Responses of birds to broken eggs in their nests

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