Human activities can hinder the breeding of a top avian predator: preliminary results

Dobromir Dobrev,Dimitar Demerdzhiev,Vladimir Dobrev

doi:10.2478/orhu-2021-0020

Abstract

Abstract The Eastern Imperial Eagle (EIE) is a large-sized, globally threatened species with a wide distribution. The species is extremely vulnerable and sensitive to human disturbance and activities in the vicinities of its nests. We analyzed the effect of human disturbance in two territories of Eastern Imperial Eagles from Bulgaria in 2008–2009. We recorded 375 cases of different types of human activity in the vicinities of the two surveyed nests – 60 cases in nest A and 315 in nest B. The most common activity around the studied nests was the passing of light motor vehicles (n=100 cases). Our results highlight that the probability of EIE’s reaction is dependent on the type of activity, distance from the nest and the duration of the activity. However, eagles’ reaction is independent from the number of intruders. We found that with the decrease of the distance to the nest, the reaction progresses and is more acute. We found statistical differences between the distance belts and the majority of alert and flight reactions that were recorded at distances up to 300 m from the nests. We reported that humans walking around nests (mainly hunters, fishermen, tourists, people illegally extracting sand in the close vicinities of the nests) result in a large number of reactions of flight off by the eagles thus, leaving the nest unattended. More research on a large scale on this topic is needed including more accurate measures to address human disturbance in EIE territories. The findings will be applied to ensure higher breeding rates and species conservation.

Highlights

The Eastern Imperial Eagle (Aquila heliaca), hereafter EIE, is a long-lived, large-sized territorial raptor with a wide range spanning from Central Europe and the Balkans to South Siberia, China and Mongolia (BirdLife International 2021)
Results show that habitat selection and breeding success are affected by urbanization and inaccessibility of the breeding territories to humans that suggests that the SIE avoids disturbance (Gonzalez et al 1992, Castano & Guzman 1995)
As a result of the surveys conducted in Spain, some authors recommended a ban of human activities in a radius of 500–800 m around nests of Spanish Imperial Eagle during the breeding season (Gonzalez et al 2006)

Summary

Introduction

The Eastern Imperial Eagle (Aquila heliaca), hereafter EIE, is a long-lived, large-sized territorial raptor with a wide range spanning from Central Europe and the Balkans to South Siberia, China and Mongolia (BirdLife International 2021). Human activities have severely affected biodiversity and raptor populations worldwide (Heath & Evans 2000, McClure et al 2018). As a result of the surveys conducted in Spain, some authors recommended a ban of human activities in a radius of 500–800 m around nests of Spanish Imperial Eagle during the breeding season (Gonzalez et al 2006). Such measures might not improve fecundity and lead to a negative attitude towards eagles. Others argue that the acquaintance of the SIE to human disturbance might increase the potential breeding habitat and adult survival of the species and improve its plasticity and tolerance to humans (Ferrer et al 2007)

Methods

Results

Conclusion