DOI: 10.5061/dryad.4f4qrfjkz
title: Feather growth rate and hormone deposition vary with elevation but not reproductive costs in resident Mountain Chickadees

description: Many organisms engage in metabolic tradeoffs to manage costs associated
 with reproductive output which often leads to these costs carrying over
 into the future. Compensatory mechanisms vary across life history
 strategies and are expected to result in near optimal fitness gains for
 the investor.  Here we investigated whether environmental
 differences associated with increasing montane elevation and variation in
 reproductive output of a resident passerine songbird, the Mountain
 Chickadee (Poecile gambeli), were related to physiological condition
 during annual molt. Higher elevations are associated with harsher
 environmental conditions during the winter, which results in later and
 shorter breeding seasons than at lower elevations. We sampled the
 outermost tail feathers from adult birds in the fall after their prebasic
 molt, which initiates closely after reproduction (e.g., after parental
 care has ceased, ~1-3 weeks). We measured the hormone corticosterone
 deposited in feathers (fCORT) and feather growth rates for evidence of
 physiological effort predicted to be driven by several units of
 reproductive output (e.g., breeding timing, clutch and brood size,
 offspring mass). There were no relationships between any measure of
 reproductive output and feather characteristics between elevations or
 across years, despite substantial variation in reproductive output in the
 wider population across this same time. However, birds at the high
 elevation site grew their tail feathers significantly faster and had
 higher fCORT deposition compared to low elevation birds. These results
 suggest that although differences in reproductive output and any related
 signals of associated physiological effort (e.g., fCORT and feather growth
 rate) may not extend into individual condition during annual molt, shorter
 breeding seasons associated with harsher environmental conditions may
 favor faster feather growth as required by earlier onset of winter.
description: This dataset was collected in a long term field system in the
 Sagehen Experimental Forest (Sagehen Creek Field Station, University of
 California, Berkelely) in the Sierra Nevada, USA during 2018-2021. The
 majority of the data is observational and was collected during the
 reproductive season of the animals monitored in the study (Mountain
 Chickadees, <em>Poecile gambeli</em>). This raw data was
 entered into ongoing database files and was not otherwise filtered or
 processed. The other subset of the data was collected in a wetlab
 environment using a standard ELISA. Raw hormone quantity values calculated
 from a standard curve were collected and corrected for feather size (both
 mass and length) but otherwise left unprocessed. 
description: # Feather growth rate and hormone deposition vary with elevation but not
 reproductive costs in resident Mountain Chickadees
 [https://doi.org/10.5061/dryad.4f4qrfjkz](https://doi.org/10.5061/dryad.4f4qrfjkz) This dataset contains three main files. The first two are .CSV files that contain the raw data of the study and the data used in all the analyses. The 3rd file is a .R file that contains all of the analysis code, variable descriptions, and any minor data transformations. 1\. AdultFeather_data_030724.csv 2\. MOCH_BreedingMaster_030724.csv 3\. Adult_feather_analysis_083023.R ### File 1: Variable Descriptions for File 1: AdultFeather\_data\_030724.csv * B_ID: individual identifier of sampled bird * Year: the year in which a sample belongs * Elevation: site location; H is for high elevation and L is for low elevation * Breeder: whether the bird was recorded breeding; all NA's are individuals with sampled feathers * Sex: male, female, or null (if sex unknown) designation * Wing.Length: the length of the wing taken when the bird was banded (mm) * Cort_pg: total Corticosterone in a sample * Cort_mm: total corticosterone divided by total length of the feather * TotalAverage: the mean length (mm) of feather growth bars * Total_length: total feather length (mm) * LengthWoutCal: total feather length minus calamus length (mm) * Total_mass: total feather mass (mg) * MassWoutCal: total feather mass minus calamus mass (mg) * J.FIRST.EGG: the julian date of when a first egg was laid * CLUTCH: the number of eggs within a nest * BROOD: the number of nestlings sampled at Day16 posthatch * MEANMASS: the mean mass of nestlings within a nest sampled at Day16 posthatch (grams) * CV: the coefficient of variation of nestling mass within a nest sampled at Day16 posthatch ### File 2: Variable Descriptions for File 2: MOCH\_BreedingMaster\_030724.csv * YEAR: the year in which a sample belongs * ELEVATION: site location; H is for high elevation and L is for low elevation * M.ID: identification of male at the nest * F.ID: identification of female at the nest * J.FIRST.EGG: the julian date of when a first egg was laid * CLUTCH: the number of eggs within a nest * BROOD: the number of nestlings sampled at Day16 posthatch * MEANMASS: the mean mass of nestlings within a nest sampled at Day16 posthatch (grams) * CV: the coefficient of variation of nestling mass within a nest sampled at Day16 posthatch ### File 3: Adult\_feather\_analysis\_083023.R The R packages used in the analysis include: tidyverse - general data organization and wrangling DHARMa - check model assumptions and fit glmmTMB - used for mixed effects models in the analysis emmeans - calculates post hoc estimates and values from main models rcompanion - extracts summary statistics from main mixed effects models