DOI: 10.5061/dryad.bvq83bkh2
title: Relative breeding timing and reproductive success of a resident montane bird species

description: Wild populations appear to synchronize their reproductive phenology based
 on numerous environmental and ecological factors, yet there is still
 individual variation in the timing of reproduction within populations and
 such variation may be associated with fitness consequences. For example,
 many studies have documented a seasonal decline in reproductive fitness,
 but breeding timing may have varying consequences across different
 environments. Using 11 years of data, we investigated the relationship
 between relative breeding timing and reproductive success in resident
 mountain chickadees (Poecile gambeli) across two elevational bands in the
 Sierra Nevada mountains, USA. Chickadees that synchronized breeding with
 the majority of the population (“peak” of breeding) did not have the
 highest breeding success; instead, birds that bred early performed best at
 high elevation, while at low elevation early and peak nests performed
 similarly. At both elevations, late nests consistently performed the
 worst. Overall, breeding success decreased with increasing relative timing
 at both high and low elevations, but the relationship between breeding
 success and timing differed among years. Our results suggest that in
 mountain chickadees, earlier breeding is associated with higher
 reproductive success, especially at high elevations, while late breeding
 is consistently associated with lower reproductive success at both
 elevations.
description: # Relative breeding timing and reproductive success of a resident montane
 bird species
 [https://doi.org/10.5061/dryad.bvq83bkh2](https://doi.org/10.5061/dryad.bvq83bkh2) Authors: Lauren E. Whitenack, Carrie L. Branch, Benjamin R. Sonnenberg, Angela M. Pitera, Joseph F. Welklin, Virginia K. Heinen, Lauren M. Benedict, Vladimir V. Pravosudov Contact Lauren Whitenack at [lauren.whitenack@gmail.com](mailto:lauren.whitenack@gmail.com) with questions ## Summary of data and code This paper investigated the relationships between relative breeding timing and breeding success of mountain chickadees. The script includes code for all analyses and figures. The data used include reproductive data from high and low elevation sites and ages of individually-marked birds. Please note that some cells in data files are blank. These cells have missing values - the data were not collected in these cases. Thus, blank values are equivalent to "NA". ## Data file: mochlow\.csv ``` Summary: 11 years of breeding data from low elevation mountain chickadees at Sagehen Experimental Forest, CA, USA. Each row contains data from a single nest associated with one season. Column descriptions: YEAR - Field season year SEASON - Winter season preceding that year's breeding season BOX - Nest box ID ELEVATION - 'H' = high elevation; 'L' = low elevation NEST.TYPE - all nests are initial nests ('INITIAL'), no renests or second nesting attempts included NEST.ID - unique ID for each nest; IDs are not reused across years M.RFID - RFID tag number of male parent M.ID - Bird ID of male, corresponds to "BirdID" column of the mochage.csv file M.TOIC - Male time of initial capture; date the male was first banded F.RFID - RFID tag number of female parent F.ID - Bird ID of female, corresponds to "BirdID" column of the mochage.csv file F.TOIC - Female time of initial capture; date the female was first banded FIRST.EGG - date of first egg laid; format = m/d/Y J.FIRST.EGG - Julian date of first egg laid CLUTCH - number of eggs at initiation of incubation BROOD - number of eggs at day 16 in the nest MEANMASS - mean nestling mass (g) CV - coefficient of variation in nestling mass ((standard deviation÷mean)×100) ``` ## Data file: mochhigh.csv ``` Summary: 11 years of breeding data from high elevation mountain chickadees at Sagehen Experimental Forest, CA, USA. Each row contains data from a single nest associated with one season. Column descriptions: YEAR - Field season year SEASON - Winter season preceding that year's breeding season BOX - Nest box ID ELEVATION - 'H' = high elevation; 'L' = low elevation NEST.TYPE - all nests are initial nests ('INITIAL'), no renests or second nesting attempts included NEST.ID - unique ID for each nest; IDs are not reused across years M.RFID - RFID tag number of male parent M.ID - Bird ID of male, corresponds to "BirdID" column of the mochage.csv file M.TOIC - Male time of initial capture; date the male was first banded F.RFID - RFID tag number of female parent F.ID - Bird ID of female, corresponds to "BirdID" column of the mochage.csv file F.TOIC - Female time of initial capture; date the female was first banded FIRST.EGG - date of first egg laid; format = m/d/Y J.FIRST.EGG - Julian date of first egg laid CLUTCH - number of eggs at initiation of incubation BROOD - number of eggs at day 16 in the nest MEANMASS - mean nestling mass (g) CV - coefficient of variation in nestling mass ((standard deviation÷mean)×100) ``` ## Data file: mochage.csv ``` Summary: Ages of mountain chickadees by year at Sagehen Experimental Forest, CA, USA. Each row contains data from a single bird associated with one season/year. Column descriptions: BirdID - Unique short ID for each individual bird that has been banded in this system Season - Winter season preceding that year's breeding season Active_breeding - Whether the bird was active during the breeding season following the winter season (Y or N) Age - Numerical age (1-9) describing a bird's age in years Age.confidence - Whether age is exact (bird banded as a juvenile) or minimum (bird banded as adult) ``` ## R Script: Relative\_Timing\_Analysis.R All analyses were conducted in R version 4.1.3. The R script associated with this dataset is annotated and includes comparison of breeding timing ranges between elevations, categorical relative timing analysis, continuous relative timing analysis, and analysis comparing timing of breeding between parental ages. The script also contains code for all figures associated with this manuscript except for Figure A1 in the Appendix. ## Change log **27 Feb 2025:** Added analyses comparing lengths of breeding seasons between elevations and comparing timing of breeding across age classes.