Apparent Survival and Fecundity of Sympatric Lesser Black-Backed Gulls and Herring Gulls with Contrasting Population Trends

• Published in: Ardea Vol. 100; no. 2; pp. 113 - 122
• Main Authors: Camphuysen, C.J., Gronert, A.
• Format: Journal Article
• Language: English
• Published: Netherlands Ornithologists Union 2012
• Subjects: apparent survival; fecundity; food limitation; Larus argentatus; Larus fuscus; Marine; population trends; sexual segregation; North Sea; ANE, Wadden Sea
• ISSN: 0373-2266
• DOI: 10.5253/078.100.0202

We investigated apparent survival (i.e. survival confounded by permanent emigration) on the basis of a colour-ring programme in which individual Lesser Black-backed Gulls Larus fuscus and Herring Gulls Larus argentatus could be monitored over time. The work was conducted in a large, mixed colony in the western Wadden Sea (Texel), where measures of fecundity were collected simultaneously. In Herring Gulls, we found a mean apparent annual adult survival of 79% in females and 86% in males. Additive year effects rather than sex provided highest model support in Lesser Black-backed Gulls, in which apparent survival for both sexes combined varied between 81% and 100% (mean ≈91%). Breeding success in Lesser Black-backed Gulls was significantly lower than that of Herring Gulls. Lesser Black-backed Gulls experienced four consecutive breeding seasons with very low fledging rates (2006–2009) as a result of cannibalism (60–67% of all hatchlings). Chick predation was generally lower in Herring Gulls. A strong population increase in Lesser Black-backed Gulls coincided with substantial population declines in Herring Gulls in the Wadden Sea in the late 20st and early 21st century. In Lesser Black-backed Gulls, apparent survival declined by about 10% in the last two study years, which could, in combination with the low fecundity, halt the current population increase. We suggest that future work should concentrate on underexplored aspects affecting fecundity and survival such as intermittent breeding and sexual differences in migration, foraging and breeding effort.