DOI: 10.5061/dryad.8kprr4xnr
title: Data for: The El Nino-Southern Oscillation dramatically reduces the frequency of reproduction and reproductive rate of a tropical forest bird

description: Although climate change has been implicated in population declines of
 tropical forest birds, there is a critical lack of data on the mechanisms
 underlying these declines. Attempts to link climatic factors to variation
 in adult survival, fecundity, or nest success have been largely
 inconclusive. Recent community-scale analyses have suggested that tropical
 birds may be less likely to breed under adverse conditions, but long-term
 data on individual reproduction are needed to test this hypothesis. Here
 we leverage 12 years of data on a lowland forest bird, the greater ani
 (Crotophaga major), to investigate how demographic parameters vary with
 phase of the El Niño – Southern Oscillation (ENSO), a major driver of
 climatic conditions in tropical wet forest. The likelihood of breeding and
 annual reproductive rate both decreased dramatically in El Niño-like
 years, with only 37.5% of adults attempting breeding in 2015 (a strong El
 Niño year). For birds that did breed, however, clutch size and daily nest
 predation rate were unaffected by climate. Of the local climate variables
 investigated, dry season length and the frequency of high temperatures
 were most closely associated with reproductive failure. These results
 indicate that El Niño conditions alter the demography of greater anis by
 reducing the likelihood of reproduction, a response that may be more
 widespread than currently recognized. We suggest that reduced reproduction
 under adverse conditions represents an important and understudied aspect
 of the life histories of tropical forest birds.
description: Data were collected from a field site in lowland Panama from
 2007-2018 from a wild population of communally breeding greater anis.
 Individuals were tracked across years and their reproductive output
 recorded. Response variables in this data set include individual clutch
 size (number of eggs laid), likelihood of laying (yes/no), and nest
 predation rate (yes/no and exposure days). Predictors include several
 climate variables measured at the study site as well as possible
 biological covariates known to affect reproductive output (number of
 laying females in the nesting group, location of nest in either emergent
 vegetation (isolated) or shoreline vegetation). Raw data are presented in
 these files, but the nest abbreviations have been re-coded to prevent data
 plagiarism. Nest abbreviations in this data set are internally consistent
 to allow replication but they differ from the abbreviations used in the
 field and in other publications. Sample sizes and nest ID varies across
 analyses because not all nests experience the full nesting cycle (i.e.
 nesting groups that do not lay eggs are included in the analysis of
 likelihood of laying, but not in the analysis of clutch size or nest
 predation. Nests that were depredated prior to the completion of the
 laying cycle are included in the analysis of likelihood of laying and nest
 predation, but not in the analysis of clutch size since clutches were not
 complete). 
description: Metadata and notes are included in a tab of the Excel file.
 Explanations and definitions of the variables are given in the text of the
 manuscript. An additional ReadMe file has been uploaded as well.