Martínez Abraín, A. Are edge bird populations doomed to extinction: A response to Munilla et al. Biological Conservation 191, 843–844 (2015).
Munilla et al. (2007) defended the idea that the population crash of common guillemots (Uria aalge) in Atlantic Spain, between 1960 and 1974, was not due to food scarcity associated to climate change, but to decreased adult survival caused by human-related factors, such as the generalization of the use of synthetic fishing nets, illegal shooting and oil spills. I strongly agree with them regarding the relevance of not using climate change as a default scapegoat for conservation problems. Often, proximate ecological factors are responsible for population declines, and can be managed if identified. However, regarding the quasi-extinction of common guillemots in NW Iberia the authors did not rule out convincingly the possibility that the local population crash was not due to massive adult emigration, rather than to reduced adult survival. In fact they admitted in their discussion that local adult survival in their population models also included adult emigration, and that they could not discard at all this possibility, although they considered it unlikely.