Different Bills-Same Location

Stuart Fraser

Alexandra Canal is not a hospitable location for wildlife, lined with industrial parks with wire fences and hemmed in in the south by Sydney Airport. Construction of the Alexandra Canal began in the 1890’s, draining a salt marsh to build the “Birmingham of Australia”. That did not work out with wool sheds being replaced by logistics depots.

The walking-bicycle track along its south-eastern bank has been an escape during the COVID19 lockdown. So it was surprising to see numerous wading bird species in a short span of the canal one Sunday afternoon in winter. Pairs of Black-winged Stilts, Royal Spoonbills, Australian White Ibises, Masked Lapwings and Silver Gulls were feeding along a 30 metre stretch. Little Black Cormorants and Pacific Black Ducks were also feeding in the canal. Two weeks later, 3 Black-winged Stilts flew overhead as I crossed a bridge over the canal in Alexandria.

As a developmental biologist (used to be called an embryologist), I am struck at how bill size and shape is so strikingly different between these species. Slight changes in development in the egg shape these different species resulting in curved, flat, spoon, sharp or gull bills-all living close together. When the water is low, the mud-covered bricks of the canal become a safe feeding ground in spite of all the plastic pollution and human activity around them.