DOI: 10.5061/dryad.12jm63z5g
title: Warm winters lead to early breeding, increased breeding effort, but lower reproductive success, in a threatened habitat specialist

description: Climate warming is affecting the phenology and life-history of animals
 around the world. In birds, although warm winters have been shown to
 advance breeding dates and affect reproductive success in a diverse range
 of taxa, few studies document whether changes in breeding phenology are
 associated with variability in reproductive effort by the adults. We
 leverage a 40-year dataset on the demography of Florida Scrub-Jays
 (Aphelocoma coerulescens, FSJ) to investigate not only whether winter
 weather affects FSJ phenology and reproductive success, but also whether
 FSJs invest more effort in reproduction following warm winters. We found
 that FSJs bred early but fledged fewer offspring in springs following warm
 winters. This reduced reproductive success came at the expense of
 increased reproductive effort (N nests built, N eggs laid, and length of
 the breeding period across all attempts) by the breeders. Given the
 well-known tradeoff between reproductive effort and survival, we highlight
 an important but typically unrecognized cost of climate warming on birds,
 in a large, well-protected population of a threatened habitat specialist,
 as revealed by a long-term study.
description: # Warm winters lead to early breeding, increased breeding effort, but
 lower reproductive success, in a threatened habitat specialist
 [https://doi.org/10.5061/dryad.12jm63z5g](https://doi.org/10.5061/dryad.12jm63z5g) ## Description of the data and file structure Demography data are included that can be used to replicate the results provided in the manuscript. The code in the associated R script can be used to run the models with the associated datasets.  These demography data include  **meansbirddata.csv** : These data can be used to replicate models for nesting date and first nest success.  Columns within this dataset:   YEAR: Year of observation TERR: Territory ID meandaytempC: The mean temperature during the day in celcsius. Helpers: Helpers present (Y/N)  Success: Nest successful (1,0) incubDAY: Julian Day of incubation initiation hatchDAY: Julian day of hatching meandrought: mean drought index for preceding winter **nestattempts.csv**: These data can be used to run the model looking at the number of nesting attempts and the mean winter temperatures.  YEAR: Year of observation TERR: Territory ID meandaytempC: The mean temperature during the day in Celsius. Helpers: Helpers present (Y/N)  NestNum: Total number of nests built by pair in  the season **neggs.csv**: These data can be used to run the model looking at the number of eggs produced and the mean winter temperatures. Columns within this dataset:  YEAR: Year of observation TERR: Territory ID Neggs: Eggs laid during the whole breeding season meandaytempC: The mean temperature during the day in Celsius.  **Nfledg.csv**: These data can be used to run the model looking at the total number of fledglings produced by a pair in a year and the mean winter temperatures. YEAR: Year of observation TERR: Territory ID meandaytempC: The mean temperature during the day in celcsius. Helpers: Helpers present (Y/N)  nfldg: Number of fledglings produced by the group in the season **firstandlast.csv**: These data can be used to replicate model 6 for the length of the breeding season.   YEAR: Year of observation TERR: Territory ID meandaytempC: The mean temperature during the day in celcsius. Helpers.x: Helpers present (Y/N)  diff: Length of breeding season in days. **Breeding_phenology_paper_code_RESUBMIT2.R** file included in the submission shows the model codes and relevant columns used for manipulating data.