Jan van Genten Sula bassana en plastics: waarnemingen op zee en op de kolonie
Sula , Volume 4 - Issue 2 p. 66- 70
The use of plastics in nests of Gannets is described using observations at Sula Sgeir and counts on Hermaness and Noss (Shetlands) in summer 1990. The occurrence of plastics in nests made of fresh green matter or mud (none, some or much) and the occurrence of nests mainly built out of plastics was assessed (table 1). Of the nests in study plots 94.5% and 88.1% on Hermaness and Noss were found to contain plastics respectively. These figures are high in comparison with Nelson’s 50% for Bass Rock, 75% for Bempton, 49% for Grassholm, and 1% for Ailsa Craig (Nelson 1978). Older, re-used nests contained distinctly larger quantities than new nests on the fringes of the colonies. Since blue and green were apparently predominating the colours of plastic were studied in more detail at the Hermaness gannetry near the Neap. Of 525 items identified as to colour (excluding plastics totally covered in faeces): green 269 (51.2%), blue 142 (27.0%), orange 73 (13.9%), red 1 (0.2%), yellow 5 (1.0%), white 25 (4.8%), grey 10 (1.9%). White and grey may have been overlooked since these were often difficult to separate from plastics covered in faeces. However, bright red and orange plastics were relatively scarce. A case of entanglement was observed on Hermaness of an adult male Gannet sky-pointing after its brood-shift. The bird was seen to lose fitness rapidly, although it faithfully took its shifts the days thereafter, not being able to leave and feed. Entanglements of Gannets at sea were recorded near North Rona and Sula Sgeir. In the latter case, 4 Gannets were fighting to free themselves from a piece of net floating at sea. This behaviour attracted vast numbers of the nearby colony and these were seen to dive into the scene, getting entangled themselves.
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