Mar

15

2008

Report on the deployment of satellite tags on Bar-tailed Godwits Limosa lapponica menzbieri at Roebuck Bay, NW Australia (Feb 18-23, 2008)

Introduction

The journey of Bar-tailed Godwit ‘E7’. Image: © 2007 USGS Alaska Science Centre.

As one aspect of the Pacific Shorebird Migration Project during February 2007, in New Zealand, 16 Bar-tailed Godwits (Limosa lapponica baueri) were implanted with satellite transmitters (PTTs) to gather data on their northward migration. This study went better than could have been hoped for with the batteries lasting, not only until the birds reached their breeding grounds in Alaska, but all through the southward migration. This wonderful result proved once and for all that the Alaskan breeding Bar-tailed Godwit undertakes the longest single non-stop migration in the avian world. This was best illustrated by the now famous ‘E7’ as she covered a 29,000 km round trip from Miranda Shorebird Centre, Firth of Thames on the North Island of New Zealand to staging sites in the Yellow Sea and on to breeding areas in western Alaska before the epic journey back across the Pacific Ocean.

After the success of the 2007 work, consultations began between Nils Warnock of PRBO Conservation Science (PRBO), Bob Gill and Lee Tibbitts of the United States Geological Survey Alaska Science Centre (USGS), Clive Minton of the Australasian Wader Studies Group (AWSG), Theunis Piersma of the Netherlands Institute for Sea Research (NIOZ) and Chris Hassell of the Global Flyway Network (GFN) to extend this work to the menzbieri sub-species that spends the non-breeding season in north-west Australia and breeds in the Yakutia region of Eastern Siberia. With the continued generous funding from the David and Lucile Packard Foundation the talk became action and a team of researchers gathered at the Broome Bird Observatory (BBO) to undertake the work between February 18 and 23 2008.

Field work

A satellite-tagged Bar-tailed Godwit ‘A7’ in the hand. Image: © 2008 Adrian Boyle.

The birds to be implanted with PTTs were captured by cannon net in 4 catches, one of which yielded no godwits. The weather during February is very hot and humid with regular rain. We were lucky in that catching was not restricted too much by heavy rain. The first catch was a regular catch with the net set just above high tide and with limited twinkling we caught 116 birds. Seven Bar-tailed Godwits had surgery, performed with great expertise by veterinarians Dan Mulcahy of USGS and Brett Gartrell of Massey University, New Zealand. All birds were successfully released 2-3 hours after surgery. For this catch we had a TV crew with us filming for the ABC’s Stateline programme. They got some excellent footage and interviews; the segment went to air on the last night of our field work and was watched by us all with great interest.

The second day’s catch was less successful with repeated bird of prey disturbances over the catching area. We only caught 3 birds and none were Bar-tailed Godwits.

The third day’s catch was a tricky affair with very heavy overnight rain persisting in to the morning and delaying the setting of the net. Eventually we went out with the whole team ready to set a net and catch promptly. We set the net well below high tide and with twinkling, decoys, luck (and no little skill!) we made a catch of 12 birds. They were many more close to the net but as I waited for them to walk in to the catching area heavy rain started to fall so I took what was available. I had expected to catch about 30 birds but the net and its sand covering were very wet and the net went slowly. Ten of the total were Bar-tailed Godwits and five underwent successful implant surgery. The remaining birds were transported back to BBO and processed in the Shade House out of the inclement weather. All birds flew well on release.

We had only planned for 3 catching days due to tides and tight travel arrangements for the overseas researchers, however we had 3 PTTs left and so some hasty rearranging of flights saw us out on the northern shores of Roebuck Bay for a fourth attempt. Once again we set the net well blow high tide, some 30 metres, as it was a high tide of 8.63 metres and on such tides the birds do not stay on the beaches but roost at inaccessible locations in and beyond the mangroves.

We started twinkling very early on had a possible catch soon afterwards but within seconds of firing all the birds flew. After some more skilled work from Maurice and Adrian we once again had birds close to the net and eventually they were catchable as the tide pushed them close enough. I fired and a good catch of 97 was made. Extraction and getting birds in to cages was hectic, with only a small team and due to the fast moving spring tide, but was accomplished successfully. The final three PTTs were implanted in birds and all went strongly on release.

There were some old birds among the re-traps with Great Knots at 15, 14 and 11+ (this bird is now individually colour-banded). We also now have Bar-tailed Godwits at 18+, 14+ and 12+ colour-banded and others at 18+ and 15+ with engraved leg flags from this latest field work.

Two of the birds carrying PTTs were retraps and are 13 and 5+ years of age as they set off with their precious cargo.

As of March 12 2008 all 15 PTTs are communicating effectively with the ARGOS satellites and providing data about the birds’ whereabouts in Roebuck Bay. During regular colour-band re-sighting field work 7 of the birds have been seen in the field at roost sites looking strong and healthy. In addition to the thin aerial protruding from their feathers they can be identified by their large black flags engraved through to white with a single letter and a single digit.

A satellite flagged Bar-tailed Godwit in a roost on Roebuck Bay. Note the aerial extending over the tail and the black flag with white engraving. Image: © 2008 Jan van de Kam.

The Future

In mid-March 2008 the PTTs will automatically switch on their regular reporting schedule of 6 hours on and 36 hours off. This should allow the batteries to last at least until the birds arrive on their Arctic breeding grounds. Any additional data received after mid-June (i.e. after approximately 400 hours of transmission time) will be a bonus. You will be able to follow the migrations of the Roebuck Bay Bar-tailed Godwits by visiting the USGS Migration page.

Acknowledgements

  • Projects such as this take an enormous amount of money and effort, not just in the field work stage but during all the meticulous planning. Please bear with me while I thank the many people involved:
  • The considerable financial contributions from David and Lucile Packard Foundation, Point Reyes Bird Observatory Conservation Science, United States Geological Survey Alaska Science Centre, US Department of Interior and are gratefully acknowledged.
  • Microwave Telemetry Inc is thanked for the development and manufacturing of the PTTs used in this study.
  • To Vogelbescherming-Nederland (BirdLife Netherlands), thanks for funding my full-time position.
  • The team in the field did a great job, having my Broome team with me fills me with confidence so thanks to Adrian Boyle, Maurice O’Connor, Helen Macarthur, Andrea Spencer, Yindi Newman and Jan Lewis. Also Mavis Russell, Petra de Goeij, Grant Pearson and Theunis Piersma (all honorary Broome team members).
  • Bob Gill, Nils Warnock, Lee Tibbitts, Colleen Handel for field work and being instrumental in getting the project going here in Broome.
  • To the highly skilled Vets Dan Mulcahy and Brett Gartrell. To John Curran for veterinary assistance and vital support with medication supplies.
  • To Andrea Spencer, Maurice O’Connor and Helen Macarthur for wonderful food and plenty of it!
  • The BBO wardens Pete Collins and Holly Sitters for hosting us and for field work.
  • To Annie Tibbitts for field work.
  • To Graeme Hamilton, Alison Russell-French and Rob Davis of Birds Australia for field work.
  • To Jan Van de Kam for images of all the birds.
  • To the AWSG committee for support of this initiative.
  • And last but not least to Clive Minton for continuing his unfailing support of me over the past 12 years.

Previous page »