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),

Friday, 21 April 2017

Here come the Cuckoos!

The stop-start nature of this spring's migration has continued over the past week but breaks in the weather fronts allowed through a nice flurry of Ring Ouzels with over 60 records yesterday alone. Over the past week Ring Ouzels have been reported from the Isle of Wight to Edinburgh with 17 at Burnham Overy in Norfolk on the 20th April and 27 in the Cot Valley in Cornwall on the 18th April. Wheatears also arrived in good numbers and the graph below from BirdTrack shows that after a lag earlier on, the percentage of BirdTrack users seeing Wheatear has now caught up with the average for this time of year.

Graph showing percentage of BirdTrack complete lists featuring Wheatear
Graph showing percentage of BirdTrack complete lists featuring Wheatear

This is the best time of year to look out for Red-rumped Swallow and right on cue there have been half a dozen or so sightings over the past week. If you're visiting any coastal locations or freshwater marshes over the coming week look out for Swallows with very pale (sometimes reddish) rumps!

Red-rumped Swallow by Richard Crossley (The Crossley ID Guide Britain and Ireland) [CC BY-SA 3.0 (], via Wikimedia Commons

With high pressure dominating through well into next week we can expect a good arrival of migrants. We should see Pied Flycatcher, Whimbrel, Yellow Wagtail, Hobby and Arctic Tern all arriving in good numbers and more of our Turtle Doves returning too. We are receiving more reports now of House Martins returning to their nest sites, if you have any breeding near you then we need your help with our House Martin nest survey.

Three of our satellite-tagged Cuckoos are back in Europe now with one already back at his breeding grounds in the UK. Over the next two to three weeks we'll be heading rapidly towards the peak for Cuckoo records so if you want to hear a Cuckoo this year, this is the time to get out and listen. If you're very lucky you may even encounter an early Bee-eaterSquacco Heron or Purple Heron and it is worth looking out for rarer waders like Pectoral Sandpiper and Marsh Sandpiper stopping off on passage.

Cuckoo by Robin Lee
Cuckoo by Robin Lee

Over the course of the weekend, a cold weather front moving from north to south through Britain could produce a decent 'fall' of grounded migrants. Saturday morning looks like your best bet to head to a coastal watch point to witness this phenomenon for yourself, especially if there is a little rain early on . There is the potential for much colder weather early next week, with snow over much of Scotland and down to central England. How will our recently arrived migrants (and early breeders) cope with this cold snap? 

Thursday, 13 April 2017

Still waiting

The stop, start nature of this spring migration continues. The quiet spells in the weather provide windows of opportunity for migrants heading north through France and Spain, only for them to be closed by the next front to move through. This Friday and Saturday are a good example.

During the night of Thursday into Friday the conditions in France and across the Channel look good for birds wanting to make a move (see chart below). 

However, fast-forward to the same period on Friday going into Saturday and a front in the channel will have a blocking effect on birds heading north over the channel. 

Of course it will depend on the actual timing of the front moving through. If it is a little late, birds could set off across the channel and be grounded on the south coast as they encounter the front. If it moves earlier than forecast birds might be grounded in northern France, unable to move until the front has passed.

So, what does this mean for the weekend?

As the spring progresses more and more birds will take advantage of any window in the weather. We should see pulses of arrivals that by now should include Swallows in particular as they do still seem thin on the ground. Yellow Wagtail, Tree Pipit and Redstart should also be a feature, along with Ring Ouzel, Cuckoo and House Martin.

A few Garden Warbler should join the Blackcaps, although it feels like there are still a lot of Blackcap to arrive too. Reed Warblers should also take advantage of quiet overnight weather and make it back to their reedbed territories.

Where are all the Wheatears? It is a little worrying that Wheatear is trailing well behind its historic average in BirdTrack. The purple arrow on the graph is where it should be, whilst the blue dots are where we are this spring. Hopefully, they are just held-up and will flood in as soon as conditions allow, but you have to wonder what sort of winter they have had.

 BirdTrack reporting rate for Wheatear

On the rarity front, the warm southerly airflow we saw last weekend did bring a few overshoots with it in the shape of two or three Purple Herons, a Little Bittern, a couple of Western Subalpine Warblers, a Night Heron, a couple of Red-rumped Swallows and Woodchat Shrikes, two or three Black Kites and at least one Hoopoe. However, pride of place must go to the splendid male Rock Thrush that was found on St Martins, Isles of Scilly.
Rock Thrush courtesy of

Friday, 7 April 2017

The floodgates are about to open!

During the last few weeks migration has been somewhat stuttering. Breaks between weather fronts crossing Europe allowed birds to move only for them to be stopped by the next batch of fronts to move through. That might be about to change this weekend as high-pressure moves over the UK. The winds will turn southerly, and at least for a short while will come from as far south as North Africa. This should open the floodgates for birds such as Swallow, Blackcap and Willow Warblers, birds that should be fairly widespread at this time of the season but are still a little thin on the ground.

Hobby by Jason Thorpe
Hobby by Jason Thorpe
We are still a week or so away from the peak migration period but we should see lots of birds arriving in the next few days.  Hobby, Grasshopper Warbler, House Martin, and Sedge Warbler  could arrive in force, along with the first flood of Whitethroat and, as the winds turn more south-easterly around mid-week, a few Lesser Whitethroat too.

Redstart should be seen more widely, and Pied Flycatchers are worth looking out for too.  In fact with the conditions looking so good, most of our summer migrants should be represented over the next few days, perhaps with the exception of those that have a late spring arrival time, such as Swift, Spotted Flycatcher and Quail.

Cuckoo by Charles Tyler
Cuckoo by Charles Tyler
Six out of our seven satellite tagged Cuckoos are still south of the Sahara in West Africa but we do have one that has crossed the desert. Hampshire Cuckoo "Selborne", has been in northern Spain for around a week and will probably make the final leg of his journey home in the next week. Although none of our tagged Cuckoos have made it as far north as the UK, Cuckoo is definitely worth listening out for in the next few days and keep an eye on the Cuckoo tracking maps for daily updates on the position of our tagged birds. 

At sea, Common Terns on the move could be joined by the first Arctic Terns of the spring, and when terns are on the move skuas move too, so there ought to be a few Arctic and Great Skuas seen.

Arctic Skua by Moss Taylor
Arctic Skua by Moss Taylor
Conditions look to be perfect from the early hours of Friday morning right through to at least the early part of next week, and whilst the south coast ought to be the place to be, we could all enjoy spring arrivals during this time.

Black Kite by Jill Pakenham
Black Kite by Jill Pakenham

With the warm winds coming from so far south, overshooting spring migrants should also be a feature. Along with the possibility of a few more of the birds we have seen during the last week, Red-rumped Swallow, Black-winged Stilt and Woodchat Shrike. With the forecast weather it looks like we could be in for an arrival of southern herons, Purple Heron, Little Bittern and Night Heron are all on the cards. We could also see the odd Black Kite and maybe Sardinian Warbler.

The conditions are also good for departing migrants and it is worth keeping an eye out for the last Redwings and Fieldfares, and at sea, Brent Geese.