Recent breeding experience improves egg ejection behaviour
Data files
Nov 27, 2025 version files 22.04 KB
-
README.md
2.79 KB
-
swallows_BL_analysis.R
8.84 KB
-
Swallows_BL_data.csv
10.41 KB
Abstract
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.
Dataset DOI: 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.