Munilla, I. & Velando, A. The Iberian guillemot population crash: A plea for action at the margins. Biological Conservation 191, 842 (2015).

We would like to thank Dr. Martínez-Abraín for his interest in our study on the collapse of the Iberian guillemots (Munilla et al., 2007) as it gives us the opportunity to comment on the importance of some of the issues concerning the conservation of marginal, rear edge populations. In our retrospective analyses of the quasi-extinction of Iberian guillemots, we found that the only demographic parameter which explained the dra- matic population crash that occurred between 1960 and 1974 was the disappearance of breeding adults.