Tuesday, 3 March 2009

Pleasant addition to the garden

As a licensed bird ringer, I operate a net in my garden fairly regularly to catch and ring birds that happen to be visiting the feeding stations. For the most part these are familiar species, like Blue Tit, Blackbird and Greenfinch, and the information that I collect not only helps to determine where these birds go but it also helps researchers at the British Trust for Ornithology to follow changes in annual survival rates over time. Every now and then my routine ringing receives a welcome boost, either from a report that one of the birds ringed in my garden has turned up somewhere else (I have had a Greenfinch go to Guernsey and a Collared Dove go to the Wirral) or because something unusual has ended up in my net. Over the years I have been fortunate in my town-centre garden to have caught Blackcap, Redwing and even a juvenile Reed Warbler. Since it has been a fairly quiet winter bird-wise in the garden, the sight of a Marsh Tit in the net was something of a red-letter day, adding to the list of unexpected visitors.

The Marsh Tit is one of a pair of species that look very similar, so much so that the other partner in the pair, the Willow Tit, was the last British breeding bird to be identified and named. These two small tits share a buff, grey-brown plumage, off-white cheeks and a black cap and bib. There are some subtle differences in these features, notably in the glossiness and size of the cap, the shape of the bib and the colour of the feather edging on the main wing feathers. However, recent work has shown that such features may be unreliable in some cases, leaving the only clear means of separating the two species as their vocalisations and, usefully, the colour of the biting edge of the bill. In Marsh Tit the biting edge of the bill is pale along its length; something that is not seen in Willow Tit. Contrary to its name, the Marsh Tit is often associated with drier woodland habitats, where it nests in cavities excavated by other species (including those excavated by Willow Tit, which it can usurp).

Marsh Tit is the more commonly encountered of the two species within Norfolk (and indeed elsewhere these days) and it seems to be increasing its use of garden feeding stations. However, both species have undergone declines in their breeding populations, a pattern that has caused some concern among conservationists. Changes within woodland habitats are thought to be the underlying cause of the decline and efforts are being undertaken to help these birds recover something of their former status.

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