets the cat lady: Protecting bird species of continental importance in our own backyards (Abstract). Proceedings of 4th International Partners in Flight Conference.
Dunn, E.H., Tessaglia, D.L., 1994. Predation of birds at feeders in winter. Journal of Field Ornithology. 65:8-16.
Gehrt, S.D. 2007. Urban Coyote Ecology and Management: The Cook County, Illinois, Coyote Project. Ohio State University Extension Bulletin no. 929.
George, W.G. 1974. Domestic cats as predators and factors in winter shortages of raptor prey. Wilson Bulletin. 86: 384-396.
Gorman, J. 2003. Bird lovers hope to keep cats on a very short leash. New York Times (03.18.2003)
Kilgannon, C. 2006. On Long Island, cats and birds clash, and people take sides. New York Times (03.20.06)
Lee, J.S. 2008. Airport cat roundups resume, as do protests. New York Times (06.03.08)
Lepczyk, C.A., A.G. Mertig and J. Liu. 2003. Landowners and cat predation across rural-to-urban landscapes. Biological Conservation. 115:191-201.
Meyers, R. 2007. Cat shooter Stevenson flies the coop. The Daily News: Galveston County (11.30.07)
Murphy, K. 2007. Birder admits killing cat, but was it animal cruelty? New York Times (11.14.07)
Patrick, G.R. and K.M. O’Rourke. 1998. Dog and cat bites: epidemiologic analyses suggest different prevention strategies. Public Health Reports. 113:252-257.
Patronek, G.J. 1998. Free-roaming and feral cats – their impact on wildlife and human beings. Journal of American Veterinary Medical Association 212:218-226.
Pearson, O.P. 1964. Carnivore-mouse predation: an example of its intensity and
bioenergetics. Journal of Mammalogy. 45:177-178.
Williams, S.E. 2008. Bridge worker gets citation for too many cats. The Daily News: Galveston County (01.08.08)
Ogan, C.V.; Jurek, R.M. 1997. Biology and Ecology of feral, free-roaming, and stray cats Pages 87-92 in J.E. Harris, and C.V. Ogan, (eds.), Mesocarnivores of northern California: biology, management, and survey techniques, workshop manual. August 12-15, 1997, Humboldt State University, Arcata, CA. The Wildlife Society, California North Coast Chapter, Arcata, CA 127 p.
Unknown. 2007. Government may step in to save birds from cats in Cape May. The Associate Press (08.05.07)
Unknown. 2008. Cape May's feral cats to be moved to protect birds. The Associate Press in South Jersey News Online (03.05.08)
Zimmer, C. 2006. A common parasite reveals its strongest asset: stealth. New York Times (06.20.2006)
There is perhaps no topic in bird conservation as contentious and controversial as that of outdoor house cats and birds. This is especially evidenced by an incident that occurred in Texas that drew national media attention, and polarized bird lovers and cat lovers across the U.S.
In November of 2006 Jim Stevenson, director of the Galveston Ornithological Society and author of the “Wildlife of Galveston,” was out birding at a favorite spot near the San Luis Pass channel bridge spanning in Galveston in November of 2006. He found a group of federally endangered Piping Plovers roosting among the grassy beach dunes below the bridge. As he watched the birds, a feral cat, from a nearby cat colony, began stalking the plovers. To protect the birds, he attempted to capture the cat and failed. The next day, Stevenson returned with a rifle and shot the cat that had been stalking the plovers the day before (Barcott 2007). It was a shot that set off a powder keg of debate and legal proceedings.
A bridge toll operator had been feeding and maintaining the feral cat colony that lived below the bridge. He considered the 15-20 cats to be his pets (Williams 2008). He became outraged when Stevenson killed the cat he had nicknamed Mama Cat (Murphy 2007) and called the police. Stevenson was arrested and charged with animal cruelty, which carried a penalty of up to two years in jail and a $10,000 fine (Barcott 2007, Murphy 2007). The case went to trial and eventually charges against Stevenson were dropped because of a deadlocked jury (Williams 2008).
Shortly after his trial, Stevenson had to flee Texas for a period of time because of death threats and a reported attempt on his life (Meyers 2007). Unfortunately, this case illustrates how emotion-fueled this issue is and both sides mean well for the animals that they love.
How Many Cats? How Many Dead Birds?
The introduction of domesticated cats into North America was innocent enough. It’s thought they were brought from Europe in the early 1800’s to help control rodents in eastern seaboard cities (George 1974). However, while their intended targets were rodents cats are opportunistic and will prey upon whatever they can catch. Almost a century after their introduction North America’s cat population had grown substantially as did their impact on non-target species, like birds.
In his 1915 book, “Wild Bird Guests,” Ernest Harold Baynes began compiling some early estimates of how many outdoor cats existed in the U.S., and how many birds they killed annually. Baynes reported that Frank Chapman, a prominent ornithologist of the time, calculated that a single cat could kill as many as fifty birds in a single season, and that the estimated 25 million cats of New England could kill 500,000 birds annually. Similarly, Baynes reported that another ornithologist had estimated 70,000 farm cats in Massachusetts were killing 700,000 birds every year in that state (Baynes 1915).
In 1972 the American Humane Association estimated 31 million cats existed throughout the U.S. (Ogan and Jurek 1997). By 1990 there were an estimated 60 million cats owned by households in the U.S, according to U.S. Census data (Coleman et al. 1996). These numbers do not include feral or semi-feral cats that are not considered pets. Recent estimates by the American Bird Conservancy put the number of pet cats in the U.S. closer to 90 million. A 1997 report by the Progressive Animal Welfare Society (PAWS) estimated that 50 million cats lived outdoors, as feral animals, in urban alleys, abandoned buildings, and parks across the U.S. Conservatively, anywhere from 40 to 80 million cats may roam the outdoors and perhaps many more when we consider feral cat colonies.
A survey of landowners in southeast Michigan estimated that approximately 15-56% of landowners had outdoor cats and the total number of cats ranged from ~800 to ~3100 and killed between ~16,000 and ~47,000 birds (Lepczyk et al. 2003). Sadly, the researchers suggest this may be an underestimate of both the number of outdoor cats and the number of birds killed in the region. While rural landowners typically had more outdoor cats, urban areas had higher cat densities (cats per hectare (ha)). Additionally, over 20 species of birds were reported as prey items, with sparrows and Blue Jays being the most frequently reported prey items (Lepczyk et al. 2003).
A 1996 study from Wisconsin suggests that the 1.4 to 2 million estimated free-ranging outdoor cats in that state may kill anywhere from 8 to 219 millions birds every year. If we assume that other states have approximately the same number of free-ranging outdoor cats that kill the same estimated number of birds, a rough calculation would find that there are approximately 70 to 100 million outdoor cats in the U.S. that kill anywhere from 400 million to 11 billion birds annually. Another estimate suggests there are at least 120 million free-roaming cats that kill an estimated 500 million to 3 billion birds annually (Dauphiné 2008). If either estimate is accurate, then the annual avian mortality caused by outdoor cats is potentially comparable or greater to mortality resulting from collisions. It’s also scary to think that birds make up only an estimated 20% of the prey items of outdoor cats. Small mammals make up an additional 70%, with the remaining 10% being other animals including reptiles and amphibians (Coleman et al. 1996).
Ecological interactions between birds and cats
As bird-lovers, we might be concerned that providing bird-feeders in our backyard might increase the number of birds that are preyed upon by cats, especially given that a 1994 study based on Project FeederWatch data suggests that cats account for 29% of the predation of birds at feeders (Dunn and Tessaglia 1994). A survey study in Michigan found that the number and density of bird feeders in a landscape was not correlated with the number of birds killed by outdoor cats (Lepczyk et al 2003). This means that it doesn’t matter if you have one feeder or dozens of feeders in your backyard, cats will potentially kill the same number of birds in your yard.
A study in Georgia found that 28 outdoor cats visited a yard over the course of a two year period. 26 of those cats were considered to be feral cats. Two were domesticated cats that were allowed to roam outdoors. The number of cats preying upon birds in the yard was enough to result in a decreased abundance of birds in the yard (Dauphiné and Cooper 2008). As bird lovers we have to be aware that creating habitat for birds in our backyards may expose birds to higher levels of predation from cats, if there are a lot of outdoor cats roaming our neighborhoods. Being aware of this is important because it allows us to take measures to help reduce predation pressures from cats.
While direct predation on birds is what we think about when we think about bird-cat ecological interactions, we must remember that cats can affect birds in other ways as well. For example, as an efficient predator, cats are a potential competitor for predatory birds; competing for rodent prey.
One study found that six cats were capable of removing 4200 mice from a 35 acre study plot in just eight months (Pearson 1964).
The predation behavior of three cats was observed over the course of five years to measure what kind of impact they could make in the potential prey items of raptors in a 20 acre area. Between 1967 and 1971 the three cats caught almost 484 prey items with 42% of those prey items being Prairie Voles (Microtus ochrogaster). Young cottontail rabbits (Sylvilagus floridanus) made up the greatest volume (40%) of prey items (George 1974). Both species are major prey items of a variety of raptor species including Red-tailed Hawks (Preston and Beane 1993), American Kestrel (Smallwood and Bird 2002), and especially the winter diet of Northern Harriers (Macwhirter and Bildstein 1996).
Beyond predation or competition outdoor cats may also cause stress on birds that might affect their survivability and their ability to reproduce (Dauphiné 2008).
Trap and Release Programs
One of the biggest problems with outdoor cats is that they are capable of being prolific breeders, and because outdoor cats are often subsidized by well-meaning humans who feed them (Patronek 1998), the off-spring of outdoor cats possess a greater likelihood of surviving to adulthood than many natural predators might have. As a result, outdoor cat populations can become disproportionately large and have a greater impact on native wildlife populations. While it may not sound pleasant, unfortunately the most effective solution is trapping and euthanizing outdoor cats (Andersen et al. 2004).
Some well-meaning cat-lovers have promoted an alternative remedy to this problem, in lieu of euthanasia, by promoting “Trap, Test, Vaccinate, Neuter, and Release” (TTVNR) programs. The idea behind these programs is that by trapping outdoor cats, testing them for diseases, and neutering them before releasing them back into the outdoors, it reduces the capability of outdoor cats to increase their populations which lessens the number of cats preying on birds and other animals.
While the idea sounds good in theory, it is extremely flawed. Outdoor cats, regardless of whether they have been neutered or not, still prey upon birds. Secondly, TTVNR cats often are managed in cat colonies by individuals or groups of volunteers from animal welfare organizations. These cat colonies increase the density of predatory cats in a given area, where they have the potential of having a greater impact on local wildlife populations.
In the summer the beaches of Cape May, New Jersey host federally threatened Piping Plovers, a small migratory shorebird related to American Killdeer. The beaches are also home to a TTVNR cat colony very near to the plover nesting beaches (AP 2007). The cats pose a threat to the threatened plovers; preying upon the adult plovers while on their nests, their eggs, and the young plovers that are born flightless. In order to protect the Piping Plovers Cape May’s City Council implemented a plan to move feral cat colonies at least 1000 feet away from beaches that host Piping Plover nest colonies. This was decided only after federal agencies threatened to withhold necessary funds that would enable Cape May to replenish its beaches. The 1000 foot buffer was a compromise between what cat lovers wanted and what US Fish and Wildlife Service (USFWS) officials had a promoted—a one mile buffer (AP 2008). While the 1000 foot buffer may have fulfilled Cape May’s commitment to the USFWS to receive the necessary federal funding for its beaches, it may do little to protect Piping Plover nest sites as cats can easily cover the 1000 foot distance while hunting.
Cape May is not alone with regard to conflicts between outdoor cat colonies, their advocates, bird nesting colonies, and the people who watch and protect birds. Feral cat colonies have been established on Long Island’s South Shore beach alongside Piping Plover nest colonies (Kilgannon 2006). Florida in particular has potentially some of the largest feral cat colonies, because cats are regularly abandoned by people who stay in Florida in the winter but travel north in the spring and summer. Florida also has some of the most emotionally charged battles over endangered species and feral cat colonies (Gorman 2003).
In some cases feral cat colonies may pose a threat to human health in a different way. The Port Authority of New York and New Jersey has had to take action to round up feral cats at J.F.K. International Airport due to the potential threat the cats pose to planes on runways. The action to capture the feral cats was mandated by the Federation Aviation Authority, which regulates how wildlife and other animals are managed around airports. The action has met with opposition from the Humane Society and other animal activist groups (Lee 2008).
In an attempt to curb TTVNR efforts many groups are stepping forward to make the problems with these programs known. The Association of Wildlife Veterinarians and the National Association of State Public Health Veterinarians, through written statements, have publicly opposed TTVNR programs (Burton and Doblar 2004). The American Bird Conservancy launched the Cats Indoors! in 1997 in an effort to keep both cats and birds safe by teaching cat and bird lovers alike about the importance of keeping cats indoors. These programs, while important, have yet to be shown to truly effective at reducing the problem of outdoor cat colonies and their impacts on birds.
Safety of Outdoor Cats
Beyond the threat that outdoor cats pose to birds and other wildlife they may also be a threat to themselves and to people.
Outdoor cats are susceptible to any number of environmental stressors like inclement weather conditions and cold temperatures.
Outdoor cats are also vulnerable to larger predators, even in urban settings that might seem relatively sheltered from wildlife. Recent studies by researchers at Ohio State University have found that feral cats composed at least 1% of the diet of urban coyotes in Chicago, but that coyotes in urban settings may also kill outdoor cats as a way of removing potential competitors for prey items (Gehrt 2007). In southern California the presence of coyotes in habitat fragments had a positive influence on bird populations in the fragments. Coyotes preyed upon cats in the fragments, which helped keep cat populations in check. As a result, scrub-breeding birds in habitat fragments with coyotes had greater bird diversity. 21% of coyote scat samples collected during the study contained the remains of cats that had been preyed upon by the coyotes. Additionally, 25% of radio-collared cats in the study were preyed upon (Crooks and Soulé 1999).
One important finding of the southern California study found that cat owners around the habitat fragments were surveyed and reported that 42% had lost a cat to coyote predation. Additionally, when coyotes were thought to be present in an area 46% of cat owners restricted their cats’ outdoor activities (Crooks and Soulé 1999).
Disease can also be a major source of mortality and injury for outdoor cats, and these diseases pose a threat to people as well.
A study of animal bites in El Paso, Texas in 1995 found that a majority of cat bites (89%) resulted from provoking cats, and women and adults in general were more likely to be bitten. The disturbing finding of the study, however, was that 92% of cat bites were from cats that had not been vaccinated against rabies (Patrick and O’Rourke 1998). In 2002, a major advocate of outdoor cat colonies was bitten while feeding the feral cats in the colony on Singer Island in Florida. The cat was rabid, and as a result the cats in the colony were destroyed by the county for public health reasons (Gorman 2003).
Feline Leukemia is another disease that outdoor cats are susceptible of contracting. According to the Cornell Feline Health Center (2006) 2-3% of all cats in the U.S. are infected with the Feline Leukemia virus, but that infection rates rise significantly to 13% or greater in cats that are in high risk of infection. Outdoor cats, especially those in feral cat colonies, are especially susceptible to risk of infection because they are exposed to other cats of unknown infection status and because they have a higher risk of being bitten by an infected cat. Feline Leukemia is a common source of cancer in cats, but can also weaken their immune system sufficiently enough to make them susceptible to a variety of other diseases. Fortunately, tests have shown that cats may not be able to pass the disease to humans, however the other diseases that they may be susceptible to, from a weakened immune system, may be transmitted to people.
One disease in particular that deserves more attention due to its potential impacts on humans is Toxoplasmosis. Toxoplasmosis is a disease caused by a parasitic microorganism named Toxoplasma gondii.
According to the Center for Disease Control (CDC) (2008) 60 million American are infected with Toxoplasmosis. Once infected with the microorganism you’re infected for life. Fortunately, most healthy people don’t realize they are infected because T. gondii establishes a balance between itself and the host’s immune system. However, pregnant women, children, the elderly and others with compromised immune systems are more susceptible to the effects of T. gondii.
In most healthy individuals, an infection by T. gondii may produce flu-like symptoms until the parasite is established in the immune system of its host (Zimmer 2006). However in pregnant women, the microorganism can result in miscarriage, a stillborn child, and the birth of children with abnormally enlarged or smaller heads (CDC 2008).
In some cases T. gondii infection can result in lesions of the eyes, though typically only occurs in T. gondii uses a body’s dendritic cells to quickly travel throughout a body. Dendritic cells are commonly found in the spleen and lymph nodes and help regulate a body’s immune system. When T. gondii infects a body it hijacks dendritic cells and directs these cells to move throughout the body, which enables the microorganism to travel into places it would not normally be able to including our brains (Zimmer 2006).
Some scientists suspect there may be a connection between schizophrenia and Toxoplasmosis infection in humans, though this hasn’t been well established yet. Researchers at Johns Hopkins University found that soldiers diagnosed with schizophrenia were twice as likely to have blood samples exhibiting Toxoplasma infection than soldiers not diagnosed with schizophrenia (Zimmer 2006).
Right now you might be asking yourself what does human schizophrenia and Toxoplasmosis have to do with feral cats. Well, cats are a carrier and distributor of the T. gondii microorganism.
TO BE CONTINUED…
Literature Cited
Andersen, M.C., B.J. Martin, and G.W. Roemer. 2004. Use of matrix population models to estimate the efficacy of euthanasia versus trap-neuter-return for management of free-roaming cats. Journal of the American Veterinarian Medical Association. 225:1871-1876.
Barcott, B. 2007. Kill the cat that kills the bird? New York Times (12.2.07)
Baynes, E.H. 1915. Wild bird guests: how to entertain them. E.P. Dutton & Company. New York.
Burton, D.L. and K.A. Doblar. 2004. Morbidity and mortality of urban wildlife in
the midwestern United States. Pages 171-181 in Shaw et al., (eds.), Proceedings 4th International Urban Wildlife Symposium.
Coleman, J., S. Temple and S. Craven. 1996. A conservation dilemma—The Free-ranging Domestic Cat. The Probe. 127:1-2, 5.
Cornell Feline Health Center. 2006. Feline Leukemia Virus. Prepared by the American Association of Feline Practitioners and the Cornell Feline Health Center, Cornell University, College of Veterinary Medicine, Ithaca, New York 14853-6401.
www.vet.cornell.edu/fhc/brochures/felv.html
Crooks, K.R. and M.E. Soulé. 1999. Mesopredator release and avifaunal extinction in a fragmented system. Nature. 400: 563-566.
Dauphiné, N. 2008. Impacts of domestic cats on birds in North America (Abstract). Proceedings of the 4th International Partners in Flight Conference.
Dauphiné, N. and R.J. Cooper. 2008. Conservation meets the cat lady: Protecting bird species of continental importance in our own backyards (Abstract). Proceedings of 4th International Partners in Flight Conference.
Dunn, E.H., Tessaglia, D.L., 1994. Predation of birds at feeders in winter. Journal of Field Ornithology. 65:8-16.
Gehrt, S.D. 2007. Urban Coyote Ecology and Management: The Cook County, Illinois, Coyote Project. Ohio State University Extension Bulletin no. 929.
George, W.G. 1974. Domestic cats as predators and factors in winter shortages of raptor prey. Wilson Bulletin. 86: 384-396.
Gorman, J. 2003. Bird lovers hope to keep cats on a very short leash. New York Times (03.18.2003)
Kilgannon, C. 2006. On Long Island, cats and birds clash, and people take sides. New York Times (03.20.06)
Lee, J.S. 2008. Airport cat roundups resume, as do protests. New York Times (06.03.08)
Lepczyk, C.A., A.G. Mertig and J. Liu. 2003. Landowners and cat predation across rural-to-urban landscapes. Biological Conservation. 115:191-201.
Meyers, R. 2007. Cat shooter Stevenson flies the coop. The Daily News: Galveston County (11.30.07)
Murphy, K. 2007. Birder admits killing cat, but was it animal cruelty? New York Times (11.14.07)
Patrick, G.R. and K.M. O’Rourke. 1998. Dog and cat bites: epidemiologic analyses suggest different prevention strategies. Public Health Reports. 113:252-257.
Patronek, G.J. 1998. Free-roaming and feral cats – their impact on wildlife and human beings. Journal of American Veterinary Medical Association 212:218-226.
Pearson, O.P. 1964. Carnivore-mouse predation: an example of its intensity and
bioenergetics. Journal of Mammalogy. 45:177-178.
Williams, S.E. 2008. Bridge worker gets citation for too many cats. The Daily News: Galveston County (01.08.08)
Ogan, C.V.; Jurek, R.M. 1997. Biology and Ecology of feral, free-roaming, and stray cats Pages 87-92 in J.E. Harris, and C.V. Ogan, (eds.), Mesocarnivores of northern California: biology, management, and survey techniques, workshop manual. August 12-15, 1997, Humboldt State University, Arcata, CA. The Wildlife Society, California North Coast Chapter, Arcata, CA 127 p.
Unknown. 2007. Government may step in to save birds from cats in Cape May. The Associate Press (08.05.07)
Unknown. 2008. Cape May's feral cats to be moved to protect birds. The Associate Press in South Jersey News Online (03.05.08)
Zimmer, C. 2006. A common parasite reveals its strongest asset: stealth. New York Times (06.20.2006)
Tuesday, February 08, 2011
More Evidence that Birds Can Adapt to Urban Noise Conditions
A new study by researchers from Universidad Nacional Autónoma de México and the Museo Nacional de Ciencias Naturales shows that House Finches are capable of making short-term adjustments to their vocalizations in urban environments, which typically are louder than more natural environments.The study suggests that some bird species are capable of adapting to urban acoustic environments.
ABSTRACT
Experimental evidence for real-time song frequency shift in response to urban noise in a passerine bird
Eira Bermúdez-Cuamatzin, Alejandro A. Ríos-Chelén,Diego Gil and Constantino Macías Garcia
doi: 10.1098/rsbl.2010.0437
Biol. Lett. 23 February 2011 vol. 7 no. 1 36-38
Research has shown that bird songs are modified in different ways to deal with urban noise and promote signal transmission through noisy environments. Urban noise is composed of low frequencies, thus the observation that songs have a higher minimum frequency in noisy places suggests this is a way of avoiding noise masking. Most studies are correlative and there is as yet little experimental evidence that this is a short-term mechanism owing to individual plasticity. Here we experimentally test if house finches (Carpodacus mexicanus) can modulate the minimum frequency of their songs in response to different noise levels. We exposed singing males to three continuous treatments: low–high–low noise levels. We found a significant increase in minimum frequency from low to high and a decrement from high to low treatments. We also found that this was mostly achieved by modifying the frequency of the same low-frequency syllable types used in the different treatments. When different low-frequency syllables were used, those sung during the noisy condition were longer than the ones sang during the quiet condition. We conclude that house finches modify their songs in several ways in response to urban noise, thus providing evidence of a short-term acoustic adaptation.
New Animated Bird Movie--This Spring
Coming this April is a new animated movie, titled "Rio," by the creators of the "Ice Age" movies.Like the movie "Happy Feet" this upcoming movie uses characters based on real bird species, catchy music, and vivid animation to tell an interesting story and address conservation issues.
The movie focuses on the last two parrots of a species called Blue Macaw in the movie and the need to breed these remaining individuals to save the species from extinction.
The movie focuses on the last two parrots of a species called Blue Macaw in the movie and the need to breed these remaining individuals to save the species from extinction.
It also touches upon the impact that animal smuggling and illegal pet trade can have on bird populations.
The Blue Macaw characters seem to be based on actual species, like the Spix Macaw and the Hyacinth Macaw, which have suffered as a result of illegal pet trade and habitat loss. Fortunately, Hyacinth Macaws have not been decimated to the extremely low levels of the birds in the movie, however Spix Macaws disappeared in the wild in 2000 and around 120 individuals remain in captivity today. It's hoped that captive breeding coupled with habitat restoration will allow for the reintroduction of the birds back into their native habitat eventually.
So go see Rio this April and consider supporting organizations that are helping to save parrot species from extintction.
Sunday, January 17, 2010
Identifying minimum patch sizes for breeding success in birds
A new study illustrates the importance of understanding the minimum patch size that an at-risk bird needs to reproduce. Jerrod Butcher and fellow researchers from Texas A&M University looked at the effect of habitat patch size on two songbirds in north-central Texas.
For the federally endangered golden-cheeked warbler, they found that birds did not successfully breed in patches smaller than 15-20 hectares indicating that a threshold exists at that size below which the birds do not reproduce. However, the study also found that the warblers established territories in patch sizes as small as 2.9 hectares (the smallest studied) and paired in patches as small as 4.1 hectares.
From a conservation perspective, this study shows that research looking at just the presence-absence of the warblers (or even bird pairings) would substantially underestimate the minimum habitat patch size needed to sustain a viable population.
The researchers also looked at white-eyed vireos, a habitat generalist, and as predicted found no evidence of a minimum patch size threshold for breeding success - the vireos successfully reproduced in patches as small as 4.1 hectares.
One of the benefits of identifying patch size thresholds is that by looking at how different environmental variables change when you cross the threshold, you can get clues on what factors are influencing the bird behavior. In this vein, the researchers looked at two variables along the patch size gradient: 1) brown-headed cowbird parasitism; and 2) abundance of arthropods - the food source for the birds.
However, the researchers found no relationship between either variable and patch size, which means they likely are not explanations for the threshold. So more research is needed to figure out why golden-cheeked warblers do not breed in patches smaller than 15-20 hectares.
This study also raises the issue of whether small patches act as ecological traps for the golden-cheeked warblers resulting in population sinks that further threaten the species. This could occur if small patches are attractive to the warblers leading to numerous small territories where the birds are not able to reproduce. However, the study authors warn against jumping to that conclusion. They write,
"Patches of habitat less than 20 hectares in area may not be large enough to sustain a viable population of golden-cheeked warbler in the long-term; however, such patches may benefit populations if the patches can sustain breeding pairs in the short term."
Nevertheless, they advise that managers across the distribution range of golden-cheeked warbler be cautious about decreasing vegetation patches below 20 hectares. Similar research on minimum patch-size thresholds for breeding success could be important for the conservation of other at-risk birds.
--Reviewed by Rob Goldstein--Conservation Maven
Butcher, J., Morrison, M., Ransom, D., Slack, R., & Wilkins, R. (2010). Evidence of a Minimum Patch Size Threshold of Reproductive Success in an Endangered Songbird Journal of Wildlife Management, 74 (1), 133-139 DOI: 10.2193/2008-533
For the federally endangered golden-cheeked warbler, they found that birds did not successfully breed in patches smaller than 15-20 hectares indicating that a threshold exists at that size below which the birds do not reproduce. However, the study also found that the warblers established territories in patch sizes as small as 2.9 hectares (the smallest studied) and paired in patches as small as 4.1 hectares.
From a conservation perspective, this study shows that research looking at just the presence-absence of the warblers (or even bird pairings) would substantially underestimate the minimum habitat patch size needed to sustain a viable population.
The researchers also looked at white-eyed vireos, a habitat generalist, and as predicted found no evidence of a minimum patch size threshold for breeding success - the vireos successfully reproduced in patches as small as 4.1 hectares.
One of the benefits of identifying patch size thresholds is that by looking at how different environmental variables change when you cross the threshold, you can get clues on what factors are influencing the bird behavior. In this vein, the researchers looked at two variables along the patch size gradient: 1) brown-headed cowbird parasitism; and 2) abundance of arthropods - the food source for the birds.
However, the researchers found no relationship between either variable and patch size, which means they likely are not explanations for the threshold. So more research is needed to figure out why golden-cheeked warblers do not breed in patches smaller than 15-20 hectares.
This study also raises the issue of whether small patches act as ecological traps for the golden-cheeked warblers resulting in population sinks that further threaten the species. This could occur if small patches are attractive to the warblers leading to numerous small territories where the birds are not able to reproduce. However, the study authors warn against jumping to that conclusion. They write,
"Patches of habitat less than 20 hectares in area may not be large enough to sustain a viable population of golden-cheeked warbler in the long-term; however, such patches may benefit populations if the patches can sustain breeding pairs in the short term."
Nevertheless, they advise that managers across the distribution range of golden-cheeked warbler be cautious about decreasing vegetation patches below 20 hectares. Similar research on minimum patch-size thresholds for breeding success could be important for the conservation of other at-risk birds.
--Reviewed by Rob Goldstein--Conservation Maven
Butcher, J., Morrison, M., Ransom, D., Slack, R., & Wilkins, R. (2010). Evidence of a Minimum Patch Size Threshold of Reproductive Success in an Endangered Songbird Journal of Wildlife Management, 74 (1), 133-139 DOI: 10.2193/2008-533
Monday, January 11, 2010
State endangered-species lists are failing to protect species that need help the most
A new analysis of birds on state endangered species lists suggests that some species receive insufficient protection while others are receiving protection unnecessarily.
This may be attributable to the fact that state endangered species lists are composed by policy process rather than by scientific process.
Birder's World has a good article highlighting the new analysis.
You can also find the analysis, by Jeff Wells of the Boreal Songbird Initiative, at PLoS ONE.
In Ohio, the following species are listed as endangered (e) or threatened (t) though their listing could be considered questionable based on the new analysis. Many of the species on these lists are based on local rarity and rarity is prioritized, however rarity may be detrimental to conservation efforts.
-Yellow-bellied Sapsucker(e): Primarily migratory(2) through Ohio with a resident population estimate in the state of about 400 birds, while the global population estimate is 9,000,000 individuals (1).
-Loggerhead Shrike (e): The global population for this species is estimated at 4,200,000 individuals while Ohio's estimated population is roughly 300 individuals(1). Loggerhead Shrikes invaded Ohio in the mid-1800's as deciduous forests were replaced by agricultural fields and then declined by the 1930's (2).
-Lark Sparrow (e): a species that spread into Ohio in the 19th century as land use became primarily agricultural. Their occurrence in the state was sparse and varied from place-to-place until in the 1960's they were restricted to the Oak Openings preserve near Toledo, Ohio (2). Peterjohn suggests that at most Ohio hosted about 12 breeding pairs in the Oak Openings region (2), while the global population estimate is 9,900,000 individuals (1).
-Dark-eyed Junco (t): The global population estimate for this species is 260,000,000 whereas(1) the Ohio breeding population is roughly 30-50 individuals(2).
Some species should probably be given greater priority given that Ohio hosts a relatively large portion of the global population of these species.
-Cerulean Warbler is considered a species of concern in Ohio, however the global population for this species is estimated at 560,000 individuals (1). Ohio hosts an esitimated 70,000 breeding Cerulean Warblers, or ~13% fo the total population(1). Ohio's role in the management of this species is potentially great and proper habitat management may bolster global population numbers.
-Henslow's Sparrow, an Ohio species of concern, hosts an estimated population of 6,000 individuals or ~7.5% of the global population of 80,000.
While some birders and state naturalists may be inclined to disagree with this new analysis, because it may impact their state lists, the proposal of species listing and management based on a more scientific process should result in more efficient and cost-effective management practices.
1 Partner in Flight Landbird Population Estimates Database, Version 2004
2 Peterjohn, B. G. 2001. The Birds Of Ohio. The Wooster Book Company. Wooster, Ohio.
This may be attributable to the fact that state endangered species lists are composed by policy process rather than by scientific process.
Birder's World has a good article highlighting the new analysis.
You can also find the analysis, by Jeff Wells of the Boreal Songbird Initiative, at PLoS ONE.
In Ohio, the following species are listed as endangered (e) or threatened (t) though their listing could be considered questionable based on the new analysis. Many of the species on these lists are based on local rarity and rarity is prioritized, however rarity may be detrimental to conservation efforts.
-Yellow-bellied Sapsucker(e): Primarily migratory(2) through Ohio with a resident population estimate in the state of about 400 birds, while the global population estimate is 9,000,000 individuals (1).
-Loggerhead Shrike (e): The global population for this species is estimated at 4,200,000 individuals while Ohio's estimated population is roughly 300 individuals(1). Loggerhead Shrikes invaded Ohio in the mid-1800's as deciduous forests were replaced by agricultural fields and then declined by the 1930's (2).
-Lark Sparrow (e): a species that spread into Ohio in the 19th century as land use became primarily agricultural. Their occurrence in the state was sparse and varied from place-to-place until in the 1960's they were restricted to the Oak Openings preserve near Toledo, Ohio (2). Peterjohn suggests that at most Ohio hosted about 12 breeding pairs in the Oak Openings region (2), while the global population estimate is 9,900,000 individuals (1).
-Dark-eyed Junco (t): The global population estimate for this species is 260,000,000 whereas(1) the Ohio breeding population is roughly 30-50 individuals(2).
Some species should probably be given greater priority given that Ohio hosts a relatively large portion of the global population of these species.
-Cerulean Warbler is considered a species of concern in Ohio, however the global population for this species is estimated at 560,000 individuals (1). Ohio hosts an esitimated 70,000 breeding Cerulean Warblers, or ~13% fo the total population(1). Ohio's role in the management of this species is potentially great and proper habitat management may bolster global population numbers.
-Henslow's Sparrow, an Ohio species of concern, hosts an estimated population of 6,000 individuals or ~7.5% of the global population of 80,000.
While some birders and state naturalists may be inclined to disagree with this new analysis, because it may impact their state lists, the proposal of species listing and management based on a more scientific process should result in more efficient and cost-effective management practices.
1 Partner in Flight Landbird Population Estimates Database, Version 2004
2 Peterjohn, B. G. 2001. The Birds Of Ohio. The Wooster Book Company. Wooster, Ohio.
Arctic Terns Longest Migrants....Still
By HENRY FOUNTAINNY TIMES
To reach elite status in many airline frequent-flier programs, you have to log at least 50,000 miles in the air in a year.
Somewhere in Greenland there’s an Arctic tern that could qualify.
Arctic terns have a reputation as long-distance travelers, migrating to the Southern Ocean from breeding grounds in the Arctic. Researchers have suggested the round-trip distance might be as much as 25,000 miles.
But those were only estimates. While location-tracking tags have been used with large birds like albatrosses, Arctic terns, at less than four ounces, were too small to carry them.
Now Carsten Egevang of the Greenland Institute of Natural Resources and colleagues have devised a miniature data logger that, at 1/20th of an ounce, is light enough. It records light intensity, using the timing of sunrise, sunset and length of twilight to determine latitude and longitude.
In The Proceedings of the National Academy of Sciences, the researchers report on the journeys of 11 terns fitted with the devices. The birds, which began their trips in Greenland or Iceland in August, took two routes south, some hugging the African coast and others crossing from West Africa to Brazil to follow the South American coast. They stopped for about three weeks in the mid-Atlantic east of Newfoundland, a rich feeding zone.
Once they reached the Southern Ocean, they spent four months flying primarily east and west, again in areas that are rich in food. They returned in May and June having traveled, on average, about 44,000 miles. One tern totaled 50,700 miles, which is the longest animal migration ever recorded electronically.
Monday, December 21, 2009
Can restoration be too small? Negative effects on avian behavior...
Many conservation practitioners operate with a common assumption that all ecosystem restoration is good no mater the size of the project area. A new study in the Journal of Applied Ecology contradicts this notion by showing that when it comes to tropical reforestation and the effect on birds, bigger is better and too small may be bad.
The work by Emily Morrison and fellow researchers is groundbreaking not just because it shows the importance of patch size in restoration but because it looks at animal behavior to reach its conclusions. Most studies evaluate restoration success with birds by looking at metrics like species diversity.
This study though looked at just four birds - cherrie’s tanagers, rufous-capped warbler, common tody-flycatcher and plain wren - and compared their insect foraging behavior across restored forest patches of different sizes.
They found that in the smaller patches the birds attacked insects at a lower rate (i.e fewer attacks per minute) and exerted more effort while foraging (i.e more jumping around). They also found that arthropod density was nearly twice as great in larger reforestations (greater than 3500 square meters) than smaller ones (less than 350 square meters).
Together these results indicate that birds in the smaller patches are having a more difficult time foraging for food which may have negative consequences for their fitness. This in turn may impede restoration success given that birds in the tropics play an important role in a number of ecosystem processes such as pollination and seed dispersal. Interestingly, a more conventional assessment looking at just species diversity likely would not have picked up on this problem.
These results have practical applicability because conservationists - whether in the tropics or elsewhere - are constantly weighing restoration size against project cost. Obviously, much more research is needed to determine how widely these results translate to other settings. In the case of tropical forests the authors recommend,
"Thus, forest restoration efforts using a patch-based planting scheme should consider patch size as an important factor that is likely to affect the quality of the patches as habitat for birds that use woody habitat. We recommend that small patches be avoided and that patches of at least a few thousand square metres be planted when resources are available."
--Reviewed by Rob Goldstein
Morrison, E., Lindell, C., Holl, K., & Zahawi, R. (2009). Patch size effects on avian foraging behaviour: implications for tropical forest restoration design Journal of Applied Ecology
The work by Emily Morrison and fellow researchers is groundbreaking not just because it shows the importance of patch size in restoration but because it looks at animal behavior to reach its conclusions. Most studies evaluate restoration success with birds by looking at metrics like species diversity.
This study though looked at just four birds - cherrie’s tanagers, rufous-capped warbler, common tody-flycatcher and plain wren - and compared their insect foraging behavior across restored forest patches of different sizes.
They found that in the smaller patches the birds attacked insects at a lower rate (i.e fewer attacks per minute) and exerted more effort while foraging (i.e more jumping around). They also found that arthropod density was nearly twice as great in larger reforestations (greater than 3500 square meters) than smaller ones (less than 350 square meters).
Together these results indicate that birds in the smaller patches are having a more difficult time foraging for food which may have negative consequences for their fitness. This in turn may impede restoration success given that birds in the tropics play an important role in a number of ecosystem processes such as pollination and seed dispersal. Interestingly, a more conventional assessment looking at just species diversity likely would not have picked up on this problem.
These results have practical applicability because conservationists - whether in the tropics or elsewhere - are constantly weighing restoration size against project cost. Obviously, much more research is needed to determine how widely these results translate to other settings. In the case of tropical forests the authors recommend,
"Thus, forest restoration efforts using a patch-based planting scheme should consider patch size as an important factor that is likely to affect the quality of the patches as habitat for birds that use woody habitat. We recommend that small patches be avoided and that patches of at least a few thousand square metres be planted when resources are available."
--Reviewed by Rob Goldstein
Morrison, E., Lindell, C., Holl, K., & Zahawi, R. (2009). Patch size effects on avian foraging behaviour: implications for tropical forest restoration design Journal of Applied Ecology
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