Flying under the radar
At the end of the opening morning of Duck Season in South Australia, hunters on the Cortina lakes were asked for their assessment of Blue-winged shoveler numbers as part of an informal research project. “Enough to have at least a couple in the bag,” one h
This isn’t science by any stretch of the imagination, but in the absence of any attempt to produce a more rigorous assessment, it is at least something. Almost universally, the assessment of hunters, who have a keen eye and are frequently sharing the same habitat as the shoveler, is contrary to the aerial surveys. This century, the Eastern Australia Waterbird Survey has recorded very limited numbers of shoveler, yet hunters see them all the time. The survey has recorded significant numbers in the past, including more than 20 000 following the floods of the early 1980s and similar spikes following every drought breaking flood event since, but in between the observed numbers flat line.
Understandably, hunters question whether the observed numbers of shovelers in the annual aerial surveys indicate low abundance, or just the difficulty in reliably counting them from an aircraft.
The only way to answer that question is to apply science, something Field & Game Australia is pursuing.
Our scientific knowledge of Australian ducks in general is poor and very little has been done to build on the landmark work of Harold James (Harry) Frith in the middle of last century.
Frith received a copy of the first edition of Cayley’s What Bird is That? for his tenth birthday. He later dedicated his major work, Waterfowl in Australia, “to my father who taught me about birds”.
Frith’s pioneering studies on the breeding, feeding and movement of Australian ducks are considered his major contribution to ecology. In a series of research papers titled The
Ecology of Wild Ducks in NSW, Frith detailed the response of the main wild duck species (Pacific black duck, Grey teal, and Wood
duck) to rainfall events.
A large-scale banding program revealed the apparent random scattering of wild ducks from wetlands where water and/or food was becoming scarce was not the full story.
In 1957, Grey teal banded at Gum Creek in NSW were trapped on Humpty Doo station in the Northern Territory, showing the vast distance they would travel to find suitable feeding grounds.
Frith recorded that the indigenous population was unable to recognise it, thus supporting the author’s impression the Grey teal very rarely visits that region.
In 1953, Frith began banding ducks and over the decade the shifts from flood to drought across the Murray-darling area allowed him to observe the marked effect on duck behaviour and populations.
In 1955 during a minor flood down the Lachlan River, Frith hunted several ducks and found their testes were sexually mature. He then drove 160 km to get ahead of the floodwaters and hunted several more ducks. Their testes were sexually inactive.
It was for Frith dramatic confirmation of what he had begun to suspect: that breeding was linked to water levels.
Consecutive flood years in 1956 and 1957 provided the natural laboratory to evidence how ducks adapted to their unpredictable environment to ensure the continuation of their species.
Frith had a knack of making his own luck.
In 1957, while investigating the impact of Magpie geese on crops around Darwin, Frith witnessed Grey teal began arriving in their thousands. He phoned an urgent request for traps and banded 5000 birds.
Over the years, the bands recovered from those birds revealed an extraordinary pattern of explosive dispersal in times of drought.
Later work showed that in times of drought Grey teal might not breed for several years, yet within only 10 days of an increase in water level they could become sexually active and lay eggs.
Decades before the controversial Murray-darling Basin Plan was struck, Harry Frith foreshadowed the need for action.
“When hydroelectric and irrigation schemes finally control all floods, the Grey teal and many other waterfowl will have few places left to breed,” he said. “To prevent this, the replenishment of billabongs along inland rivers must be ensured and the coastal swamp refuges protected. Most importantly, the states and the Federal Government must agree on a common resource policy and involve biologists in the planning of water conservation.”
Frith’s seminal works greatly enhanced our understanding of wild ducks, but Bluewinged shoveler were not banded as part of his work during the 1950s.
The national bird banding database records only 23 banded shovelers, the earliest in February, 1956 and the last in March, 2014.
Only three bands have been recovered, including a bird banded in December, 1959 at Joanna, SA that was found dead 10.5 years later near Wollangambe, NSW.
Harvest data is available but in isolation, it adds little to our knowledge of distribution and migration movements.
Frith’s shoveler observations in the 1950s were limited to nesting preferences.
Shoveler have a very wide range: in eastern Australia it can be found from as far south as Tasmania to Cairns in the north, but it is also found in New Zealand where it is known as the Australasian shoveler.
Across the ditch, significantly more research has been done into movement and morbidity of shoveler, but it does not substitute for knowledge gained in the specific Australian context.
There is an opportunity to broaden our understanding of our least understood Wood duck species.
The International Cooperation for Animal Research Using Space (ICARUS) Initiative is opening new avenues to observe migratory movements of small animals and birds through a satellite system.
Described as the “Internet of animals” the project allows researchers to fit a tiny sensor-laden tag to small creatures like ducks. The tags have a GPS receiver, 3D accelerometer, and temperature, humidity, pressure, altitude, and heart rate sensors. The tags are also equipped with solar panels and rechargeable batteries.
The tags store data and send in batches to a computer aboard the International Space Station, which processes the information and beams it down to earth. The smallest tag weighs 2.5 g. It is a long way from the image of Harry Frith climbing trees in swamps to observe breeding behaviour. Frith’s work remains important, but it is time to build on our knowledge of our unique duck species, starting with the Blue-winged shoveler.
Australasian Shoveler — Anas rhynchotis. Photo; Judy Gallagher