Table 3.

Across-years selection differentials and selection gradients (± 1 SE) of morphological traits on annual apparent survival for cliff swallows in southwestern Nebraska, U.S.A., across all years, 1997–2010. Selection differentials are taken from regression coefficients for each trait from its top-supported individual covariate model that did not include climate (PDSI; Table 2). The selection gradients are the regression coefficients of the top-supported model using all morphological traits (Table 2, model 2). Significant values (p < 0.05) are bolded. Blank entries are for terms not supported in the top models and thus considered non-significant.

Trait	Selection differential (± SE)		Selection gradient (± SE)		Correlational selection coefficient (± SE)
	Directional	Nonlinear	Directional	Nonlinear	*tarsus	*bill length	*bill width
wing length	0.047 ± 0.010						−0.015 ± 0.012
tail length	0.094 ± 0.010		0.085 ± 0.012				0.015 ± 0.012
tarsus length	0.024 ± 0.010	−0.157 ± 0.012	−0.022 ± 0.010	−0.176 ± 0.012		0.073 ± 0.011	−0.018 ± 0.011
bill length	0.161 ± 0.011		0.149 ± 0.012				0.022 ± 0.011
bill width	0.105 ± 0.011		0.067 ± 0.011