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

Birdsongs provide population clues

Microphone array improves estimate of Ovenbird density.
Emma Marris

Published online 27 November 2009 Nature doi:10.1038/news.2009.1112

As any birder will tell you, most birds in the forest are easier heard than seen. Now two scientists have figured out a way to estimate bird population densities by recording their songs with an array of microphones.

The method offers an alternative to a common way to estimate population densities: the human ear. Humans listeners are often used in bird studies, but people are far from perfect, says Murray Efford of the University of Otago in Dunedin, New Zealand. In particular, "we aren't good at telling how far away sounds are," he says.

Efford and Deanna Dawson of the United States Geological Survey in Laurel, Maryland, have come up with a method that uses multiple microphones scattered through the woods. By recording in several places simultaneously, researchers can estimate each bird's acoustic 'footprint' — the area around it where it can be heard.

The size of the footprint depends on parameters such as the loudness of the birds and the acoustic properties of the forest. So Efford and Dawson must try different values for such parameters until they find a good match with the data recorded by the microphones. When all is done, the duo can estimate bird density without knowing the birds' locations or the size of the forest.

Twitter tweet!

They tried out their method on ovenbirds (Seiurus aurocapilla) at the Patuxent Research Refuge near Laurel, Maryland. Only male ovenbirds sing, and the technique estimated their density at around one male bird per every five hectares (click here to hear the ovenbird's song). The findings matched well with estimates gleaned from catching the little songbirds in nets. What's more, the researchers found that the new technique was more precise than estimates based on netting. The work is published online in the Journal of Applied Ecology1.

The researchers say that the method could be used to estimate densities of other hard-to-spot animals, including whales and dolphins. Len Thomas, a statistical ecologist at the University of St Andrews, UK, for instance, is already using a similar method as part of an effort to monitor Minke whales (Balaenoptera acutorostrata) by their sounds. Sightings of these whales in the Pacific can be counted on one hand, but males make a distinctive "boy-yoy-yoing" sound, so hydrophones can measure their song footprints, just like the ovenbirds.

However, Thomas says that Efford and Dawson's method only provides part of the picture for Minke populations. The method estimates only the densities of sounds, not of animals, and in the case of the whales, uncertainty about what percentage of males call and how often they do so make it hard to extrapolate to an estimation of the population density.

Efford adds that the new technique will work best with animals that make repetitive sounds at constant loudness. That means it could be especially useful for estimating population densities of other kinds of birds. "A lot of birds are blurting out the same thing over and over again, persistently and monotonously," he says.

The monotony may have gotten to Efford, after listening to ovenbird songs over and over for the study. "It is a particularly irritating and insistent call," he admits.

References
Dawson, D. K. & Efford, M. G. J. Appl. Ecol. 46, 1201-1209 (2009).

Native Garden Workshop--3.28.09 @ Aullwood Audubon Center & Farm

When I was child I watched an old black-and-white horror film called “The Day of the Triffids.” It was about deadly alien plants from outer space, called triffids, which come to earth to kill humans; most of who were blinded by the lights of a meteor shower that brought the triffids to our planet and could not see the approaching threat until it was too late. That movie terrified me back then.

Imagine my surprise then when I grew up and learned that there were real invading, killer plants spreading across our world; their spread being blindly aided by humans who helped move the plants from place-to-place and habitat-to-habitat, and in many cases were intentionally planting them.

Of course the real invaders are not aliens from a different planet, but from right here on earth, and while these alien invasive plants are not necessarily chasing down and killing humans they are causing the deaths of many plant and animal communities around the globe.

Many common invasive plants started out innocently enough as beautiful ornamental plants used for landscaping, or as potential food and medicinal purposes. In many cases, the U.S. Government was responsible for the spread of many of invasive plants in the U.S.

When “The Day of the Triffids” was released in 1962 it had been almost thirty years since the severe drought and the resulting great dust storms had spread beyond the Dust Bowl region of the country resulting in the collapse of the U.S. agriculture system and economic hardship for much of the country. The U.S. government stepped in with innovative programs to stabilize both agriculture and the economy. One of those programs was the Soil Erosion Service, which transformed into the Soil Conservation Service, and is known today as the U.S. Department of Agriculture’s Natural Resource Conservation Service. The Soil Conservation Service, like its name suggests, was tasked with revising agricultural practices at the time to conserve and prevent the further loss of top soil in Midwestern farm states like Wisconsin. The Service developed a variety of beneficial farming practices to reduce erosion, like terracing and contour cropping. Another practice the Service developed was the creation of wind rows and plantings for wildlife food and cover, which were comprised of fast-growing plants with spreading roots to hold soil in place, and potential food crops, like berries, that might benefit a variety of wildlife. Some of these plants that were promoted included Multiflora Rose (Rosa multiflora), honeysuckles (Lonicera spp.), and privets (Ligustrum spp.).

Today, we are paying the price for the decisions of our past, both economically and ecologically. Researchers with Cornell University estimate that $120 billion are spent annually on economic losses and environmental impacts due to all invasive animals, plants, and microorganisms in the U.S.

There are an estimated 17,000 native plant species in the U.S., and many many more that are considered introduced. Of the introduced plant species in the U.S. approximately 5,000 have escaped and become invasive in natural habitats. $100 million/yr is spent on controlling these invasive plants in the U.S. In agricultural systems invasive weed plants contribute to nearly $24 billion in crop losses every year, another $1 billion annually on forage losses in pastures, and ranchers spend an estimated $5 billion/yr controlling weeds that may be toxic to cattle in pastures and ranges. In residential areas it’s estimated that $500 million are spent annually by homeowners to control invasive weed species in lawns and landscaping, and $1 billion is spent on weed control management on golf courses.

While there has been much research on the impact of invasive plants on native plant communities, we are beginning to gain a better understanding of how invasive plants are impacting animal communities. Birds, which share close relationships with plants, may face the greatest danger posed by invasive plants.

To learn why and how you can start using native plants in your landscaping projects consider attending the Native Gardens Workshop at Aullwood Audubon Center & Farm on March 28th, 2009. You can get more details and register for the workshop by contacting Aullwood directly.

Protecting Habitats While Fighting Climate Change

A new statement issued by the National Audubon Society reports that over the last 40 years 177 bird species have experienced range shifts northward during the winter, potentially as a result of climate change. On average, ranges have shifted by at least 35 miles, however at least 60 species are reported to have experienced range shifts of over 100 miles or more. The study is based on citizen science data collected during the organization’s annual Christmas Bird Count.

This report comes only weeks after another report issued by the National Oceanic and Atmospheric Administration (NOAA) that concluded that climate change will be largely irreversible for at least 1000 years after all carbon emissions are completely halted, based on current emission projections.

While many are promoting legislative action to reduce carbon emissions, the question remains whether legislation will be enough to truly make a difference. While there is no doubt that there is need to regulate the reduction of carbon emissions, achieving meaningful permanent regulation will be difficult.

Competing interests between environmentalists, agencies, energy producers, and other stakeholders will make it difficult to reach an agreement that is mutually beneficial environmentally and economically. Additionally, as we’ve seen with the weakening of many important environmental policies in the past several years, legislation is prone to short lifetimes as political administrations come and go.

Fortunately, there are possible solutions that may actually help. Preservation and creation of green spaces, like forests and grasslands, may help sequester atmospheric carbon and act as carbon sinks while also serving as habitat for birds and other wildlife.

Likewise, understanding how birds utilize different areas will be important for understanding how to prioritize efforts to protect and restore critical habitats that can also serve as carbon sinks.

A report that appeared in Science this week brings new hope to conservationists about the possibility of understanding bird movements during migration. Researchers with York University have used mini tracking devices have been able to track the movements of Purple Martins and Wood Thrushes throughout their migration. While the sample size was small, what they found was that stopover habitats for some species may be more critical than for others, especially for species experiencing dramatic population declines.

Conserving bird habitats and fighting climate change are not mutually exclusive activities, but it’s going to take more than just signing petitions and promoting legislation to make a substantial change. We will need to be more proactive in preserving and restoring habitats through efforts at many levels to protect the bird species that we love in the short term and to reduce the impacts of climate change in the long term.