Nijlganspul Alopochen aegyptiacus uitgebroed en opgegeten door een Buizerd Buteo buteo

In 2010, a Buzzard Buteo buteo in the northern Netherlands was found incubating an egg of her own (53.95 x 43.81 mm), together with a single egg of an Egyptian Goose Alopochen aegyptiacus (64.58 x 51.08 mm). On 11 May, the Buzzard egg was pipping, whereas the Egyptian Goose egg contained a calling chick (but had not yet pipped). On 14 May, the nest contained a recently hatched Buzzard and ditto Egyptian Goose chick (day 0). The latter was vocalising continuously, and tried to crawl underneath the Buzzard chick (ambient temperature 10°C, weak sunshine). The nest was empty of prey (remains). During the next nest visit, on 16 May, the gosling was found decapitated with part of its neck eaten. Apparently, it had died very recently. Whether the gosling had been killed, or had died from starvation, was not known. The Buzzard chick was raised successfully. Egyptian Geese colonised The Netherlands in the 1970s; in 1977, for example, just 77 pairs were registered. The increase has continued, with some 4500-5000 pairs by 1998-2000. Take-overs of raptor nests by Egyptian Geese have been recorded repeatedly; the data of the Dutch Raptor Group for 2010, for example, showed 7 cases for Buzzard (total number of nests checked 1162), 2 cases for Goshawk Accipiter gentilis (N=425 nests), 2 cases for Kestrel Falco tinnunculus (nestboxes, N=487) and 1 case for Sparrowhawk Accipiter nisus (N=274 nests). As a cause of nest failure in raptors in The Netherlands, despite the large population of Egyptian Geese, take-overs by Egyptian Geese are of minor importance. Apparently, egg discrimination is poorly developed in Buzzards and Goshawks (or not relevant). In the Goshawk, eggs are unmarked as in Egyptian Goose, whereas the largest lengths and widths (respectively 65.0 mm and 49.99 mm in 4054 eggs from The Netherlands) overlap with those of Egyptian Geese. Similarly, the largest Buzzard eggs (length 68.1 mm, width 48.5 mm, N=3521 eggs) are as large as those in Egyptian Goose, albeit usually blotched to a varying degree.