Hi Kurtis,
I've often wondered about this. I'm not a biologist so I am only offering my
observations and guesses.
I've seen the gulls at Homebush Bay do exactly the same thing. Sometimes just
after sunset and only when it is very still and hot they will fly high above
Powells Creek (above where they would normally roost on the wrecks and in the
refuge) and fly around in a swirling mass of gulls, some of them making tight
turns. It certainly looks as if they are catching flying insects and the fact
that they only do it on still and hot nights would support this assumption.
The difference with the harbour bridge is that here they only do it on
occasional nights and the episode does not last that long. There are no lights
in the immediate vicinity as there are no tall structures like the bridge.
There is Rhodes shopping centre and the Liberty Grove buildings with Rhodes
giving off a lot of light but the gulls' activities are not centred around
these; they are over the creek. My guess is that here they are feeding on a
mass insect emergence where the insects take to the sky to mate.
I think gulls are certainly adept at catching flying insects and the lights of
the bridge would provide a magnet for them on a regular basis. As gulls are
opportunists, they will keep an eye on what other gulls are up to. Aside from
discarded chips & burgers, I've seen a similar frenzy of feeding activity on
king tides when the high water washes leaf debris down the creek. The gulls
congregate together in midstream to pick at the leaves for castaway insects.
Cheers,
Jono
---- Kurtis Lindsay <> wrote:
> Hi all,
>
>
>
> For many years I have noticed large flocks (~100) of Silver Gulls flying
> high over the Sydney Harbour bridge at night.
>
> The birds seem to fly in loose flocks, and fly around in circles.
>
>
>
> I have always wondered about what might be the cause for this behaviour.
> Here are some of my theories:
>
>
>
> 1. The gulls are hunting insects attracted by the lights on the wing -
> has anyone seen gulls catch an insect on the wing before? Would there be
> enough insects up there to sustain such a large flock for such an extended
> period of time? If so is it the migratory Bogong moth they're attracted to?
>
>
>
> 2. The gulls are courting/mating - so loaded up with hormones the
> gulls continue courtship through the night, in the only place lit-up enough
> to do so ,under the bright lights of the bridge.
>
> At times birds are seen flying close to each other but there
> doesn't appear to be any obvious courtship. What does Silver Gull courtship
> involve?
>
>
>
> 3. The gulls are dazed and confused by the bright lights, and continue
> to fly around in circles. If this is so, why aren't there more dead/stressed
> seagulls found on the harbour bridge in the mornings?
>
>
>
> 4. The gulls choose to stay awake in a lit-up area as a predator
> avoidance technique, the bridge providing a safe haven and a clear flight
> path for a continuous safe flight throughout the night.
>
>
>
> Can anyone else shed light on this bizarre phenomenon?
>
>
>
> Kurtis
>
>
>
> ===============================
> www.birding-aus.org
> birding-aus.blogspot.com
>
> To unsubscribe from this mailing list,
> send the message:
> unsubscribe
> (in the body of the message, with no Subject line)
> to:
> ===============================
===============================
www.birding-aus.org
birding-aus.blogspot.com
To unsubscribe from this mailing list,
send the message:
unsubscribe
(in the body of the message, with no Subject line)
to:
===============================
|
