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"Bird populations"
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Impacts of the Northwest Forest Plan on forest composition and bird populations
The Northwest Forest Plan (NWFP) initiated one of the most sweeping changes to forest management in the world, affecting 10 million hectares of federal land. The NWFP is a science-based plan incorporating monitoring and adaptive management and provides a unique opportunity to evaluate the influence of policy. We used >25 years of region-wide bird surveys, forest data, and landownership maps to test this policy’s effect on biodiversity. Clearcutting decreased rapidly, and we expected populations of olderforest–associated birds to stabilize on federal land, but to continue declining on private industrial lands where clearcutting continued. In contrast, we expected declines in early-seral–associated species on federal land because of reduced anthropogenic disturbance since the NWFP. Bayesian hierarchical models revealed that bird species’ population trends tracked changes in forest composition. However, against our expectations, declines of birds associated with older forests accelerated. These declines are partly explained by losses of older forests due to fire on federal land and continued clearcutting elsewhere. Indeed, the NWFP anticipated that reversing declines of older forests would take time. Overall, the early-seral ecosystem area was stable, but declined in two ecoregions—the Coast Range and Cascades—along with early-seral bird populations. Although the NWFP halted clearcutting on federal land, this has so far been insufficient to reverse declines in older-forest–associated bird populations. These findings underscore the importance of continuing to prioritize older forests under the NWFP and ensuring that the recently proposed creation of early-seral ecosystems does not impede the conservation and development of older-forest structure.
Journal Article
How do en route events around the Gulf of Mexico influence migratory landbird populations?
Habitats around the Gulf of Mexico (GOM) provide critical resources for Nearctic–Neotropical migratory landbirds, the majority of which travel across or around the GOM every spring and fall as they migrate between temperate breeding grounds in North America and tropical wintering grounds in the Caribbean and Central and South America. At the same time, ecosystems in the GOM are changing rapidly, with unknown consequences for migratory landbird populations, many of which are experiencing population declines. In general, the extent to which events encountered en route limit migratory bird populations is not well understood. At the same time, information from weather surveillance radar, stable isotopes, tracking, eBird, and genetic datasets is increasingly available to address many of the unanswered questions about bird populations that migrate through stopover and airspace habitats in the GOM. We review the state of the science and identify key research needs to understand the impacts of en route events around the GOM region on populations of intercontinental landbird migrants that breed in North America, including: (1) distribution, timing, and habitat associations; (2) habitat characteristics and quality; (3) migratory connectivity; and (4) threats to and current conservation status of airspace and stopover habitats. Finally, we also call for the development of unified and comprehensive long-term monitoring guidelines and international partnerships to advance our understanding of the role of habitats around the GOM in supporting migratory landbird populations moving between temperate breeding grounds and wintering grounds in Mexico, Central and South America, and the Caribbean.
Journal Article
Finding a dove for Gramps
As a boy and his mother participate in the annual bird count, he misses his grandfather, who went south for the winter, and watches especially for Gramps' favorite bird. Includes facts about the history and purpose of the Christmas Bird Count, how to participate, and a bird checklist.
Book
The role of the North American Breeding Bird Survey in conservation
The North American Breeding Bird Survey (BBS) was established in 1966 in response to a lack of quantitative data on changes in the populations of many bird species at a continental scale, especially songbirds. The BBS now provides the most reliable regional and continental trends and annual indices of abundance available for >500 bird species. This paper reviews some of the ways in which BBS data have contributed to bird conservation in North America over the past 50 yr, and highlights future program enhancement opportunities. BBS data have contributed to the listing of species under the Canadian Species at Risk Act and, in a few cases, have informed species assessments under the U.S. Endangered Species Act. By raising awareness of population changes, the BBS has helped to motivate bird conservation efforts through the creation of Partners in Flight. BBS data have been used to determine priority species and locations for conservation action at regional and national scales through Bird Conservation Region strategies and Joint Ventures. Data from the BBS have provided the quantitative foundation for North American State of the Birds reports, and have informed the public with regard to environmental health through multiple indicators, such as the Canadian Environmental Sustainability Indicators and the U.S. Environmental Protection Agency's Report on the Environment. BBS data have been analyzed with other data (e.g., environmental, land cover, and demographic) to evaluate potential drivers of population change, which have then informed conservation actions. In a few cases, BBS data have contributed to the evaluation of management actions, including informing the management of Mourning Doves (Zenaida macroura), Wood Ducks (Aix sponsa), and Golden Eagles (Aquila chrysaetos). Improving geographic coverage in northern Canada and in Mexico, improving the analytical approaches required to integrate data from other sources and to address variation in detectability, and completing the database, by adding historical bird data at each point count location and pinpointing the current point count locations would further enhance the survey's value.
Journal Article
Urban Ornithology
Urban Ornithologyis the first quantitative historical analysis of any New York City natural area's birdlife and spans the century and a half from 1872 to 2016. Only Manhattan's Central and Brooklyn's Prospect Parks have preliminary species lists, not revised since 1967, and the last book examining the birdlife of the entire New York City area is now more than fifty years old.
This book updates the avifaunas of those two parks, the Bronx, and other New York City boroughs. It treats the 301 bird species known to have occurred within its study area-Van Cortlandt Park and the adjacent Northwest Bronx-plus 70 potential additions. Its 123 breeding species are tracked from 1872 and supplemented by quantitative breeding bird censuses from 1937 to 2015. Gains and losses of breeding species are discussed in light of an expanding New York City inexorably extinguishing unique habitats.
eBook
Brown-headed Nuthatches pero esta no ha cambiado en 75 anos
Birds face many human-induced environmental challenges that we associate with population declines. Because of this, we need more ways to monitor populations before they become endangered. Several authors have proposed that fluctuating asymmetry, or nondirectional deviation from bilateral symmetry, could be used as an indicator of population declines. Fluctuating asymmetry is linked to developmental instability and stress associated with environmental challenges such as habitat loss in populations of birds and other animals. Two key premises of the argument for linking fluctuating asymmetry and population declines are that (1) fluctuating asymmetry changes over time, and (2) change over time results in overall population- or species-level differences in fluctuating asymmetry. 1 evaluated these premises by measuring tarsus and hallux lengths of museum specimens primarily from 1875-1950 in a pair of closely related species with different population statuses--the White-breasted Nuthatch (Sitta carolinensis) and the Brown-headed Nuthatch (S. pusilla). Since Brown-headed Nuthatch populations are decreasing whereas White-breasted Nuthatch populations are increasing, I predicted that Brown-headed Nuthatches would have increasing fluctuating asymmetry over time whereas White-breasted Nuthatches would have no change or decreasing fluctuating asymmetry over time, and this would result in Brown-headed Nuthatches having more overall fluctuating asymmetry in both morphological traits than White-breasted Nuthatches. The percent asymmetry of tarsi and halluces for Brown-headed Nuthatches were at least 1.5X higher than the corresponding values for White-breasted Nuthatches, which supported the second premise. However, since I also found that there was a great deal of interindividual variation and no change in fluctuating asymmetry over time in either species, it is still unclear whether fluctuating asymmetry could be used to help monitor populations for evidence of decline before they reach endangered status. Future studies should more broadly and deeply explore the associations between avian population declines and fluctuating asymmetry. Received 6 January 2020. Accepted 23 February 2021.
Journal Article