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Urban Great Tits Bred Earlier but Some Adjusted Less to Spring Temperature

Great tit on the ground in Kraków, Poland
Research · Reproduction & development

Great tits (Parus major) generally began breeding earlier in cities than in nearby forests, but reduced adjustment to spring temperature was found in only some urban populations. The study combined five long-term European urban–forest systems and was published in Proceedings of the Royal Society B on 1 April 2026.

The researchers compared laying dates, the response of laying date to spring temperature and variation among individual birds. The data came from Montpellier and Paris in France, Antwerp in Belgium, Malmö in Sweden and Harjavalta in Finland, and included 12,609 first-clutch laying dates. This temperature response describes phenological plasticity: how strongly breeding timing shifts between warmer and colder springs. For an insect-eating songbird, that flexibility can help breeding remain synchronized with seasonal food peaks as spring conditions vary from year to year.

Urban birds laid earlier in four of five study systems

Great tits in the urban habitat laid earlier than their paired forest populations in four of the five study systems, with average differences ranging from 2.16 to 4.82 days. The broad pattern is consistent with earlier spring conditions in cities, although the study did not assign the difference to one factor such as temperature, artificial light, food or vegetation.

Only some cities showed weaker temperature tracking

In two urban populations, Montpellier and Paris, laying date changed less with annual spring temperature than in the corresponding forest population. The other three systems did not show clear evidence of reduced urban plasticity, so earlier urban breeding did not imply a universally weaker temperature response.

Variation among individual laying dates was greater in three urban populations: Montpellier, Antwerp and Harjavalta. Within the urban sites alone, the proportion of impervious surface around nest locations had little effect on laying date or its response to spring temperature. The results therefore show substantial city-to-city variation rather than one uniform urban pattern.

Sources and image credit

  1. Cuchot, P., Thompson, M. J., Biard, C., Eens, M., Eeva, T., Gervais, L., Isaksson, C., Matthysen, E., Senar, J. C., Teplitsky, C., & Charmantier, A. (2026). Facing rising temperatures in urban environments: The role of phenological plasticity in an urban-dwelling passerine, Parus major. Proceedings of the Royal Society B: Biological Sciences, 293(2068), 20251883.Primary peer-reviewed open-access study, published online 1 April 2026. The author list reflects the publisher correction issued on 10 June 2026.
  2. Cuchot, P., Thompson, M. J., Biard, C., Eens, M., Eeva, T., Gervais, L., Isaksson, C., Matthysen, E., Senar, J. C., Teplitsky, C., & Charmantier, A. (2026). Correction to: ‘Facing rising temperatures in urban environments: the role of phenological plasticity in an urban-dwelling passerine, Parus major’ Cuchot et al. Proceedings of the Royal Society B: Biological Sciences, 293(2072), 20261155.Publisher correction, published 10 June 2026, adding Erik Matthysen to the author list; the article itself was corrected.

Image: Jakub Hałun — great tit photographed in Kraków, Poland, 12 May 2021. Source: Wikimedia Commons. Representative image for this story; not presented as an animal or scene from the reported study or event. · CC BY-SA 4.0 · Source

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