Among factors selecting for rapid growth rates in avian young are those that cause mortality of whole broods (e.g., predation, weather) (Ricklefs, Ecology 50:1031-1039, 1969). Abert's Towhee (Pipilo aberti) endures a high rate of nesting mortality caused by predation and brood parasitism (Finch, Condor 83:389, 1981; Condor 85:355-359, 1983). Predation is the principle factor causing loss of whole
... [Show full abstract] broods. Nesting mortality may have an important role in the development of life history traits (e.g., nestling growth, clutch-size, number of broods/season) in Abert's Towhee, yet little is known about these traits (but see Finch, Wilson Bull. 96:703-707, 1984). In this study, I describe growth rate of nestling Abert's Towhees and discuss its possible adaptive significance. I studied nestlings of Abert's Towhee in honey mesquite (Prosopis glundulosa) habitat of the lower Colorado River Valley 10 km N of Ehrenberg, Yuma Co., Arizona.