Superb camouflage

Superb camouflage

While studying waders in northern Norway I was repeatedly impressed by the adaptation of these birds in their use of camouflage as their main defense from predators. Camouflage only works well if an animal does not move, relying on their cryptic plumage patterns to conceal them until the very last moment as potential predators, including humans pass by. This tends to make them rather difficult to study.

A Broad-billed Sandpiper hides amongst sedges

One species of wader which breeds in mires on the tundra is the Broad-billed Sandpiper Limicola falcinellus and they are very easily overlooked. These birds, about Starling-size, forage on mats of sphagnum moss on the edge of mire pools, creeping through the sedges. Their plumage has a background of dark browns like those of the muddy surface, with pale stripes that resemble the blades of the sedges. They match their habitat exactly.

Easier to see if you can pick out an eye

And if you think these are difficult to see, try to find the bird in the next photograph.

A Jack Snipe lies quiet amongst the sedges

Another species that lives in these mires is the Jack Snipe  Lymnocryptes minimus. Their plumage is like that of the Broad-billed Sandpipers, and the birds are of similar size. These two unrelated species have adapted similar plumages and behaviour, and they breed successfully, so their convergent evolution is evidence of the effectiveness of their survival strategy.

Even when seen close up they are not easy to discern

As I look down on these birds and admire their adaptation to their habitat, I often think to myself, how many have I walked past?

From above, the stripes on the Jack Snipe resemble the pale old leaves of the sedge

I study many cryptic species, but these waders are some of the the trickiest birds to find, they are true masters of the art of camouflage.

Once again, if it weren't for the eye....

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?

Arctic waders

Adult Wood Sandpiper

Here are a few photographs of waders and their chicks which I was studying recently in northern Norway. Part of the work, which is organised by my brother Rab, involves finding and catching both adults and chicks to ring them in order to help discover such information as where they live in the non-breeding period, whether they return to nesting or natal sites, and how long they live.

A pair of wood sandpipers, ringed and ready for release

The most abundant wader species in the tundra mires is the Wood Sandpiper Tringa glareola and the Broad-billed Sandpiper Limicola falcinellus is one the less common and seldom seen species. Most of the waders live in extensive mires, hidden by lush growth of sedges and other marsh plants.

An adult Broad-billed Sandpiper is measured -  the sexes are similar in plumage, but can be differentiated by size

Wader nests and chicks are notoriously difficult to find due their cryptic plumage and seclusive behaviour, arctic-breeding species are especially so. Wood and Broad-billed Sandpipers nest in the mires and it takes very specialized skills and a very very keen eye to find them.

A Broad-billed Sandpiper nest and chicks lie hidden in a mire

Broad-billed Sandpiper chicks in the nest

Four Wood Sandpiper chicks, a typical brood size

A single Wood sandpiper chick is extremely difficult to see when creeping through the sedge

Broad-billed Sandpiper

A Broad-billed Sandpiper in breeding plumage

I have recently returned from a trip to Norway where I have been helping my brother Rab on a long-term study of the birds in the norther marshes, including the breeding biology of Broad-billed Sandpipers Limicola falcinellus. Typically of Arctic-breeding waders, these birds fly north to nest as soon as the snow melts and their breeding grounds are clear enough for them to feed and build a simple nest on the floating mires. The main function of their journey is to find a nursery area for rearing their chicks, and the whole breeding period from egg-laying to fledging is over in a matter of weeks, Then the birds fly south to their wintering grounds, which to date are unknown for the Norwegian population. To help answer this question we began tagging birds with geo-locators, and plan to re-catch the birds next year to download data which should indicate where the birds have spent the non-breeding period, the longest part of their lives.

The broad bill

One of the individual characteristics of wader species is the specific bill shape, and the broad bill of these sandpipers is not usually appreciated when seen in the field in profile. However, when the bird is in the hand, it is obvious. As these birds spend most of their time in their winter quarters, it is likely that their bill is adapted for catching certain prey there, giving them advantage over other species for a specific food source. The bill is not only broad, but has delicate flutings along its length, which suggest that the bill is a very tactile and maneuverable organ, not just a simple horny probe.

The not-so-simple bill of a Broad-billed Sandpiper