GROWTH AND BREEDING BIOLOGY OF CASPIAN TERNS (STERNA-CASPIA) IN 2 COASTAL CALIFORNIA ENVIRONMENTS

The breeding biology and growth of Caspian Tern (Sterna caspia) chicks were studied during the 1987 breeding season at Bolsa Chica Ecologica l Reserve (BC), Huntington Beach on the southern California coast and at Elkhorn Slough (ES), near Moss Landing, on the central California c oast in 1978. Both habitats are ecologically similar and may be charac terized broadly as coastal Pacific estuarine environments. Three metho ds of analysis were used to compare chick growth patterns at the two c olonies. Growth data were fitted using a logistic model, a modified Ri chards flexible curve model, and a nonparametric smoothing technique t o determine summary growth statistics. Chicks reached as asymptotic si ze (A) of 570 +/- 4.03 g on day 33 at ES and 566 +/- 3.85 g on day 32 at BC. Chicks at ES achieved a slightly greater (6%) instantaneous pea k rate of growth than chicks at BC. Although small differences were ev ident in magnitude and instantaneous rate parameters between these sit es, estimators of overall growth rate (i.e., K-L and t(10-90)) and sha pe parameters (t, P, and M) were similar, indicating homogeneity in th e growth processes of these two populations. Caspian terns grew more s lowly than other temperate tern species, possibly owing to physiologic al limitations imposed by their large size, but the shape of their gro wth curve exhibited a logistic form similar to other tern species.