Het legbegin van Grote Lijsters Turdus viscivorus nader bekeken

Laying dates of Mistle Thrushes were calculated by backdating from the age of nestlings (Appendix 1) or using nest visits during egg laying. Based on nest cards in the SOVON nest record scheme, 7.7% (n=39) of the clutches was started in March. During systematic searches for nests throughout the breeding season by the author, it was found that a larger fraction (17.7%, n=29) started in March. The earliest clutch was initiated on 20 March and the majority of pairs started laying in the first decade of April (Figure 1). In the first half of May a small second peak is apparent, probably second breeding attempts. Mistle Thrushes appeared not to have delayed their breeding season compared to studies in the early 1900s, as was earlier suggested by Ottens (2000).