Spatial distribution of breeding Red-necked Grebe (Podiceps griseigena) in the littoral zone of lake Takem, Sweden

Wagner, Bálint M. A. (1997) Spatial distribution of breeding Red-necked Grebe (Podiceps griseigena) in the littoral zone of lake Takem, Sweden. MAGYAR VÍZIVAD KÖZLEMÉNYEK, 3. p. 189. ISSN 1416-1389 (nyomtatott); 1419-6107 (elektronikus)

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Abstract

The Red-necked Grebe is known to feed on small aquatic animals in the breeding season These food items are also an important food source for many fish species Lake Takerri in southern Sweden is well known as an eutrophic lake with a dense fish population Ornithologists have regularly counted the breeding birds in this lake fór several decades. The Red-necked Grebe began to breed in the lake at tne end of the 70s and has since then become well established with almost 100 pairs m some years. This is at variance with other recent studies in southern Sweden, where Red-necKed Grebe was found not to breed in ponds with a dense fish population. In 1991-1992. the distribution of Red-necked grebes, macroinvertebrates, fish, vegetation and water depth were investigated in Lake Takern The littoral zone of the lake consists of dense stands of the reed Phragmttes australis, with areas of sparse reed stands and open water The nests were situated in areas of sparse reed beds, and the average water depth was 0,44 m, compared to the open littoral zone with an average depth of 0,93 m. The fish (tench Tinea hnca, rudd Scardinius erythophthalmus, perch Perca fluviatilis, roach Rulilus rutilus) were absent or very rare in the reed beds but abundant in the open littoral. The results indicate that there exist a habitat division between breeding Red-necked Grebe and fish in Lake Takern and that this may have to do with the distribution of food sources.

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