Effects of Short-Term Food Deprivation on Growth of Hand-Reared American Kestrels

Abstract

Sudden prey reductions were simulated to examine their impact on growth parameters of nestling American Kestrels (Falco sparverius) hand-reared in captivity. The experimental design consisted of three treatments: (1) 15 nestlings fed ad libitum (control individuals), (2) 15 nestlings that were starved for 24 hr when 7 days old, and for 36 hr when 21 days old, and (3) 15 nestlings that were starved for 36 hr when 14 days old and for 48 hr when 28 days old. Fitting biometrical data to the logistic model (body mass and the length of antebrachium, tarsus and beak) or linear models (length of the ninth primary and the central rectrix), no significant differences were found for the growth parameters of each trait between control and starved birds. This revealed no long-term effects caused by temporary starvation. Although starved individuals suffered a significant weight loss following the periods of food deprivation, they recovered mass in 2-4 days by increasing food ingestion when the ad libitum diet was restored. This flexibility of the growth of mass can be seen as an adaptive mechanism to permit compensation in day to day fluctuations of the food supply. Although American Kestrels show reversed sexual size dimorphism prior to fledging, males and females responded similarly to starvation.