Wednesday, 30 July 2014

Broad-billed Sandpiper

The broad bill
Following on from the previous post on birds in Norway, here is a brief update of the work done this year as part of a long-term study of Broad-billed Sandpipers Limicola falcinellus. These birds are difficult to find in their breeding habitat of extensive mires with floating mats of vegetation, which can be treacherous (to us), and over the years a tremendous team of expert fieldworkers have taken part in the project. This was my fourth season and I am grateful to my brother Rab Rae and Karl-Birger Strann for organising the study. Simon Foster and Shona Quinn were the other team members this year.

The species has two recognised races divided by their breeding ranges; the western nominate race breeds in Scandinavia and nearby Russia, and the eastern sibirica race breeds in a largely unknown range somewhere in Siberia. The main difference between the races, if they are different, is size, the latter being larger. The highest numbers of wintering birds are found in Asia and as far south as Australia, while the winter range of the western race is described as coastal and estuarine mudflats from Africa to India. All rather vague, and is there an overlap between the races' wintering ranges? There are many unknown details of this elusive wader.

Broad-billed Sandpiper breeding habitat in northern Norway
The birds are only in their breeding grounds from May to July, taking advantage of the abundant invertebrate life in the arctic mires to raise their young. Apart from their display flight when they first arrive they are largely unseen or heard. They spend their time weaving through the dense growth of sedge, they are small, about the same weight as a bunting, and perfectly camouflaged for the habitat, so they are very difficult to find, let alone study.

Broad-billed Sandpipers are inconspicuous as they creep through the sedge-covered mires
The breeding behaviour of Broad-billed Sandpipers in this study has been described and published by  Rae et al 1998, but conservation of a migratory species requires knowledge of their movements, behaviour and habitat requirements at both ends of their distribution. So, we have begun a study of their migration using geolocators. These are tiny, 0.6g devices, Intigeo-W65 from Migrate Technology, which have up to two years recording time. As these birds return to their same breeding areas each year it is planned to catch the birds again next year, remove the geolocators and download the data which will show where the birds have been during the non-breeding period.

The birds were ringed with individual-colour combinations of rings
and fitted with a tiny geolocator (above the knee)
Another aspect of the bird's life which is not clearly understood is the difference in plumage between adult and first-year breeding birds. It is important to know the age of birds when studying them as younger and older birds can behave differently. Most descriptions of the Broad-billed Sandpiper plumage has been of birds caught on wintering or passage grounds, when they are not fully moulted into their summer colouring. From our work so far, we seem to be able to confirm that birds in their first year have three dark outer primary feathers (four including the reduced 11th). This is because they are freshly moulted feathers, in about March, not long before the birds flew north, and they contrast with the paler older primaries which were moulted at the end of the previous year. However, not all first year birds have this feature, and if they have all-old primaries, they resemble older birds which moult all their primaries over one period at the end of the previous year.

One-year old birds have dark outer primaries
So, we are looking for other possible patterns in the bird's plumage which might help distinguish between young and old birds. One feature, might be the colouring of the feathers on the back, rump, scapulars and coverts, which are black with rich rufous edges in the full breeding plumage. Perhaps there are differences between the ages there, but further study is required to test this.

The primaries on birds more than one year old are all a similar pale (faded) brown colour
It only took minutes to catch the birds in a mist net (once they had been found, which can take days), measure and tag them. Then they were off, back into the mire where they disappeared again. We saw them a week later with chicks, which are even smaller and more cryptic to see.

By now, both the adults and their fledglings will be ready to fly south. So if anyone sees a colour-ringed Broad-billed Sandpiper do please report where and when. Help add a little bit of information to this secretive bird.

The birds were processed quickly and soon ready for release

They all flew off back into the mire 

But where are they now?

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