Which wader, when and why?

This is a quick summary of wader migration, for British and Irish birdwatchers. The maps are taken from the migration book Time to Fly by Jim Flegg, published by the British Trust for Ornithology, and most of the images are kindly provided by Graham Catley.

Autumn wader migration is one of the high-points of a birdwatcher’s calendar but why does it start in July (or even June), are the Dunlin that we see in August the same ones that are present in December, what are the vagrant waders we should be looking out for and which species migrates from here to Galapagos and Peru?

Starting simple – birds from the northeast

For two wader species that arrive in Britain and Ireland in the autumn, the migration story is straightforward: Grey Plovers and Bar-tailed Godwits fly here from the northeast.

The Grey Plovers we see in winter are birds from western Siberia, leaving in a southwesterly direction in autumn to escape the cold and taking up territories on the mud of our estuaries. As spring comes to an end, they moult into a smart summer plumage, ready for departure in May. Having bred, the first Grey Plovers will return in July and some of these birds will travel further south to west Africa. There’s a WaderTales blog about the global migration pattern of the species.

Bar-tailed Godwit migration

All of our Bar-tailed Godwits fly from the northeast but there are two subspecies to consider; there are passage birds from eastern Siberia that move to Africa for the winter, and birds from further west in Siberia, Finland, Sweden and Norway that spend the winter in western Europe. There’s more about Bar-tailed Godwit migration in this blog.

Other northeastern-breeding waders turn up each autumn, such as Curlew Sandpiper and Little Stint, but weather patterns and breeding success will dictate just how many we see on our side of the North Sea.

Adult Curlew Sandpiper

As is common in most wader species, adult Curlew Sandpipers get here earlier than juveniles, which don’t turn up until August or September.  Most adult Curlew Sandpipers seem able to make long migratory journeys between Siberia and wintering grounds as far away as South Africa but juveniles stop more frequently, many using coastal sites in Europe and Africa as they make their way south.

The breeding distribution of Broad-billed Sandpiper and Temminck’s Stint stretches further west than those of Curlew Sandpipers and Little Stints, but we see far fewer of the first pair of species. The migratory strategies of Broad-billed Sandpiper and Temminck’s Stint take them southeast and south, respectively, at the end of the breeding season, rather than southwest. In Britain & Ireland, they are both more likely to be seen on spring passage than in the autumn (BirdTrack data).

Other eastern arrivals

Woodcocks pour into Britain and Ireland between October and December

Lapwing, Woodcock and Curlew are all birds that breed in the UK but their local numbers are dwarfed by arrivals from the east each autumn. There are three WaderTales blogs that include information about the migration of these important species.

• Lapwing moult
• Conserving British-breeding Woodcock
• Is the Curlew really near-threatened?

The UK and Ireland are particularly important wintering areas for Curlew – one of many of the large wader species that are globally threatened as discussed in this blog.

Scandinavian and Russian breeders

Spring & autumn movements of Common Sandpiper

Common, Green and Wood Sandpipers are not really high-arctic waders. When they head south, many to travel to African countries, they are not as dependent upon coastal resources as other waders.

The beeding distribution of Common Sandpiper is further west than those of the other two species and there are lots of movements of ringed birds between Britain and Ireland and Scandinavia (see map in BTO’s on-line ringing report). There is more about the migration of the rapidly declining UK population in Not-so-Common Sandpipers.

A relatively small number of Scandinavian Green Sandpipers spend the winter in Britain and Ireland but there is a strong autumn passage (see map to the left). There’s a blog about Green Sandpipers here. Wood Sandpipers appear in smaller numbers, with a tiny proportion of the large fennoscandian population passing through en route to Africa (unusually there were hundreds of birds around at the end of July 2019).

The Spotted Redshank is similarly distributed to the three sandpipers mentioned above and we see relatively few each year, although 60 were caught together on the Wash in late July 1975. It was a memorable catch! There is a whole blog dedicated to Spotted Redshank migration and abundance change here.  The Marsh Sandpiper’s distribution is further east still, so we see very few of them.

Three of the UK’s rarest breeding waders – Greenshank, Ruff and Dotterel – are on the western fringe of much bigger continental breeding populations. The most numerous is the Greenshank, about 1000 pairs of which nest in Scotland. Scottish birds mainly winter around the coast of these islands but there is a strong autumn passage of Scandinavian and Russian birds, travelling as far south as Ghana. Read more about Greenshanks here.

There are only about 600 pairs of Scottish-breeding Dotterel but we also see passage birds heading north to Scandinavia or south to Spain and North Africa. Here’s a blog about the threats to Scottish Dotterel.

Although a few Ruff (map to right) do breed here in some years, the vast majority are seen on migration between European/Scandinavian breeding areas and wintering areas in Europe and west Africa. This paper reveals that it is the females that travel further and consequently have different patterns of autumn moult than males. Analysis of ringing recoveries of British ringed Ruff showed that females tended to migrate to Africa while males tended to winter in Europe.

Birds from the west – mostly

There are four Arctic wader species that we associate with northwesterly spring migration to Greenland and even as far as Canada – Knot, Sanderling, Turnstone and Purple Sandpiper. A May trip to the Outer Hebrides, the Solway, Morecambe Bay, the Dee or the Severn will reveal swirling flocks of these waders, resplendent in their fresh summer plumage. These birds will be feeding up for the flight to Iceland – the next stage of a journey which will take some of them to northeast Canada.

Most of the Turnstone that winter in the British Isles will head off to Greenland and Canada to breed but we also see a spring and autumn passage of birds from the continental population. These birds breed as close as Finland and can fly as far south as the Atlantic coast of southern Africa.

It’s a similar, although less clear-cut story, for Sanderling (map above), with most wintering birds thought to be from breeding populations in Greenland. In May, more Greenlandic birds arrive from as far south as South Africa, as you can read in Travel advice for Sanderling. In spring and autumn we see passage Sanderling travelling between the Russian Arctic and Africa, particularly on the east coast of England.

As can be seen from the map, Knot add an extra tweak; our wintering birds are mostly heading for breeding grounds in Canada and Greenland, via Iceland, but some stage in northern Norway instead. Some Russian birds drop in in on autumn migration, with fewer on spring migration.

Purple Sandpipers that spend the winter around our shores are drawn from a diverse range of breeding areas, such as the mountains of southern Norway, the islands of the Arctic ocean that lie north of Scandinavia and Russia, Iceland’s uplands, and further west in Greenland and eastern Canada. The birds mix in the winter but there is a tendency for Norwegian birds to be found on North Sea coasts, south of Aberdeen, and Canadian birds in the north and west. See information and references here.

Waders that breed here

Golden Plovers on the move

When we add in species that breed in these islands, the migration story gets even more complicated. Take Golden Plovers, for instance. A bird found on the wintry mudflats of the Firth of Forth probably bred close by, in the hills of lowland Scotland, one in an East Anglian field would probably have crossed the North Sea from Scandinavia or Europe, while one in Ireland is quite likely to be from Iceland, although it also could have flown from the east. It is a similar story for Snipe but birds in the west of these islands have an even stronger link to Iceland. There’s a blog about the migration of Snipe and Jack Snipe. Redshank mix more; any flock could include relatively local birds, Icelandic birds, breeders from further north within the UK and birds that cross the North Sea. Not as many wintering Redshank are of continental origin as might be expected.

Oystercatcher – the ringed bird in Greenland was  blown off course

Oystercatchers demonstrated the international tensions that can be caused by migration, when the culling of birds in the Burry Inlet of South Wales in the 1970s upset Norwegians. Cockle-eating winter habits may have been an issue for fishermen in Wales but the Oystercatcher is a popular breeding bird in Norway, where they nest in rural gardens and on roof-tops. Although there can be a mix of nationalities on any winter site, Icelandic Oystercatchers are most likely to be seen in the west and north and Scandinavian birds in the east. There is more about Oystercatchers here.

Our breeding Ringed Plovers winter in a wide range of locations. For instance, many colour-ringed, breeding birds in Norfolk stayed near their nest sites while others migrated to France, Ireland and Scotland. There is a strong passage of birds between wintering areas in Africa and southern Europe and northern breeding areas in Canada, Greenland and Iceland, in the west, and Scandinavia in the east.

There is a relatively small population of Whimbrels breeding here, almost all of which are in Shetland. Most of the birds we see elsewhere are of Icelandic or continental breeding origin, with large numbers seen on spring migration between Africa and Iceland in May, at the same time as other birds are leaving to head east. There is a WaderTales blog about Whimbrel migration.

Dunlin: Yellow arctica. Green schinzii. Orange alpina.

The most complex story is probably told by the Dunlin. Three races can be encountered in these islands – arctica, alpina and schinzii. Arctica are the most westerly birds, passing through in spring and autumn as they travel between Greenland and Africa, and alpina are the most easterly. The Dunlin we see in the winter are these alpina birds; they moult out of grey winter plumage and into the brightest plumage of the three races in the spring. Our breeding birds are schinzii, the same subspecies found in Iceland, southern Scandinavia and southern Greenland. These birds head to the coasts of northern Africa for the winter.

Dunlin races neatly demonstrate that differential patterns of migration are separated by time as well as direction of travel. In May, British-breeding schinzii birds may well be on eggs but there will be flocks of alpina on the coast, resplendent in summer plumage but still waiting for their cue to depart. They will leave with black-bellied Grey Plovers and glowing orange Bar-tailed Godwits, heading for breeding areas such as the Taymyr Peninsular of Siberia.

Black-tailed Godwits

Juvenile Black-tailed Godwits, newly arrived from Iceland

There are many WaderTales blogs about Black-tailed Godwit but these three illustrate the very different timings and movements of the two subspecies that we see in Europe – limosa and islandica. Islandica spend the winter in western Europe and breed in Iceland. The small number of limosa breeding in Britain head south each autumn to join the much larger populations from The Netherlands and neighbouring countries, heading for Iberia and western Africa.

• Godwits in Godwits out: springtime on the Washes illustrates how the breeding cycles of the two subspecies differ.
• Godwits and Godwiteers shows how observations of individual birds build up to create patterns of migratory movements.
• Dutch Black-tailed Godwit numbers down by nearly 75% tells of the challenges being faced by limosa birds, at a time when islandica numbers are increasing.

Heading south

For four species, these islands are at the northern edge of the breeding range – Little Ringed Plover, Stone-curlew, Avocet and Black-winged Stilt. Little Ringed Plovers that breed along river valleys, on gravel pits and in other industrial sites largely spend the winter in western Africa. Most stone-curlews leave behind the heaths and fields of England to feed in open farmland and uplands of Spain and North Africa, although a few now spend the winter here.

Avocets are quite mobile; there is a lot of autumn movement within Britain, especially into the south and west of England, but BTO-ringed birds can turn up anywhere from The Netherlands to Morocco. The newly-arrived Black-winged Stilts are expected to spend the winter in Africa or southern Europe.

Phalaropes

Red-necked Phalarope

In one of the most amazing recent migration discoveries, RSPB scientists followed the journey of a Red-necked Phalarope using a geolocator. This Shetland-breeding bird didn’t migrate southeast to the Arabian Gulf, like its Scandinavian cousins. Instead it behaved like an Icelandic bird, flying west to the Canadian coast and then south and further west to the Pacific Ocean, between Galapagos and the west coast of South America. See this BOU blog. I guess that any Red-necked Phalaropes seen in England on passage are most likely to be Scandinavian birds, Grey Phalaropes are thought to be birds heading from Arctic breeding grounds to the Atlantic Ocean coast of Africa, and Wilson’s Phalaropes are vagrant birds from North America.

American vagrants

Pectoral Sandpiper

Westerly winds across the Atlantic deliver American vagrants to these shores, especially during autumn storms, when birdwatchers look for Buff-breasted Sandpipers, American Golden Plovers and peeps (small shorebirds).

The American wader that probably turns up most frequently in Britain and Ireland is the Pectoral Sandpiper. Males of the species are unusually mobile, even during the breeding season, when they fly thousands of kilometres on the hunt for successful matings. There’s a blog about this. Come the autumn, the vast journeys some Pectoral Sandpipers make between eastern Canada and Argentina may bring them a long way east, far out from the eastern coast of the United States, as they follow great circle routes. Although this explains many Pectoral Sandpiper records, especially in Ireland, it is likely that other birds are from the western end of the breeding distribution, in Russia. The arrival of young Pectoral Sandpipers in August, at the same time as Curlew Sandpipers and Little Stints, may well suggest migration from the east. See this paper in British Birds.

Other long-distance migrants that may make it across the Atlantic include White-rumped Sandpiper, Baird’s Sandpiper, two species of dowitcher and Lesser (or even Greater) Yellowlegs  – and there’s always the challenge of trying to prove that a stint is actually a Semipalmated Sandpiper or a Least Sandpiper.

What else?

If you want to learn more about the migration of the birds of Britain and Ireland then the BTO’s Migration Atlas or Time to Fly are great places to look.

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Graham (@grahamfappleton) has studied waders for over 40 years and is currently involved in wader research in the UK and in Iceland.  He was Director of Communications at The British Trust for Ornithology until 2013 and is now a freelance writer and broadcaster.