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.

Growth and development of house sparrows (Passer domesticus) in response to chronic food restriction throughout the nestling period

“…In both our control and food-restricted house sparrows, we observed rapid increases in tarsus length during the first week post-hatch, followed by slowed growth to day 12. Growth of the tarsus, skull and wing of food-restricted house sparrows was maintained in line with that of adequately fed controls, which is in agreement with previous studies showing prioritization of skeletal growth (relative to mass gain) in altricial young faced with acute or chronic, moderate restriction (Negro et al, 1994;Lacombe et al, 1994;Lepczyk and Karasov, 2000;Moe et al, 2004). An equivalent prioritization of skeletal growth was observed in our preliminary study of 25% chronic restriction lasting until 25days post-hatch in house sparrows (Killpack et al, 2010).…”

“…A number of studies have shown that altricial (Lepczyk and Karasov, 2000;Moe et al, 2004), semialtricial (Negro et al, 1994;Reid et al, 2000) and semi-precocial (Takenaka et al, 2005) birds that are food-restricted during the nestling period maintain skeletal growth despite reductions in the mass of the whole body and soft tissues. Some studies of chronic food restriction show that if birds receiving inadequate quantities of food during the nestling period decrease structural growth, then decreased competitive ability within the nest, delayed fledging and reduced recruitment and survival after fledging may result (Cruz and Cruz, 1990;Searcy et al, 2004;Mock et al, 2009;Miller, 2010).…”

Effects of breeding date and weather on nestling development in White StorksCiconia ciconia

“…However, an experimental study showed that in Marsh Tit and American Kestrels Falco sparverius nestlings in natural conditions do not grow at a maximum rate (Martin 1987, Negro et al 1994, Nilsson & Gårdmark 2001. Furthermore, Kosicki et al (2004) showed that White Storks' synchronized departure in autumn reduces migration costs, and birds are encouraged by others to finish their stay in the breeding grounds and start migration to wintering grounds.…”

Effects of a short period of elevated circulating corticosterone on postnatal growth in free-living Eurasian kestrelsFalco tinnunculus

“…Food restriction studies have shown that delays in growth may be partly or fully compensated for through a prolongation or acceleration of growth (e.g. Emlen et al, 1991;Negro et al, 1994;Bize et al, 2003;Bize et al, 2006) possibly with associated costs (Metcalfe and Monaghan, 2001). Because this study was done in the wild, we examined whether compensatory growth occurred under natural, rather than ad libitum, food conditions.…”