Recent breeding experience improves egg ejection behaviour

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..., , # 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...,