25/02/12 - More Shelduck...more old friends!

Another good day (Friday 24^th) with a catch of 13 new and 10 re-trap Shelduck in one of the traps (along with 10 new Mallard and a Coot). 

The next Webs count in March will tell us how many Shelduck are present  throughout the valley but 90 were counted by a local farmer roosting on his pond one evening last week - probably a good indication that it’s around the 100 mark at the moment. A quick look at the figures caught this year reveal 47 new birds ringed so far, with 13 re-traps from previous years and the one control - a total of 61 different birds handled so far this year. 

It’s nice to have a good sample of the population marked and once again shows a high degree of turnover of breeding birds from one season to the next, especially as we ringed 59 birds out of the population last year. Of the 11 re-traps from previous years, 6 were originally caught in 2011 and 2 from 2010, 2006 and 2005. So clearly some of the birds are site faithful (certainly for one or two years and some even longer). Smaller numbers of birds, mainly pulli (with a higher mortality rate), were ringed in 2007-2009 which may account for the ‘non-appearance’ of birds from those years. 

Although the whole reserve covers over 1000 hectares, which stretches some 10 Km along the River Derwent and the Pocklington Canal corridors, its often amazing how site specific some birds are. A male Mallard caught at Bank Island in a whoosh net catch yesterday was originally ringed in the same whoosh net area (10 x 10m) at Bank Island on 30/05/10. Nice to know he’s dodged the lead shot and wintering Peregrines for two winters! However, topping that was GN12614, a Mallard caught and ringed at Wheldrake on 28/06/99 and re-caught today at North Duffield Carrs. That’s nearly 13 years since ringing and makes it atleast 14 years old. Interesting that it’s not been re-caught since, so you have to wonder where it’s been since we last saw it. It’s certainly a good age for such a popular quarry species, the longevity record from the BTO ringing in the UK is 20 years and 5 months. 

Continuing the Mallard theme, Mike & Craig had a control female Mallard - GR37501 today (one ringed somewhere else by another ringer). This is the first time we've controlled a Mallard in the Lower Derwent Valley, so it will be most interesting to see where it's come from....