We measured growth of Roseate Tern (Sterna dougallii) chicks at a colony in Connecticut in 10 successive years. Data on body mass during the first three to four days of life were fitted to a quadratic regression model, yielding three parameters of early growth for each of 1,551 chicks: mass at hatching (Mo), linear growth (a) and quadratic growth (b). First chicks in each brood (A-chicks) exceeded second chicks (B-chicks) in each of the three growth parameters; A-chicks from broods of two grew faster than single chicks during the first three days. Mo depended on egg mass, hatch order, hatch date, and year. The linear coefficient (a) depended on hatch date, hatch order, and year, but not on egg mass or Mo. The quadratic coefficient (b) depended on a, hatch date, Mo, and hatch order. Subsequent growth and survival of chicks were predicted well by these parameters of early growth, with b contributing more to these predictions than Mo or a. After controlling for effects of early growth, none of the other variables measured (hatch date, egg mass, parental age, hatch interval between chicks, mass difference between chicks, female-female pairing, or trapping) contributed significantly to explaining later growth and survival. Year effects were substantial in only two of the 10 years of study. Individual pairs were consistent in performance (as indexed by chick growth) in successive years. These results suggest that growth and survival of Roseate Tern chicks are determined primarily by parental quality; much of the information about parental quality is expressed by the time the eggs are laid, and most of it is expressed by the time the chicks are three days old.
Additional publication details
Variations in growth of roseate tern (Sterna dougallii) chicks: II. Early growth as an index of parental quality