3.2 Chick growth

We modeled the growth of 166 brant goslings (99 females, 67 males) from 105 nests, 390 snow goose goslings (195 females, 195 males) from 215 nests, 250 observations of 188 semipalmated sandpiper chicks from 94 nests, and 118 observations of longspur broods from 56 nests. Excluding the intercept-only null models, conditional R 2values ranged from ≥0.73 (snow goose) to ≥0.97 (longspur) and marginalR 2 ranged from ≥0.31 (snow goose) to ≥0.92 (longspur) across all model sets (Tables S1–S4), indicating that the combinations of fixed and random variables in our model sets satisfactorily accounted for variation in avian growth. For all species, null models received no support (wi = 0) in multimodel comparisons, and models with only age and sex (herbivores) or age alone (insectivores) as covariates were likewise poorly supported (wi = 0; Tables S1–S4) except for longspurs, where a model fitting only age had the second-highest model weight (wi = 0.14; Table S4) in the model set. For all species, the model-averaged parameter estimates for juvenile age were positive (Table 4), unsurprisingly indicating the strong influence of age on body mass. Additionally, the model-averaged parameter estimates of sex for both goose species (Table 4) indicated that male goslings weighed more than females of the same age, as expected (Ankney, 1980; Hupp et al., 2017).
TABLE 4 Model-averaged predictor variables (±95% confidence interval) from analysis of factors affecting the mass of chicks of black brant (BLBR), snow geese (LSGO), semipalmated sandpipers (SESA), and Lapland longspurs (LALO) at the Colville River, Alaska, 2012–2017. Values in bold highlight variables with confidence intervals that do not overlap 0. All predictor variables except age and sex were standardized prior to analysis; see Table 2 for species-specific variables