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Migration Madness By Jenny Allan
The month of October brings with it beautiful sunrises, but even more excitingly (for birders at least) migrant birds. At this time of year birds, some weighing as little as 5g, traverse the swathes of sea that cut the UK off from the European mainland. Some birds coming to us, some leaving.
Bird migration is a worldwide phenomenon which has puzzled ornithologists in the past and is a feat of endurance with some birds such as Arctic Terns travelling over 40,000 miles each year, from the North Pole to the South Pole. Usually migrating birds will be travelling to warmer climes as winter approaches, and cooler climes as summer approaches. During migration, navigation is one of the most important things. In previous years how birds do this has been a mystery, but now it is believed birds navigate in a variety of ways. One navigation method employed by some birds uses a complicated method, involving cryptochrome in the retina, and photons, to help them to magnetically orientate, and therefore navigate.
In October many species will be passing through Sandwich Bay, with hirundines heading south down to Africa, Redwings (and other thrushes) filtering in from Scandinavia, warblers also passing through, heading off to southern Europe and Africa, and many more species. Rarities also often pop up all around the UK at this time of year, with birds blown off course (or just lost) on migration, from places as far away as North America and Asia! Sandwich Bay gets its fair amount of migrants passing through (and rarities) due to its geographic location; it's one of the closest points in the UK to Europe, and an obvious stopping or passing through point for migrant birds heading in, or out of the UK.
This time of year is usually my best time for birding, as it often is for many other people. When I go for walks along my local patch in Thanet, or around Sandwich Bay, I sometimes have the pleasure of seeing species such as a flock of Goldcrests in coastal scrub, a Black Redstart flicking around on rocks, and this year one of the best birds had to be a surprisingly showy Desert Wheatear in a cabbage field.
A particularly striking migrant species I sometimes see is the Yellow-browed Warbler. This dainty member of the leaf warblers, with flashy yellow and green plumage, is a bit smaller than a Chiffchaff and breeds in deciduous, mixed and coniferous forests in Siberia, through to the eastern Urals region of Russia, and winters in places as far south as Southeast Asia, but every year in autumn (particularly in October) somewhere in the region of 100-350 birds pass through the UK on their southern migration, with a few hanging around for the rest of the winter months. Some years, however, there can be over 700 individuals passing through!
Yellow-browed Warblers can be typically found on the eastern coast of the UK (however a few make it inland and to the west coast), flicking around in coastal scrub, and in the canopy of coastal woodland, often associating with other species such as Goldcrests, and often looking for their favoured food; spiders and insects.
Last year at Sandwich Bay there were only eight Yellow-browed Warblers recorded, whereas 23 were recorded in 2019 and 53 in 2018. This year is also predicted to be a poor year numbers wise for Yellow-browed Warblers with very few records so far in the UK, and none at Sandwich Bay. It’s unclear as to why some years there are large influxes of Yellow-browed Warblers and some years there are very poor numbers, but it is thought it could be down to direction and strength of wind, and weather conditions in general. However, despite the predictions it's always worth scanning through the coastal scrub in case one of these warblers turns up!