DOI: 10.5061/dryad.9w0vt4bvq
title: Recent breeding experience improves egg ejection behaviour

description: Recognizing one’s own eggs is crucial for birds, especially for hosts of
 brood parasites that must identify and reject different-looking parasitic
 eggs. While birds seem to possess a ‘template image’ of their eggs,
 whether it is innate or refined over time remains unclear. We addressed
 this question by experimentally inserting either artificial mimetic eggs
 (ME) or non-mimetic eggs (NME) into the nests of barn swallows (Hirundo
 rustica) during the pre-laying stage. We harnessed the potential of our
 individually marked population to perform a unique comparison between
 naïve first-time breeders and experienced females, as well as females with
 ‘old’ (from a previous season) and ‘recent’ (from the previous breeding
 attempt within the same season) experience, allowing us to investigate the
 role of memory. We found that neither naïve nor experienced females
 ejected NME more often than ME, suggesting that the template image does
 not play a primary role in egg recognition. Instead, awareness of own
 egg-laying might be the crucial mechanism at play, facilitating nest
 sanitation behaviour. Lastly, we provide the first evidence that this
 mechanism improves with recent breeding experience.
description: # Recent breeding experience improves egg ejection behaviour Dataset DOI:
 [10.5061/dryad.9w0vt4bvq](https://doi.org/10.5061/dryad.9w0vt4bvq) ##
 Description of the data and file structure ### Files and variables ####
 File: swallows_BL_analysis.R **Description:** This file contains the code
 used to reproduce the analyses presented in the manuscript. #### File:
 Swallows_BL_data.csv **Description:** This dataset contains data on
 experimental parasitisms (presentation of artificial objects in the nest)
 in barn swallows. Each row corresponds to a unique breeding attempt
 ('attempt' variable) and female ('female' variable,
 identified by a unique ring number). ##### Variables * year: breeding
 season, between 2021 and 2024. * locality: code for breeding locality. *
 nest: unique nest ID number. * female: unique female ring ID. * attempt:
 breeding attempt number within a given season, 1 being the first
 (earliest) attempt. * season_experienced: whether at the time of the
 experiment, a given female has experience seeing its own eggs within the
 breeding season, coded as 0 (no - indicates the first breeding attempt) or
 1 (yes - indicates the breeding attempt is not the first of the year). *
 life_experience: whether at the time of the experiment, a given female has
 any breeding experience, regardless of how long ago the last breeding
 attempt was. Coded as 0 (no) or 1 (yes). * fresh: whether at the time of
 the experiment, a given female has "recent" breeding experience,
 i.e., has laid eggs during a given breeding season. Coded as 0 (no) or 1
 (yes). * old: whether at the time of the experiment, a given female has
 "old" breeding experience, i.e., from a previous breeding season
 only. Coded as 0 (no) or 1 (yes). * naive: whether at the time of the
 experiment, a given female is naive, i.e., has no prior breeding
 experience during her lifetime. Coded as 0 (no) or 1 (yes). * exp:
 experience type, coded as naive (none), old (experience acquired during
 the previous breeding season), or fresh (acquired during the current
 breeding season). * object: type of object inserted in the nest, with ME:
 mimetic egg or NME: non-mimetic egg. * response: female response towards
 the object, either acceptance (0) or rejection (1). * days: days elapsed
 between object insertion and female response. * time to egg laying: number
 of days between object presentation and laying of the first egg.
 Quantified only if the response was a rejection (response=1), otherwise
 systematically coded as 0 in the case of an acceptance. *
 parasitismMINUSlaying: duration of the object presentation in the nest, in
 days. ## Code/software All analyses described in the code file
 **swallows_BL_analysis.R** were performed using R 4.4.0 and the following
 packages: brms (2.21.0), tidyverse, tidybayes.