Mutterings from the Marsh
Nearly nine months since the release date on January 22, and things are looking good for the first trial cohort of 20 pateke at Habitat te Henga.
Although rarely seen, their radio transmitters give the show away and let us know they have tended to take up residence in separate parts of the wetland. Many are clustered within a few hundred metres of the release site, while others have shunned their companions and are contentedly at the extremes of the wetland, west or east.
Required by the Pateke Recovery group to monitor the birds intensively for the fist six months, but only at monthly intervals beyond, we have been able to have volunteers maintain a weekly survey. With spring upon us and with certain pairs sticking close to each other we hope the more frequent monitoring will give us an indication if nesting is occurring.
Another more sombre reason though is that if a mortality signal is generated, we might be aware sooner and be able to recover a body to possibly determine cause of death. Three times we have had the mortality tone, and two carcasses were found while in the third case the transmitter was accurately tracked to almost 2-metre deep water. Was this a death or a case of harness failure? With that possibility and with an analysis of one carcass that showed no signs of predation but rather a tarsus fracture indicating a probable duck vs. vehicle incident, we have been fairly pleased with our predator control measures.
With no mortality tones in almost five months the population of 16 remaining birds seems nicely stable. But hang on you say, 16 plus three is 19 –what about the 20th? Well you might ask, as pateke channel 54 disappeared after five days and its signal could not be detected near or far at any of three local water reservoirs or along the extensive west coast beaches. Until it returned after 154 days! The prodigal’s return was welcomed but she obviously had other ideas and went again after a couple of weeks.
Maintaining predator control has been a large group of volunteers who check traps- some on their own properties, others checking traps on private or public land. Almost half of the traps though, are tended by our contractor who walks two 12 -14 km trap lines on a regular two weekly schedule. This large number of traps has allowed us to conduct an experiment which is ongoing.Alternate traps are baited with salted rabbit meat or a commercial dried rabbit product. The Statistics Department of Auckland University is analysing the results and by next year will be able to tell us if one is more efficient a lure than the other.
A contentious topic recently, but one I’ve been promoting is the use of UAV not for the casual model aircraft enthusiast, but as a genuine conservation tool. Chancing upon a local UAV manufacturer I was able to get him to look into using a UAV [drone] as an aerial radio receiver.
Drones with cameras used for conservation purposes are commonplace but the use of a drone to be able to track multiple radio frequencies could be a first and for a secretive species such as pateke [or kiwi] might greatly enhance monitoring. Test flights have taken place and for an idea of what the UAV looks like, a short video is on the facebook.com/habitattehenga site.
Other activities include a recent extensive survey of fernbird at three sites comparing the Forest & Bird reserve where predator control has been maintained for 15 years to two new sites only trapped over the past 18 months. This will give baseline date to use when we are able to add rodent control to some of the new sites. Spotless crake were to come in for a similar survey using sound playback in early October.
Meanwhile bittern are being seen more and more frequently. Nice to think it is due to our pest management, but it’s as likely to be due to more observations by interested persons. As with most conservation though, the hardest task is fundraising and a second translocation next year is dependant on successful applications. I’ll tell you how that went in a future update.