Changes in composition and structure of breeding bird communities due to successive changes in ecosystems

Abstract

Successive changes in ecosystems are due to natural and/or anthropogenic influences. These changes influence species richness and structure of phyto- and zoocenoses. Birds represent a good indicator for changes of habitats type. Four types of habitats were closely examined. Those habitats were low-grass stone steppe, high-grass steppe, steppe with presence of single shrubs, open areas with prevalence of Jeruselem thorn and low-grown trees and low forests. Species richness increases with the rising of both grass stature and thickness of shrubs. In the low-grass steppe ecosystems only 8 breeding species are present, whereas in low forests - 31. Highest density was observed in the open areas with shrubs – approximately 43 p/10ha, whereas in the low-stemmed forests it decreases to 14.66 p/ha. The percentage of dominant species decreases and those of satellite species increases from 3 in steppes to 25 in woods. The value of Sorensen's similarity coefficients (over 70%) shows high similarity between species richness of low-grass steppe and high-grass steppe. Similarity between open areas and low-grown woods is over 60%.

Keywords

• birds
• breeding communities
• Dobrudzha
• dominant species
• density
• successive changes