Saturday, 29 November 2014

Manor Farm Country Park - November 2014

It was an absolutely glorious start to the day this morning, and well worth the pre-dawn start.  We had arrived on site at 6:30 with the aim of getting at least some nets up and open before first light, and achieved that goal. Chris had to leave at around 9:30 so we limited ourselves to just six nets, which in the event was ample.

Sunrise over Manor Farm Country Park

The target species was as ever House Sparrow for my RAS project, and to colour ring birds for next years breeding season, but of course anything else that happens upon a net is also ringed. The session was very successful with a total of 33 birds ringed, 21 House Sparrow (16 new and five retraps), four Goldcrest (all new), two Dunnocks (one new and one retrap), two Robin (one new and one retrap) and three Blue Tits (two new and one retrap).

In a previous post I have discussed ageing House Sparrows in the winter, and have spent considerable time looking at the bill colour of birds, particularly males. The bill colour in males is a secondary sexual characteristic, and when sexually active in the breeding season, it becomes jet black. According to various published papers it reverts back to the pale brown or horn colour of females in the winter months.  Studies have shown that the change in colour is driven by the presence of testosterone, but one study concluded that the darkening of the bill was the result of synergistic effects of gonadotropins and testosterone (Anderson, T.R. 2006: Biology of the Ubiquitous House Sparrow - from Genes to Population. Oxford University Press).

Given that we are now at the end of November, the bill colour of male birds should no longer be black, yet two of the males clearly still had black bills.

House Sparrow - Manor Farm CP. This bird was originally ringed 2nd January 2010 and is now approaching five years since its initial ringing date
House Sparrow - Manor Farm CP. This bird was first ringed on 7th March 2014 so presumably bred in 2014

By contrast the bird below was ringed as a 3J on 22nd June 2014 and therefore is a first year bird and will not yet have bred. The bill colour of this male is the typical colour of a juvenile or female, indicating that the bird has yet to become sexually active. Another thing to note about this known juvenile is the extent of fringing on the head feathers, which is considerably greater than in the two known adult males.

First year male House Sparrow - originally ringed on 22nd June 2014 as a juvenile.

The three male below were all new birds. Given that I have been ringing at the site for over 15 years there is a pretty good chance that the majority of the new birds ringed each winter are juveniles. I admit I am never going to catch every single new bird at the site, and it is often surprising how many unhinged birds I see each visit, but a fair percentage of the adult birds at the site will be ringed.

Therefore looking at the images of the three birds below, the colour of the bill and the extent of fringing on the head feathers, could these three be juveniles too? Of the three the first bird is perhaps the least likely since it does have very dark lores and mask, and fringing is not as extensive as the other two birds below, nor in fact the known juvenile above. Looking at the two adult birds, they are showing very obvious white patches above the eye and where the black mask meets the grey feathers of the forehead, which the bird below is not exhibiting. Personally, I think all these three birds are juveniles.

House Sparrow Manor Farm CP, first ringed 29th November 2014
House Sparrow Manor Farm CP, first ringed 29th November 2014
House Sparrow Manor Farm CP, first ringed 29th November 2014

Whilst ringing the other birds of note recorded were one Raven, 27 Redwing, two Fieldfare, one Little Egret, one Grey wagtail, five Pied Wagtails and two Little Owls.

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