Friday, 25 August 2017

Horrid autumn- 25/8/17

A Horrid factoid- The Mound, in my factoid of 20/8/17, was said to offer 'alternative viz mig possibilities'. A fib. It offers much better possibilities.

Firstly, diurnal migrants following the shoreline are always in larger numbers than those over water.
Second, waders/wildfowl cutting inland often do so east of Horrid, so are silhouetted against the early morning sun. The mound gives a longer period in better light, as birds approach the shore.
Third, the mound has a much wider clear field of view.
Fourth, flights along the river itself, along Long Reach, although more distant are less obscured by Nor and Bishop saltings.
The only real drawback is it sits on the edge of the main car park, and so attracts a great many ornithomuggles from 08:30 onwards. You have been warned.



Point- quiet again, one Blackcap.

Viz mig- 5 Yellow Wagtail south-west and 45 Swallow west. 31 Common Tern south, two Arctic Tern south, three flocks of 25, 27 and 31 Grey Plover in high from the north-east (also six Black-tailed Godwit high west).

Offshore- Four Greenshank, 32 Great Crested Grebe, 28 Little Egret.

I'm extremely cautious about Terns.

I've had flocks that I've seen well change upriver from my Common to another's Arctic. Not every birder will be familiar with the 2014 article by Keith Vinicombe in British Birds. It describes exactly the same problem happening routinely elsewhere. I would urge you to seek out a copy if you have not seen it. I offer:

"...whereas the Common Tern is a bird of inshore waters, apparently hugging the European and West African coasts during its, The Arctic Tern is a highly pelagic species, its annual migrations showing strong parallels with, for example, those of the Manx Shearwater.. There seems to be little reason why large numbers should pass through southern Britain, either off the coasts or inland. Those that intentionally do so are perhaps mainly birds taking the shortest route to and from breeding colonies in northeast Britain, the Netherlands, southern Scandinavia and the Baltic.

" is recommended that birders in southern Britain work on the assumption that, in normal circumstances, Common Terns are far more numerous than Arctic Terns, outnumbering them by somewhere in the region of 5:1 to 180:1, the ratio usually being higher if there are breeding colonies of Common terns nearby. In the south it seems that Arctic Terns are likely to outnumber Commons only after westerly gales and/or in late September and October, after the peak of the Common Tern migration is past and when most records of Arctics relate to the more easily identified juveniles..."

(Vinicombe, K. 'The Migration of Common and Arctic Terns in southern England', British Birds 107, April 2104, 195-206)

The article details the identification problems that might be leading to misreporting. My highlighting the article here is not to get into the whys and wherefores of misidentification, but more to remind people that the Medway estuary is 'inland' and really does not appeal to the more pelagic species; Arctic shouldn't be turning up regularly. It is perhaps best to always go for an approach of 'this really should be Common...' when claiming a passing bird to species here, and make sure you get really good views of the clinching features (as I made sure I did today).

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