Gjøkparasittisme hos heipiplerke: Noen erfaringer fra Øyerfjellet sesongen 2005

Abstract

In a mountainous area of Øyerfjellet 17 nests of the Meadow Pipit Anthus pratensis were found during the season of 2005. Five or possibly six of these nests were parasitized by the Common Cuckoo Cuculus canorus, giving a parasitizing rate of 29.4% and 35.3%, respectively. The nests were regularly controlled, and two nests were found deserted by the Meadow Pipit probably during the start of the nesting period, whereas three Cuckoo chicks were hatched. Nearly hatched eggs or newly hatched chicks were found ejected from these three Meadow Pipit nests. When comparing the egg clutches from parasitized nests with unparasitized nests, it was roughly estimated that a mean of 1 ½ Meadow Pipit eggs were missing in the parasitized nests. All the five Cuckoo eggs had a pale brownish colour. When considering this brownish colour, it was suggested that mimicry of the Meadow Pipit eggs and the Cuckoo egg were slightly better in the three nests of completed hatching than in the two nests being deserted. The pattern and markings of the eggs showed good mimicry between eggs of Meadow Pipit and Cuckoo except for the pigment concentration at the broad end of many Meadow Pipit eggs.