We assessed the influence of climatic, environmental, and biological factors on nest attentiveness of female Black Brant (Branta bernicla nigricans). Within females, nest attentiveness varied significantly with time of day, rainfall, ambient temperature, incubation day, and (incubation day) 2 . We examined variation among females in individual investment in reproduction by comparing the amounts of nutrients invested in the clutch with those invested in incubation. We compared nest attentiveness with the amount of nutrient reserves available to test the hypothesis that a trade-off exists between nutrient investment in eggs and investment in incubation. Among females, nest attentiveness was lower in 1992 (x = 82%) than in 1993 (x = 87%) and increased with clutch volume and mass. Our results show that environmental conditions influence incubation behavior in Black Brant. We detected a trade-off between investment in eggs and nest attentiveness, but the results are also consistent with the hypothesis that females vary in individual quality and this variation influences egg production as well as incubation.
American black duck (Anas rubripes) populations declined by more than 50% between the 1950s and 1990s, and the species serves as a flagship for conserving salt marsh habitats along the Atlantic Coast. Black ducks have generally been well studied throughout the annual cycle, but surprisingly, we lack a synthetic, quantitative understanding of their space use during the winter. This limits our ability to prioritize habitat acquisition and restoration efforts. We used >17,000 telemetry locations from 235 black ducks ranging from Connecticut to Virginia to study home range composition and space use during winter in relation to habitat quality, urbanization, and severe weather. Despite substantial environmental variation, home range sizes were similar among regions and years. Smaller home and core ranges contained a greater proportion of salt marsh habitat, and ducks experiencing more 4-day freeze events had larger home and core ranges. Ducks exposed to prolonged periods of cold weather had smaller core ranges when those areas comprised more energy-rich freshwater habitats. When we examined individual telemetry locations, we found that ducks used irregularly inundated high marsh more at night, presumably for foraging, and urban habitats more during the day and evening crepuscular periods. We found that black ducks used regularly inundated low marsh less on days where the temperature never rose above freezing, and instead used subtidal areas and forested wetlands more. Finally, we found ducks were marginally more likely to use freshwater habitats during high tides. Our study confirms that
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