Night calls

Valerie and Michael Fay prepare to distribute equipment to the listening team. Photo by Alyth Grant
Valerie and Michael Fay prepare to distribute equipment to the listening team. Photo by Alyth Grant
Prof Jean Fleming releasing a young tokoeka into the ecosanctuary in 2012. Photo by Neville Peat
Prof Jean Fleming releasing a young tokoeka into the ecosanctuary in 2012. Photo by Neville Peat

A team of volunteers has been monitoring kiwi calls at night at Orokonui Ecosanctuary to track their locations and the formation of pairs, writes Michael Fay.

 

The forecast is for a dry and windless night, and two hours before the meeting time the 40 volunteers of the listening team had received the go-ahead ... with the understated warning, ''Wrap up in your warmest clothes.''

It is just on sunset when the big team of listeners gather at the Visitor Centre to begin their evening's work of counting kiwi calls. It takes so many of us because the topography and tree cover of the Orokonui valley ensure even the loudest kiwi calls cannot be heard over any great distance.

The listeners are a mixed group; experienced people from last year's study and a new, younger set, mostly specially recruited postgraduate zoology students with sharp hearing.

We all gather round to be put into pairs and issued with our equipment - fluoro vest, record sheets, compass and bearing table - and to synchronise watches and cellphones, as an accurate record of the time of calls is crucial.

The first pair of listeners immediately set off on the trek to their allotted post near the tallest tree: there is only just time to get there and get set up before it is time to start listening at precisely 45 minutes after sunset. It is generally quiet there, but there are kiwi around, and if we are lucky one of the birds might decide to inspect this intrusion, and scuffle around the listeners' boots for a few minutes.

The remaining listeners are dispersing to 11 other listening posts: one each on the northern and southern boundaries (these are the people with clipboards and head torches, huddled in several layers of clothing and seated on deck chairs that puzzle some passing drivers), three more inside the sanctuary, and three each on the western and eastern boundaries.

On a clear and mild night it can be very pleasant on the slopes of Mopanui. There are the stars that will rotate through 30deg during our two hours of listening, a satellite or two, about 10pm the train rumbling under the mountain, house lights turning off after 10.30, a donkey braying, frogs piping and even the squealing croak of a tuatara.

On other nights, when there is a cloying damp fog and the temperature is heading towards zero, two hours can seem a long, long time, even when broken by the mournful hoots of the morepork.

Staying alert is a challenge, as on average each listening post will hear only three or four kiwi calls, up to seven in the south and quite possibly none at all at some of the northern posts. But when it does happen we are busy: start counting the number of chirrups, set bearing needle to the direction of call and estimate its distance from you, identify sex of bird and finally note the time when the call ceases and all the other information too.

When the two hours are up, we drop off our completed forms and gear to the collection box at the visitor centre, maybe exchange a few comments about what we have heard, but soon disperse, as it is late and will be past midnight before we are in bed.

After 1500 volunteer hours built up over eight listening nights this year and 18 last year, it is analysis time: a mix of arithmetic to calculate how many calls were heard at each listening post and then a mix of imagination and detailed field knowledge to create a map for each night, showing where the calls were coming from.

The data shows a big fall in female calls compared with last year, which in most circumstances would be worrying, but in the special circumstances of the ecosanctuary it is probably good news.

It means our population of adolescent kiwi have grown up, and the reduction in female calls and their location can be attributed to their having found mates and no longer having the need to announce their presence.

We believe there are at least seven, possibly nine, breeding pairs of kiwi on our hillside and are looking forward to the patter of chicks' big feet through the leaf litter this spring.

- Michael and Valerie Fay have been monitoring and recording the movements of Haast Tokoeka at the Orokonui Ecosanctuary since their introduction in 2010, first while the kiwi wore transmitters, and since.

Add a Comment