No wild-goose chase
A ground-breaking Fish & Game study is helping researchers shed light on the nesting habits of mallard ducks, which should have spinoffs for other species of waterfowl. Jamie Troughton reports.
A thin breeze with echoes of snow slides across Te Awamutu's Lake Mangakaware, rustling raupo and rippling the surface of the small rural waterway. Though frost in surrounding paddocks has only just melted, David Klee is sweating in a short-sleeved bush shirt, squinting into the low sun on a stunning Waikato winter morning.
The Fish & Game officer leans back into his work. He glides a borrowed dinghy across the lake surface as he rows towards a noisy chattering of swans, geese and duck.
In the stern of the small boat, field technician Julia Unfried navigates using a hand-held aerial and directional radio receiver and, as they get closer, geese suddenly erupt off the water and fly off amid an indignant cacophony.
Seconds later, a flight of mallard ducks take off from the middle of the lake.
Unfried tracks them intently with the aerial, nodding towards the front pair; a hen and drake. Duck number 474, the hen, has been identified and sighted. Klee gives a grin, satisfied by her willingness to fly that she hasn't started nesting yet, then pivots the dinghy around and heads back to shore.
In case the radio tracking isn't a dead giveaway, this ain't no wild goose-chase.
Klee and Canadian Jenn Sheppard, a PhD student at Auckland University, are spearheading a major Fish & Game study gathering vital data on New Zealand mallard nesting and breeding habits.
While mallards are this country's key game bird species, much about their breeding habits and how changes in their environment affect population are still unknown.
Having surgically implanted transmitters into 120 female mallards earlier this year, the scientists have been using radio technology to monitor them during the breeding season.
The study is expected to take between three and four years, with data used to develop population models and fine-tune management of the resident game-bird species.
Now they're nearly ready to move into the next phase - tagging nesting ducks to get a better idea of nest success and brood survival in two research sites, one in Waikato and the other in Southland.
"We know that climate plays a massive role when it comes to changes in population, especially with the amount of good-quality, seasonally-flooded wetland areas," Klee explains. "We've had four or five years of drought-like conditions and that's affected North Island populations, while changes in habitat also play a significant role."
He sweeps an arm across an undulating, lush-green Waikato pastureland deep in the throes of calving.
"We've got a pretty homogenous landscape these days and in the last 20 years, it's probably had less to do with large wetland drainage and more to do with habitat degradation. Current land prices mean farmers are trying to get as much production out of their land as possible and I understand that completely but it also means we've lost a lot of nesting cover."
Initial studies last year showed that both nest success and brood survival was low, with predators - especially cats and hawks - playing a role and large numbers of ducks forced into ‘linear habitats,' like drain banks.
All of which is a big change for self-confessed "bird nerd" Sheppard, who wrote her master's thesis on mallard habitat selection trade-offs while studying the vast Prairie Pothole Region in North America.
Covering parts of three Canadian provinces and five states of the USA, the snowed Pothole wetlands are five times the size of the North Island and host more than 60 percent of the continent's breeding ducks. "In North America, they have more obvious nest predators," Sheppard, who arrived from the University of Saskatchewan on a Fish & Game scholarship in March, explains. "One of the biggest drivers of nest and duckling failure is mink, raccoon and skunk, which you don't have here, but you have different predators and we're not entirely sure how they affect the duck population.
"The ducks here also have a bit more relaxed type of life cycle - they don't have to migrate and they're not forced to nest the minute the snow's off the ground and have the ducklings able to fly by the time the next snow comes."
As well as Sheppard's intellectual experience, she's also brought with her a range of valuable contacts in the Canadian branch of Ducks Unlimited, a world-leader in wetlands and waterfowl conservation.
Husband Simon is also a more-than-capable field technician, while Sheppard is also studying under the supervision of Dr Todd Dennis (University of Auckland), Dr Todd Arnold (University of Minnesota) and Dr Courtney Amundson (Alaskan Wildlife Service).
Sheppard's master's study was only one of more than 100 published papers taken from a massive eight-year study of the Pothole region and Klee hopes, if enough data can be gathered, to stimulate similar interest in New Zealand mallards.
"Providing that we collect the data well and get as much as we possibly can at this stage, we can keep coming back and reanalysing aspects of this study in five or 10 years' time," Klee says.