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.

Thursday 26 September 2019

26th September - 2nd October

The warm sunny weather at the end of last week combined with a southerly airflow provided the conditions several species needed to head south, species like House Martin and Swallow were noted in mixed flocks at a few locations. Numbers of both these species will fall away very quickly now with very few individuals noted after mid-October.  In the last blog, we predicted that the southerly winds could bring Hoopoe, Alpine Swift, Red-rumped Swallow, Red-backed and Woodchat Shrikes to our shores, 4 out of 5 can’t be a bad return with Woodchat Shrike being the only species not to be found.  Rarity wise a Short-toed Treecreeper in Kent and a Blue Rock Thrush on the Isles of Scilly were the stand out birds.

Species Focus

Yellow-browed Warbler has become synonymous with autumn for many birdwatchers, much like the Swallow heralds the beginning of summer, autumn starts when the first of the Yellow-browed Warblers arrive. This small brightly marked warbler was once a rare bird in Britain and Ireland, with very few records before the 1960’s but since then there has been a huge increase in sightings with some locations hosting multiple individuals and places like Fair Isle have had days when over 80 birds have been noted. The distinctive high-pitched rising tse-weee call is often the first indication a bird is present and when seen, this bird, with its distinctive yellow stripe above the eye and double wing bar, is truly a gem of a bird.

Yellow-browed Warbler - Photo Trevor Codlin

Species that have their peak in reporting rates at this time of year include Snipe, Skylark and Reed Bunting all of which spread out across the country in readiness for the forthcoming winter months. A couple of closely related species replace each other at this time of year, as the last of the Whinchats depart so the numbers of Stonechats increases. A similar pattern can be seen with Willow Warblers as they are replaced by Chiffchaffs that migrate just that bit later than them.

BirdTrack reporting rate graph showing how as the reporting rate of Whinchat falls
the reporting rate for Stonechat increases.

BirdTrack reporting rate graph showing how as the reporting rate of
Willow Warbler falls the
 reporting rate for Chiffchaff increases.

Weather for the week ahead

The Northern Isles may well be the place to be during the early part of this period as southeasterly winds dominate for a few days. Yellow-browed Warblers are already turning up but something altogether rarer is on the cards, Pallas’s Grasshopper and Lanceolated Warbler are both possibilities and maybe something even more exciting like a White’s Thrush. Further south, most of the country will be in a westerly airflow for most of the week, with stormy conditions at times as low-front follows low-front across the country. At this time of the year in these conditions, a North American landbird isn’t out of the question – Red-eyed Vireo and Blackpoll Warbler are favourite but with a Chestnut-sided Warbler on the Azores, who knows?

Will the run of Westerlies bring a Red-eyed Vireo from America? - Photo by Joe Pender

By Paul Stancliffe and Scott Mayson

Thursday 19 September 2019

19th – 25th September

As predicted, the north and north westerly airflow of the last week produced an arrival of Pink-footed Geese and Whooper Swans to the UK, along with a few Grey Phalaropes and a distinct movement/arrival of Wigeon. The same winds that brought the geese and swans here were probably also responsible for the arrival of Lapland Buntings, with birds being seen from the northern isles to Scilly. Perhaps indicating a late breeding season, Swifts continued to trickle out of the UK while Swallows and martins are beginning to move in force. With winds becoming lighter towards the end of the week Meadow Pipit migration began to ramp up too.

Meadow Pipit BirdTrack reporting rate

Whilst the influence of hurricane Dorian wasn’t felt immediately last week the arrival of several North American waders this week showed it did have an effect, several Semi-palmated, White-rumped and Buff-breasted Sandpipers were found but it was the double figures of American Golden Plover that stole the show, at least fifteen were found. There was also a small arrival of Long-billed Dowitchers, but the star billing of the Dorian effect has to go to the Common Nighthawk that was found in Argyll.

Species Focus
Lapland Bunting is a scarce passage and winter migrant to the UK, typically arriving here towards the end of September. It is one of the most abundant and widespread arctic passerines, breeding from southern Norway across Siberia to the Bering Sea and from Alaska east across Canada to west and southeast Greenland. Most winters between 200 and 500 are typical in the UK but in some winters many more are found, mostly in saltmarsh or coastal fields but not exclusively, with birds often found far inland in similar habitat.
The dry, rolling ‘tiddlip-tew’ flight call, uttered on take-off or whilst flying over, is often the first sign of a Lapland Bunting but when located on the ground it is a very distinctive bird, showing an obvious chestnut nape, dark, spotted upper breast on clean white underparts, and a black-framed pale cheek below a broad supercilium flaring behind the eye. With a good showing already this autumn, it might be one to look out for this winter.

Lapland Bunting BirdTrack reporting rate

Weather for the week ahead

During the weekend the country will mostly be sat in a southeast and southerly airflow, but as the week progress the winds in the south are going to swing to the southwest and in the north remain in the east, at times coming straight out of Scandinavia.

Yellow-browed Warbler by Andy Mason

Over the next couple of days there ought to be a mass exodus of Swallows and House Martins, taking advantage of the relatively light winds and warm temperatures as a result of a high-pressure system centred to the south and east of us. There is a low pressure system centred in the Atlantic to the south of Greenland and Iceland that may well bring a few more North American waders to Ireland’s shores, and who knows? Maybe the first Red-eyed Vireo of the autumn.  Enjoying a week of easterly airflow the northern isles ought to shine, with the first push of Yellow-browed Warblers, along with a few Common Rosefinches and maybe something much rarer like a Collared Flycatcher in the offing. With Pallid Harrier being a scarce migrant these days we could expect a few of these to be found during the next week. The warm southerly winds might also bring the odd Hoopoe, Alpine Swift, Red-rumped Swallow and Red-backed and Woodchat Shrike to southern Britain.

Mid to late September is a time for finches to start moving with Linnet being the herald of this, and we should also see a distinct increase in the numbers of Wigeon, Teal and Red-throated Divers on the move. The easterly airflow should bring the first Dark-bellied Brent Geese to many sites along the east and south coast. Mid-September to mid-October is when migration peaks and we will be keeping a very close eye on the weather forecast during the next few weeks to help us keep ahead of the game.

Paul Stancliffe & Scott Mayson

Thursday 12 September 2019

12th -18th September

The past week has certainly felt a bit more autumnal with a definite chill in the air first thing in the morning and ever-shortening days as we slowly move towards the autumn equinox. Migration for many species slowed with the usual suspects for this time of year either missing or only in low numbers. Wrynecks, for example, were very thin on the ground with only a smattering of birds across the UK, with a distinct bias to the south and east. Commoner migrants such Redstart, Whinchats, Pied Flycatchers, and Spotted Flycatchers, as well as scarce migrants like Red-backed Shrike, and Barred Warbler all, saw a dip in their reporting rates this week as the northerly winds of the weekend gave way to lighter winds of a westerly bias, in effect stalling migration.

BirdTrack reporting rate graph for Whinchat showing a drop in reporting rate most
probably linked with unfavourable migration conditions

The effects of ex-hurricane Dorian weren't really felt as it passed to the north of the UK on the 11th September with a band of rain crossing the country being the only indication it had hit us. Perhaps it will be the early part of this week that species such as Baird's, Semipalmated and Pectoral Sandpiper and American Golden Plover turn up in good numbers and maybe something rarer like Yellow Warbler or Solitary Sandpiper?

The continued westerly airflow in the coming week means it is difficult to predict the intensity of migration and the species involved but the coming week is the peak migration time for species like Gannets, Guillemots and Razorbills which will also be heading south away from their breeding cliffs to winter off north-western Africa and the Mediterranean in the case of Gannet and the North Atlantic and the North Sea for Guillemot and Razorbill. Whilst coastal sites are best for these species any strong onshore winds can result in some, especially young birds, turning up on inland water bodies with Gannets even being seen flying down motorways.
Coming from Iceland and Greenland it is hardly surprising that the first Pink-footed Geese of the winter turned up last week on the northerly and north-westerly airflow, even though they are a week or so ahead of the historical average from BirdTrack data. Small flocks were seen on Fair Isle, the east coast of Scotland and North Norfolk, and with more, if the same weather forecast next week we could see more arriving along with the first Whopper Swans of the autumn. The majority of the world's population of Pink-footed Geese (estimated at around 225,000 birds) winter in the UK, in Scotland and Norfolk.

BirdTrack reporting rate for Pink-footed Goose showing the earlier than normal arrival last week.

These aren't the only wildfowl arriving to winter in the UK, Wigeon and Pintail numbers will start to build in the coming weeks as birds arrive from Northern Europe and Russia to take advantage of the relative warmth of UK winters.
Any strong westerlies at this time of year could also produce Grey Phalarope, this species spends the winter at sea but can be blown close to shore or even inland given the right conditions and can stay for a few days, entertaining the crowds with their mesmerising feeding technique which involves spinning around on the water to pick off insects pulled to the surface.

Species focus

Wheatears for many people signify the start of spring as they are one of the first summer migrants to reach the UK, but autumn can also produce large falls of this much-loved passerine. Wheatears of the race oenanthe bred in the UK but many of the Wheatears seen at this time of year will be of the Greenland race, leucorchoa, which undertake one of the longest transoceanic migrations, from their breeding grounds in Greenland and northeast Canada to their wintering grounds just south of the Sahara. It is believed that many individuals fly non-stop from Greenland to Britain and Ireland and other parts of Europe. These Greenland birds are slightly stockier, longer-legged and longer winged than their European counterparts and tend to stay around for a few days as they fatten up before continuing their southward migration.

Wheatear -Photo by Allan Drewitt

BirdTrack reporting rate for Wheatear showing the autumn peak in mid-September.

Weather for the week ahead.

The week ahead promises to deliver a mixed bag of weather with the wind direction seemingly changing from day-to-day. High-pressure over the southern half of the UK over the weekend and the resultant light winds should help those migrant departing out shores- swallows and martins ought to feature in visible migration counts and warblers, Reed, Sedge ad Willow, along with Whitethroat and Lesser Whitethroat, should be a feature amongst grounded migrants. Both Meadow Pipit and Grey Wagtail also take advantage of these lighter winds and a steady stream of these is often a feature of clear autumn mornings.
With a stronger northerly wind direction forecast for the middle of next week keep an eye on the sea for Great Skuas which can often be seen harrying the southbound Gannets and larger gulls.

Grey Wagtail - Photo John Dunn

Scott Mayson and Paul Stancliffe

Thursday 5 September 2019

5th -11th September

It’s been 3 weeks since the last migration blog and a lot can happen during that time,
especially when birds are departing for the coming winter months. During the next couple
of weeks we will be updating the blog on a weekly basis to bring you the most up to date
news of what is on the move, what to expect in the coming week (based on the weather
forecast and the time of year) and a few predictions of what rare and scarce species
may turn up, so a little of something for everyone.
Last month we started the blog with a follow up on the Two-barred Crossbill influx that
occurred mainly on the Shetland isles. The number of birds being reported fell away
towards the end of the month and, for now, seems to have come to an end with only the
odd single bird being reported.
We also highlighted  Aquatic Warbler in the last blog and since it was published single
Aquatic Warblers have been seen in Dorset, Somerset, Hampshire, Powys and Cornwall,
making it a good autumn so far for this species, let’s see what the next few weeks bring.
The past week has been particularly good for Pied Flycatchers with birds reported across
the country with a particular bias to the south and east coasts, which is to be expected for
a species that will be heading towards France and Spain on their southward migration.

BirdTrack reporting rate graph for Pied Flycatcher showing the spike in
reports in late August compared with the historical average

So what should we be looking out for in the coming week? The weather patterns at
the moment show a northeasterly airflow over the weekend which could result in
good numbers of Wrynecks, Barred Warblers, Whinchats and Red-backed Shrikes. East
coast locations will give you the best chance of seeing one of these species and with
the Spurn migration festival taking place this weekend why not go along and join one of
the guided walks? ( Scarce species seen at this time of
year include Citrine Wagtail, Booted, Arctic and Bonelli’s Warbler, Lesser Grey Shrike and
Tawny Pipit, all of which have a peak reporting rate in early September.
Whilst the numbers of some waders like Wood, Green and Common Sandpiper fall
away for Bar-tailed Godwit the early part of September is when numbers in the
UK peak.  Having bred in the Arctic Circle from Lapland east to Taymyr in Russia
birds head to the UK to either winter here or use it as a stopover before heading
onwards to West Africa. Bar-tailed Godwits tend to prefer estuaries and saltwater
habitats more than their freshwater loving Black-tailed cousins but that doesn’t mean
they don’t turn up away from the coast. Reservoirs can host small flocks of Bar-tailed
Godwits and they can often appear alongside Whimbrels as they also pass through the UK.

Bar-tailed Godwit - some will still be in breeding plumage at this time of year. Photo Nick Clayton.

So far it has been a quiet year for seabirds such as Cory’s and Great Shearwater, but as
we progress into September there is still time to find these amongst the southbound
Manx Shearwaters. Balearic Shearwater is a species marked as critically
endangered on the IUCN European Red List of species but September is the best
month of the year to see them, with hotspots including Portland Bill, Portgwarra and
Berry Head. Some birds reach the North Sea and places like Flamborough Head, Spurn
and Sheringham are all worth a look from given the right conditions. Leach’s Petrel is
another seabird to have a peak in their reporting rate during September with the west
coasts being particularly productive following westerlies brought on by low-pressure
weather systems rattling across the Atlantic. You can find a video on how to separate
Leach’s Petrel from the commoner Storm-petrel here.
Two seabirds to look out for this week, particularly with westerly winds forecast, are Fulmar and Sooty Shearwater. Right now both are on the move but for very different reasons, and with very different destinations. The Fulmars on the move will be birds dispersing away from their breeding sites. It is thought that most of them will not go very far, staying in the North Atlantic, periodically visiting nesting cliffs or prospecting possible nest sites for the future. However, the Sooty Shearwaters are on their spring migration, moving through the North Atlantic on their way to their natal islands further south for the forthcoming breeding season, which takes place during our winter. For some, this will involve a flight of over 10,000km (6,500 miles).

Sooty Shearwater - Photo by Joe Pender

Species focus

Ortolan Bunting is a scarce visitor to the UK with the majority of sightings occurring in
September, but like many species, the number of records has steadily been falling each
year. During the period 1968-1969, a total of 87 birds were noted but in the period
2010-2016 only 33 birds were seen. In recent years however there has been an upturn in
records, with 74 reported in 2016, and this has in no short way been the result of
increased sound-recording of nocturnal migrants, or nocmig which accounted for 30 of
the 74 records. More research needs to be done to see how widespread and regular this
nocturnal movement of Ortolan Buntings is but it at least shows they are using the UK
during their migration and possibly in greater numbers than the reports of birds seen
during the day may indicate. 
Sonogram of Ortolan Bunting call - Nick Moran

Weather for the week ahead.

The weekend's weather looks to be set for north westerlies along the North Sea coasts and a mixture of north westerlies and westerlies for the rest of Britain and Ireland. Seawatching during this period from any west or east coast location could produce Leach's Petrel, Skuas, Manx and Sooty Shearwaters, and Guillemot and Razorbills. The rest of the week is dominated by westerly airflows with the remnants of hurricane Dorian due to hit the top of Scotland and the Northern Isles from mid-week. This westerly bias to the wind direction could result in Nearctic waders arriving with species like Buff-breasted, Bairds, Semipalmated and Pectoral Sandpipers the most likely species to occur.

Scott Mayson and Paul Stancliffe