LENSINK R (1988) Diurnal migration in Twente, 14-21 oktober 1984. LIMOSA 61 (2): 61-66.

In the period 15-21 October 1984, the diurnal migration was registered on three observation posts in Twente, eastern Netherlands. The observations started half an hour before sunrise and ended at 14hOO (two posts) or half an hour after sunset (one post). The number of migrating birds (N) was corrected for the difference in observation period (Nc). For 25 species the diurnal pattern of migration is given (fig. I, appendix). All species but one (Buzzard), had the onset (10%) in the early morning (ot), the median (50%) was reached before noon, the end (90%) was spread over the entire afternoon (fig. 2). The percentages in the early morning differed roughly between 20 and 70%. Six species showed a second peak in the late afternoon (fig. 3). Six basic patterns of diurnal migration could be recognized (fig. 4): (I) nocturnal migrants with pronounced migration in early morning and late afternoon (tail and head of nocturnal migration, respectively), (2,3) species with a peak in the (early) morning, (4) the same but with a second peak in late afternoon in some cases, (5) species that migrate during the whole day, (6) species migrating mostly during the middle of the day. The percentages in the early morning in Twente are quite similar to those mentioned in two other sources (appendix). The diurnal patterns are probably basically defined by endogenous factors. The numbers of migrating birds within the basis pattern depend more on exogenous factors. The occurrence of a peak in the late afternoon seems to be restricted to favourable weather conditions. The factors that define the occurrence of the diurnal patterns in the field need further examination. ##### Eurasian Sparrowhawk Accipiter nisus Common Buzzard Buteo buteo Northern Lapwing Vanellus vanellus Black-headed Gull Chroicocephalus ridibundus = Larus ridibundus Stock Dove Columba oenas Common Wood Pigeon Columba palumbus Eurasian Skylark Alauda arvensis Meadow Pipit Anthus pratensis White Wagtail Motacilla alba Dunnock Prunella modularis Fieldfare Turdus pilaris Song Thrush Turdus philomelos Redwing Turdus iliacus Mistle Thrush Turdus viscivorus Great Tit Parus major Western Jackdaw Coloeus monedula Rook Corvus frugilegus Common Starling Sturnus vulgaris Eurasian Tree Sparrow Passer montanus Brambling Fringilla montifringilla Common Chaffinch Fringilla coelebs Brambling Fringilla montifringilla European Greenfinch Carduelis chloris Eurasian Siskin Carduelis spinus Common Linnet Carduelis cannabina Common Reed Bunting Emberiza schoeniclus

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