DOI: 10.5061/dryad.g1m27
title: Data from: Breeding timed to maximize reproductive success for a migratory songbird: the importance of phenological asynchrony

description: Phenological advances and trophic mismatches are frequently reported
 ecological consequences of climate warming. Trophic mismatches occur when
 phenological responses to environmental conditions differ among trophic
 levels such that the timing of resource demand by consumers becomes
 decoupled from supply. We used 25 years of demographic measurements of a
 migratory songbird (the black-throated blue warbler Setophaga
 caerulescens) to compare its breeding phenology to the phenology of both
 its caterpillar prey and the foliage on which caterpillars feed.
 Caterpillar biomass in this forest did not show a predictable seasonal
 pulse. Nest initiation by warblers in this northern hardwood forest was
 therefore not timed to coincide with a peak in food availability for
 nestlings. Nonetheless, timing of first clutches was strongly associated
 with spring leaf expansion (slope ± SE = 0.56 ± 0.08 days per day of
 change in leaf phenology, R2 = 0.66). Warblers adjusted the timing of
 breeding to early springs mainly by shortening the interval between
 arrival and clutch initiation, but this likely has limits because recent
 early springs are approaching the relatively inflexible dates when birds
 arrive on the breeding grounds. Although the timing of first nests did not
 match 1:1 with leaf-out phenology, the adjustments in breeding time
 maximized mean annual reproductive success. Nest predation had the
 greatest effect on annual reproductive success, but the ability of nesting
 warblers to appropriately track leaf phenology accounted for effects on
 annual reproductive success comparable to the influence of variation in
 caterpillar abundance and conspecific density. Nesting phenology in
 black-throated blue warblers was generally well matched to the timing of
 leaf-out, even though the match was not 1:1. Without measurements of
 reproductive success, these unequal phenological shifts might otherwise
 have been interpreted as having negative ecological consequences.
description: BTBW_annual_dataAnnual summaries of field data on black-throated blue warbler reproduction (1986-2010) gathered at the Hubbard Brook Experimental Forest in Thornton, NH, USA. Notes on column headings are as follows: prop.F.ASY = proportion older (ASY) females; Acsa.budburst = day of sugar maple (Acer saccharum) budburst (Day 1 = 01 January); Acsa.canopy = day of nearly complete (90%) expansion of sugar maple leaves; arrival.50 = median arrival date of male black-throated blue warblers; clutch.init.50 = median clutch initiation date of black-throated blue warblers; mean.cats = mean dry caterpillar biomass (mg/8000 leaves) across the whole season; ln.mean.cats = seasonal mean dry caterpillar biomass, natural log-transformed; mean.first.cats = mean dry caterpillar biomass (mg/2000 leaves) in the early season; ln.first.cats = mean dry caterpillar biomass (mg/2000 leaves) in the early season, natural log-transformed; high_day = day of the count with the highest caterpillar biomass; density = breeding black-throated blue warblers per 64ha; survival = daily nest survival rate; mean.fledged = average annual reproductive success (mean number of young fledged per pair per year).BTBW_data_Dryad.csv