Why don't all birds lay early? Causes and consequences of breeding timing for a long‐lived migratory seabird
8 affiliations
- 1Department of Biology University of Oxford Oxford UK
- 2Department of Animal and Plant Sciences University of Sheffield Sheffield UK
- 3Norwegian Institute for Nature Research Trondheim Norway
- 4School of Molecular and Life Sciences Curtin University Perth Western Australia Australia
- 5University of Lausanne Lausanne Switzerland
- 6School of Environmental Sciences University of Liverpool Liverpool UK
- 7Graduate School of Environmental Studies Nagoya University Nagoya Japan
- 8Department of Vertebrate Ecology and Zoology University of Gdańsk Gdańsk Poland
Abstract
The relationship between earlier laying and higher breeding success is well‐established in avian species. However, a wide distribution of breeding timings is often maintained within a population, and the causes and consequences of this variation require further exploration, particularly as many avian species advance breeding phenology in response to climate change.
Using a 16‐year dataset combining colony observations and biologging of Manx shearwaters (Puffinus puffinus), we show that earlier laying does not always result in higher breeding success, with later laying becoming less costly in recent years.
We additionally report a slight advancement in breeding timing within breeding pairs, despite finding no temporal trends in spring bloom onset. Nonetheless, birds adjusted lay date in response to interannual variation in phytoplankton bloom timing, and years with stronger Celtic Sea blooms exhibited stronger selection for early breeding.
Breeding timing was also influenced by repeatable individual differences in migratory behaviour, with birds undertaking generally earlier, shorter migrations to less southerly destinations laying earlier across years.
However, lay date was not determined solely by individual behaviour. In this long‐lived species with stable pair bonds, the arrival date of the second‐returning bird constrained advancement in laying.
This study suggests that variation in breeding timing is maintained through the combined effects of fluctuating selection, persistent individual differences, variation in non‐breeding duration and pair‐level processes.
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BibTeX
@article{siddiqidavies2026dont,
title = {{Why don't all birds lay early? Causes and consequences of breeding timing for a long‐lived migratory seabird}},
author = {Katrina Siddiqi‐Davies and Natasha Gillies and Hector Bailey and Sarah Bond and Annette Fayet and Holly Kirk and Lewis Lancaster‐Reeves and Joe Morford and Oliver Padget and Akiko Shoji and Martyna Syposz and Joe Wynn and Tim Guilford},
journal = {The Journal of Animal Ecology},
year = {2026},
month = oct,
doi = {10.1111/1365-2656.70363},
url = {https://doi.org/10.1111/1365-2656.70363},
note = {CC BY 4.0},
}
RIS
TY - JOUR
TI - Why don't all birds lay early? Causes and consequences of breeding timing for a long‐lived migratory seabird
AU - Katrina Siddiqi‐Davies
AU - Natasha Gillies
AU - Hector Bailey
AU - Sarah Bond
AU - Annette Fayet
AU - Holly Kirk
AU - Lewis Lancaster‐Reeves
AU - Joe Morford
AU - Oliver Padget
AU - Akiko Shoji
AU - Martyna Syposz
AU - Joe Wynn
AU - Tim Guilford
PY - 2026
DA - 2026/10/10
JO - The Journal of Animal Ecology
DO - 10.1111/1365-2656.70363
UR - https://doi.org/10.1111/1365-2656.70363
AB - The relationship between earlier laying and higher breeding success is well‐established in avian species. However, a wide distribution of breeding timings is often maintained within a population, and the causes and consequences of this variation require further exploration, particularly as many avian species advance breeding phenology in response to climate change. Using a 16‐year dataset combining colony observations and biologging of Manx shearwaters (Puffinus puffinus), we show that earlier laying does not always result in higher breeding success, with later laying becoming less costly in recent years. We additionally report a slight advancement in breeding timing within breeding pairs, despite finding no temporal trends in spring bloom onset. Nonetheless, birds adjusted lay date in response to interannual variation in phytoplankton bloom timing, and years with stronger Celtic Sea blooms exhibited stronger selection for early breeding. Breeding timing was also influenced by repeatable individual differences in migratory behaviour, with birds undertaking generally earlier, shorter migrations to less southerly destinations laying earlier across years. However, lay date was not determined solely by individual behaviour. In this long‐lived species with stable pair bonds, the arrival date of the second‐returning bird constrained advancement in laying. This study suggests that variation in breeding timing is maintained through the combined effects of fluctuating selection, persistent individual differences, variation in non‐breeding duration and pair‐level processes.
SN - 0021-8790
SN - 1365-2656
ER -