Mid-winter temperatures, not spring temperatures, predict breeding phenology in the European starlingSturnus vulgaris

Abstract

In many species, empirical data suggest that temperatures less than 1 month before breeding strongly influence laying date, consistent with predictions that short lag times between cue and response are more reliable, decreasing the chance of mismatch with prey. Here we show in European starlings (Sturnus vulgaris) that mid-winter temperature ca 50–90 days before laying (8 January–22 February) strongly (r2 = 0.89) predicts annual variation in laying date. Mid-winter temperature also correlated highly with relative clutch size: birds laid later, but laid larger clutches, in years when mid-winter temperatures were lower. Despite a high degree of breeding synchrony (mean laying date 5–13 April = ±4 days; 80% of nests laid within 4.8 days within year), European starlings show strong date-dependent variation in clutch size and productivity, but this appears to be mediated by a different temporal mechanism for integration of supplemental cue (temperature) information. We suggest the relationship between mid-winter temperature and breeding phenology might be indirect with both components correlating with a third factor: temperature-dependent development of the starling's insect (tipulid) prey. Mid-winter temperatures might set the trajectory of growth and final biomass of tipulid larvae, with this temperature cue providing starlings with information on breeding season prey availability (though exactly how remains unknown).

Individual quality and double-brooding in a highly synchronous songbird population

“…In some species this variation can be quite marked; for example, in Black Redstarts (Phoenicurus ochruros), the proportion of females initiating more than 1 clutch per season varied from 84% to 42% across 10 yr (Weggler 2006). In contrast, we found no annual variation in the proportion of double-brooding among 3 yr, which is likely due to the small interannual variation in laying dates in European Starlings (64 days; Williams et al 2015). Similarly, neither the frequency of double-brooding nor the success of second broods was related to relative laying date, which is also consistent with the high level of breeding synchrony within years in European Starlings (Feare 1984), even though other life-history traits are related to laying date in this species (e.g., clutch size; Williams et al 2015;and recruitment;Smith 2004).…”

“…In contrast, we found no annual variation in the proportion of double-brooding among 3 yr, which is likely due to the small interannual variation in laying dates in European Starlings (64 days; Williams et al 2015). Similarly, neither the frequency of double-brooding nor the success of second broods was related to relative laying date, which is also consistent with the high level of breeding synchrony within years in European Starlings (Feare 1984), even though other life-history traits are related to laying date in this species (e.g., clutch size; Williams et al 2015;and recruitment;Smith 2004). In other species, for which an effect of laying date on doublebrooding has been reported, the range of first-egg dates is relatively large; e.g., in the well-studied Eurasian Great Tit (Parus major), the range of first-egg dates within years averages 27 days (n ¼ 59 years; M. Visser personal communication), compared with only 12 days in our study population.…”

Breeding phenology and performance for four swallows over 57 years: relationships with temperature and precipitation

“…Since neither species is present on the breeding grounds during the winter, it seems likely that winter temperature and precipitation is affecting Barn and Tree Swallow breeding phenology and performance through insect availability (Williams et al 2015). Snow pack is an important factor affecting overwinter insect survival (Templer et al 2012); reductions in snow pack associated with warmer temperatures and/or reduced precipitation (like we currently observe in the Maritimes; Mekis and Vincent 2011, Vincent et al 2012 may result in an earlier, but less abundant and diverse insect population (Finn and Poff 2008).…”

“…Although many studies examine the relationship between spring temperatures and breeding phenology (e.g., Winkler 1999, Hussell 2003), recent work has also demonstrated that winter temperature can affect breeding phenology and performance of insectivorous birds (Williams et al 2015). This is likely due to the effects of temperature and/or precipitation on overwinter insect survival and development (Irwin and Lee 2000, Musolin and Saulich 2012, Templer et al 2012).…”

Spring temperatures influence selection on breeding date and the potential for phenological mismatch in a migratory bird

“…, Williams et al. ), and the existence of genetic and phenotypic correlations between various life‐history traits suggests that suites of these traits likely change in concert with each other as a response to long‐term climate change (Winkler et al. , Sheldon et al.…”