Growth rates of Great Erget (Casmerodius albus), Snowy Erget (Egretta thula), and Black-crowned Night-Heron (Nycticorax nycticorax) chicks to 18 days-of-age were estimated from repeated measurements of chicks in broods of three young. Weight gain (g/day) or increase in length (mm/day) of forearm, tarsus, or culmen did not between Black-crowned Night-Heron chicks at a colony in Rhode Island and a colony in Texas (USA). In Black-crowned night-Herons and Great Egrets, the last chick (C-chick) to hatch had lower growth rates than the first (A-) or second (B-) hatched chick. Black-crowned Night-Heron and Great Egret A-chicks gained weight faster than Snowy Egret A-chicks; however growth rates of the forearm, tarsus, or culmen each were not different among the three species. Equations based on the growth rate of culmen, forearm, or tarsus for repeatedly measured A-chicks estimated age of Great Egret, Snowy Egret, and Black-crowned Night-Heron chicks collected elsewhere to within two days of known age.
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Growth rates of great egret, snowy egret and black-crowned night-heron chicks