Saturday, 29 October 2011

Garden Ringing and Leucistic Birds - 28th October 2011

Ringing activities on Friday 28th October were restricted to my garden due to car trouble, and having to hang around waiting for the garage to call. Even so I was still able to get my hands on 33 birds, although most of them were Blue Tits, so it wasn't a particularly pleasant experience!! Surprisingly, most of the birds captured were new juveniles, as opposed to retraps, which is the normal trend. Among the Blue Tits however there was a selection of little gems, the first of which was a female Nuthatch. Nuthatches are cracking birds and are one of my favourite groups, and I have been fortunate to catch many over the years. Unfortunately, despite juvenile birds only undergoing a partial post juvenile moult, there appear to be no valid plumage differences, and therefore you just have to enjoy their splendor.

Nuthatch - October 2011

Goldfinches used to be a common garden species for me, but recently the number of birds present in the area seems to have plummeted. So catching two in an afternoon ringing session was a notable feature. In contrast to Blue Tits, Goldfinches are a delight to handle....

Goldfinch - October 2011

                                       ....and in contrast to Nuthatches they can be aged and often sexed. An obvious feature as with most passerines is the shape of the tail feathers, juveniles have pointed tail feathers whereas adults have rounded ones.

Juvenile Goldfinch Tail - October 2011

It is also often possible to see a moult limit within the greater coverts on juvenile birds. Although it is not really possible to see in the picture below, this bird had two old juvenile greater coverts.
Goldfinch Wing - October 2011

Sexing birds is possible by the colouration of the nasal hairs, they are generally black in males and blackish or light grey in females. In addition, the red on the forehead extends behind the eye, as seen in the picture below.

Goldfinch Head - October 2011

A first year male Chaffinch was another little gem, but the most striking bird was a partially leucistic Great Tit. Overall this bird had a pale wash to it, but the tail was predominantly white and this made the bird look quite striking in flight.

Partial Leucistic Great Tit - October 2011
Partial Leucistic Great Tit - October 2011
Partial Leucistic Great Tit - October

I am not really sure what causes leucism in birds, but it will be interesting to see if this bird retains this lack of colour once it undergoes its post nuptial moult next year. I remember reading a BTO article about a leucistic Common Redpoll, which when retrapped after a moult  it had adopted normal colouration.

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