Seasonal differences in escape behaviour in the urban hooded crow, Corvus cornix

Ivana Novčić,Vanja Parača

doi:10.25225/jvb.21066

Abstract

This study examined escape behaviour of hooded crows, Corvus cornix, in an urban environment, in Belgrade, Serbia, with the goal of assessing the effect of breeding season on components of escape behaviour; flight initiation distance (FID), distance fled (DF), and escape method (flying vs. running/walking). Using GLMMs, it was shown that FID was longer during the breeding season, and increased with alert distance. DF was significantly influenced by escape method, with birds escaping for distances greater than 10 m more often when flying, whereas escape method itself was significantly influenced by FID, with birds escaping more often by flying at greater distances from an approaching predator. The majority of individuals (78%) fled for distances < 10 m after initiating escape, and escaped by walking or running (67%). Our results show that hooded crows, although adapted to living in highly urbanized environments, may be more risk-averse during the breeding season, which may allow them to more successfully take care of their young.

Highlights

When approached by a predator, an individual must make a decision on whether to flee or not, depending on the fitness benefits and costs of escape in a given moment (Ydenberg & Dill 1986, Lima & Dill 1990)
We aimed to assess the effect of breeding season on components of escape behaviour – flight initiation distance (FID), distance fled (DF), and escape method, while controlling for other confounding variables
Behavioural and environmental variables The data were collected in November and December 2020, and in April and May 2021. As part of another project, we actively monitored crow nests in several locations in the city, so we were confident that observations conducted in April and May included the period of reproduction

Summary

Introduction

When approached by a predator, an individual must make a decision on whether to flee or not, depending on the fitness benefits and costs of escape in a given moment (Ydenberg & Dill 1986, Lima & Dill 1990). If an animal escapes too early, e.g. when a predator is at a safe distance and does not represent an immediate threat, it loses an opportunity to engage in fitness enhancing activities, such as foraging, mating or brood protection (Cooper 1999, 2000, de Jong et al 2013). Animals escape at longer distances when approached directly, at faster speed, and/or by a greater number of predators (Burger & Gochfeld 1981, Geist et al 2005, Bateman & Fleming 2011). Some activities, such as mate guarding and feeding, as well as morphological

Objectives

Methods

Results

Conclusion