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, 27 April 2011

Where are all the migrants?

Migration is usually monitored at coastal watchpoints and bird observatories, where careful daily counts of visible migration, birds flying overhead, and grounded migrants are taken. These counts give the first indication of how our summer visitors have fared over the winter months.
The situation this spring has been very different with many observatory websites reporting very quiet days, in fact looking at the various websites gives the impression that it has been a very poor spring for migrant birds, and by association a bad winter. This couldn't be further from the truth. In the very settled conditions birds have had a relatively easy migration and have flown high over the coast, too high to be seen by observers on the ground, and nocturnal migrants just haven't been grounded.

A walk around my local patch, Lakenheath Fen, on Monday morning confirmed the presence on territory of many summer migrants. Reed and Sedge Warblers were in full song everywhere, as were Whitethroats and seven Grasshopper Warblers. Two Nightingales were singing around the car park, a pair of Common Terns looked settled in on the washland and there was a good number of Swallows, Sand Martins and House Martins feeding over the water, and four Cuckoos were singing for over three hours non-stop. In fact the Fen was alive with summer visitors - a very different picture from the one that coastal observers are getting.

Nightingale by Edmund Fellowes

However, it's not all over yet, we are now coming to the peak migration time and as the winds turn north and north-easterly over the next few days birds could well be forced to fly lower over the coast, and nocturnal migrants could well be grounded. We could see some large counts of hirundines during the day and grounded warblers and chats at first light, particularly on the south and east coasts, and, in the next day or two Swifts should arrive in force, the only thing that might stop them is if the northerly winds become too strong. This is an event that I always look forward to, as it seems that all of the UK's Swifts arrive on the same day, or two.

Black Tern by Lawrence G Baxter
So this weekend enjoy the summer migrants already on territory, look out for the mass arrival of Swifts, which can often be accompanied by Black Terns as they feed over large waterbodies, and if the chance arises, go hunting for grounded migrants at the coast. And, even though the winds have turned northerly it is always worth keeping an eye out for southern overshoots - Black-eared Wheatear could be on the cards.

Thursday, 21 April 2011

Migrants heading straight for their breeding sites

The weather at the weekend was full of promise - light south to south-easterly winds, warm temperatures and along the south coast, a band of low cloud. The perfect recipe for grounded migrants and overhead visible migration.

So, were we up to our knees in birds that had arrived overnight and had been forced down by the cloud? Well, not exactly. Grounded migrants were encountered but only in small numbers, particularly on the south coast. The east coast fared a little better with Saturday being a Ring Ouzel day; small numbers were seen at several sites along with good numbers of Wheatears, and four Bee-eaters were seen on Sunday.

Above: Ring Ouzel by Tommy Holden

This doesn't mean that migration has come to a standstill, although it can look like it has at coastal watchpoints and observatories. Birds are still arriving but are overflying the coast at a height that makes them almost impossible to see and hear, and are arriving straight in to their breeding areas. This is giving us land-locked birders the opportunity to follow migration as it happens with the arrival of new birds.

The weather is set to remain fairly settled with the light winds coming from the east and south-east again this weekend, with perhaps a little more cloud on Sunday. So, the focus could again be on the east coast, and although the predicted east coast shrike didn't turn-up last weekend, it has to be on the cards for this one.

Friday, 15 April 2011

Birds get moving again

Migration pretty much stalled on Monday, Tuesday and Wednesday. A strong north-westerly wind set in, making it extremely difficult for birds heading north to make any headway. In these conditions birds just sit it out, rest and refuel for the next leg of the journey. Birds did still trickle in, but migration was not a patch on what it was last week.

Some birds did however manage to arrive. The first Golden Oriole of the year was seen on Monday in Devon, and more Hoopoes were seen - this could prove to be one of the best springs ever for this species. New in, was an Iberian Chiffchaff in Norfolk, two Red-rumped Swallows in Kent and two Bee-eaters in East Yorkshire.

On Thursday the wind turned southerly and dropped in strength, this was the signal for birds to begin moving again . With this in mind I got out in search of grounded migrants at Dungeness, Kent. I didn't experience a classic rush of migrants but did find plenty of grounded birds where the day before there had been none. My tally included 20 Common Whitethroats, 15 Willow Warblers, 6 Wheatears, and single Lesser Whitethroat, Redstart and Ring Ouzel.

Above: Wheatear by Jill Pakenham 

On the sea Common Scoters were actively migrating east through the Channel and in one hour I counted 217. Terns were also moving in the same direction with the same hour producing 120 Sandwich Terns and 65 Common Terns. All of these birds will be making their way into the North Sea, heading for breeding grounds around it's shores. The movement also included 3 Red-throated Divers, 4 Red-breasted Mergansers and 70 Gannets.

Above: Sandwich Tern by Jill Pakenham

With the wind remaining in the south this weekend, migration should pick up pace again and we could experience another rush with the arrival of lots of common migrants and a few more southern overshoots. The wind is promising to have more east in it than last weekend so the focus could very much be on the east coast. More Bluethroats could be on the cards and possible an early Red-backed Shrike or two and this could well be the weekend for the mass arrival of House Martins.

Wednesday, 13 April 2011

Strong north-westerlies slow things down

After the rush of the weekend, the moderate to strong North-Westerly winds that set in on Monday made it difficult for Northward-bound migrants to make any headway. Prior to migration, birds feed up frantically, storing fat all over their bodies - in the pit of the throat, in loops around their bellies, in their wing-pits and even on their thighs.

Once fully loaded, a small songbird can, on average, fly around five-hundred miles if the weather conditions are suitable - light winds from any direction are good but light Southerlies are ideal. Flying into a strong headwind reduces the distance a fat-loaded bird can fly, so it is better to land, rest and feed up in readiness for the next leg of the journey.

That it seems is what many birds have done during the early part of this week. On Monday, Willow Warblers did just that but on this side of the Channel. Visible migration watchers at Hegistbury Head, Dorset, awoke to a fall of Willow Warblers with at least 400 grounded there overnight on Sunday.  Take a look at the BirdTrack reporting rate (and animated map) for Willow Warbler which shows how dramatically numbers of this species have increased.

Above: Willow Warbler by Jill Pakenham

For the rest of the week the winds are turning Southerly and will be fairly light. In these conditions we can expect the arrival of more birds, and a small low pressure system over the Channel on Thursday could see many of them grounded on the south coast.

Birds from the Med continue to be found, giving further evidence of the scale of the arrival that happened last weekend. More Hoopoes and Woodchat Shrikes have been found, along with a single Iberian ChiffchaffOn the common migrant front, there have been more Grasshopper Warblers and Nightingales. The first Turtle Doves are here and the first migrant Golden Oriole has been seen in Devon - our breeding birds won't be back for at least another two weeks.

So for anybody out and about this week, Thursday looks like the best bet to witness visible migration and the spectacle of seeing large numbers of grounded migrants. It's certainly the day I plan to be out looking for grounded migrants at Dungeness.

Monday, 11 April 2011

The biggest weekend?

Well. Was it the biggest weekend? It didn't provide the predicted Moussier’s Redstart, or the large arrival of House Martins. However, Moussier’s Redstart seems to be one of the few Mediterranean overshoots not to turn up. There was at least half a dozen Purple Herons, a similar number of Woodchat Shrikes, and almost a dozen Hoopoes. Two each of Subalpine Warbler, Whiskered Tern, Short-toed Lark and Red-rumped Swallow were found, along with singles of Little Crake and Great Reed Warbler. The predicted Black Kite may have arrived fashionably late with BirdGuides reporting one at 08.09 on Monday morning in Norfolk.

But what of our common migrants? There might not have been a huge arrival of House Martins but good numbers of Pied Flycatcher, Tree Pipit, Ring Ouzel and Greenland Wheatear arrived, along with smaller numbers of Nightingale and Grasshopper Warbler. There was also several reports of Lesser Whitethroat and Garden Warbler. Lesser Whitethroats migrate from Africa around the eastern end of the Mediterranean to get to the UK, so the south-easterly winds on Friday and Saturday will have assisted these early birds. The weather conditions on the coast have been clear and sunny and as a result numbers of grounded migrants have been quite small. In these conditions birds overfly the coast and arrive straight on to their breeding territories.

Garden Warbler by Tommy Holden

Friday, 8 April 2011

Big Migration Weekend

For anyone following spring migration, this week has seemed more like the second week in May than the second week in April. There have been multiple arrivals of Hoopoes, Bee-eaters, Alpine Swifts, Purple Herons, Short-toed Larks and Woodchat Shrikes, along with singles of Western Subalpine and Sardinian Warblers, Whiskered and Gull-billed Terns and Red-rumped Swallows, to mention a few.

Above: Bee-eater by Su Gough

Common migrants have also been plentiful, Redstarts and Common Whitethroats turned up in force, a week or so earlier than expected. Swifts have been seen on Orkney and the Outer Hebrides and in Norfolk and Cuckoos have been seen at several sites at least ten days ahead of schedule.

All of these birds have been assisted to the UK by the warm southerly airflow that we are experiencing, and this is to continue over the weekend and into next week, with the wind turning to the magical south-east on Saturday. This could be the day to be out. These light winds make ideal conditions for migrants heading north from Africa but as can been seen from the list of Mediterranean birds above the southerly winds sometimes make it difficult for birds to put the brakes on. 

So, what can we expect? This weekend has the potential to be the biggest weekend of the spring. There should be lots of common migrants arriving at coastal watchpoints. More Swallows, Redstarts and Cuckoos should make it to inland sites, along with the first real influx of House Martins and Sedge Warblers.  Who knows what else might turn up from the Mediterranean. Black Kite has to be on the cards but a Moussier's Redstart would be the icing on many a birdwatcher's cake. With high pressure extendng all the way from northern England to the deserts of the Sahara this might not be such a crazy suggestion!

Take a look at our interactive BTO Migration Timeline to keep track of all the arrivals.
Above: Black Kite by Jill Pakenham

Tuesday, 5 April 2011

Promise of Cuckoos this weekend


Above: Cuckoo by Edmund Fellowes

The promise of the first large arrival of Swallows at the beginning of the week was spoiled somewhat by the strength of the south-westerly wind. High pressure over most of southern Europe did mean that some migrants that breed there failed to put the brakes on and duly arrived here in the UK.

Above: Hoopoe by Andy Mason

Around a dozen Hoopoes, three Alpine Swifts, three Purple Herons and singles of Western Subalpine Warbler, Short-toed Lark and Black Stork were all seen. The winds have kept migration slow this week but promise to turn south-easterly and weaken on Saturday, and with high pressure dominating from North Africa to the UK providing ideal migration conditions, this weekend has the potential to be the biggest of the spring so far. My prediction will be the first multiple arrival of Cuckoos into the UK, around ten days ahead of their average arrival date. Take a look at our migration timeline.