On the egg-covering phenomenon of the great crested grebe (Podiceps cristatus) and the black-necked grebe (P. nigricollis)

Kogut, IV.

Vestnik Zoologii. november-december; 336: 99-105, 126

1999


Accession: 021484276

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Abstract
Egg-covering behaviour in two Grebe species was studied during 1990-1994 and 1996-1997 in 4 regions of the West Ukraine. Generally, both the Great Crested Grebe and the Black-necked Grebe show a strong tendency to cover their clutches with nest material when disturbed. The proportion of covered clutches seems to be significantly lower in the earliest and the latest stages of incubation period that accords with literature data. The best explanation for the pattern observed is offered by the ethological hypothesis. A possible conflict between arious behavioural patterns during early and late incubation may result in weakening motivation to incubate and so in decreasing the egg covering intensity. The possible role of other factors (way of disturbance, water reservoir type, vegetation density, coloniality, age etc.) is also discussed. The influence of these factors in the proportion of covered clutches seems to be statisticaly unsignificant.