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Lesser spotted eagle

Main facts

The Lesser Spotted Eagle (Aquila pomarina) is migratory-breeding and migratory species in Bulgaria. In the past it was a common bird in the country but in the period 1950 – 1980 its numbers show an uninterrupted decrease (Simeonov et al., 1990). At present nearly 50% of its population (460 – 520 breeding pairs) is concentrated in the Eastern Rhodope Mountain, Sakar Mountain, Derventski Vazvishenia Hills and Strandzha Mountain. There are scattered records from Dobrudzha Plain, Danubian Plain, Thracian Plain, the Western Rhodope Mountain, Sredna Gora, Vitosha, Plana mountains, etc. During autumn migration it concentrates in high numbers in the area of the Bay of Burgas.

Conservation status

IUCN Red List of Threatened Species: Least Concern (LC). Included in the Bulgarian Red Data Book as Vulnerable (VU) B(1a)+C. In Bulgaria it is protected by the law.

Species description

The Lesser Spotted Eagle (Aquila pomarina) is a medium-sized diurnal bird of prey of the Accipitridae family. Its body length is 61 – 66 cm, its wingspan – 145 cm, and it weighs an average of 1 600 gr. The species has age dimorphism. Adults have brown plumage. They are hard to distinguish from adult Spotted Eagles (Aquila clanga); differences include slightly smaller size and colouration of the underwings: flight feathers are black, coverts – brown (in Spotted Eagle colours are reversed). Juvenile birds are chocolate brown with a visible rufous patch on nape; upperwings have two lines of white spots – a key feature for distinction from juveniles of Spotted Eagle. Underside of body covered in light streaks. Voice: during the breeding season Lesser Spotted Eagle often produce a sharp ‘v-yeek, v-yeek’; out of the breeding season – a repeated yap ‘ky-ye, ky-ye’, similar to a small dog barking. When soaring the head-on profile of the wings is slightly drooping.

Species biology and ecology

Birds from the European population are migratory. The Lesser Spotted Eagle feeds on rodents, amphibians, reptiles, small birds and insects.

Monogamous bird, building its nest on high trees. Nests mainly on broadleaf trees at an altitude of 6 – 25 m above the ground. The female lays 2 (1 – 3) eggs in early May; incubation lasts 38 – 41 days. The young leave the nest at about 55 days of age. Winters in Africa. Spring migration occurs in March – April, autumn migration is in August – October. During migration Lesser Spotted Eagles form sparse flocks and mix with groups of buzzards, kites and other eagle species.

Cases of hybridization with the Spotted Eagle (Aquila clanga) have been documented.

Lesser Spotted Eagles live in wild forests of beech, oak or mixed, in old shelterbelts and other woodland areas in the vicinity of spacious grass communities and agricultural land, where the birds hunt.

Distribution

The breeding area of the Lesser Spotted Eagle stretches from the Elba River valley to Belarus and Leningradska District in Russia, Hungary, Slovakia, the Baltic countries, the Balkan Peninsula, Asia Minor, the Caucasus and Northern Iran. More than 95% of the global population of the species is concentrated in Europe. Its breeding population is estimated to be between 14 000 and 19 000 pairs (BirdLife 2014). It winters mainly in Western Asia and Eastern Africa; its main migration route passes through the Bay of Burgas, the Bosphorus and the Gulf of Aqaba.

Threats

  • Habitat changes as a result from intensive forest management

Logging in old-growth forests, selective felling of old trees and forestation of pastures lead to the destruction of the breeding and feeding grounds of the Lesser Spotted Eagle.

  • Intensive agriculture and farming

The use of high quantities of pesticides and the introduction of monocultures typical for intensive agriculture lead to changes in the hunting grounds of birds of prey and to a decrease in the numbers of key prey species.

  • Fires 

Fires can result in the direct destruction of occupied nests. Due to climate change on a global scale fires have become a greater threat for areas of crucial importance to the Lesser Spotted Eagle.

  • Disturbance 

During the breeding period, forest management activities in the vicinity of the nests of the Lesser Spotted Eagle can compromise the breeding of the birds. Inadvertent disturbance by tourists, hikers and mushroom and herb pickers can make the eagles abandon their nest.