Fish & Game launches satellite tracking to probe duck behavior
Media release from Auckland/Waikato Fish & Game
Fish & Game launches satellite tracking to probe duck behaviour
As a scientist, how do you snoop more effectively into the habits of the female mallard duck – and study how she nests and breeds, and how many young she manages to rear?
The answer, for Fish & Game’s experts delving into all these ‘population dynamics’ is to track them down and pinpoint their location more efficiently – in a first for New Zealand game bird studies – using a satellite-based system known as Argos.
Argos was developed by the French space agency in cooperation with U.S. space and oceanic agencies. It’s now used worldwide, a key component in many global bird and animal research programs.
Argos was first used to track albatrosses nearly 20 years ago, and the ‘spectacular’ results achieved made it a popular choice for ‘animal tracking purposes’ in following years. Since then researchers have used the Argos system over the decades to track everything from polar bears in Alaska and caribou in Canada, to storks in Asia.
Now Waikato-based Fish & Game officer David Klee has teamed up with Rotorua-based colleague, senior Fish & Game officer and long-time mallard researcher, Matthew Mc Dougall, to study mallard hens and their offspring using Argos in a $300,000 three-year project.
David Klee explains that he and his fellow researchers are in the process of trapping 40 mallard hens which are caught in baited ‘funnel traps’ – before being fitted with transmitters which are harnessed to their bodies.
The ducks are fitted with different combinations of transmitter; all have a VHF (very high frequency) unit but not all have the satellite transmitters. The satellite transmitters provide an initial fix on the bird’s position, then the VHF allows for its exact location to be pinpointed.
Mr Klee says the Argos system works by sending a signal once a day to the satellite as it passes over. It works on the so-called Doppler Effect, in simple terms measuring sound waves to work out the duck’s location.
“ As the satellite moves overhead, it picks up a signal from the duck and fixes its location based on the wavelength – whether its longer or shorter.
“We can dump this information straight onto a Google Earth map and then we can click on the map to see the duck’s position – latitude and longitude, and the date and time the bird was pinpointed.”
The satellite system even provides a score of how accurate the fix is, Mr Klee adds. “If it’s rated a three then the bird should be within 200 metres of the spot pinpointed.”
Pinpointing the bird’s location is really only the start of their investigations. “Then we have to get in the car and drive – try and track the bird to find out exactly where it is, whether it has paired up, whether it has mated…what exactly it’s doing. ”
A university student recruited to help with this stage, will head into the field armed with a hand-held receiver to locate the bird. Even if a transmitter-carrying duck dies, a ‘mortality switch’ is activated to inform the researchers. The units also have a ‘time since death’ feature which allows the tracking team to confirm to the hour, when death occurred.
Earlier tracking studies have shown that mallard ducks don’t move very far from the place they were banded, most less than 50km, so it’s unlikely the satellite study will show “large-scale migratory movements.” To date, only one bird has travelled any real distance, leaving its capture site south of Hamilton and flying to a farm north of Morrinsville.
So what then are the key aims of the study? Broadly, the Fish & Game officers are gathering vital data on mallard nesting and breeding habits; the study one of a number of mallard research initiatives.
“What we want to find out is when the birds are nesting, when their eggs were laid, how many hatched, and then be able to follow the offspring through to fledging (when they start flying).”
Mr Klee says that they’re trying to get a better understanding of ‘productivity’ – the number of birds that make it to this fledging stage.
“The ducks have got to pair up and mate, and nest, lay eggs that successfully hatch into birds that survive to fledging stage.”
So what then are the key factors that may be limiting the growth of mallard and grey duck populations? Studies in the United States for example, have identified high ‘nesting mortality’ but in the U.S. “there’s a whole guild of animals involved – badgers, eagles, snakes, you name it, that we don’t have.”
In New Zealand it’s known that nests are predated by mustelids predominantly – ferrets and stoats. “If we find nest survival is a problem, we can do things like provide nest boxes for mallards.”
We’re looking to see just how serious a problem nest predation really is, says Mr Klee , and whether certain types of vegetation can make it less of an issue – and what long term plantings might enhance the mallards’ habitat.
“We often receive anecdotal reports that pukeko, hawks, shags and eels are all responsible for taking ducklings. The long-term solution for trying to get hatchlings through this stage may be habitat manipulation, such as planting better cover species or intensive predator control.
“The study is very much management-focussed. The overriding aim is identify key life stages that are limiting the number of birds in the population. We need this information to better manage our stock and increase our maximum sustainable harvest over time.”
The study’s findings should allow them to focus on such “opportunities” for increasing productivity through changes that can be made to the ducks’ habitat.
Other questions they hope to answer in the study include: if large numbers of females don’t breed, known as ‘0 hens,’ what does that mean and how does their body condition influence breeding? Also, are there females double-nesting during the season?
Mr Klee hopes the Argos study will provide data that they haven’t been able to gather to date, to give them a “a better understanding of mallard productivity.” Years of research have been based on summer trapping and hunter surveys, techniques which are valuable in their own right but have their limitations.
Depending on the results obtained from the Argos study, Fish & Game staff hope to identify “opportunities to improve productivity in any given year through long term habitat manipulation and enhancement.”
That translates roughly into ‘if we can improve the living conditions for these ducks we’ll end up with lots more of them.’
Image Argos One : Fish & Game officers gently tighten the harness which holds the transmitters in place.
Argos 2 : Wired and ready…a female mallard duck showing the transmitter pack and aerial.
Argos 3: Auckland-Waikato Fish & Game Officer David Klee holds a mallard with its back-mounted transmitter pack.