Dieval H.,Groupe de Recherche en Ecologie Comportementale et Animale |
Giroux J.-F.,Groupe de Recherche en Ecologie Comportementale et Animale |
Savard J.-P.L.,Wildlife Research Division
Wildlife Biology | Year: 2011
Common eiders Somateria mollissima nest in colonies on islands of the St. Lawrence Estuary in Quebec, Canada. After hatching, attending females must reach suitable brood-rearing habitats while non-attending females and adult males must find appropriate moulting sites. The aim of our study was to determine the biotic and abiotic factors that influence the distribution of common eiders during the brood-rearing and moulting periods. We conducted biweekly surveys and recorded the number of ducks by age and sex in 2003 and 2004 at 68 sites along a 200-km stretch of the south shore of the St. Lawrence River. We further classified adult females according to the presence or absence of young. We evaluated human disturbance during the surveys and developed a sinuosity index describing shoreline protection. We determined the nature of the substrate and an estimate of food abundance for a subsample of sites (N = 38). At the scale of the estuary, common eiders did not distribute randomly but used the same sites in both years. Broods preferred mainland sites near nesting islands. Non-maternal females and males were located further east along the estuary, but their numbers were lower than expected based on the size of the breeding population, indicating that some birds undertake a moult migration outside of the area. In the eastern portion of our study area, densities of non-maternal females increased significantly as summer progressed. The distribution of common eiders was influenced by food abundance and type but was not related to our indices of human disturbance and shoreline protection. Males were associated with mussels, non-maternal females with both mussels and gammarids, while maternal females with ducklings were associated with periwinkles. Few of the sites used by common eiders along the south shore of the St. Lawrence Estuary are currently protected and measures should thus be taken to insure their conservation. © Wildlife Biology, NKV.
Pearson S.F.,Wildlife Research Division |
Knapp S.M.,University of Arizona
PLoS ONE | Year: 2016
Habitat selection that has fitness consequences has important implications for conservation activities. For example, habitat characteristics that influence nest success in birds can be manipulated to improve habitat quality with the goal of ultimately improving reproductive success. We examined habitat selection by the threatened streaked horned lark (Eremophila alpestris strigata) at both the breeding-site (territory) and nest-site scales. Larks were selective at both spatial scales but with contrasting selection. At the territory scale, male larks selected sparsely vegetated grasslands with relatively short vegetation. At the nestsite scale, female larks selected sites within territories with higher vegetation density and more perennial forbs. These nest-site scale choices had reproductive consequences, with greater nest success in areas with higher densities of perennial forbs. We experimentally manipulated lark habitat structure in an attempt to mimic the habitat conditions selected by larks by using late summer prescribed fires. After the burn, changes in vegetation structure were in the direction preferred by larks but habitat effects attenuated by the following year. Our results highlight the importance of evaluating habitat selection at spatial scales appropriate to the species of interest, especially when attempting to improve habitat quality for rare and declining species. They also highlight the importance of conducting restoration activities in a research context. For example, because the sparsely vegetated conditions created by fire attenuate, there may be value in examining more frequent burns or hotter fires as the next management and research action. We hope the design outlined in this study will serve as an integrated research and management example for conserving grassland birds generally. © 2016 Pearson, Knapp. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
Pearson S.F.,Wildlife Research Division |
Giovanini J.,Weyerhaeuser Company |
Jones J.E.,Weyerhaeuser Company |
Kroll A.J.,Weyerhaeuser Company
PLoS ONE | Year: 2015
Riparian ecosystems integrate aquatic and terrestrial communities and often contain unique assemblages of flora and fauna. Retention of forested buffers along riparian habitats is a commonly employed practice to reduce potential negative effects of land use on aquatic systems. However, very few studies have examined long-term population and community responses to buffers, leading to considerable uncertainty about effectiveness of this practice for achieving conservation and management outcomes. We examined short- (1-2 years) and long-term (∼10 years) avian community responses (occupancy and abundance) to riparian buffer prescriptions to clearcut logging silvicultural practices in the Pacific Northwest USA. We used a Before-After-Control-Impact experimental approach and temporally replicated point counts analyzed within a Bayesian framework. Our experimental design consisted of forested control sites with no harvest, sites with relatively narrow (∼13m) forested buffers on each side of the stream, and sites with wider (∼30m) and more variable width unharvested buffer. Buffer treatments exhibited a 31-44% increase in mean species richness in the post-harvest years, a pattern most evident 10 years post-harvest. Post-harvest, species turnover was much higher on both treatments (63-74%) relative to the controls (29%). We did not find evidence of local extinction for any species but found strong evidence (no overlap in 95% credible intervals) for an increase in site occupancy on both Narrow (short-term: 7%; long-term 29%) and Wide buffers (short-term: 21%; long-term 93%) relative to controls after harvest. We did not find a treatment effect on total avian abundance. When assessing relationships between buffer width and site level abundance of four riparian specialists, we did not find strong evidence of reduced abundance in Narrow or Wide buffers. Silviculture regulations in this region dictate average buffer widths on small and large permanent streams that range from ∼22-25 m. Guidelines for this region are within the range of buffers included in our study, in which we observed no evidence for avian species loss or for a decline in species abundance (including riparian associated species). © 2015 Pearson et al. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
Good T.P.,National Oceanic and Atmospheric Administration |
Pearson S.F.,Wildlife Research Division |
Hodum P.,University of Puget Sound |
Boyd D.,National Oceanic and Atmospheric Administration |
And 2 more authors.
Marine Pollution Bulletin | Year: 2014
Organochlorine contaminants in upper trophic-level consumers inhabiting Puget Sound are consistently higher than in those species inhabiting other west coast locations. We analyzed persistent organic pollutants (POPs) in the six most common fish prey of rhinoceros auklets breeding on Protection Island (Puget Sound), Tatoosh Island (WA coast), and Destruction Island (WA coast). Wet-weight concentrations of POPs ranged widely (PCBs: 1.6-25.0. ng/g; DDTs: 0.2-56.0. ng/g; PBDEs:
Schrimpf M.B.,University of Washington |
Parrish J.K.,University of Washington |
Pearson S.F.,Wildlife Research Division
Marine Ecology Progress Series | Year: 2012
Many productive ocean ecosystems are also highly variable, resulting in complex trophic interactions. We analyzed interannual patterns in the diet of a seabird, the common murre Uria aalge, in a region of high oceanographic productivity, the northern California Current, to investigate how these top predators adjust their chick provisioning to cope with environmental variability. Murres relied chiefly on Pacific herring Clupea harengus pallasi and surf smelt Hypomesus pretiosus to provision chicks, although they regularly returned 8 other fish taxa. Provisioning success was measured by the energy return rate to chicks, which in turn was disarticulated into energy per meal (quality) and meal delivery rate (quantity). Parents exhibited 'compensation' during 2 years in which smaller, low quality prey were returned more quickly than in years with normal (i.e. 'good') provisioning. Despite the increased delivery rate, energy return rates were still lower in 'compensation' vs. 'good' years. The lowest energy return rates occurred in 3 'poor' years, during which ocean productivity was also depressed. Our results suggest that murres in this system have the ability to shift provisioning strategies to deal with some variability in prey resources, but not when limited by exceptionally poor environmental conditions. © Inter-Research 2012.