Abstract
Many avian species in Europe breed earlier as a result of higher temperatures caused by global climate changes. Climate change means not only higher temperatures but also more frequent extreme weather events, sometimes contrasting with the long-term trends. It was suggested that we should look closely at every extreme phenomenon and its consequences for the phenology of organisms. Examining the limits of phenotypic plasticity may be an important goal for future research. Extremely low spring temperatures in 2013 (coldest spring in 40 years) resulted in birds laying unusually late, and it was followed in 2014 by the earliest breeding season on record (warmest spring in 40 years). Here, we present results concerning breeding phenology and double-broodedness in the Great Tit (Parus major) and the Blue Tit (Cyanistes caeruleus) in 2013 and 2014 in an urban parkland and a deciduous forest in central Poland. Great Tits started laying eggs 18.2 days later in 2013 than in 2014 in the parkland, whereas the analogous difference was 21.1 days in the forest. Blue Tits started laying eggs in the parkland 18.5 days later in 2013 than in 2014, while the analogous difference was 21.6 days in the forest. The difference in the proportion of second clutches in Great Tits between 2013 (fewer second clutches) and 2014 (more second clutches) was highly significant in the parkland and in the forest. This rather large extent of breeding plasticity has developed in reaction to challenges of irregular inter-annual variability of climatic conditions. Such a buffer of plasticity may be sufficient for Blue Tits and Great Tits to adjust the timing of breeding to the upcoming climate changes.
Highlights
It was suggested that the recent extreme weather events can be treated as a natural experiment that may elucidate the mechanisms by which birds adjust their phenology to fluctuating environments (Wesołowski et al 2016)
The question is whether current changes in the timing of breeding can be attributed to evolutionary changes in response to the documented selection pressures, or whether they result from individual plasticity—the capacity of an individual to fit its phenology to environmental conditions (Charmantier et al 2008; Piersma and Gils 2011; Charmantier and Gienapp 2014)
We report on responses of Great Tits and Blue Tits (Cyanistes caeruleus) to extreme spring temperature variation between 2013 and 2014
Summary
Museum of Natural History, Faculty of Biology and Environmental Protection, University of Łódź, Kilińskiego 101, 90-011 Łódź, PolandThe impact of climate changes on populations of birds has recently been under extensive study (Mitrus et al 2005; Potti 2009; Wesołowski and Cholewa 2009; Goodenough et al 2011, 2015; Chmielewski et al 2013; Whitehouse et al 2013). It has been shown that many avian species in Europe breed earlier as a result of higher temperatures caused by global climate changes (Both and Visser 2005; Wesołowski and Cholewa 2009; Bauer et al 2010; Matthysen et al 2010; Fletcher et al 2013; Bartošová et al 2014). It was suggested that the recent extreme weather events can be treated as a natural experiment that may elucidate the mechanisms by which birds adjust their phenology to fluctuating environments (Wesołowski et al 2016). If phenotypic plasticity plays a major role in adjusting to unpredictable weather conditions in spring, examining the limits of plasticity may be an important goal for future research (Charmantier et al 2008; Piersma and Gils 2011; Stamps 2015; Wesołowski et al 2016)
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