Estimation and testing of parameters in Richards growth model for western grebes.

Growth rate coefficients for dark- and light-phase western grebes (Aechmophorus occidentalis) are compared with the Richards' growth model. The statistical assumptions necessary to estimate and test parameters are carefully scrutinized. Autocorrelations of the residuals are removed with an autoregressive model, and heterogeneity of variance of the residuals is corrected with weighted least squares. A model allowing random variation in the process of growth is also suggested as being a more realistic representation of the process. No differences were detected between dark- and light-phase growth rate coefficients.