The role of breeding experience on the\ud foraging specialization of a pelagic marine\ud predator, the Cory's sheawater

Abstract

Experience is believed to be an important factor determining the foraging\ud success of animals, but there are still very few studies investigating how foraging\ud abilities develop over time. In this study, the spatial distribution and foraging tactics\ud of inexperienced and experienced individuals of a Procellariiform seabird species, the\ud Cory’s shearwater (Calonectris diomedea borealis) breeding on the Portuguese\ud continental shelf was compared. Kernel analysis and a multivariate analysis\ud (MADIFA) showed that while the experienced birds were relying on known static\ud features such as the bathymetry of the area, inexperienced birds were using larger\ud areas that were explained by different static and dynamic variables each year. The\ud foraging areas of the two groups overlapped less and less for each year, while stable\ud isotope signatures were becoming more and more similar, as inexperienced birds were\ud foraging on higher trophic prey closer to the coast, like the experienced birds. Linear\ud mixed models comparing home ranges and foraging areas calculated for each group\ud showed that the experienced birds were in general more successful in detecting\ud favourable foraging grounds, except in 2011, when the results showed the opposite.\ud Interestingly, the reproductive success of the inexperienced birds was significantly\ud higher than for experienced birds during that season