Response of birds to broken eggs in their nests

We tested the responses of two bird species which nest on unmovable substrates (e.g., cavities and walls) to simulated and actual egg damage in their nest. Tree Swallows (Tachycineta bicolor) and Barn Swallows (Hirundo rustica) removed broken eggs and continued to incubate the rest of their clutch, but response times took up to 8 days, and observed rejection rates were lower than reported for some other passerines. Collectively, these data and other studies suggest that broken eggs represent a continuing selection pressure to which all birds respond, although there appears to be some variability among species in the strength and speed of the response to damaged eggs.