1. It is commonly believed that the smaller clutch size of tropical compared with temperate birds is a response to a high predation rate. If this is true, one would expect incubation and fledging periods in the tropics to be shorter than in temperate regions, but they are generally thought to be longer in the tropics than in northern temperate areas. 2. In this paper we show that among passerines in both the Old and the New World, there is little or no difference in either incubation or fledging periods between temperate and tropical areas. 3. We suggest that tropical birds differ from temperate ones in their clutch size and extended post-fledging periods, which is necessary for juvenile survival, but probably not in other life history parameters.
- Clutch size