Migratory wader monitoring
One of the key objectives of the Victorian Wader Study Group is to gather comprehensive information on waders in Victoria to contribute to flyway wide conservation strategies in addition to being a source of information and education of the general community.
The core activities of the VWSG migratory wader monitoring are focused on collecting data for population dynamics (age ratios and survival analysis) for target species. This is complemented by the use of geolocators for long-term monitoring, e.g. Ruddy Turnstone.
The key activities of the VWSG are:
- Long-term monitoring of percentage juveniles in catches
- Survival analyses
- Light-level geolocator studies
- Satellite transmitter studies
- Biometrics and moult
- The Latham’s Snipe Project
Much VWSG effort goes into catching annual samples of several species to assess the percentage of juveniles in a population. There is good reason to consider these age ratios to be directly related to annual breeding success. It is a unique dataset; age ratios have not been monitored in such a systematic way, for such a long time, in any other shorebird site in the world.
Seven species are the primary focus for catching to monitor annual percentage juvenile trends:
- Red-necked Stint
- Curlew Sandpiper
- Sharp-tailed Sandpiper
- Ruddy Turnstone
- Bar-tailed Godwit
- Red Knot
Survival analysis tells the probability of a bird being alive from one year to the next. Survival can be assessed at different age classes, but the VWSG is primarily seeking to understand adult survival. Survival estimates rely on first capturing and marking individual birds, followed by both targeted recapture efforts and observation-based resighting efforts (i.e. searching for marked birds in the field).
The drivers behind geolocators includes understanding migration routes, stopovers, breeding sites and success and disease monitoring. The results have been exciting, valuable and have both confirmed knowledge gleaned from flag sightings and recoveries, plus added much additional, sometimes contrasting knowledge.
The geolocator program commenced in Victoria in 2009 and has so far contributed an enormous amount of information on the migratory behaviour of Ruddy Turnstones . Over time, the turnstone geolocator programs has evolved into a longitudinal study of the species at King Island. This has provided one of the only opportunities in Australia to monitor changes in timing or tracks/stopovers and breeding characteristics as a result of climate change and habitat change.
In 2016 VWSG also deployed 60, 0.3g geolocators on Red-necked Stint, our most abundant species. While successfully retrieving 14 of these geolocators, the loggers did not allow assessing the birds’ breeding locations; they “disappeared” in the continuous daylight above the Arctic circle. With availability of improved loggers in 2018 we undertook an ambitious program to study and compare the migrations of Red-necked Stint and Curlew Sandpiper that regularly utilised the tidal shoreline at Yallock Creek on Western Port. Both species have greatly overlapping ecologies, yet highly contrasting population trajectories.
Satellite transmitter studies
Satellite transmitters are an exciting research tool, and enable discovery of the migration routes of shorebirds very directly, with no biases caused by distribution of active birdwatchers, no need to recapture birds, or to make large catches. However, because of the substantial costs of transmitters, the VWSG has tended to be involved with substantial transmitter studies in partnership with funded research projects (usually university research). The VWSG also contributes to wader tracking projects with the AWSG.
Biometrics and moult
There is a huge bank of data on the biometrics and moult of a wide range of species, much of which has been published in a descriptive manner and some which has been subject to more quantitative analyses. Analysis of biometric data can inform on whether there have been changes in phenology or physical changes over time that may match environmental changes. This has recently been demonstrated by Marcel Klaassen with an analysis of Ruddy Turnstone data.
The key biometric measurements that are recorded are head-bill length, bill length, wing length, weight, primary moult and percent breeding plumage.
The Latham’s Snipe Project
The VWSG supports and hosts the Latham’s Snipe Project, which is conducted out of Federation University by Birgita Hansen. This project is the only one that uses mist-netting for regular catching of snipe, and is conducted primarily in Canberra at the Jerrabomberra wetlands (although the project started in Port Fairy). It aims to improve our knowledge of the ecology and migration of the species. More information can be found on the Latham’s Snipe Project website.