title: Mid-winter temperatures, not spring temperatures, predict breeding phenology in the European starling Sturnus 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 (r (2) = 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).
authors.affiliation: Department of Biological Sciences , Simon Fraser University , Burnaby, British Columbia, Canada V5A 1S6.
authors.forename: Tony D
authors.initials: TD
authors.lastname: Williams
authors.affiliation: Department of Biological Sciences , Simon Fraser University , Burnaby, British Columbia, Canada V5A 1S6.
authors.forename: Sophie
authors.initials: S
authors.lastname: Bourgeon
authors.affiliation: Department of Biological Sciences , Simon Fraser University , Burnaby, British Columbia, Canada V5A 1S6.
authors.forename: Allison
authors.initials: A
authors.lastname: Cornell
authors.affiliation: Department of Biological Sciences , Simon Fraser University , Burnaby, British Columbia, Canada V5A 1S6.
authors.forename: Laramie
authors.initials: L
authors.lastname: Ferguson
authors.affiliation: Department of Biological Sciences , Simon Fraser University , Burnaby, British Columbia, Canada V5A 1S6.
authors.forename: Melinda
authors.initials: M
authors.lastname: Fowler
authors.affiliation: Department of Biological Sciences , Simon Fraser University , Burnaby, British Columbia, Canada V5A 1S6.
authors.forename: Raime B
authors.initials: RB
authors.lastname: Fronstin
authors.affiliation: Department of Biological Sciences , Simon Fraser University , Burnaby, British Columbia, Canada V5A 1S6 ; Department of Biological Sciences , University of Windsor , 401 Sunset Avenue, Windsor, Ontario, Canada N9B 3P4.
authors.forename: Oliver P
authors.initials: OP
authors.lastname: Love
keywords: breeding phenology; clutch size; egg-laying date; temperature; tipulids