Nestling house wrens: weight and feather growth

Abstract

Six models were tested for weight and feather growth of nestling house wrens (Troglodytes aedon). For weight growth, the logistic model with an asymptote A of 10.4 g and a growth-rate constant K of 0.52 day−1 was best. Curves for weight growth of individuals varied, and some birds had pronounced weight recession. Growth of primary feather 10 followed the Gompertz model with A and K equal to 18.8 mm and 0.32 day−1, respectively. Growth of rectrix feather 6 could best be described by the von Bertalanffy model with a forced A value of 32.5 mm and K equal to 0.12 day−1. Fitting of the models to rectrix feather length was complicated because fledging occurred when growth was only 37% complete as opposed to 84% complete for primary feather growth. The variation among broods of growth parameters and nestling time ranged up to 54.5%. First and second broods did not differ significantly in these parameters and brood size could not account for much of the observed variability. Weight growth and primary feather growth were linked, but this was not the case for weight and rectrix, or for primary and rectrix feather growth. Some birds that failed to fledge had depressed growth. Weight growth and recession are particularly well suited for investigating natural and man-made environmental stresses such as gamma radiation.