Figure 3
From: Nocturnally migrating songbirds drift when they can and compensate when they must
Migrant flight behaviors.
(a) Modeled mean heading and track directions as inferred by GAMM to account for fixed and random spatiotemporal effects. Birds followed mean tracks between 203.56–204.91° at coastal sites and 190.07–203.64° at inland sites (Supplementary Table S2). Birds’ headings were further west than they traveled, between 241.60–252.06° for coastal sites and 226.26–229.71° for inland sites (Supplementary Table S2). We found differences in means of coastal and inland track directions (LMM: P = 0.038) as well as heading directions (LMM: P < 0.001). Linear change in migrant heading and track for coastal and inland regions revealed significant temporal shifts in coastal track (GAMM: P < 0.001) and heading (GAMM: P < 0.001). Inland sites showed non-significant, near-zero changes in track (GAMM: P = 0.763) and heading (GAMM: P = 0.804). Wind heading was a significant non-parametric factor for all cases (GAMM: P < 0.01). (b) Mixed-effect model output depicting migrant behavior through the night for coastal and inland regions. Higher values of the slope of alpha indicate a stronger propensity for a drift behavior (0 = full compensation; 1 = full drift). Transparent lines represent site-specific behaviors and error bars 95% confidence intervals. Arrows represent preferred direction of movement. Individual radar coefficients interpolated using a generalized additive model.
