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Autumn bird migration news: Storm force transatlantic migrants

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Nick Moran & Paul Stancliffe (BTO) Nick Moran & Paul Stancliffe (BTO) | 15:21 UK time, Friday, 16 September 2011

Red-eyed vireo

The red-eyed vireo arrived after a journey of 5,000km © Joe Pender

At this time of the year, storms can often bring birds to Britain and Ireland from far-flung places, and as the tail-end of hurricane Katia lashed our western shores earlier this week, it brought transatlantic migrants with it. Over 60 buff-breasted sandpipers arrived, with a single flock of 14 seen on Loop Head in County Clare, Eire.

They were not alone, over 30 pectoral sandpipers and a single solitary sandpiper were also found. The latter sharing the Isles of Scilly with the only American landbird to arrive, a red-eyed vireo, which was found on St Mary's on Tuesday. This bird, about the size of a dunnock, will have travelled at least 5,000km to get here.

pectoral sandpiper

The pectoral sandpipers, a transatlantic migrant © Ashley Fisher

So what effect has this had on migration here? The strong winds during the early part of the week effectively brought migration to a halt for many of our smaller birds. Now that the winds have died down, migration will again be in full swing, with hirundines (swallows and martins), pipits and finches making up a large part of any movement. The BirdTrack reporting rate for swallow shows this increase well as birds are counted at migration watchpoints.

Red-backed Shrike

The red-backed shrike might arrive on in the east Neil Calbrade/BTO

Most of the action this week has been in the west but with the light south-easterlies forecast for Friday, the eastern side of the country could be the place to be, with wryneck and red-backed shrike a strong possibility on an early weekend walk. By Saturday lunchtime and in to Sunday the strong westerlies are due to return, swinging focus back to the west, where we could have a repeat performance of the early part of this week.

Question of the week: What causes falls of migrants?

During ideal conditions for migration (light winds and clear skies) migrant birds have little problem following a predetermined heading towards where they want to migrate to. However, for long distance migrants the conditions can change during their migration and they can be drifted off-course by the prevailing winds and find themselves over the open ocean.

Once over the ocean it seems that a migrant bird is unable to compensate for the original drift that got it there in the first place, and they continue in the direction that the wind is taking them until land is found. Or they perish in the sea, as many migrants in this situation must do.

Once on land, a migrant is able to once again re-orientate and head off on the original course, albeit sometimes in a very different part of the world, the red-eyed vireo on the Isles of Scilly this week is a prime example of this. (This was beautifully caught on camera by mpgoodey, a member of our photo group)

Of course large numbers of birds can be caught-up in bad weather events and can literally fall out of the sky once land is found, resulting in large falls of a variety of species seeking shelter and food. One of the most famous falls occurred in September 1965 on the east coast, involving 15,000 common redstarts, 8,000 northern wheatears, 5,000 pied flycatchers, 3,000 garden warblers and many others.

Birds can also occur in falls when they encounter heavy rainfall and will drop from the sky to seek shelter until the rain has passed.

Have you noticed any birds leaving yet? Anything unsual or suprising? As always, we'd love to hear, so post a comment below.

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