DOI: 10.5068/d1n09c
title: Demographic consequences of phenological asynchrony for North American songbirds

description: Changes in phenology in response to ongoing climate change have been
 observed in numerous taxa around the world. Differing rates of
 phenological shifts across trophic levels have led to concerns that
 ecological interactions may become increasingly decoupled in time, with
 potential negative consequences for populations. Despite widespread
 evidence of phenological change and a broad body of supporting theory,
 large-scale multi-taxa evidence for demographic consequences of
 phenological asynchrony remains elusive. Using data from a
 continental-scale bird banding program, we assess the impact of
 phenological dynamics on avian breeding productivity in 41 species of
 migratory and resident North American birds breeding in and around
 forested areas. We find strong evidence for a phenological optimum where
 breeding productivity decreases in years with both particularly early or
 late phenology and when breeding occurs early or late relative to local
 vegetation phenology. Moreover, we demonstrate that landbird breeding
 phenology did not keep pace with shifts in the timing of vegetation
 green-up over a recent 18-year period, even though avian breeding
 phenology has tracked green-up with greater sensitivity than arrival for
 migratory species. Species whose breeding phenology more closely tracked
 green-up tend to migrate shorter distances (or are resident over the
 entire year) and breed earlier in the season. These results showcase the
 broadest-scale evidence yet of the demographic impacts of phenological
 change. Future climate change-associated phenological shifts will likely
 result in a decrease in breeding productivity for most species, given that
 bird breeding phenology is failing to keep pace with climate change.
description: Bird capture data were collected as part of the Monitoring Avian
 Productivity and Survivorship (MAPS) program, a collaborative long-term
 bird-banding project operating across North America. Data were obtained
 from 179 banding stations. Each banding station consisted of 6–20 mist
 nets operated approximately every ten days beginning as early as May 1
 (start date varying slightly by location) through August 8 (ordinal dates
 121–220 in a non-leap year), which span the breeding season for most birds
 in North America. Only species/locations/years with at least 15 total
 captures, at least 5 of those being juveniles, species/locations with at
 least 5 years of data, and species with at least 15 locations/years of
 data were considered. Bird breeding phenology was
 calculated using the capture dates of juvenile birds at MAPS stations.
 This measure of breeding phenology is indicative of the time of year at
 which young birds are fledging. For each species, at each location, in
 each year, our metric of breeding phenology was the mean date of first
 capture across all juveniles captured at that station that year. Following
 Saracco et al. 2019, we exclude subsequent captures of the same individual
 after its first capture.  For each station, effort
 hours was calculated as the proportion of net-hours (total area of mist
 nets multiplied by the number of hours that these nets were deployed)
 during the period where juveniles were captured, excluding the first 2.5%
 of juvenile captures to remove outliers, following the procedure used by
 Saracco et al. 2019.  Climate data was downloaded from
 climatena.ca. <strong>Works
 cited</strong> J. F. Saracco, R. B. Siegel, L.
 Helton, S. L. Stock, D. F. DeSante, Phenology and productivity in a
 montane bird assemblage: Trends and responses to elevation and climate
 variation. Glob. Change Biol. 25, 985–996 (2019).
description: Data from the Monitoring Avian Productivity and Survivorship
 (MAPS) program are curated and managed by The Institute for Bird
 Populations and were queried from the MAPS database on
 2019-10-16.