Standardized regression coefficients were 0.53 for numbers of invertebrates and -0.38 for variance in daily minimum air temperature, indicating that mean growth ratio of ducklings per brood was more sensitive to invertebrate numbers than to variance in daily minimum air temperature. There was no incidence of total brood loss. We determined final body mass for 31 of 36 ducklings that died during the 17-day experiment. Intrabrood correlation in survival was 0.029, a value sufficiently close to zero to justify treating fates of ducklings in the same brood as independent.
Solid line denotes probability function from logistic regression.