Skip to main content
Dryad

Offspring sex ratio is affected by pre-breeding rainfall and hatching order in a cooperative breeding bird

Grieves, Leanne1; Tabh, Joshua2; Hing, Sheng3; Quinn, James3

Published Oct 10, 2023 on Dryad. https://doi.org/10.5061/dryad.8sf7m0cw3

Cite this dataset

Grieves, Leanne; Tabh, Joshua; Hing, Sheng; Quinn, James (2023). Offspring sex ratio is affected by pre-breeding rainfall and hatching order in a cooperative breeding bird [Dataset]. Dryad. https://doi.org/10.5061/dryad.8sf7m0cw3

Abstract

Selection may favour sex ratio adjustment when the fitness benefits of producing male or female offspring vary. In birds, sex ratio bias at hatching has been particularly well-studied in cooperative breeding species, primarily in helper-at-the-nest systems wherein young remain with their parents and help raise subsequent broods. In these systems, breeding females are expected to skew offspring sex ratio in favour of the helping sex if sufficient resources exist. In communal laying systems multiple group members breed and raise the young and offspring dispersal varies, making it difficult to predict whether and how breeders should skew offspring sex ratio. We tested for sex ratio bias in smooth-billed anis (Crotophaga ani), a communal laying cuckoo with low within-group relatedness, high offspring dispersal, and high annual turnover in group membership. One male performs nocturnal incubation and sires more offspring, suggesting these males may have higher reproductive variance and thus that it may be beneficial for his mate to produce more male offspring. We hypothesized that pre-breeding rainfall influences food availability and thus offspring sex ratio, predicting that breeding females skew production towards the more beneficial sex (i.e., males) in high food years, consistent with the Trivers-Willard hypothesis. Females may also adjust sex ratio across the hatching order, so we predicted a male-bias in first hatched chicks in larger broods that should experience greater competition. Contrary to our first prediction, more male chicks hatched when pre-breeding rainfall was lower. In partial support of our second prediction, marginally more first hatched chicks were male in larger broods. Based on these results, we propose the nestling competition hypothesis and predict that when nestling competition is high (i.e., in poor years and in large joint broods), mothers should produce more of the more competitive sex.

README

Reference Information

Provenance for this README

  • File name: README_SexRatio.md
  • Author: Leanne A Grieves
  • Other contributors: J.K.R. Tabh, J.S. Hing, J.S. Quinn
  • Date created: 2023-10-04
  • Date modified:

Dataset Version and Release History

  • Current Version:
    • Number: 1.0.0
    • Date: 2023-10-04
    • Persistent identifier: DOI: PENDING
    • Summary of changes: n/a
  • Embargo Provenance: n/a
    • Scope of embargo: n/a
    • Embargo period: n/a

Dataset Attribution and Usage

  • Dataset Title: Data for the article "Offspring sex ratio is affected by pre-breeding rainfall and hatching order in a cooperative breeding bird"
  • Persistent Identifier: PENDING
  • Dataset Contributors:
    • Creators: Leanne A Grieves, Joshua K.R. Tabh, J. Sheng Hing, James S. Quinn
  • Date of Issue: 2023
  • Publisher: McMaster University
  • License: Use of these data is covered by the following license:
    • Title: CC0 1.0 Universal (CC0 1.0)
    • Specification: https://creativecommons.org/publicdomain/zero/1.0/; the authors respectfully request to be contacted by researchers interested in the re-use of these data so that the possibility of collaboration can be discussed.

  • Suggested Citations:

    • Dataset citation:

      > Grieves, L.A., J.K.R. Tabh, J.S. Hing, J.S. Quinn. 2023. Data for the article "Offspring sex ratio is affected by pre-breeding rainfall and hatching order in a cooperative breeding bird", Dryad, Dataset, PENDING

    • Corresponding publication:

      > Grieves, L.A., J.K.R. Tabh, J.S. Hing, J.S. Quinn. 2023. Offspring sex ratio is affected by pre-breeding rainfall and hatching order in a cooperative breeding bird. Animal Behaviour. Submitted. DOI: PENDING

Contact Information

  • Name: Leanne A Grieves
  • Affiliations: Department of Biology, School of Earth, Environment and Society, McMaster University; Macaulay Library, Cornell Lab of Ornithology, Cornell University, Ithaca, NY, 14850
  • ORCID ID: 0000-0002-6836-2177
  • Email: lag296@cornell.edu
  • Alternate Email: lagrieves@gmail.com
  • Address: e-mail preferred
  • Alternative Contact: postdoctoral co-PI
    • Name: James S Quinn
    • Affiliations: Department of Biology, McMaster University
    • Email: quinn@mcmaster.ca
    • Address: Life Sciences Building 435, McMaster University, Hamilton, ON L8S 4L8

Additional Dataset Metadata

Acknowledgements

  • Funding sources: Natural Sciences and Engineering Research Council of Canada (NSERC) postdoctoral fellowship awarded to LAG and discovery grant to JSQ. Wilson Ornithological Society grant to J.S.Q. and J.K.R.T., Queen Elizabeth II Graduate Scholarships to J.K.R.T. and J.S.H.

Dates and Locations

  • Dates of data collection: Field data collected between September and December 2005, 2011-2014
  • Geographic locations of data collection: Fieldwork conducted in Cabo Rojo National Wildlife Refuge, Puerto Rico (see publication for details)
  • Other locations pertaining to dataset contents: Wet lab work performed by LAG, JKRT, and JSH at McMaster University.

Methodological Information

  • Methods of data collection/generation: see manuscript for details

Links to other publicly accessible locations of the data

  • DOI: PENDING

Data and File Overview

Summary Metrics

  • File count: 14
  • Total file size: 13.4 MB
  • Range of individual file sizes: 2.1 KB - 799 KB
  • File formats: .csv, .txt, .pdf

Table of Contents

  • SexRatio-4Oct23.csv
  • SexRatioMS-SI-27Sept23.pdf
  • SexRatioRCode.txt

Setup

  • Unpacking instructions: n/a
  • Relationships between files/folders: Detailed in file useage
  • Recommended software/tools: RStudio 2023.03.0; R version 4.0.3

File Usage

  • Main analyses: SexRatioRCode.txt
  • Require files
  • SexRatio-4Oct23.csv

File/Folder Details

Details for: SexRatio-4Oct23.csv

  • Description: a file containing nest ID, offspring sex, brood size, and precipitation data for use in this study.
  • Format(s): .csv
  • Size(s): 23.7 KB
  • Dimensions: 323 rows x 13 columns

  • Variables:

    • CANID: bird ID (unique identifier)
    • Year: study year (breeding season)
    • Territory: breeding group
    • Nest: Nest ID
    • Sex: offspring (chick) sex
    • Obs.Prop.Male: proportion of males in brood
    • Exp.Prop.Male: expected proportion of males in brood
    • Obs.Over.Exp: observed divided by expected
    • Hatch.Category: position in hatching order (first hatched, last hatched, or middle hatched chicks)
    • Brood.Size: brood size (total chicks hatched from brood)
    • First.Egg: date first egg was laid
    • First.Chick: date first chick hatched
    • Breed.Precip: total precipitation 30 days prior to date first egg was laid

    Details for: SexRatioMS-SI-27Sept23.pdf

  • Description: a .pdf file containing supplementary materials (Figures and Tables) referred to in main article text. See main article for more details
  • Format(s): .pdf
  • Size(s): 166 KB
  • Dimensions: na
  • Read file for details <br> Details for: SexRatioRCode.txt
  • Description: a text file containing the R code used for all analyses presented in this paper. The file is currently formatted for use with R Studio
  • Format(s): .txt
  • Size(s): 207 KB
  • Dimensions: na
  • See file annotations for details. Briefly, in this observational study across 5 breeding seasons, we evaluated the influence of pre-breeding season rainfall, hatching order, and brood size on the proportion of male offspring in a brood (model 1) and the likelihood of first hatched offspring being male (model 2)

END OF README

Methods

Data were collected from wild breeding smooth-billed anis at a single study site (Cabo Rojo National Wildlife Refuge) over 5 breeding seasons (2005, 2011-2014). Nests were located and monitored regularly throughout each breeding season to determine the beginning of egg laying, onset of incubation, beginning of hatching, and end of hatching. We used molecular techniques to determine the sex of each chick.We used rainfall data collected from a U.S. Fish and Wildlife Service weather station on the Cabo Rojo NWR (17°58’23" N, 67°09’46" W; data available at https://wrcc.dri.edu/cgi-bin/rawMAIN.pl?txPCAB). Rainfall data from this station during the breeding season were not available for 35 study days, largely due to the U.S. government shutdown in 2013. To determine rainfall for these days, we used data from the USGS-NRCS/SCAN weather station near the main entrance to the refuge (17°59’00’’N, 67°10’00’’; data available at https://wcc.sc.egov.usda.gov/nwcc/site?sitenum=2066). Data organization and analyses were conducted in R version 4.0.3 (R Development Core Team, 2021), using base R and the packages dplyr (Wickham et al., 2023) and lme4 (Bates et al., 2015). Data visualization was done using the package ggplot2 (Wickham, 2016). We followed all applicable international, national, and institutional guidelines for the care and use of animals in research.

Funding

Natural Sciences and Engineering Research Council