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.



Wednesday, 10 July 2019

Autumn migration gets underway



There has been a lot of chatter both on social media and elsewhere that this has been a poor spring for some of our most loved summer migrants, particularly Swifts, Swallows and House Martins. Looking at the BirdTrack reporting rate graphs for these three species, all of them were reported at lower levels compared to their historical averages. Swallows arrived bang on time, whilst House Martins initially appeared to be arriving earlier but then dropped below the historical average and Swifts were around 1-2 weeks late. A cold northeasterly airflow could explain the drop in House Martin arrival in week 15 (WC 08/04/2019) which is also noticeable on the Swallow plot. The delay in arrival for Swift is also most likely due to an easterly airflow during week 16, which then turned to a southerly airflow during week 17 and in turn produced an upsurge in Swift sightings.




We will have to wait until the publication of 2019 BBS (Breeding Bird Survey) report in May 2020 before we can asses any population changes for these three species.

Back to the here and now, July migration is headlined by waders such as Spotted Redshank, and Green Sandpipers, which are amongst the first to head back. The females of both species are the first to depart as they leave the males to incubate the eggs and raise the young. The males and young of both species migrate later and start to appear in late July and early August. Green Sandpipers can turn up anywhere from saltwater lagoons on the coast to small vegetated ponds inland, their distinctive white rump in flight gives the impression of a large House Martin, and a high pitched three-note whistle is often given during flight. See the Green Sandpiper identification video https://tinyurl.com/y4wg3zrl for more.

Green Sandpiper - Vic Froome


Storm Petrels breed at a few locations in the UK, mainly on Scottish Islands and a few Islands off the coast of Wales, South West England and the west coast of Ireland. In July however, they are often recorded away from these traditional breeding areas and it is a long-held belief that these relate to ‘Wanderers’, non-breeding or failed breeders that are looking for potential new breeding areas. These movements can be rapid and over large distances, as illustrated by a bird ringed in Norway that was caught 613km away in North Yorkshire the very next day.

NOS Adult 26-07-2002 Lindesnes Fyr, Lindesnes:57°58'N 7°3'E(Vest-Agder) Norway

E760828 Caught by ringer 27-07-2002 Upgang, Whitby:54°29'N 0°38'W(North Yorkshire)   613km  SW  0y 0m 1d

Storm Petrel - Joe Pender

For more, please visit the BTO Storm petrel identification video https://tinyurl.com/y6rf2gk3

All of the BTO satellite tagged Cuckoos have now left the UK and have reached their first stopover sites in southern Europe. This year BTO scientists are following 11 satellite-tagged Cuckoos as they make their way to central Africa. Currently four of them are in France, six in Spain and one in Croatia, unfortunately, a twelfth bird was killed flying into a window at Dungeness. Having moved from Sherwood Forest, Nottinghamshire, this bird, named Robinson, was well on its way south. Migration is full of hazards. Follow the Cuckoos as they undertake their huge southward journeys at www.bto.org/cuckoos

During the last couple of weeks there has been a large arrival of Painted Lady butterflies into the UK off the back of warm south and southeasterly airflow, two birds almost certainly arrived on the same weather system, the Little Bustard in Gloucestershire and the Blue-cheeked Bee-eater in Highland - if the Painted Lady invasion continues as the weather begins to warm again next week, we might be in for a summer mega.


What to look out for during the rest of July.

At this time of year, south westerlies can produce Cory's Shearwaters and Balearic Shearwaters, with headlands in the south-west the best place to sea watch from. A pelagic trip from the Isles of Scilly could result in sightings of the once mythical Wilson's Petrel.

Together with the more expected Green, Common and Wood Sandpipers, other vagrant wader species can often be found in late July with Terek, White-rumped, Pectoral and Buff-breasted Sandpipers being the most likely.

Other species on the move in late July include Quail, Little Gull, Black Tern,  and Common Scoter, with the latter species often turning up on inland reservoirs so keep an eye out for these.


Little Gull - Graham Catley


At the moment there is also a small influx of Two-barred and Common Crossbills happening, mainly on the Shetland Isles. The last influx was July 2017 and was confined to Shetland Isles with the exception of a single female on the Isle of May. In  2013 the influx was more widespread with birds scattered across the UK, will the same happen this year? A few Common Crossbills have been seen as far south as the Isles of Scilly, so it may be worth checking your nearest coniferous woodland. Larch cones are the favourite of Two-barred.

A Sooty Tern seen this year on the 24th June along the Yorkshire coast was subsequently seen again on the 9th July and is probably the bird from last year that was first seen on 7th July 2018 disappearing between  9th-19th July before relocating to Ythan Estuary where it stayed from 21st July -5th August. Perhaps it will head back there again this year? 

Friday, 16 November 2018

A Swift arrival

The migration highlight in the last two weeks was an unexpected arrival of Swifts from 3 November onwards, with three species noted around the country. While there were a handful of Common Swifts reported, the majority of sightings involved the much rarer Pallid Swift, with over 30 and perhaps as many as 50 individuals observed.


BirdTrack reporting rate for Pallid Swift

Pallid Swift is seen annually in Britain in small numbers, influxes involving more than 10 birds had previously occurred only in 1999 (11 records), 2001 (12) and 2004 (15). The majority of the sightings came from the east coast, with only a handful from south coast counties and inland sites. Besides Britain, one was seen briefly in Ireland and up to 20 Pallid Swifts were also noted in the Netherlands, where there had only been 12 records previously.

Pallid Swift by Martin Cade
A potential reason for the influx may be that unusually for European swifts, Pallid Swift is double brooded, with the last brood fledging in October. Additionally, the sustained southerly winds throughout early November may have pushed birds northwards. The presence of a Little Swift at Hartlepool, Durham joining a Pallid Swift already present is intriguing as the nearest breeding grounds are along the southern Mediterranean coast. Did the Pallid Swifts in this influx come from North Africa rather than Iberia or the eastern Mediterranean?

Little Swift by Damian Money
The week ahead looks potentially quite interesting, with high pressure building over western Russia and Scandinavia over the weekend. This could potentially bring a spell of colder weather from the middle of next week onwards, with the easterly winds likely to bring more winter thrushes and wildfowl amongst others to our shores. It is getting a bit late in the season for most rarities by this stage, but given the origin of the winds, a Desert Wheatear, or perhaps even a Desert Warbler, seem like potential arrivals.

Stephen McAvoy

Friday, 2 November 2018

Skuas on the move


While not making for the most pleasant observation conditions, strong north to northeasterly winds in late autumn can produce good movements of seabirds and other migrants along the east coast of Britain. The weather last weekend fitted this exact pattern and those who braved the cold, biting wind were not disappointed.

Pomarine Skua by Joe Pender

The most eye catching spectacle was the passage of Pomarine Skuas with several sites logging day totals of more than 100 birds. Amongst the highest counts were 150+ off Flamborough, East Yorksire, 180+ off Gibraltar Point, Lincolnshire and 200+ moving south past Spurn, East Yorkshire. The latter represents a new day count record for the species at the site. However, these counts were eclipsed by the over 500 logged passing Hornsea, East Yorkshire. The BirdTrack reporting rate graph clearly shows last weekend’s movement



The strong winds brought with them a wide variety of other seabirds, including the first large movement of Little Auks. Several sites registered double figure counts, with a high count of over 150 passing Flamborough. Divers and shearwaters were also noted, including a handful of White-billed Divers. The rarest seabird logged was probably the King Eider moving along the North Norfolk coast over the weekend and early last week.

For passerine migrants, there were good counts logged for Redwing and Fieldfare arriving in off the North Sea, while large flocks of Starlings were also noted. As in the previous week, a few flocks of Waxwings were noted moving west with the thrushes and Starlings - it is well worth keeping an eye on any berry rich hawthorns in the coming weeks!



A common theme in the last weeks has been a rapid switch of wind directions, and this weekend is no exception. After the spell of northerlies in recent days, the prevailing wind moves back to a south – southeasterly direction as the remnants of Hurricane Oscar pass northeast off the coast of Ireland and Scotland. Having stayed well out in the Atlantic in the last week, it is unlikely that this weather system will bring any new arrivals of North American origin, though potentially the first white-winged gulls could arrive, and rarer gulls are always a possibility, including Laughing or Franklin’s Gull.

Stephen McAvoy


Friday, 26 October 2018

Eastern Promise

As expected, the northerly winds meant that migration was relatively quiet this week. However, a trickle of birds continued to arrive, most notably Common Crossbills. From Tuesday onwards, daily totals of up 200 birds were noted at Sandwich Bay Bird Observatory, Kent. Smaller numbers were recorded elsewhere along the south coast. The BirdTrack reporting rate graph shows as above average for the last few weeks so it is worth checking any local sites for birds on the move.



Thrushes and finches continued to arrive, albeit in smaller numbers with counts from bird observatories along the east coast in the low hundreds for both Fieldfare and Redwing. Most sites also held a Short-eared Owl or two and late October/early November is the peak time for this species based on BirdTrack reports.

Short-eared Owl by Mark Taylor/BTO



More unusual migrants included small numbers of Stock Doves arriving in off the North Sea along the south and south east coast. While birds breeding in Britain and Ireland are considered to be sedentary, the populations of Stock Dove in Scandinavia and eastern Europe are migratory. A handful of Waxwings were reported along the east coast, with most seen as fly-overs only.

Over the course of the weekend, the winds gradually shift from northwest to east, with strong northerly winds forecast for Saturday morning. Over 70 Pomarine Skuas were logged passing Titchwell, Norfolk this morning and tomorrow looks like a good day for this species, and other skuas, to be found along the east coast. The first Little Auks of the autumn may well be reported moving past offshore as well.

Little Auk by Morris Rendall/BTO

Based on current forecasts, the winds will remain easterly until Tuesday at least, which may well bring an arrival of Siberian migrants, including commoner species such as Brent Goose and Bewick’s Swan. Given the origin of the winds, a late arrival of Yellow-browed and Pallas’s Warblers seems possible, and any Wheatear is worth checking for something rarer, such as Desert or Pied Wheatear. There is always the potential for something unexpected turning up – a Siberian Rubythroat would brighten any day!

Stephen McAvoy

Friday, 19 October 2018

Rare arrivals from east and west


Arriving quickly from the east coast of the United States and Canada, the remnants of Hurricane Michael did not directly impact Britain and Ireland last Monday, diverting southwest towards NW Iberia at the last moment instead. Despite this, the outliers brought several very rare North American birds with them. The first species to be found was also one of the rarest, with Britain’s second Grey Catbird found at Land’s End, Cornwall late on Monday. It remained on site all through the week, allowing many birders to catch up with this species. The offshore islands closest to the track of ex-Hurricane Michael were also good places to be with Cape Clear, Co. Cork holding a triple crown of Swainson’s Thrush, Scarlet Tanager and the first Veery for Ireland. Birders on the Isles of Scilly discovered Bobolink, Grey-cheeked Thrush and Red-eyed Vireo, though the former was only seen briefly. Away from the southwest, there were sightings of Red-eyed Vireo on Inishmore, Co. Galway and a Baltimore Oriole on Barra, Outer Hebrides. The fast moving nature of this Hurricane, taking just over 48 hours to cross the Atlantic, likely helped these birds survive the crossing. Who knows what other species may have been discovered if it had made landfall in Ireland or Britain?

Following on from the strongly southerly winds the previous weekend, Pallid Swifts were found in Kent, East Yorkshire and Northumberland. However, these were outshone by Britain’s first White-rumped Swift at Hornsea Mere, East Yorkshire last Sunday. With an increasing population in Iberia, this species should now be on the radar in similar conditions in future years.

Along the North Sea coast of Britain, strong northeasterly winds last Monday brought fresh arrivals of thrushes and finches arriving ‘in off’. Redwing, Fieldfare, Goldcrest and Brambling arrived, while scarcer migrants included Bluethroat, Red-flanked Bluetail, several Great Grey Shrikes and a probable Two-barred Warbler in Norfolk. The first Waxwings of the autumn were also reported from Shetland, Yorkshire and Norfolk – will this winter see another invasion?

Waxwing by Jeff Baker/BTO

Looking ahead, the weekend looks set to be dominated by high pressure, and the calm mornings are ideal for visible migration watches with larks, thrushes and finches on the move. The reporting rate graph on BirdTrack shows that late October is the peak for Skylark, Siskin and Brambling amongst others. One to listen out for is Richard’s Pipit, with fly-overs likely to be found anywhere. The BirdTrack reporting rate graph shows a clear peak in late-October, and it is well worth being familiar with the flight call (for example https://www.xeno-canto.org/439042).

Reporting rate graph of Richard's Pipit

On Sunday afternoon, the wind looks set to switch to northwesterly over most of Britain and Ireland, which will likely help birds staging from Iceland to our shores, for example Brent Goose and Whooper Swan.

Stephen McAvoy

Friday, 12 October 2018

Looking east and west

The spell of northeasterly winds last weekend appears to have opened the floodgates for birds wanting to cross the North Sea from western Scandinavia. There was a notable passage of thrushes, consisting mainly of Redwing and Song Thrush, with a few Ring Ouzel noted. The movement also included some flocks of Fieldfare – appearing a little early based on the BirdTrack reporting rate.

Fieldfare by Luke Harding/BTO

Other winter visitors on the move included Whooper Swan and Brent Goose, while good numbers of duck were reported moving past coastal watchpoints along the east coast, especially on Sunday when the northeasterly winds were at their strongest.

Scarcer species noted included several Barred Warblers, the first Great Grey Shrikes of the autumn and the first significant arrival of Yellow-browed Warblers along the east coast.  Up until this weekend, it had been a very quiet autumn for this species by recent standards. However, 39 logged at Spurn, Yorkshire on the 7th October was both a record day count for the site and a very good count for this autumn. Over 20 were also logged at nearby Flamborough Head, Yorkshire, and single figure counts came from many coastal sites.

Great Grey Shrike by Graham Catley/BTO

Although the winds switched back to west–southwesterly from Monday onwards, these were sufficiently light that birds managed to cross the North Sea, with further arrivals of Song Thrush and Redwing. New arrivals included the first Brambling and several Olive-backed Pipits. Above average numbers of the latter have been reported from Poland and Germany so far this autumn, so more may yet be found.

On Thursday and Friday, the winds switched to a southerly direction in the wake of Storm Callum moving north off the west coast of Ireland. These winds originate from the Mediterranean basin and mid to late October is peak time for Pallid Swift in Britain so it will interesting to see if the southerly winds will push any our way.

Pallid Swift reporting rate on BirdTrack


Looking ahead, there are two weather systems to watch. On the east coast of Britain, there is potential for more northeasterly winds on Monday and Tuesday, which will likely bring more Scandinavian migrants, and perhaps something rarer. In the southwest, the remnants of Hurricane Michael could arrive on the same day. Having caused significant damage in northwestern Florida, this storm moved rapidly along the east coast of the United States and Canada. As of this morning, the storm could reach southwestern Ireland and Cornwall on Monday lunchtime, though there is still some uncertainty on the precise track the storm will take across the Atlantic. If it does reach our shores, it may well bring some very rare North American birds, with likely candidates including Chimney Swift, Red-eyed Vireo and Grey-cheeked Thrush. There is always the chance of something unexpected – a repeat of either Canada or Golden-winged Warbler would be very welcome!

Stephen McAvoy

Thursday, 20 September 2018

Mixed bag of migrants


With a turbulent run of weather forecast for the coming week it makes predicting what will be migrating rather interesting shall we say. As deepening depressions rattle their way across the Atlantic they bring strong westerlies to our shores and periods of heavy rain. These weather systems cannot only dump large quantities of rain but can also provide us with a smattering of transatlantic vagrants, such as American peeps (or sandpipers as we know them) and maybe a rare 'Yank' warbler. Pectoral Sandpiper and Semipalmated Sandpiper have already made landfall in the UK this year but are likely to be joined by more individuals as well as the possibility of other species such as Least Sandpiper or Killdeer.
Strong westerlies can make for good seawatching conditions along the west coast with species such as Sabine’s Gull and Long-tailed Skua mixed in with the more expected Arctic and Pomarine Skuas and Kittiwakes. Sometimes these species are forced further inland by the strong winds so any reservoirs or large lakes are worth checking.

Sabine's Gull - Moss Taylor

As these weather systems make their way across the UK they will start to draw in a northerly and easterly airflow, opening the door for another suite of birds to arrive. For many birdwatchers this time of year is synonymous with Yellow-browed warbler, once the preserve of twitchers this is now an expected migrant with several hundred birds turning up in a good year. No longer is it just a coastal bird either, with individuals being found with greater regularity at inland sites. At this time of year any wind direction with a hint of east opens the possibility of something ‘off the radar’ turning up from the far east and have include Thick-billed Warbler, Brown Flycatcher and Yellow-browed Bunting.
For those species that arrive here for the winter northerly winds will aid their migration and numbers of Pink-footed Goose should increase and other wildfowl such as Shoveler, Wigeon and Teal should also arrive in ever growing numbers.
Reporting rate for Shoveler from BirdTrack


Waders will also be on the move as this years young, which typically migrate after their parents, start their first migration to wintering grounds, Bar-tailed Godwit, Knot, Turnstone and Sanderling can often form large groups and can turn up anywhere.

Sanderling - Jill Pakenham