Disturbances to Urban Waterbirds

To: <>
Subject: Disturbances to Urban Waterbirds
From: "Jon " <>
Date: Mon, 26 Jan 2009 00:23:51 +1100
Hi Stephen,

We have been doing night surveys at the Waterbird Refuge (WBR) for SOPA for
the last two years monitoring shorebird movements in and out of the WBR to
record movements of godwits from Hen & Chicken Bay and sharp-tailed and
curlew sandpipers from Mason Park into SOP. These shorebirds have been using
WBR as a night-time roost for some time and appear to "favour" WBR over
roosts at Hen & Chicken Bay and occasionally Mason Park at night time. This
appears to be independent of tide times. This may be due to disturbance at
these sites or perhaps their having near-360 degree views of the horizon at
WBR where this is restricted at the other sites. You mentioned that the
birds probably feel safer at WBR than at other sites and I believe this to
be the case with the waders. However, we have noticed over the course of the
surveys that stilts in particular are particularly flighty at dusk and will
often call and sound alarms and congregate in tight clumps. I believe this
may be an anti-predator response, particularly a defensive measure against
peregrine falcon that is active at dusk, as they will become restless as it
is getting dark, tighten into a clump and then subsequently disperse to feed
again when it is completely dark. My assumption is that they have an
effective curfew between the time that they can no longer detect approaching
raptors and the time when raptors are no longer a danger. They will also act
in a similar manner to passing night-herons and even bats after it is dark.
We have never recorded stilts being harassed by passing aircraft although
they have been disturbed by cyclists with headlamps using the paths along
the edge of the WBR.


Jon Irvine

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