BTO migration blog

Spring and autumn are exciting times for anyone who watches birds. Here on this blog we will make predictions about when to expect migrant arrivals and departures, so that you know when and where to see these well-travelled birds.

Friday, 28 April 2017

Migration about to spring into action - guest blog by Ben Porter

The nature of migration generally this spring has been one of sudden flurries followed by slow trickles. This week continued along much the same lines: a glorious weekend with a southerly airflow and wide isobars saw the floodgates open for northbound migrants to stream into the country. Coastal localities were inundated with Willow Warblers, Blackcaps and Wheatears, and species like Redstart, Sedge Warbler, Whitethroat, Ring Ouzel and Grasshopper Warbler took advantage of the passing weather front to move in from the continent. Then the traffic lights turned red: a complete flip in the airflow saw bitter northerly winds dominating for much of the week; temperatures plummeted into the single figures and flurries of snow and hail across the north of the UK further added to the week’s wintry feel.
Willow Warbler by Ben Porter

The calm conditions over the weekend made for some great arrivals here on Bardsey: bushes were brimming with Willow Warblers and Blackcaps; Grasshopper Warblers sent out reeling songs from the damper wetlands; Swallows and Sand Martins zipped northward overhead; and seemingly every grassy knoll and bank was topped with a Wheatear! Greenland-race Wheatears have been one of the dominating migrants on the island this week, their larger size and deeper orange belly contrasting with a flash of white as they alight with hard ‘chacking’ calls. An excellent arrival saw over 250 birds on the 20th, although the national reporting rate on Birdtrack still shows below-average occurrence. It looks like the pressure front next week is going to help these leucorhoa birds make their long-distance flights to the Arctic tundra via Iceland and Greenland.

Wheatears by Ben Porter
Wheatears by Ben Porter

Cuckoos and Turtle Doves have yet to make it over the Irish Sea to the island, although both species reached Scotland this week, with a Turtle Dove on the isle of Rhum and a Cuckoo in Lothian! Three of the BTO’s satellite-tagged Cuckoos are now north of the Pyrenees and should make the home stretch to join ‘Selborne’ with a brisk south-east tailwind in the next week. Keep up to date with their movements here

A smattering of colourful scarcities arrived in the UK this week, including Golden Oriole, multiple Hoopoes, at least three Bee-Eaters (one of which even paid London a visit!), White-spotted Bluethroats, Serin, Red-footed Falcons and the spring’s first Savi’s Warbler. We can expect to see plenty more of these overshooting continentals as we enter May, plus some non-passerine visitors such as Temminck’s Stints on inland reservoirs. Conversely, Waxwing numbers are likely to dwindle as birds continue to dissipate north-east – we still had around 600 birds in the country last week, although they were absent from Ireland, Wales and the South-west.

Whimbrels should arrive in earnest over the next ten days as we approach their peak spring reporting period. The numbers here on Bardsey Island are still below-average for the time of year. Contrast that to the national picture, and the reporting rate is slightly above the historical average, fast-approaching 7.5% of Birdtrack user’s lists. Keep an eye out for colour-ringed birds amongst migrating flocks: they are most likely to be from Iceland, but a few sites in the UK also carry out colour-ringing on these waders, including Bardsey Bird Observatory. Make sure you report colour-ring sightings and email the Iceland project ( should you see any. It’s through anaylsis of ringing recoveries and recent satellite tracking that has revealed some impressive autumn movements of Icelandic Whimbrels from Iceland to North Africa. It’s also indicated that most birds on the east coast – both in spring and autumn – are likely to be Scandinavian.
Whimbrel ring recoveries from BTO. Whimbrel images by Ben Porter

Early May is one of the best times of year to catch up with trips of Dotterels as they touch down on hill tops and coastal spots en route to their breeding grounds. A scattering of birds have already been seen over the last week, including at favoured sites such as the Great Orme in North Wales. Lancashire’s Pendle Hill will no doubt host a few of these superb waders in the next few days.

So what of the week to come? A low-pressure system rolling in from the Atlantic over Saturday and Sunday will see the strong winds switching around to the south-east, which could provide the encouragement needed for migrants to move up through France and continue northwards in the UK. A widening of isobars and an area of high pressure over France and Iberia in the earlier part of the week should make for a good arrival of more warblers, chats and waders. Temperatures should climb a little higher too, which will hopefully encourage the invertebrate life to emerge and provide weary migrants with much-needed refueling!
Low pressure is due to arrive on Saturday - image from Met Office.

We’ve almost welcomed back the full complement of spring migrants as far as songbirds are concerned, although Spotted Flycatchers have yet to appear, and the peak arrivals of Wood Warblers, Pied Flycatchers, Yellow Wagtails, Garden Warblers and Lesser Whitethroats will probably occur over the next week or two given the promising outlook.
Spotted Flycatcher by Ben Porter
Spotted Flycatcher by Ben Porter

If you’re heading out over the weekend, listen out for the liquid gold song of the Nightingale – birds should be back on breeding territories very soon. The bright sunny weather forecast for early next week will be perfect for Common Swifts to scythe their way overhead in screaming flocks. If you haven’t already, why not consider fitting a Swift nestbox to your house? There is just enough time before they return! There are plenty of tips at

The reporting rate for Common Tern and Arctic Tern is on the increase, and the strong winds this weekend might make seawatching a productive option to spot flocks passing by. You might also be in with a chance of seeing Pomarine, Arctic and Great Skuas passing the coast. Rarities in the coming week could take the form of more overshooting continental migrants such as Black-Winged Stilts and Golden Orioles, although the south-easterly wind might favour perhaps a Collared Flycatcher, Citrine Wagtail or Red-throated Pipit even on the east coast.
Red-throated Pipit by Ben Porter
Red-throated Pipit by Ben Porter
This blog was kindly contributed by Ben Porter (@BardseyBen),

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