The Second Kaka Count - 7th September 2008 by John Ogden

Environmental News Issue 16 Spring 2008

Again this was a splendid effort, with a total of 50 people involved on Great Barrier, returning 46 data sheets. The basic data obtained is given in Table 1 and a comparison with the previous count in Table 2.

The figures for the winter count show a dramatic reduction on those obtained in summer. After the first count I estimated the kaka population to be in the range of 200—300 birds. Using the same methods after this count gives an estimate of 75 to 175 birds. The estimates assume that the ‘maximum number counted’ (1) is too high because some birds would have been counted twice, and that the upper-limit should be raised by c. about 75—100 to account for birds not seen or heard by anyone ( i.e. “in the bush”).

The % decline averages 48% over all three methods of ‘estimating numbers’. This change is too great to be accounted for by the small reduction in counting effort (number of data sheets returned), especially as we counted morning and night and achieved a better geographical coverage of the island, on this second count. It implies either that kaka numbers have declined dramatically since the summer, or else that the kaka are far less conspicuous at this time of year. This could arise because they are ‘in the bush’, or because they are quieter or less active. However, other counts at Glenfern Sanctuary from 2002 to 2006, where kaka is the most conspicuous bird, show no significant changes in conspicuousness between seasons. A number of observers commented that kaka became more noticeable soon after the count – i.e. in Sept.

The difference between morning and evening counts indicates that generally morning is a better time to count than evening. If this is so, then the reduced count this time is even more significant, because the boxing day count was carried out in the evening (when the number counted should have been a bit lower ).

It is possible that a proportion of the kaka population is “off island” during the winter and return in Spring (September). Suzi Philips reports that numbers on the mainland build up between May and September

(Contact Suzi on kakawatchnz@gmail.com or the web site: <http://maps.google.com/maps/ms?ie=UTF8&hl=en&msa=0&msid=10755183049485 1460726.00000113677d44d50225e&z=9>).

Birds have been reported flying between Great Barrier and Hauturu, and between great Barrier and Coromandel, so a winter exodus, when food is scarce, is quite possible. This is clearly an important aspect for future research and cooperation between mainland and GBI bird counters.

With regards to other notes made on the data sheets: four people noted having heard kaka only or mainly at night. A long list of tree species being visited was obtained with pines (5) top of the list, followed by puriri (4), pohutakawa (3), banksia, gums and kanuka (2) and 10 other species reported once only.

Thanks to all participants (list too long to include!)