Feather and claw hydrogen isotope values
The feather hydrogen isotope (δ2Hf)
values were significantly higher and predicted latitudes were
significantly lower in resident than in migrant juncos (Fig. 2 a, b, e,
f; S1, S2; Table S1). The two populations exhibited non-intersecting
ranges of δ2Hf values, suggesting
distinct, non-overlapping breeding latitudes (migrants
δ2Hf range = -121.07 – -98.8 ‰;
residents δ2Hf range = -60.0 – -42.9
‰; Fig. S1, S2). The claw hydrogen isotope
(δ2Hc) values did not differ between
migrants and residents, suggesting that they overwintered at the same
latitude (Fig. 2c, d, g, h; S1, S2; Table S1). Difference in the
latitude of breeding and development of immature juncos provide a strong
rationale to investigate the difference in the neuroendocrine response
between resident and migrant junco populations.