Environmental variation and the evolution of large brains in birds - Sayol, Ferran (Centre de Recerca Ecològica i d'Aplicacions Forestals) ; Maspons, Joan (Centre de Recerca Ecològica i d'Aplicacions Forestals) ; Lapiedra i González, Oriol (Harvard University. Department of Organismic and Evolutionary Biology) ; Iwaniuk, Andrew N. (University of Lethbridge. Department of Neuroscience) ; Székely, Tamás (University of Bath. Department of Biology and Biochemistry) ; Sol, Daniel (Centre de Recerca Ecològica i d'Aplicacions Forestals)