Hello Birding-Ausers,
In the 'Outdoors' supplement to the Friday 3rd Nov 2000 edition of the Brisbane
daily newspaper, "The Courier -Mail", there was a welcome and timely article on
wader-watching in the Wynnum-Manly area of South East Queensland, Australia.
Hopefully, articles like this will help people to realize there is more to life
around places like Moreton Bay than jet-skis and canal developments.
However, there was a couple of statements in the article that I found
'interesting'.
Statement 1/ "The main feature which distinguishes waders from water birds and
sea birds
is their typical long legs, which are essential for any species wading through
shallow water in search of food".
This seems to me to be somewhat of an over generalisation.
I would have thought that the main feature distinguishing waders (or perhaps a
better term is 'shorebirds') is their preference of habitat.
A number of water bird species have legs much longer (even in proportion to
overall body size) than the waders, eg, herons, storks, ibis, egrets.
Also, many water birds have short legs (ducks) but still obtain most of their
food in
the water, shallow or deep, without the action of 'wading'.
Some seabirds, such as gulls, have legs proportionally as long as the legs of
many of the waders.
Some waders such as Ruddy Turnstone have relatively short legs.
A number of 'other' species such as pitta, lyrebird, magpie-lark are also
relatively long-legged but are not waders.
Many waders obtain their food without entering the water except 'accidentally'
at the very edge
of the 'flow' where the sand or mud has been softened.
For example, Brett Lane in Shorebirds of Australia, 1987, states that the
Red-necked Stint
feeds mostly on wet and drying mud above the edge of the water.
The Red-necked Stint is a wader with rather short legs.
The same Author in the same publication says that the Little Curlew, a wader
with relatively long legs, feeds in dry grasslands.
Also, he seems to say that the Eastern Curlew and Whimbrel both obtain their
food on intertidal mudflats suggesting, in my mind, that they don't take
advantage of their long legs to feed in the water.
I have certainly observed Godwits feeding in shallow water, so their long legs
may be an advantage in their case.
Other wader species do feed in shallow water but I don't believe that a typical
feature of waders is long legs.
I believe that most seabirds have short legs because they spend little time
actually on land and only need legs to act as shock absorbers when they do land
to roost, rest and nest.
Statement 2/ "While some waders, such as the dotterels and ruddy turnstones,
have short
beaks for extracting prey near the shoreline, other birds, such as the eastern
curlew and whimbrels, have long, curved beaks to forage in deeper water".
Surely the shape and size of the bill is more to do with the type of food taken
and the distance under the mud or sand the food is.
It is my understanding that most of the food waders utilise is either on the
surface of or under mud, sand or rocks.
Most waders feed above the waterline irrespective of the length of their bill.
Eastern Curlew and Whimbrel feed on intertidal mudflats out of the water (ibid).
They use the length and shape of their bill to obtain food unavailable to
shorter-billed
waders.
Godwits and Curlew Sandpipers do obtain some of their food while wading in
shallow
water (ibid).
Godwits have been observed to immerse their head completely under the waterwhile
feeding.
Surely this is because they have plunged their bills deep into the sand/mud
under the water.
They are probably feeding there because few other birds do and the water has
made the sand/mud soft.
However, their long bill is still being used to obtain food 'under-ground'
rather than food that is in the water or on the surface of the 'ground' under
the water.
The short, sharp bill of the Ruddy Turnstone would seem to be ideal for turning
stones and predating Sooty Tern eggs.
Are there any comments on my assertions?
Bob Inglis
Woody point SEQld, Australia.
27 deg 15min S; 153 deg 5 min E
E-mail:
WWW: http://www.powerup.com.au/~inglisrc
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