Locating Nests of Birds in Grasslands From a Mobile Tower Blind

Locating nests of grassland passerines can be difficult, labor intensive, and disruptive to birds and vegetation. We developed a mobile tower blind for observing adult bird behavior and used it to locate nests in a western Montana grassland. We compared nest-search efficiency of behavioral observations from the tower versus the ground. Nests of savannah sparrow (Passerculus samhvichensis) were found in a higher proportion of territories searched from the tower (13/16 = 82%) than from the ground (4113 = 3 1%). Average search time for each nest found was lower from the tower (44 min) than from the ground (127 min). Both were lower than when we used drags made of rope or cable and chain (411 min). but nests were found earlier in the nesting cycle when we used drags. Adult birds were agitated and reluctant to approach and reveal their nests whenever an unconcealed observer was present in or near their territory. In contrast, normal behavior resumed within a few minutes after an observer entered the tower, even when the tower blind was within 10m of the nest. Observing behavioral cues from a tower blind provides substantial advantages for locating nests of savannah sparrows and probably other grassland birds. but effectiveness of the approach likely varies among species and habitats

Prevalence of Influenza A viruses in wild migratory birds in Alaska: Patterns of variation in detection at a crossroads of intercontinental flyways

<p>Abstract</p> <p>Background</p> <p>The global spread of the highly pathogenic avian influenza H5N1 virus has stimulated interest in a better understanding of the mechanisms of H5N1 dispersal, including the potential role of migratory birds as carriers. Although wild birds have been found dead during H5N1 outbreaks, evidence suggests that others have survived natural infections, and recent studies have shown several species of ducks capable of surviving experimental inoculations of H5N1 and shedding virus. To investigate the possibility of migratory birds as a means of H5N1 dispersal into North America, we monitored for the virus in a surveillance program based on the risk that wild birds may carry the virus from Asia.</p> <p>Results</p> <p>Of 16,797 birds sampled in Alaska between May 2006 and March 2007, low pathogenic avian influenza viruses were detected in 1.7% by rRT-PCR but no highly pathogenic viruses were found. Our data suggest that prevalence varied among sampling locations, species (highest in waterfowl, lowest in passerines), ages (juveniles higher than adults), sexes (males higher than females), date (highest in autumn), and analytical technique (rRT-PCR prevalence = 1.7%; virus isolation prevalence = 1.5%).</p> <p>Conclusion</p> <p>The prevalence of low pathogenic avian influenza viruses isolated from wild birds depends on biological, temporal, and geographical factors, as well as testing methods. Future studies should control for, or sample across, these sources of variation to allow direct comparison of prevalence rates.</p

International migration patterns of Red-throated Loons (<i>Gavia stellata</i>) from four breeding populations in Alaska

<div><p>Identifying post-breeding migration and wintering distributions of migratory birds is important for understanding factors that may drive population dynamics. Red-throated Loons (<i>Gavia stellata</i>) are widely distributed across Alaska and currently have varying population trends, including some populations with recent periods of decline. To investigate population differentiation and the location of migration pathways and wintering areas, which may inform population trend patterns, we used satellite transmitters (n = 32) to describe migration patterns of four geographically separate breeding populations of Red-throated Loons in Alaska. On average (± SD) Red-throated Loons underwent long (6,288 ± 1,825 km) fall and spring migrations predominantly along coastlines. The most northern population (Arctic Coastal Plain) migrated westward to East Asia and traveled approximately 2,000 km farther to wintering sites than the three more southerly populations (Seward Peninsula, Yukon-Kuskokwim Delta, and Copper River Delta) which migrated south along the Pacific coast of North America. These migration paths are consistent with the hypothesis that Red-throated Loons from the Arctic Coastal Plain are exposed to contaminants in East Asia. The three more southerly breeding populations demonstrated a chain migration pattern in which the more northerly breeding populations generally wintered in more northerly latitudes. Collectively, the migration paths observed in this study demonstrate that some geographically distinct breeding populations overlap in wintering distribution while others use highly different wintering areas. Red-throated Loon population trends in Alaska may therefore be driven by a wide range of effects throughout the annual cycle.</p></div

Migration patterns, stopover sites and wintering areas for Red-throated Loons breeding on the Arctic Coastal Plain (ACP) in northern Alaska.

<p>A) East Asian migration of Red-throated Loons. B) Pacific migration of a single Red-throated Loon from the Arctic Coastal Plain breeding area. Red dots represent breeding area locations, yellow dots are fall stopover sites, blue dots are wintering area locations, and green dots are spring stopover sites.</p

Migration patterns, stopover sites, and wintering areas of Red-throated Loons from 3 breeding populations.

<p>Red-throated Loon breeding areas in Alaska include the A) Seward Peninsula (SP), B) Yukon-Kuskokwim Delta (YKD), or C) Copper River Delta (CRD). Red dots represent breeding area locations, yellow dots are fall stopover sites, blue dots are wintering area locations, and green dots are spring stopover sites.</p

Average distance (km, ± SD) of migrations to fall stopover sites and wintering areas by Red-throated Loons.

<p>Red-throated Loon breeding populations represent Alaska’s Arctic Coastal Plain (ACP), Seward Peninsula (SP), Yukon-Kuskokwim Delta (YKD), and Copper River Delta (CRD).</p

Average latitude of Red-throated Loons at important stages of the annual cycle from 4 different breeding populations.

<p>Red-throated Loon breeding populations represent Alaska’s Arctic Coastal Plain (ACP), Seward Peninsula (SP), Yukon-Kuskokwim Delta (YKD), and Copper River Delta (CRD).</p

Average temporal migration patterns by Red-throated Loon breeding population.

<p>Line length represents date ranges from earliest arrival to latest departure. Average date of arrival denoted by diamond (◊), and average date of departure denoted by asterisk (*). Multiple lines represent different spatially distinct stopover or wintering areas used by loons from a breeding population. Breeding areas represent Alaska’s Arctic Coastal Plain (ACP), Seward Peninsula (SP), Yukon-Kuskokwim Delta (YKD), and Copper River Delta (CRD).</p