Monday, 5 January 2009

Garden feeders reveal an army of diners

Spending some time at my parents’ house over Christmas has enabled me to take stock of a different garden feeding station. Although many of the bird species putting in an appearance at the hanging feeders are familiar, others would constitute a red-letter day were they to appear in my garden at home. Species like Bullfinch, which are such regular visitors to my parents’ rural patch, seem to like the fact that it is well connected by a network of hedgerows to the series of small woodlots that are a feature of this rural Wealden landscape. By comparison, the attractions of urban Thetford are unlikely to suit the shy and retiring nature of this boldly marked finch.

One feature that has struck me over the past few days is the sheer volume of birds passing through the feeding station. It is clear from the composition of the visiting flocks that a good number of birds take in the garden as part of a wider foraging circuit that also covers much of the local woodland. The nature of the woodland itself is evident from the visiting birds; the stands of beech and oak contributing the Blue and Great Tits, while the blocks of conifers that still adorn much of the local heathland are no doubt the source of many of the Coal Tits and Goldcrests.

Some idea of the numbers of birds involved can also be gained from a short spell of ringing. As a licensed bird ringer, I am in the fortunate position of being able to catch wild birds and mark them with specially developed metal rings. Each ring carries a unique number and, should the bird be subsequently found, this provides an insight into its longevity and movements. Many people assume that ringing birds only tells us where they go (think of Swallows wintering in Africa) but researchers also use the information to examine survival rates and productivity, two vital components that ultimately influence whether a population increases or diminishes over time.

In this particular instance, however, one of the by-products of ringing in my parents’ garden is an understanding of the numbers of birds passing through the feeding station. When you look out the window there, you may see half a dozen Blue Tits around the feeders at any one time and it would be easy to assume that it is the same half dozen individuals that you see at various times throughout the day. Stick up a net and fit the individuals that you catch with rings and it soon becomes apparent that you are talking about a population of many dozens of Blue Tits passing through the feeding station over the course of a short winter’s day.

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