Individual specialization in diet by a generalist marine predator reflects specialization in foraging behaviour

1 We studied chick diet in a known-age, sexed population of a long-lived seabird, the Brünnich's guillemot (Uria lomvia), over 15 years (N = 136; 1993–2007) and attached time–depth–temperature recorders to examine foraging behaviour in multiple years (N = 36; 2004–07). 2 Adults showed specialization in prey fed to offspring, described by multiple indices calculated over 15 years: 27% of diet diversity was attributable to among-individual...