Nesting of Grey Heron (Ardea cinerea L.) on Sea Islands of South Primorye

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The nesting of Grey Heron (Ardea cinerea L.) on rocks of sea islands of the Great Peter's Bay was observed periodically from 1969. There are the following three colonies, being numbered (in 1982) 630 pairs on Furugelm Island, 23 pairs on the of Gildebrandt Is. and 69 pairs on a small rock off Butakov Cape. The colony of Furugelm Is. increased in number approximately by 10 times from 1969 to 1982 most of all due to establishment of Marine State Reserve in 1980. Evidently, heronries on islands appeared not long ago, migrating here from the continental coast. This species arrives in south Primorye in middle March, egg laying in the insular colonies in the first half of April, chicks appear in the first half of May and nests are left in early July. Most nests are built just on rock ledges or on the ground; material for nests used (n=8) consists of Chenopodium sp. (57.8%) and Artemisia sp. (32.1%). An average number of eggs in clutch, was 3.4 (n=26) in 1972 and 3 (n=25) in 1979; number of fledglings (average) was 1.33 (n=15) in 1980. Behavior of chicks at the age of more than one month is characterized specific features connected with the terrestrial location of nests allowing to move lightly within the heronry in any direction. They taken away food in chicks from other broods (about 15 chicks gather around the bird with food); cases of kill of the youngest ones by oldest both in their own brood and from the others are common, aggressiveness of chicks increase in time of feeding; one case of cannibalism was observed when a fledgling ate two chicks from the neighbouring nest. A main reason of mortality is a slaughter of the youngest chicks by eldest; chicks from the late broods survive rarely being killed from trauma or hunger. Herons forage on the continent. A distance from colonies to feeding grounds ranges from 10 to 35km. Chicks are basically fed with the following fishes occurring in brackish and freshwater reservoirs: Carassius auratus, Phoxinus lagowskii, Leuciskus brandtii, Gasterosteus aculeatus, Hyporhamphus sajori and Gymnogobius macrognatus.