Sunday, 23 August 2020

Trial run

Last autumn I spent some time trying out various spots along the North Downs to test their suitability as sites from which to watch migrating birds. Colley Hill, Box Hill and Denbies Hillside were all given a go, along with a few places further north, on spurs of higher ground (Mogador, Banstead and Canons Farm included). All of them provided some good birding, with sessions at Colley Hill and Box Hill being particularly noteworthy. Those latter two sites are both a minimum of a 20-25 minute car journey. What I would really like is for a regular vis-mig spot to be within walking distance from home. There are two sites that have produced some memorable visible-migration within minutes from the front door.

The first is my Banstead, Surrey back garden, where I have, in the past, recorded such numbers as 4,145 Redwings flying west (8th October 2018), and 1,175 House Martins moving south-west (24th September 2019). Finch passage can be obvious, mainly Chaffinches, but they do include regular Bramblings. Also to be expected are Starlings, small numbers of pipits, larks, pigeons and the odd scarce bird, such as Woodlark, Crossbill or Hawfinch. One drawback to the site is the reduced field of view thanks to a mature Ash tree, neighbouring roof tops and other tall vegetation, all, of which, hide portions of the sky.

The second site is Canons Farm, which I can reach on foot in 20 minutes. It has a good track record for hirundine passage, and I have had the privilege to witness 6,710 House Martins and 4,000 Swallows streaming south (21st September 2017); another 1,900 House Martins move south-west (25th September 2014); and several days of thrush movements in the high hundreds. However, there does not seem to be a particular place on the farm where movement is 'funnelled' and easy to observe (apart from the valley at Chipstead, which adds another 25 minutes onto my walk.)

There might just be a happy medium. Between the two sites - and closer to home - is Nork Park. It slopes up from north to south and allows far-reaching views towards north-west London, with, crucially, unimpeded all-round vision. From home I have often noticed a preference for birds, particularly thrushes, to use the dip at its northern end as a fly-line - from the park this would be much easier to observe than I can from the house. It does seem that any movement across this general area is on a broad front, with just a couple of places where a bit of funnelling takes place, so the park's uninterrupted and far-reaching views should produce the goods. It's got to be worth a try. Tomorrow morning will see the trial run begin. It is already on Trektellen...

Previous local autumn visible migration. Yellow arrows: hirundines. Orange arrow: thrushes. All on a broad front.

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