Figure 3: Changes in resource availability during the breeding and non-breeding season.
From: Environmental variation and the evolution of large brains in birds
We measured resource availability (mean±s.e.m.) using the enhanced vegetation index (EVI) in the breeding areas during summer (light grey bars) and winter (dark grey bars). In the breeding areas of residents from higher latitudes (N=50), short-distance (N=230) and long-distance migrants (N=87), there is a larger decrease in EVI during winter (PGLS, P value<0.001, Supplementary Table 10) compared with residents from mid (N=326) and low (N=459) latitudes. Migratory birds skip this decrease in resource availability by moving to wintering areas in lower latitudes (black bars).
