Sources, sinks, and drains in double breeding bird species?

The recognition of a second breeding season in some migratory bird species by Rohwer et al. (1) creates an interesting scenario for conserving migratory bird populations. Previously, conservation biologists assessed sources as large undisturbed habitats and sinks as degraded breeding grounds (2), and treated fragmented and deforested habitats in nonbreeding “wintering” areas as drains on the population. In light of a second, and perhaps vital, breeding season in midmigration, a dichotomous source–sink model is no longer applicable.