BORDER INCIDENTS 2: SWIMMING SHOREBIRDS. THE
CASE OF THE SPOTTED REDSHANK
Most shorebirds wade, but do not swim readily, which is why they are called
waders in many languages, e.g. 'vadere' in Norwegian, leading to many puns
on my name. (In America the name wading birds seems to be used primarily
for herons and their ilk, and our waders become shorebirds, also an
excellent name, even though some of them never are seen on any shores). Of
course, as everywhere in biology, there are exceptions also to this rule:
phalaropes ('svømmesniper'=swimming snipes in Norwegian) are primarily
swimming birds and outside the nesting season even ocean birds, and Avocets
also swim often and readily.. But most other typical shorebirds generally
avoid swimming when they can, even though some like to wade into water to
their bellies. In years of observations of shorebirds one notches up a
few records of swimming shorebirds, but they almost always fall into one
of three categories: 1) There are young of the year involved. Especially
young Oystercatchers I have seen swim quite many times, adult hardly ever.
2) The birds are in immediate danger of a predator, and escape into the
water. I have seen this several times for Common Sandpipers, once also for
a Redshank; and 3) The birds land in water that is deeper than they
thought. This you probably all have witnessed now and then. A flock of e.g.
godwits circles over a pool, tries to land, but the water is deeper than
they thought, and they are forced to swim. Usually they fly up again at
once, and try elsewhere. Such mishaps I have noted for many shorebirds,
esp. those that habitually wade in quite deep water, like godwits,
dowitchers, Tringa snipes, and also Red Knots and Curlew Sandpipers. Red
Knots often associate with Bar-tailed Godwits, so tend to land among them,
but they have somewhat shorter legs and I have several times seen them
miscalculate.
But there is one shorebird that seems to be the exception to these rules,
and that is the Spotted Redshank Tringa erythropus, a bird that nests on
the marshy wetlands of the far north, and migrates almost all over the
world. These birds are beautifully sooty black all over in summer, with
the eponymous lighter spots on the back; they have a long bill and long
legs, but neither are much longer than e.g. in the Greenshank T. nebularia,
which often occurs in the same areas. The call, a brisk tu-WEET, is very
characteristic and often makes it possible to recognize the birds from
afar. But although quite characteristic, the Spotted Redshank is
nevertheless a 'typical Tringa', with the same build as the other members
of the genus: greenshanks, yellowlegs and Redshank for example.
Nevertheless, if you see a swimming shorebird, it is virtually always a
Spotted Redshank! I had noted this already in Holland before I moved to
Norway, and published a short note on the subject; as so often is the case,
it turned out that I was not the first one to notice this. During my work
at the Delta Institute in Yerseke, Holland, in 1963-65 we did monthly bird
counts in a number of salt and bracksih water habitats, and there I often
came across Spotted Redshanks in the water, not only swimming, but also a
few times diving, very quick dives, it is true, and even once or twice
up-ending like elegant small and nervy ducks.
When I moved to N.Norway a few years later, I kept a special eye on the
Spotted Redshanks on their nesting marshes in E. Finnmark. And yes, they
swam regularly also here, in the freshwater . Alarming Sotsniper (Sooty
Snipes, the Norwegian name) often landed not on the shore butdirectly in
the water and swam around for a while, before again repeating their
circling round me with complaining calls. I also watched one dive,
apparently chasing prey---maybe amphipods or shrimps---in brackish pools on
the saltmarshes of the Porsangerfjord.
And to my great surprise and joy the half dozen Spotted Redshanks that I
watched in some pools near Barathpur in November 1988 during a Sunbird trip
to India acted in just the same way, swimming around in the middle of the
pool, upending a few times, and even showing a few short dives! So this
seems definitely to be a characteristic of this entire species, and in this
respect they are clearly quite different from the other Tringa that I know
well. Redshanks, the species that I know best, almost never swim
voluntarily, nor do Wood and Green Sandpipers. Greenshanks often wade in
deep water, and may pursue small fish and shrimps in wild chases (they also
now and then bathe superenthousiastically), but nevertheless I never see
them swim for any amount of time. I have much less experience with
yellowlegs, but again I have never seen them swim for any amount of time.
Is this just because by now I 'see what I want to see', or do you agree
that there are real differences in behaviour between these closely related
species??
Wim Vader,
Tromsø Museum
9037
Tromsø, Norway
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