Why do cavity nesters have a longer nestling period than open nesters? A comparative study of alternative hypotheses.

Abstract

To reduce predation on their progeny, passerines evolved two basic nesting patterns: (1) concealing nests or constructing them in inaccessible places, or (2) breeding inside cavities where offspring are relatively protected. These two nesting patterns seem to lead to different length of nesting cycle. Nice (1957) was the first to report that cavity-nesting species have a longer nestling period than open-nesting species. Why does such a difference in nestling period exist? The goals of my study were: (1) to verify the earlier observation that cavity nesters have a longer nestling period than open nesters; (2) to test the assumption that predation is more intense on nest contents of open nesters than cavity nesters, thereby presenting an important selective force favoring different lengths of the nestling periods of the two groups; and (3) to test two hypotheses on the occurrence of different length of nestling periods between the two groups of passerines. (Abstract shortened by UMI.)