On A Whimbrel & A Prayer #1
April 11, 2017
Five years ago, The Australasian Wader Studies Group (AWSG) began experimenting with the use of satellite transmitters for tracking the migration of shorebirds visiting north-west Australia.
In November 2013, five 5g satellite transmitters were deployed on Little Curlew in Roebuck Bay, Broome. A further three transmitters were put onto Little Curlew at 80 Mile Beach in February 2015. The target species was then switched to Grey Plover in February 2016, with five units again being deployed at Broome.
Some extremely useful new data has been generated on the migrations of both species, although the results have been mixed, with many transmitters ceasing to function when a bird was part way through migration.
It is exciting to track birds with satellite transmitters because up-to-date location data is received as the bird flies or rests during migration. This occurs either in real time or at a maximum of two days behind the recorded event. One disadvantage of this technology is that it it is difficult to determine the cause of technical or other failures because there is often no direct evidence for the cessation of transmissions apparent.
Such is the situation already for our satellite transmitters in 2017. Four of the five Whimbrel with 5g transmitters are still giving regular signals from the area where the birds were originally caught. Only one has disappeared, either because the bird was predated, or because the transmitter failed.
However, all five of the satellite transmitters deployed on Grey-tailed Tattler have already ceased sending transmissions! This is a disastrous outcome for an outlay of $25,000 on these new, super light-weight 2g units.
These units differ in a number of ways from the 5g units. In particular, the aerial doubles-up as the harness system to attach the transmitter to the bird via wing-loops and a neck-loop. The harnesses superficially appear very light-weight and potentially vulnerable to damage. The fact that this is probably the cause of the premature failures is supported by the fact that one of the Tattlers was sighted and photographed in the field at 80 Mile Beach on 7-8 April still carrying its transmitter but with part of the harness damaged and the aerial missing.
The first bird to be fitted with a satellite transmitter was LA the Whimbrel on 12 February at Eighty Mile Beach. Since the deployment of the transmitter, LA has spent all of its time near the area where it was captured and released 40km to 50km south of the Anna Plains Station entrance to Eighty Mile Beach (Figure 1.). LA is a 2nd year bird (born in the 2015 breeding season) so it will be interesting to see if it will migrate north this year.
Whimbrel KS and KU were captured on 24 February at West Quarry at Roebuck Bay. Unlike LA, these two birds have not spent much time around the catching site since they have been fitted with satellite transmitters. Most of the time they were at Dampier Creek at the western end of Roebuck Bay and occasionally visited Crab Creek, the salt marsh in the east and even beaches west of the Broome township (Figure 2.). Both KS and KU are mature birds born in or before the 2014 breeding season and as such, are expected to start migrating north in a few weeks time.
Later on at the end of March, the local team in Broome set up mist nets for two consecutive nights at the salt marsh just north and east of the Broome Bird Observatory and successfully captured two more Whimbrel – JX on 25 March and JZ on 26 March – which were fitted with the last two 5g transmitters.
Unfortunately, the transmission from JZ stopped the day after deployment. The cause of this could be either transmitter failure or predation in Roebuck Bay, which has a healthy population of birds of prey.
Similar to KS and KU, JX spent most of its time at the western end of Roebuck Bay near Dampier Creek and occassionally flew to Crab Creek and the salt marsh in the east (Figure 3.).
All five Grey-tailed Tattlers fitted with the 2g transmitters were caught and released at Eighty Mile Beach. The birds were captured at the section of beach 40km south of the Anna Plains Station entrance of the beach and released the following day.
HYC, HYV, HVD and HYP were released on the 14th of February. HYC lingered at the release site for three days and then signals indicated the bird flew inland, which was unusual for a Tattler (Figure 4.). The transmitter stopped working on the 25th of February, but then come back to send lower quality signals on 7 March. This pattern suggests the bird may have been predated and the transmitter carried to an inland location by the predator where the transmitter is still occasionally receiving enough solar energy to transmit a signal.
Since then, HYV, HVD and HYP moved southward along the beach as a group (Figure 5.). Seven days after they were released, they were back to where they were first caught 40km south of the Anna Plains Station entrance. HYV stayed at this spot until mid-March and then moved up the beach 15-20km from the Anna Plains Station entrance in late March.
Unfortunately, we lost the signal from HVD on 11 March, HYP on 9 March and HVD on 21 March. HVD was last sighted on 7-8 April, still carrying its transmitter, but with part of the harness damaged and all of the aerial missing.
Captured and released a day later, the fifth Tattler HVT behaved a bit different to the others. Upon releasing on 15 February, it first spent three days north of the 0km Anna Plain Station entrance, and then spent 3 days moving southward to where it was first caught at 40 km. HVT has been staying around that area since then until the last signal receive on 30 March (Figure 6.).
Regardless of the early failure of these transmitters on the Tattlers, it is still very interesting to see the high site fidelity of these individuals to certain section of 80 Mile Beach.
The AWSG would like to thanks Doris Graham for her generous donation to cover the purchase cost of five 5 gram satellite transmitters for Whimbrel.
These projects would not have been possible without the fieldwork efforts of the AWSG NWA 2017 Expedition members, and the local Broome volunteers – Adrian Boyle, Grace Maglio, Kerry Hadley, Chris Hassell, Jon Hall, Frank O’Connor and Jason Richardson.
KS photographed in Yilan County, Taiwan on 26 April 2017 (Photo by LIN Jer An) © 2017. Used with permission.
Little Curlew being fitted with a satellite transmitter by Robert Bush © 2016. Used with permission.
Gery Plover fitted with 5g satellite transmitter by Robert Bush © 2016. Used with permission.
Whimbrel being fitted with a 5g satellite tag by David Chang © 2017. Used with permission.
Whimbrel released with satellite transmitter on 80 Mile Beach by Prue Wright © 2017. Used with permission.
Grey-tailed Tattler released with satellite transmitter by Robert Bush © 2017. Used with permission.
All figures and tables prepared by Katherine Leung for the AWSG.