Thursday, 26 April 2012

A tree-nesting goose

It was the raucous calls of the male Egyptian Goose that led me to suspect that the female was nearby and it was not long before I spotted her, crouched in the entrance of a tree cavity. It looked as if the female had been about to leave the cavity in which her nest was placed to take a break from incubation and grab some food. I moved away and took up a position further along the river, one that allowed me to watch back from a distance, the geese undisturbed. The female soon joined the male and the two crossed the river to feed on the short turf of a nearby paddock. I did not have time to hang about and watch her return to the nest, but now that I knew where it was I could come back another day.

Although Egyptian Geese may nest on the ground, they are more commonly found nesting in large tree cavities, such as this one in the broken limb of a mature Horse Chestnut. The limb protruded above the river, occupying a position above a particularly deep section on a bend. Monitoring this nest was not going to prove easy – boat and ladder looking likely.

Somewhere within what appeared to be a significant cavity, there would be a pile of grey down, with a few white underbody feathers mixed in, and up to a dozen large, creamy white eggs. The female could spend up to a month incubating these, beginning her task once the last egg had been laid and the clutch completed, and soon after hatching the young would leave the nest. As with all tree-nesting ducks and geese, the young have to jump from the nest and so face a daunting descent onto water or, more usually, hard ground. It is a wonder that they do not injure themselves as they fall to earth. At least these goslings would only have an eight-foot leap into the water that lay below.

The Egyptian Goose is a familiar enough within the county but it is worth remembering that this is a non-native species, introduced from South Africa. The East Anglian population is well-established and self-sustaining, the breeding range now expanding into central and southern England. Unlike several other introduced wildfowl, the Egyptian Goose population has been slow to expand. One of the reasons for this may be that it nests so early in the year and the resulting young retain their down for well over a month, something that leaves them susceptible to the chill of late winter hard weather. Additionally, it is a highly territorial species, breeding at low density and limited by the availability of suitable nest sites.

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