The 2017 field season ended successfully on 22 July. In contrast to last summer, cliff swallow reproductive success across the study area was relatively high, with only a few colonies exhibiting complete failure (like in 2016, for unknown reasons). The work this summer focused on three separate projects: studying reproductive success at different sites as part of our long-term study of fluctuating selection, repeating the 1980's-era fumigation experiments to study potential changes in the birds' tolerance to parasites, and a new study measuring neophobia and risk-taking (as personality components) in cliff swallows. We continued to document changes in foraging ecology since the 1980's, by taking nestling diet samples, quantifying foraging group sizes, and scoring the frequency of food deliveries to nestlings. Evidence is accumulating that the birds' foraging ecology has changed considerably over the last 30 years.
In May 2017, a 4-day period of cold and rainy weather led to another weather-related mortality event among adult cliff swallows, the first since 2004. Mortality was relatively limited. Although we picked up about 50 individuals that had died, estimated colony sizes later in the summer showed no dramatic demographic effect of the kill. We caught some living adults immediately after the cold weather and measured their wings, tails, legs, and bills to compare to those that died. This will reveal whether there was selection on body size during the weather event, and if so, was it in the same direction as we found in 1996. Results have not yet been analyzed.
Kommentare