Get access

Effects of extrinsic and intrinsic factors on breeding success in a long lived seabird


  • Sue Lewis,

  • David A. Elston,

  • Francis Daunt,

  • Barbara Cheney ,

  • Paul M. Thompson

S. Lewis (, School of Biological Sciences, Univ. of Aberdeen, Zoology Building, Tillydrone Avenue, Aberdeen, AB24 2TZ, UK, and Inst. for Evolutionary Biology, Univ. of Edinburgh, Kings Buildings, Ashworth Labs, West Mains Road, Edinburgh, EH9 3JT, UK and Centre for Ecology and Hydrology, Hill of Brathens, Banchory, Aberdeenshire, AB31 4BW, UK. – D. A. Elston, Biomathematics and Statistics Scotland, Macaulay Inst., Craigiebuckler, Aberdeen, AB15 8QH, UK. – F. Daunt, Centre for Ecology and Hydrology, Bush Estate, Penicuik, Midlothian, EH26 0QB, UK. – B. Cheney and P. M. Thompson, School of Biological Sciences, Univ. of Aberdeen, Lighthouse Field Station, Cromarty, IV11 8YJ, UK.


There is growing concern over the impacts of climate change on animal species. Many studies have demonstrated impacts of climate change at the population level, and density dependent effects of climate are frequently reported. However, there is an increasing recognition of the differential impact of such factors on individuals since there is marked variation in individual performance. We investigated the relationships between breeding success and environmental conditions (winter NAO and one year lagged winter NAO) and intrinsic effects (colony size, pair bond duration, past breeding success rate) in the northern fulmar Fulmarus glacialis, using data from a long-term study commenced in 1950. There was a negative trend in breeding success over time, and a negative relationship with winter NAO and lagged winter NAO, which themselves had shown positive increases over the study period. The effects of lagged winter NAO remained after accounting for the linear trend. There was no evidence of density dependence, with breeding success positively related to colony size. We found strong evidence that breeding success was negatively related to pair bond duration but positively related to past breeding success rate. There was also an interaction between these two intrinsic effects such that those pairs that had historically been successful maintained success with increasing pair bond duration, whereas less successful pairs showed a decline. The prediction that there would be a differential impact of extrinsic factors among pairs was supported by an interaction between past breeding success rate and winter NAO, such that pairs with low past success rate exhibited a sharp decline in breeding success with increasing winter NAO, whereas more successful pairs did not. It is critically important to understand interactions between extrinsic factors and individual heterogeneity since a differential impact on individuals will affect population structure, and hence population dynamics.