Hand-Rearing Corvids for Reintroduction: Importance of Feeding Regime, Nestling Growth, and Dominance

Abstract

Captive propagation has become increasingly important in preventing extinction in many avian species, including the Hawaiian crow (Corvus hawaiiensis) and Mariana crow (C. kubaryi). We used 3 surrogate species, common raven (C. corax), American crow (C. brachyrynchos), and black-billed magpie (Pica pica), to develop eaptive-rearing protocols for endangered corvids. Here we compare the health, growth, and survival among nestlings hand-reared on 14 feeding regimes. Frequency of feeding chicks for the first 2 weeks after hatch varied from once every 30 min to once every 2 hr. From 2 weeks until near fledging age, frequency of feeding varied from once every hour to once every 3 hr. Initial amounts of food fed varied from unlimited (ad libitum) to a restricted amount (a total of 15, 25, or 40% of a chick's body mass). Combinations of frequent feeding and large amounts of food produced fast-growing, heavy birds with few fault bars in their feathers, but all hand-reared nestlings grew more slowly than wild-reared chicks. Initial amount of food offered to day-old chicks affected growth and survival more than frequency of feeding in very large passerines (e.g., common ravens). In small- to medium-sized passerines (e.g., black-billed magpies, American crows), frequency of feeding affected growth and survival more than initial amount of food.