A study examines how some birds have changed the timing of their breeding seasons during the last four decades. At mid- to high latitudes, resource availability is tied to temperature, and thus, climate change may influence the timing and duration of avian breeding. Maria Hällfors and colleagues analyzed more than 820,000 nesting records for 73 bird species. The records were collected across Finland between 1975 and 2017 and curated at the Finnish Museum of Natural History. On average, bird species both advanced and contracted their breeding period and were found to currently breed 4.6 days earlier and 1.7 days fewer than four decades ago. Specifically, 31% of species contracted their breeding period in at least one bioclimatic zone. Contracting breeding periods were common among resident and short-distance migrating species, which typically breed early in the season and have shorter breeding periods. The findings suggest that birds that breed early in the season can respond more quickly to environmental cues, reproduce sooner, and benefit more from warm conditions, compared with species that breed later in the season. Additionally, if breeding periods shift toward earlier timing and contract, community-wide patterns of bird species cooccurrence across the boreal region of Finland may be altered, according to the authors.
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Article #19-13579: "Shifts in timing and duration of breeding for 73 boreal bird species over four decades," by Maria H. Hällfors et al.
MEDIA CONTACT: Maria H. Hällfors, University of Helsinki, FINLAND; tel: +358407213474; email: < maria.hallfors@helsinki.fi >; Aleksi Lehikoinen, Finnish Museum of Natural History, University of Helsinki, FINLAND; tel: +358503182340; e-mail: < aleksi.lehikoinen@helsinki.fi >
Proceedings of the National Academy of Sciences