Sunday, 28 February 2016

The case for the Hooded Merganser

We headed down to Corsham Park in Wiltshire today, for a look at the female hooded merganser which has been present for about a week. The identification of the bird is not in doubt, but more problamatic is it's status. Is it a vagrant from North America or an escapee from a local wildfowl collection?

In support of the vagrancy theory we've certainly had plenty of impressive weather systems moving quickly across the North Atlantic recently, and there are plenty of ring-necked ducks and green-winged teal in the country at the moment, species whose credentials rarely seem to get questioned these days. Furthermore, there are also presumed wild hooded mergansers currently in the Azores and Iceland, and February is apparently the peak month for the species spring migration.

The Wiltshire bird is unringed and has a full set of flight feathers and spent most of its time a good 100m away from us, alone on the far side of the lake. It was constantly diving and catching prey. It was not associating with mallard, if anything it was actually closer to the goosander which were also on the lake. Eventually it swam across the lake and into the bay near to where we were standing and showed very well, in fact nearly as close and as well as the hooded mergansers I watched in Central Park New York in 2012.

Then two mallards swam towards us clearly expecting to be fed. The merganser quickly followed them, but it did not beg for food, quite the opposite, it continued to dive and with a high success rate, often bringing up what looked like invertebrate prey. One suggestion was that in the shallows the mallard were stirring up invertebrates from the bottom which the merganser was simply taking advantage of.

However, if it is to be taken seriously as a vagrant it needs to disappear soon. Why, well hooded merganser is a duck which in the wild migrates. If it stays in the country over the summer and into the latter part of the year and does not disappear, then it will most likely be considered an escape from a collection. On the otherhand if it disappears by April then it improves its credentials as a wild bird. Still not conclusive, but it tips the balance in favour of the vagrancy theory. Whatever the truth, it's an interesting subject and a great little bird, and I saw nothing in the birds behaviour to indicate that it was an escapee. It's on my list until for the time being at least.

Edit: This bird was accepted by the BBRC on 14/06/2016.

After seeing the star bird, we headed over to Somerset and saw a cattle egret in a field with cows and at least 12 little egrets.

UK Life: 413 (Hooded merganser); Year: 155 (Hooded merganser, cattle egret, marsh harrier)

This is clearly an adult female, with the distinct white lines on the wings and the yellow bill.

Hooded mergansers eat both invertebrates and small fish. Here it appears to have an invert and one theory is that it follows the mallards around because when they come close inshore and start scrambling for bread, they stir up inverts from the bottom. Certainly the merganser showed no interest in waiting for bread to be thrown. Not that any was thrown today, but the mallards thought it might be!

Here it is again with another invertebrate.

There's a cattle egret in there somewhere.

Everytime we visit the south midlands we see lots of impressive mistletoe, and none more so than these near Gloucester today.

1 comment:

  1. Very balanced and well written synopsis of the Hooded Merg credentials.


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