Table 1 Summary of parameters for each dimension of the ecological niche.

Dimension of the ecological niche	Proxy	Period	N_total (N_ind.)	r²c	Adjusted population repeatability (R) across years (95% CI)	Year-round consistency (correlation breeding/non-breeding)
Diet	δ¹³C	Breeding (P1)	300 (74)	0.22	0.14 (0.04–0.28)	χ²₍₁₎ = 1.2; p = 0.231
	δ¹³C	Non-breeding (S13)	130 (43)	0.71	0.25 (0.06–0.52)	χ²₍₁₎ = 1.2; p = 0.231
	δ¹⁵N	Breeding (P1)	300 (74)	0.36	0.18 (0.08–0.32)	χ²₍₁₎ = 0.3; p = 0.673
	δ¹⁵N	Non-breeding (S13)	130 (43)	0.84	0.50 (0.34–0.70)	χ²₍₁₎ = 0.3; p = 0.673
Daily activity	NFI	Breeding	187 (61)	0.44	0.38 (0.23–0.56)	χ²₍₁₎ = 13.0; p < 0.001
Daily activity	NFI	Non-breeding	160 (54)	0.44	0.19 (0.03–0.41)	χ²₍₁₎ = 13.0; p < 0.001
Habitat	SST	Breeding	101 (36)	0.44	0.18 (0–0.44)	Benguela Current (N = 44): χ²₍₁₎ = 0.02; p = 0.652 Canary Current (N = 12): χ²₍₁₎ = 8.9; p = 0.003
Habitat	SST	Non-breeding	64 (25)	0.72	0.45 (0.22-0.74)

Significant breeding/non-breeding correlation are shown in bold. NFI is the night flight index, SST is sea surface temperature (°C) recorded by GLS devices and r²c is conditional r square of linear mixed models, i.e. the variability explained by the model including both fixed and random factors. Breeding/non-breeding correlations were performed only with animals spending the non-breeding season in the Benguela Current, except for SST which was also performed for animals wintering in the Canary Current. Note that adjusted population repeatability values obtained for all traits in both breeding and non-breeding grounds were statistically significant (i.e. 95% confidence interval CI > 0) and thus trustworthy, except for SST breeding. Note that sample size (N) is not the same in all cases because input data came from different sources of information (stable isotope analyses, immersion data from GLS devices and temperature data from GLS devices).

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