Chapter 9 – Migratory shorebirds and the Australian Painted Snipe

ABBOT POINT CUMULATIVE IMPACT ASSESSMENT REPORT
and aquatic invertebrates. During the wet season there tends to be a reversible movement of fresh and
brackish waters westwards from the wetland and into Curlewis Bay.
During the dry season, however, tidal movements tend to dominate the system (GHD 2009). With very
limited freshwater inflow, much of the wetland dries and loses vegetative cover. Under such dry
conditions, the wetted expanse of the wetlands can contract to the area known as Lake Caley, in the
south eastern part of the wetland. Lake Caley provides one of the only semi-permanent non-tidal
waterbodies in the area.
WETLAND VARIABILITY OVER TIME
A critical point to understand about the wetland, is that it is a highly dynamic and seasonal system. The
water levels can vary substantially both between years and within the same year.
Abbot Point is classified as tropical savannah. Aside from it being subject to cyclones, it is also subject
to significant rainfall variability. Historical records range from approximately 2,015 mm in 1950 to
215 mm in 1915 (RGSQ, 2012). In periods of drought, food resources for migratory shorebirds and the
Australian Painted Snipe are likely to be depleted in the wetland and the birds would need to rely on
alternative wetland habitats.
Discussions with NQBP staff provided some anecdotal history of the wetland over the last twelve years.
During that time, the wetland has undergone long periods of drought, regular seasonal drying, and more
recently higher water levels. Key periods include:
• 2000 to 2007: The area was mostly in drought. During this time the wetland held some water in
summer (possibly over a three month period) and was almost entirely dry for nine months of the
year.
• 2008 to 2011: Conditions in the wetland were at higher water levels reflecting greater rainfall in the
region with the wetland retaining water for approximately nine months of the year.
• 2012: Extremely good conditions in the wetland where water levels are still very high at the time of
writing this report, which is normally when the wetland has very limited water remaining.
To illustrate the variability of the wetland over time, three aerial images are provided that show the area
of the wetland closest to the existing T1 rail loop (the wetland area was mapped as closed marsh
habitat by BAAM in summer of 2012). The images are for illustrative purposes only and do not attempt
to provide coverage across the whole of the wetland or at regularly intervals over the last decade. The
images are:
• 9 th August 2001 (Figure 9-5).
• 6 th January 2005 (Figure 9-6).
• 15 th February 2012 (Figure 9-7).
It can be seen that in 2001 and 2005 (at the time the photos were taken) the wetland was almost
entirely dry in those locations. This compares to 2012, where water levels were high.
It is likely that the state of the wetland over the most recent twelve months represents optimal condition
in terms of water levels and consequently potential habitat for shorebirds and the Australian Painted
Snipe. This is reflected in the high numbers of birds recorded in the BAAM (2012) surveys (see
Section 9.3.3).
ECO LOGICAL AUSTRALIA & OPEN LINES 9 - 14