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.

Monday 26 September 2011

Exciting Times

The period from mid-September to mid-October is one of the most exciting times of the year for anyone interested in bird migration. Summer visitors that have spent the breeding season here begin to head off in earnest, whilst their counterparts in mainland Europe often get blown or drifted across the North Sea and add to the migration spectacular.
During the right weather conditions, rare birds from both the extremes of west and east can also form part of these movements. So far this season has lived up to expectations and provided something for everyone.

Siskin by Edmund Fellowes
There have been record counts on the east coast of Siskins on the move. 2,129 were counted at Carnoustie, Angus, during the morning of 7 September. In Hampshire, 867 Grasshoppers Warblers have been trapped at one site and over forty thousand Swallows were counted over-flying Hengistbury Head, Dorset on 16 September.
Sabine's Gull by Joe Pender

The westerly gales have provided a seabird bonanza on the west coasts. 900 Sabine’s Gulls flew past Bridges of Ross, Clare on 17 September and birds also turned up on waterbodies in land-locked counties, with one Sabine’s Gull staying eleven days at Grafham Water in Cambridgeshire.
American waders are also widely distributed, with the largest arrival of Buff-breasted and Pectoral Sandpipers for many years. Seven species of North American landbirds have also been found in Britain and Ireland. Red-eyed vireo, Black-and-White-Warbler, Northern Waterthrush and Baltimore Oriole on the Isles of Scilly, and Buff-bellied Pipit, Swainson’s and Grey-cheeked Thrushes on the Northern Isles.
And it is far from over yet! This weekend saw a large movement of Black Terns through inland counties, involving several hundred birds. A single flock of 100 birds were seen at Standlake, Oxon. Meadow Pipits and alba wagtails (Pied and White), Swallows and House Martins were all counted in three figures at several sites along the east and south coasts and goose counts are beginning to increase.
Things should be a little quieter for visible migration watchers during thesettled weather over the next few days. Migrating birds fly over at a greater height, often not visible from the ground, during these conditions.

Tuesday 13 September 2011

Autumn storms

The first autumn storms have hit and have had a big effect on migration already. During strong windy conditions, migration for smaller birds comes to a halt as they seek shelter and take the opportunity to rest and, if possible feed-up in preparation to continue their journeys.The day counts of visible migration at Spurn Point illustrate this perfectly. On Sunday 11 September, prior to the winds increasing, 2,280 Swallows were counted heading south over the Point; yesterday with gale-force south-westerly winds only 33 were seen.

Strong westerlies, particularly those associated with fast tracking storms that cross the Atlantic in a day or so often bring North American birds with them, and this weekend’s storm did just that; over thirty Buff-breasted Sandpipers arrived in the UK during the weekend. This high Arctic breeding wader leaves its breeding grounds in Alaska and western Canada during August and September, heading for the Paraguayan and Argentinian pampas. The eastern breeding birds complete this huge migration in one long flight over the sea from New England to Paraguay and Argentina, so are often prone to getting caught up in these fast tracking storms. The winds also brought the first American passerine to our shores, a Red-eyed Vireo, to the Isles of Scilly. This bird would have been making its way to northern South America or Cuba.

Red-eyed Vireo above by Joe Pender

In the UK early autumn storms also bring seabirds closer to land and provide the opportunity for observers to witness some impressive movements of these maritime birds. In the last three days, over ninety Sabine’s Gulls have been seen, from Cornwall to Dumfries and Galloway, and over thirty Grey Phalaropes have been seen from coastal headlands and a few inland reservoirs, including in the London area. Both of these are true oceanic birds.

Sabine’s Gull by Joe Pender

September and October are the most exciting months in a migration watchers calendar. Light winds at anytime during this period, particularly light southerly winds, can produce huge movements of pipits, finches and hirundines – Swallows, House Martins and Sand Martins - during September, and large movement of thrushes, buntings and larks in October. Strong westerlies can bring birds from North America, whilst strong easterlies can result in birds arriving from as far away as eastern Siberia.

So what can we expect over the coming weeks?

As the weather quietens down in the next few days and with winds from the south and east we can expect large movements of finches, pipits and hirundines, as they head off to Africa and we could see the arrival of few Red-backed Shrikes.

You can follow migration as it happens by checking out the BirdTrack maps and reports.

Monday 12 September 2011

Seabird Bonanza

The westerly gales that have been battering the coasts from the Cornwall to the Outer Hebrides have resulted in some spectacular seabird counts, in particular the rarer shearwaters. During the last week, over 7,000 Sooty Shearwaters, 2,500 Great Shearwaters and 600 Balearic Shearwaters, the latter globally listed as critically endangered, were counted off south-west Cornwall, south Devon and south-west Ireland. Among these were also numerous Grey Phalaropes, Leach’s Petrels and Sabine’s Gulls. Large numbers of Gannets and, as predicted in last week’s blog Manx Shearwaters were also seen in good numbers. Some newly fledged young of the latter struggled with the stormy conditions and 491 found themselves ‘wrecked’ on Newgale beach in Pembrokeshire. The BirdTrack reporting rate shows nicely the increase of observations of this species.

Manx Shearwater by Joe Pender

All four species of Skua were also involved in this movement, with Arctic being the most numerous, again the BirdTrack reporting rate shows this increase.

As was to be expected, the fast tracking Atlantic gales brought North American Waders with them and over a dozen Buff-Breasted Sandpipers arrived on our shores, with the Isles of Scilly hosting five of them, again the west received the lion’s share but birds have been found at Rye Harbour in East Sussex and Titchwell in Norfolk.

Buff-breasted Sandpiper by Joe Pender

Despite the windy conditions Swallows and Meadow Pipits have been a feature of visible migration watches. Over 12,500 Swallows were counted heading south at Spurn Point last Saturday, with almost 8,000 Meadow Pipits heading in the same direction on Thursday.

Swallows gathering by Paul Stancliffe/BTO

The first large finch movement was also observed here on Thursday with over 600 Siskins also heading south.

With the wind set to increase again from the west yesterday, observers on the west coast should have been in for another weekend seabird fest, whilst in the east, finches and pipits should make the most of any lull in the windy conditions.

Question of the week - How do birds cope with the risks of migration?

The very act of long-distance migration has to be one of the most arduous and dangerous activities that a bird undertakes, so what can they, and indeed do they do to minimise the risks associated with long-distance migration?

For those migrants that undertake long sea or desert crossings, it is essential to store enough fat deposits to fuel these flights and many of our smaller birds spend up to three weeks feeding up and accumulating fat reserves before their departure, some will have more than doubled their normal weight.

Setting off in optimum conditions also helps to minimise the risk of being downed or blown off-course and also maximises the stored fat reserves. If birds encounter worsening conditions, many will make landfall and rest-up and feed-up until conditions improve.

Some birds migrate primarily at night, reducing the risk of predation by diurnal raptors. Flying in the cooler night air also reduces drag and minimises the use of the stored fat reserves.