Abstract
Climate change is affecting many living organisms; however, the responses of many of them remain unknown. In this paper, we present the results regarding the response of a bird species from the rallid family to the increased temperatures during the breeding season. We analysed the breeding data of Eurasian Coots nesting during 30 seasons between 1972 and 2019. During the study period, mean temperatures in April, the month when Coots start nesting, increased by 3.5 °C, and in months corresponding with the species breeding season by 2.6 °C. Breeding Coots advanced their earliest and median laying dates across the study period; however, the duration of their breeding season remained unchanged. We did not detect any significant temporal changes in clutch size, but clutches have become much more variable in size throughout the study period. Nest failures and production of offspring per nest did not change over the study period; however, the production of young per successful nest significantly declined. It is likely that this decline is the effect of mismatch between the period of food abundance (dipterans collected from water), and hatchling emergence, which is advanced due to change in climate. Future studies investigating the occurrence of dipteran resources at water bodies are needed to test this hypothesis.
Highlights
The global mean temperature has been steadily rising across the last decades, and it seems that the current warming trend is unprecedented over decades to millennia (IPCC 2014; Houghton 2015)
We have not detected any significant trend in precipitation levels, either for monthly totals or for the whole breeding season
Mean monthly humidity in April and July slightly decreased throughout the study period, but not in May and June (Mann-Kendall test, April: τ = − 0.22, p = 0.03, May: τ = − 0.14, p = 0.15, June: τ = − 0.14, p = 0.16, July: τ = − 0.28, p = 0.006), while the trend for the whole breeding season was significant
Summary
The global mean temperature has been steadily rising across the last decades, and it seems that the current warming trend is unprecedented over decades to millennia (IPCC 2014; Houghton 2015). The most clear pattern emerging from previous avian studies is that many birds advance laying dates in response to climate change (Dyrcz and Czyż 2018; Dunn 2019; Radchuk et al 2019). Many doublebrooded species have extended their seasons in response to climate change They often use multiple food resources and may take advantage of a longer vegetative season, lay more clutches and produce more offspring annually (Halupka et al 2008; Bulluck et al 2013). Higher temperature, precipitation or humidity may be associated with higher productivity of ecosystems, and higher availability of food resources (Avery and Krebs 1984; Thomas et al 2017). Similar shifts in predation pressures may be found in other ecosystems as a result of changes in vegetation cover, the rate of plant growth, altered phenology of insects, etc. (Dunn and Møller 2019)
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