# Factors Influencing Cage Escape Behavior in a Migrating Passerine at a Stop-Over Site

## TL;DR

This study explores how factors like age, sex, and movement influence the escape behavior of migratory birds in unfamiliar stop-over habitats.

## Contribution

The study reveals sex-specific risk strategies in escape behavior linked to future parental roles in sedge warblers.

## Key findings

- Birds moving more horizontally during acclimatization were more likely to escape.
- Immature males were 2.3 times more likely to escape than females.
- Escape response repeatability was low (7.3%) among recaptured individuals.

## Abstract

Cognitive abilities play a critical role for migratory birds encountering unfamiliar habitats at stop-over sites. We investigated factors (age, sex, fuel reserves, activity in a cage, and level of mercury) affecting cognitive abilities and behavior (problem-solving task—escaping from an experimental cage) in a long-distance migratory passerine, the sedge warbler (Acrocephalus schoenobaenus) at an autumn stop-over site. In our experiment, after two minutes of acclimatization, we remotely opened the door of the cage and recorded whether each bird escaped or remained in the cage. Individuals moving more along the horizontal axis of the cage during the acclimatization phase were more likely to escape from the cage. Immature males were more likely to escape from the cage than females at any given time. We interpreted this result as risk-partitioning between sexes, with males behaving in a riskier manner (being more ready to escape) compared to females, which minimize predation risk. These differences may be linked to the predisposition of both sexes in the studied species to specific parental roles. We found that the repeatability of escape response after the cage door opened was low (7.3%) for the same recaptured individuals.

Cognitive abilities play a critical role for migratory birds encountering unfamiliar habitats at stop-over sites. We investigated factors (age, sex, fuel reserves, vertical/horizontal activity, and mercury level) affecting cognitive abilities behavior (problem-solving task—escaping from an experimental cage) in a long-distance migratory passerine, the sedge warbler (Acrocephalus schoenobaenus) at an autumn stop-over site. During the experiment, after two minutes of acclimatization, we remotely opened the door of the cage and recorded whether each bird escaped or remained in the cage. A mixed-effects Cox model revealed that the probability of escaping from the cage was significantly affected by variance in horizontal movements along the horizontal axis of the cage during the acclimatization phase (in models for all individuals and immatures) and sex (in immatures). Individuals moving more were more likely to escape from the cage. Immature males, at any given time, were 2.3 times more likely to escape from the cage than females. We interpreted this in the context of risk-partitioning with males adopting a high-risk, high-reward strategy and females using a low-risk, low-reward strategy, which may be associated with a predisposition for sex-specific roles in breeding. The repeatability of escape response was low (7.3%) for the same recaptured individuals.