Date: Tue May 19 18:19:26 1998
From: alvaro@sirius.com (Alvaro Jaramillo)
Subject: Bristle-thighed Curlew foraging behaviour.
To: mpatters@orednet.org


Mike,

 I sent the following to Calbirds-l today and I have begun getting some
interesting responses. I don't think anyone forwarded it to the OBOL or
Tweeters lists, if this is the case could you help me by forwarding this? I
would like to find out as much as I can regarding the foraging habits of
these wayward curlews.

Cheers,

Alvaro


At 02:47 PM 5/19/98 EDT, EnviroLaw wrote:

>Behavior:
>
>The bird associated with Whimbrels the entire time and foraged in a similar
>manner.  It seemed particularly fond of sand crabs, and was fairly aggressive
>with the Whimbrels.   The bird's posture was much different than the
>Whimbrels, as it stood less upright, though part of this impression was
>probably caused by the bird's shorter neck and legs.  The bird was silent.
>

I was also lucky enough to see the Marin Bristle-thighed Curlew yesterday
(Monday). I arrived at 1315 or so, right as the morning group was leaving.
In fact between 1515 and 1615 I was the only birder looking at the curlew.
I enjoy birding with others, but having the curlew all to myself was a
treat. In any case, I would like to comment on the foraging habits of this
bird. Like Jennifer noted the bird was fond of 'sand crabs', I don't know
the scientific name of these critters but while the common name is 'sand
crab' or 'mole crab' I am certain that these suckers are not at all closely
related to crabs. Does anyone know the Latin name for these things? What I
noticed was that this bird was really adept at hunting for 'mole crabs'. It
would rush out on an outgoing wave, probe quickly until it got one. It
would then grab the 'mole crab' and quickly run to dry sand or even throw
the thing up towards the dry sand, presumably to keep the prey from
burrowing into the wet sand. It would then run to the 'mole crab' and
vigorously peck at the thing, presumably to kill it, or slow its movements.
While pecking and whacking the crab the curlew often assumed a 'bent kneed'
(I know they are not knees..) posture so that the body and head were closer
to the ground making it look even more squat and sturdy than the nearby
Whibrels. While it was in the wet sand all it did was forage on 'mole
crabs' while the Whimbrels pecked food from the surface of the sand rather
than probing deep for crabs as the Bristle-thighed did. It sometimes only
took approximately 1.5 minutes to find a crab and process it. Very quickly
it would go back and get more, I don't think it ever took more than 3
minutes to find a crab while foraging at the surf edge. In addition, it was
very particular with regards to the parts of the crab that it ate. In the
scope I could see that in all cases it ate the bright red eggs under the
tail of the crab, leaving the body intact. I picked up some of the crabs it
had worked over and confirmed that this was the case, the body parts had
not been eaten, only the eggs. What was interesting is that during the time
I saw it foraging, all of the crabs it picked up had eggs, is this normal?
Are the crabs hermaphroditic? Anyone know why the ratio of crabs with eggs
(presumably females) was so high? Basically, in terms of putting this in
the context of Optimal Foraging Theory the handling time of extracting the
meat from the body is probably high enough that it is not worth dealing
with it, given that the time to find a new crab (with juicy and nutritious
eggs) is so minimal. The 20 or so Whimbrels never caught a 'mole crab', the
ones they foraged on were the ones that the Bristle-thighed Curlew had
captured, presumably cleaning up the bits left by the Bristle-thighed. When
it was on dry sand the Bristle-thighed Curlew picked at things similar to a
Whimbrel, but at least during my observation it was more likely to be
foraging at the surf edge than the Whimbrels.

Very little is known about the Bristle-thighed Curlew, it would be nice to
summarize some of our observations on these birds. What have others noticed
regarding the foraging habits of this or the birds farther north? I would
love to know on what they are foraging given the unatural situation they
find themselves in here on the Pacific Coast. I would be very glad to put
together a summary of everyone's Bristle-thighed Curlew foraging info if I
get any replies. Also, could someone help me by forwarding this to Tweeters
and OBOL. Thanks.

Had 3 species of curlew in the binoculars at one time, a first for me!

Cheers,

Al.


Alvaro Jaramillo                "It was almost a pity, to see the sun
Half Moon Bay,          shining constantly over so useless a country"
California                      Darwin, regarding the Atacama desert.

alvaro@sirius.com