Dissertation Research: Life History Consequences of Post-Fledging Care

University Of Illinois At Urbana-Champaign, Urbana IL

Investigators

Abstract

Brawn 0073152 Why tropical birds lay a small, usually 2-egg, clutch is a persistent enigma. Many suggested hypotheses assume selective pressures influencing nestling mortality or adult survival explain clutch size, but supporting data are lacking. The ability of parents to care for juveniles after they have left the nest may be an important factor in the evolution of small clutch size in tropical birds and has never been investigated. This hypothesis will be tested by manipulating clutch size and parental effort per juvenile in the Spotted Antbird, a small passerine endemic to Central America. Preliminary data indicate that juveniles from smaller clutches (i.e. one egg) have enhanced post-fledging survival probability and receive proportionately greater post-fledging parental care than do juveniles from normal 2-egg clutches. A possible explanation for this result is optimal brood size may be less than two juveniles; the second egg may provide insurance against hatching failure. This experiment will provide new insights to the ecological factors that influence the life histories of tropical birds. Birds are important components of biodiversity in tropical ecosystems; understanding their life histories is important for conservation decisions. Since tropical birds produce so few eggs per nesting attempt, any increase in juvenile mortality caused by habitat loss or forest fragmentation may be extremely detrimental to the persistence of those species.