Zoeken
Zoeken kan via de modus 'eenvoudig zoeken' (één veld) of uitgebreid via 'geavanceerd zoeken' (meerdere velden). Zo kan je bv. zoeken op een combinatie van een auteursnaam (auteur), een jaartal (jaar) en een documenttype.
Boekenmand
Nuttige resultaten kan je aanvinken en toevoegen aan een mandje. De inhoud hiervan kan je exporteren of afdrukken (naar bv. PDF).
RSS
Op de hoogte blijven van nieuw toegevoegde publicaties binnen uw interessegebied? Dit kan door een RSS-feed (?) te maken van jouw zoekopdracht.
nieuwe zoekopdracht
The applicability of age ratio and brood size counts in population dynamic studies of the brent goose Branta b. bernicla
Lambeck, R.H.D. (1990). The applicability of age ratio and brood size counts in population dynamic studies of the brent goose Branta b. bernicla. Ardea 78(3): 414-425
In: Ardea. Nederlandse Ornithologische Unie: Arnhem & Leiden. ISSN 0373-2266; e-ISSN 2213-1175
|   |
| Abstract |
In wintering Brent Geese, annual assessments of the proportion of juveniles and the mean brood size have been made since the 1950s, allowing population dynamic analyses. Field procedures have never been quantitatively explored and were studied in four areas along the Dutch Wadden Sea in 1975/76. Juveniles were shown to be overrepresented in the front and adults in the centre of grazing flocks. A separation between families and other birds is accomplished already at landing. As a consequence of the flock structure, the composition of temporary subflocks can differ largely. The proportion of juveniles went down from 50% in autumn to 25% in midwinter, and increased to 40% in spring. With normally 15-20% of the Brent wintering in the entire Wadden Sea, age counts from the southern areas will overestimate the population average. In late winter and spring systematic differences in age ratio were found between different feeding habitats. Brood size ranged from 1 to 7 juveniles. The average declined from 4 in autumn to 3.2 in spring. The mean brood size in a flock was positively related with its proportion of juveniles. Changes in family behaviour with season are discussed. Field counts can best be run in conjuction with the annual midwinter census, but require a tightly organised scheme. Sampling techniques are discussed. Results will probably apply to other goose species, but consequences of shooting warrant more study. |
IMIS is ontwikkeld en wordt gehost door het VLIZ.
