INVESTIGATIONS ON BIRDS INHABITING THE LITTORAL AREA, TRANSITIONAL WATERS AND ITS SURROUNDINGS OF BULGARIAN BLACK SEA COAST DURING THE BREEDING SEASON
YANA YORDANOVA, VENCESLAV DELOV, KRUSTIO DIMITROV, STOYAN YORDANOV
Faculty of biology, University of Sofia 8 Dragan Tzankov blvd., Sofia, Bulgaria
* Corresponding author: yiroxk@abv.bg
Keywords: Littoral area, seabirds
Abstract: The coastal area has very important role in the life cycle of birds, since they actively use it for breeding, feeding and migration. In the last years human impact on the coast has increased, with many nesting areas being lost because of that. A survey of the coastal birds was completed along the littoral area of the Bulgarian Black Sea coast. The studies have been made over the spring and summer of 2016, and some additional data from the 2013 – 2016 period has also been used in the study. The observations have been made using the line transect method. The birds have been registered visually, by sound and from photos. We have studied the breeding ornithofauna in the littoral area and its surroundings. This includes the main typical habitats: coastal cliffs, sand and stone beaches, dunes. The surrounding areas include grasslands, shrublands, forests, agroecosystems and buildings, situated up to 200 m from the coastline. Additionally the registrations of some conservational important bird species in the nearby wetlands are presented. We divided the birds depending their habitats in the following categories: seabirds, which breed primary in the littoral area; seabirds and waterbirds, which may nest in other areas, but also use the littoral for breeding; terrestrial birds, which nest in other areas, but may breed in the littoral; and species of birds, which only use the littoral for feeding and resting, but do not breed here. Some of the observed species from the first group were the Yelkouan Shearwater (Puffinus yelkouan), found only as migratory and European shag (Phalacrocorax aristotelis), established as nesting in the region of Tiulenovo- Kamen bryag and Kaliakra cape. In the littoral area from the second group the dominant species is the yellow-legged gull (Larus michahellis). Other species like the white wagtail (Motacilla alba), little ringed plover (Charadrius dubius) and kenthish plover (Charadrius alexandrinus) are also reporded. The third group is most numerous and includes species like Northern Wheatear (Oenanthe oenanthe), European nightjar (Caprimulgus europaeus), European honey buzzard (Pernis apivorus), eastern olivaceous warbler (Iduna pallida), northern raven (Corvus corax) and others. Dominants in the fourth group are the great cormorant (Phalacrocorax carbo) and the black-headed gull (Chroicocephalus ridibundus). The little egret (Egretta garzetta) is common among the Ciconiformes, and at the ports and villages the hooded crow (Corvus corone) is often observed.
The biggest number of species was observed on deserted beaches without extensive human impact on them. This shows that the disturbance is an important problem for birds, with only small amount of species adapting to it.