To breed or not to breed: drivers of intermittent breeding in a seabird under increasing predation risk and male bias

A1 Journal article (refereed)

Internal Authors/Editors

Publication Details

List of Authors: Öst M, Lindén A, Karell P, Ramula S, Kilpi M
Publisher: SPRINGER
Publication year: 2018
Journal: Oecologia
Journal acronym: OECOLOGIA
Volume number: 188
Issue number: 1
Start page: 129
End page: 138
Number of pages: 10
ISSN: 0029-8549


Intermittent breeding may be adaptive for long-lived species subjected to large accessory reproductive costs, but it may also reflect reduced adaptation to the environment, reducing population growth. Nevertheless, environmental influences on breeding propensity, particularly that of predation risk, remain poorly understood and difficult to study, because non-breeders are typically not identified. Female eiders Somateria mollissima from the Baltic Sea provide an excellent testbed, because nesting females have been exposed to intensifying predation and growing male bias that may increase female harassment. We based our study on long-term data (14 years) on females captured and marked at the nest, and females individually identified at sea irrespective of capture status. We hypothesized that breeding propensity decreases with increasing predation risk and male bias, and increases with breeder age. Consistent with our hypotheses, females nesting on islands with higher nest predation risk were more likely to skip breeding, and breeding probability increased with age. In contrast, the steep temporal decline in breeding propensity could not be reliably attributed to annual adult sex ratio or to the abundance of white-tailed sea eagles (Haliaeetus albicilla), the main predator on females, at the nearby Hanko Bird Observatory. Breeding probability showed significant consistent individual variation. Our results demonstrate that spatiotemporal variation in predation risk affects the decision to breed and high incidence of non-breeding was associated with low fledging success. The increased frequency of intermittent breeding in this declining population should be explicitly considered in demographic models, and emphasis placed on understanding the preconditions for successful reproduction.


Breeding propensity, eider, Environmental cues, Non-breeders, Reproductive strategies

Last updated on 2020-20-01 at 03:41