THE RESEARCH OF GREAT EGRET PREVALENCE AND NESTING PLACES IN PRIENAI DISTRICT AND INFLUENCE OVER GREY HERON

Abstract

In Lithuania the Great egret (Ardea alba) was rare and migratory species until 1995 species. However, because of a global warming and climate change this species become much more common. First reproduction evidences recorded in Elektrėnai water reservoir, later in Drūkščiai and Senemunės lakes. The study subject is important because the population of the Great egret growing non–stop. I studied the observation and breeding areas of the Great egret in different types of water bodies (swamps, rivers, dam lakes, lakes) also the influence of Great Egret to other bird species in Prienai district. The research was based from the visual and drone collected data.

The research was conducted during 2020-2021 in the Kašonys lake, Šilavotas Dam fish pounds, Jundeliškių hydroelectric power stations reservoir and Verknės river curve, where the Great egrets were observed. The highest population size was recorded during the spring and autumn periods except the Kašonys lake where during spring on average 0.7 birds was recoded and during summer - 4.1 birds. The major reasons are surrounding noises and big population of black-headed gull in spring. The biggest population of the Great egret was recorded in Jundeliškių hydroelectric power stations reservoir where 28 individuals were observed from single point.

After completion of drone flight no nesting places of great egret was recorded. It shows that the egret come to the researched water accumulations only for feeding. Also feeding behaviour is more active during the evenings than in the mornings, on average 21% more birds were recorded in the evening.

In the neighbourhood of the Great egret, the Grey heron (Ardea cinerea) was also recorded. The population of heron was smaller than egret, on average it was only 0.9 individuals, the higher concentration were recorded in Šilavoto fish ponds where on average there were 1.8 individuals per visit. They mostly were near the Great egrets interacting and feeding with them in the migration period flock together.