Since terns spend considerable amount of time on land, either standing or
sitting, the webbed feet play an important role in thermoregulation. Sand
bars, beaches and rock platforms can be huge heat traps for terns (and other
seabirds, shorebirds etc). Webbing between the toes is well-vascularised
and is a great way for a tern to lose excess body heat while on land.
Stephen Ambrose
Ryde NSW
-----Original Message-----
From:
On Behalf Of Allan
Richardson
Sent: Sunday, 8 December 2013 4:51 PM
To: david robertson
Cc:
Subject: Terns
Hi Dave,
That is one I've only recently resolved myself.
Here in Newcastle the apparently sedentary tern is the Crested Tern since we
see them all year round. Just now juveniles are arriving in the roosting
flock, from local breeding grounds I guess.
For the most part they roost on the highest rock-shelves behind the ocean
baths, but they do also like to stand on the sand up a little further on the
Nobby's beach spit.
What I find very interesting is that they also like to sit out on the water,
sometimes in groups of 20 or 30, even under choppy conditions.
This is on the open ocean, not is closed estuarine waters.
It seems so unusual since they sit very low in the water and it doesn't look
as if their body plan is suited to sitting on the water.
They seem to loaf there as other seabirds do and they are at times observed
bathing out on deep water.
There are shallow pools available to them, but for some reason under certain
circumstances they prefer to sit on open water about 200 metres off the rock
shelf.
On a related matter I have also seen shorebirds sitting on the water and
duck-diving, although the only instance I've seen this occur was to evade
predators. I've seen a Bar-tailed Godwit in quite deep water (over 4 metres)
go to water to evade a pair of Peregrines and a Grey-tailed Tattler go to
water in the surf to evade a Brahminy Kite.
Both birds duck-dived and remained submerged to avoid the attacks of these
birds, which seems out beyond what might be considered their normal
behavioural comfort zone.
Happy observations,
Allan Richardson
Morisset NSW
On 08/12/2013, at 3:14 PM, david robertson wrote:
> Terns have perfectly good webbed feet, as good as gulls to which they
> are closely related. They spend much of their time over water but I
> have never seen a tern on water. Has anyone else?
>
> David Robertson
>
> Adelaide
>
>
>
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