Data from: Factors affecting the nesting success of Swainson's thrush (Catharus ustulatus) along an elevational gradient

Montane birds face several ecological challenges during the breeding
season, including nest predators, competition for territory, and food
availability. The continuing effects of climate change are causing shifts
in these plant and animal communities, as well as changes in abiotic
factors such as increased temperature and precipitation effects, adding
additional stressors that could affect nest survival, putting their
populations at risk. The Swainson’s thrush (Catharus ustulatus) is
migratory songbird which is moderately common and breeds along a wide
elevation gradient within this system (200-1,250m). Populations of
Swainson’s thrush were once declining, though recent research shows their
ranges to be shifting downwards, potentially as the result of increased
precipitation and temperature at higher elevations. Although lower
elevations might be more favorable in terms of climactic conditions, nest
predation is higher at lower elevations in other systems. Thus, this
species might be faced with the opposing pressures of adverse climactic
conditions at higher elevations and increased predation at lower
elevations. Nest survival is a fundamental process to population size, and
therefore, is important in evaluating how montane breeding birds are
adjusting to the changing climate. We monitored nests of Swainson’s thrush
along an elevation gradient in the White Mountain National Forest in New
Hampshire in 2016, 2018, 2019 and 2021 at two sites: Mt. Jefferson
(500-1,250m) and Bartlett Experimental Forest (200-300m). We found a
significant negative effect of rain intensity (millimeters per hour per
day) as well as a negative interaction effect of elevation with minimum
daily temperature and average daily temperature, on the daily survival
rate of Swainson’s thrush. Our results provide evidence that nesting
survival of montane breeding birds could be at risk as heavier
precipitation events become more frequent and intense, a likely outcome
due to the changing climate within the White Mountains and other montane
ecosystems, putting other passerine species at risk in this
system.