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Conservation Science for a Healthy Planet

Greatest threat to forest birds of eastern US is habitat loss on wintering grounds; magnified by climate change in future

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July 24 2017 Cornell University read full ScienceDaily article here

Within the next few decades, human-caused habitat loss looms as the greatest threat to some North American breeding birds. The problem will be most severe on their wintering grounds, according to a new study published today in the journal Global Change Biology. By the end of this century, the study’s authors say predicted changes in rainfall and temperature will compound the problem for birds that breed in eastern North America and winter in Central America.

“This is really the first study to measure the combined impact of climate change and land-use change over a bird’s full annual cycle,” says lead author Frank La Sorte at the Cornell Lab of Ornithology. “Typically, studies tend to focus on the breeding season. If you do that, you’re missing the real story which is inherently dynamic and complex.”

Migrant wintering grounds are vitally important because the birds spend a greater proportion of the year in these places…

Frank A. La Sorte, Daniel Fink, Peter J. Blancher and Steve Kelling. Global change and the distributional dynamics of migratory bird populations wintering in Central America. Global Change Biology · July 2017 DOI: 10.1111/gcb.13794

Understanding the susceptibility of highly mobile taxa such as migratory birds to global change requires information on geographic patterns of occurrence across the annual cycle. Neotropical migrants that breed in North America and winter in Central America occur in high concentrations on their non-breeding grounds where they spend the majority of the year and where habitat loss has been associated with population declines. Here, we use eBird data to model weekly patterns of abundance and occurrence for 21 forest passerine species that winter in Central America. We estimate species’ distributional dynamics across the annual cycle, which we use to determine how species are currently associated with public protected areas and projected changes in climate and land-use.
The effects of global change on the non-breeding grounds is characterized by decreasing precipitation, especially during the summer, and the conversion of forest to cropland, grassland, or peri-urban. The effects of global change on the breeding grounds are characterized by increasing winter precipitation, higher temperatures, and the conversion of forest to peri-urban. During spring and autumn migration, species are projected to encounter higher temperatures, forests that have been converted to peri-urban, and increased precipitation during spring migration.
Based on current distributional dynamics, susceptibility to global change is characterized by the loss of forested habitats on the non-breeding grounds, warming temperatures during migration and on the breeding grounds, and declining summer rainfall on the non-breeding grounds.
Public protected areas with low and medium protection status are more prevalent on the non-breeding grounds, suggesting that management opportunities currently exist to mitigate near-term non-breeding habitat losses. These efforts would affect more individuals of more species during a longer period of the annual cycle, which may create additional opportunities for species to respond to changes in habitat or phenology that are likely to develop under climate change

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