DOI: 10.5061/dryad.jh9w0vtcg
title: Phenological data for the article: Phenotypic plasticity drives phenological changes in a Mediterranean blue tit population

description: Earlier phenology induced by climate change, such as the passerines'
 breeding time, is observed in many natural populations. Understanding the
 nature of such changes is key to predict the responses of wild populations
 to climate change. Genetic changes have been rarely investigated for
 laying date, though it has been shown to be heritable and under
 directional selection, suggesting that the trait could evolve. In a
 Corsican blue tit population, the birds' laying date has
 significantly advanced over 40 years, and we here determine whether this
 response is of plastic or evolutionary origin, by comparing the
 predictions of the breeder's and the Robertson-Price (STS) equations,
 to the observed genetic changes. We compare the results obtained for two
 fitness proxies (fledgling and recruitment success), using models
 accounting for their zero-inflation. Because the trait appears heritable
 and under directional selection, the breeder's equation predicts that
 genetic changes could drive a significant part of the phenological change
 observed. We however found that fitness proxies and laying date are not
 genetically correlated. The STS therefore predicts no evolution of the
 breeding time, predicting correctly the absence of trend in breeding
 values. Our results also emphasize that when investigating selection on a
 plastic trait under fluctuating selection, part of the fitness-trait
 phenotypic covariance can be due to within individual covariance. In the
 case of repeated measurements, splitting within and between individual
 covariance can shift our perspective on the actual intensity of selection
 over multiple selection episodes, shedding light on the potential for the
 trait to evolve.
description: We studied a wild blue tit population in the Corsican forest of
 Pirio (France, lat: 42.38, lon: 8.75) dominated by evergreen holm oaks
 (<i>Quercus ilex</i>, Fagales: Fagaceae, see Blondel et al.,
 2006 and Charmantier et al., 2016 for an extensive description of the
 population characteristics). From 1976 to 2019, the
 team weekly monitored the nests boxes -provided in abundance- during the
 reproduction season, between April and June (67 boxes in 1976, 187 now,
 see Charmantier et al. 2016, for further details). Laying date was deduced
 from the number of laid eggs, as females lay one egg per day. The team
 captured and banded parents, and estimated their ages at the nest boxes,
 when chicks were at least 10 days-old. The offspring were banded when 15
 days-old, and one week later, the number of chicks surviving (fledgling
 success) was estimated for each brood.
description: Each row is a clutch. DataLDfitnessannual file
 contains phenology and fitness measures. Laying dates
 are given as dates (day/month/year) and expressed using March 1 as
 reference (for which LD= 1). Absolute and relative values are given for LD
 and fitness proxies. Parents' identities are
 called mbag (male) and fbag (female). Fledlings' identities are
 called pulbag (1 to 14 fledglings per clutch). A
 "manipulation" variable indicated whether the clutch has been
 manipulated (and fitness should not be considered).
 Missing values are indicated as "NA".
 The pedigree contains all the individuals (id) and their parents
 (dam and sire for female and male).