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Costs of reproduction and migration are paid in later return to the colony, not in physical condition, in a long-lived seabird


Life history theory suggests a trade-off between costly activities such as breeding and migration and somatic self-maintenance. However, how the short-term cost of parental effort is expressed in species with a slow pace-of-life is not well understood. Also, investigating carry-over effects of migration is most meaningful when comparing migratory strategies within the same population, but this has rarely been done. We explore this hypothesis in a long-lived, pelagic seabird, the Cory’s Shearwater, Calonectris borealis, where males display partial migration. By manipulating reproductive effort and taking advantage of the natural variation in migratory strategy, we investigate whether early reproductive failure and migratory strategy had implications on the physical condition of males on return to the colony the following year. We experimentally induced breeding failure from mid-incubation, tracked the over-winter movements of these males and of males that invested in parental effort, and assessed innate immunity, stress, and residual body mass the following year. Early breeding failure resulted in earlier return to the colony among all males, associated with greater probability of reproductive success. Residents had a lower tail feather fault bar intensity, an indicator of stress during the non-breeding period, compared to migrants. Reproductive effort and migratory strategy had no impact on physiological condition otherwise. Our results provide evidence that in species with a slow-pace of life, such as the Cory’s Shearwater, somatic maintenance is prioritised, with the costs of reproduction and migration paid in delayed arrival date.

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We are grateful to Filipe Moniz, Pedro Melo, and all helpers for assistance in the field in this long-term project, Merijn Driessen for support in the lab at the Groningen Institute for Evolutionary Life Sciences, and Sara Pardal for advice in early planning. Instituto das Florestas e da Conservação da Natureza gave permissions and support for the work on Selvagem Grande. Procedures were approved by ISPA’s Ethical Committee for Animal Welfare and carried out under licenses issued by the DGAV (Direção Geral de Alimentação e Veterinária), license number DGAV 0421/2017, and by the Instituto das Florestas e da Conservação da Natureza, IFCN licence 1/S (2017). Funding was provided by the Fundação para a Ciência e a Tecnologia (FCT, Portugal) through projects Seamigrant PTDC/BIA-ANM/3743/2014 and Oceanwebs (PTDC/MARPRO/0929/2014), and PD/BD/127807/2016 awarded to MCG. Thanks are due for the financial support to CESAM (UIDB/50017/2020 and UIDP/50017/2020) and MARE (UIDB/04292/2020 and UIDP/04292/2020) by FCT, Portugal.

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PC and JPG conceived the long-term monitoring scheme. MCG, PC and JPG developed the ideas and designed the study. MCG and CB carried out the fieldwork. MCG led the writing of the manuscript. BIT provided logistical support for the analyses of immune parameters. MCG and MAV analysed and interpreted the immune data. All authors contributed critically to the drafts and gave final approval for publication.

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Correspondence to Marie Claire Gatt.

Additional information

Communicated by Thomas Koert Lameris.

This paper advances the knowledge of how K-strategists balance costly annual cycle activities with self-maintenance. Migratory strategies have scarcely been compared at an intra-population level.

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Gatt, M.C., Versteegh, M., Bauch, C. et al. Costs of reproduction and migration are paid in later return to the colony, not in physical condition, in a long-lived seabird. Oecologia 195, 287–297 (2021).

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  • Carry-over effects
  • Fault bars
  • Life history
  • Migration
  • Physiology