|
Was it the third? or was it the
fourth? Although it said Kaka Count 4 on the data sheets it was in fact
the third, as one was missed out due to ‘other commitments’!
Anyway, the previous two counts had shown a clear decline in the kaka
counts between summer and winter, coinciding with an increase in kaka
sightings on the mainland (Suzi Phillips – Kakawatchnz). For this reason
the Trust decided to do another winter and another summer count, to
confirm the supposed ‘off-island’ winter migration. The results for the
July count are given in Table 1. This table amalgamates the results of
different observers (where there was more than one at a ‘location’) and
doesn’t show the relatively high proportion of observers who gave ‘nil’
returns for kaka sightings on the day – seven of the 33 sheets (21%).
Indeed the general absence or low activity of kaka in July was noted by
most observers and may account for the lesser response to this survey
(33 sheets returned) compared to previous ones. But absences are just as
important at presences when it comes to statistics, so please return the
sheets for the next survey even if there are no kakas to be seen or
heard! We are planning one more count in December (this year) to
hopefully confirm the trends seen so far.
Table 1. Kaka Count 25/07/10
|
LOCATION |
No of data |
Total AM1 |
Total PM1 |
Minimum |
Maximum |
|
|
sheets |
|
|
at location2 |
at location3 |
|
|
|
|
|
|
|
|
Allom Bay |
1 |
0 |
0 |
0 |
6 |
|
Awana |
2 |
4 |
7 |
5 |
6 |
|
Claris |
1 |
0 |
3 |
3 |
6 |
|
FitzRoy |
2 |
4 |
5 |
3 |
6 |
|
Harataonga |
3 |
5 |
2 |
3 |
3 |
|
Kaiaraara Bay Rd |
1 |
3 |
0 |
3 |
3 |
|
Kaitoke |
1 |
0 |
0 |
0 |
2 |
|
Kaitoke Creek |
2 |
0 |
1 |
1 |
1 |
|
Medlands |
5 |
13 |
14 |
5 |
12 |
|
Mulberry Grove |
1 |
0 |
0 |
0 |
0 |
|
Okiwi |
1 |
2 |
8 |
8 |
8 |
|
Okupu |
2 |
0 |
0 |
0 |
1 |
|
Puriri Bay |
1 |
9 |
9 |
9 |
10 |
|
Rosalie Bay |
1 |
9 |
5 |
9 |
12 |
|
Schooner Bay |
3 |
3 |
3 |
1 |
4 |
|
Tryphena |
2 |
3 |
1 |
3 |
5 |
|
Wairahi |
2 |
2 |
11 |
11 |
16 |
|
Whangapara |
1 |
0 |
0 |
0 |
2 |
|
Windy Hill |
1 |
4 |
4 |
4 |
4 |
|
TOTALS 25/07/10 |
33 |
61 |
73 |
68 |
107 |
(1) Assumes all counts by different
observers, AM and PM, were all different birds.
(2) Assumes that all birds at one ‘location’ were the same birds, so the
maximum count by any one observer is taken as the minimum for the
location.
(3) Uses the maximum estimate for birds reported at the location over
the last few weeks.
Another feature of the July data is the variation, especially in the
‘Maximum’ column. This indicates that kaka were concentrated at a few
locations, while they were present only in small numbers or absent
elsewhere. Thus, in winter the kakas may be concentrated in areas where
there are reliable food supplies – such as Peter Speck’s orchard at
Rosalie Bay, or in the Medlands valley or the Wairahi. It is interesting
too to compare this with the summer count (26/12/07) which, while
showing many more birds, showed much less variation between locations.
Table 2 indicates that this July’s count was numerically similar to that
made in early September 2008. However, all these results are only
samples of the true population size, and it is difficult to know how
many birds have not been counted or estimated by the observers. The
figures suggest to me that the winter population here is probably in the
range 75-175 birds. The Summer population may be up to 300.
Table 2. Comparisons with previous
counts
|
|
Number |
Maximum |
Minimum |
Maximum |
Coefficient |
Population |
|
|
of data |
number |
no. based |
number(3) |
of |
guestimate |
|
|
sheets |
counted(1) |
on locations(2) |
|
Variation(5) |
-4 |
|
26/12/2007 |
|
|
|
|
|
|
|
Summer |
45 |
222 |
141 |
221 |
35 |
250+/-50 |
|
07/09/2008 |
|
|
|
|
|
|
|
Winter |
40 |
136 |
61 |
117 |
32 |
125+/-50 |
|
25/07/2010 |
|
|
|
|
|
|
|
Winter |
33 |
134 |
68 |
107 |
76 |
125+/-50 |
(1) Total of all AM and PM counts by
all observers
(2) Total of the minima from all locations (i.e. assumes birds at
different locations are different)
(3) Total of maxima for locations.
(4) Assumes that population size must be greater than the minimum number
based on locations, and will also probably be greater than the maximum
estimated from the data, because some locations have not been observed.
(5) A measure of the variability between locations. Higher % indicates
higher variability – i.e. the kaka are more patchily distributed.
The total results from all three counts, and comparisons with kakawatch
results from the mainland, suggest that about half the Great Barrier
kaka move to the mainland during the winter, leaving in May, and
probably returning mostly in September. What determines which birds go,
and which stay, we do not know. Powlesland et al. (2009) suggested that
kakas breed only in years of abundant food supply. On Great Barrier the
kaka which overwinter seem to concentrate on the most reliable food
supplies, suggesting that it is a general food shortage which drives the
move to the mainland. On the other hand we could see the process in
reverse: kaka move to Great Barrier to breed because their main nest
predators on the mainland – possums and stoats – are absent from the
island (cf. Powlesland et al. 2009).
In conclusion – we know that kaka can be a nuisance or worse, but they
are also very unusual parrots, endemic to New Zealand. Their numbers
have declined nationally and their range contracted to increasingly
disjunct populations. Kaka are put in the ‘Nationally Vulnerable”
category of Miskelly et al. (2008). Great Barrier is a stronghold for
the North Island, and may well provide recruits to the populations on
the Auckland mainland and Coromandel peninsula. Our community-led
monitoring on Great Barrier is starting to indicate the significance of
our kakas here, and to suggest new lines of research. Thanks to all
participants – 101 names occur on the sheets from all 3 counts, so about
10% of the Barrier’s human population has contributed so far! Special
thanks to Sue Daly for organising the last count.
References: MisKelly et al. 2008. Conservation status of NZ birds.
Notornis 55: 117-135. (www.notornis.org.nz). Powlesland et al. 2009.
Breeding biology of the New Zealand kaka (Nestor meridionalis). Notornis
56: 11-33.
See also:
http://www.kakawatchnz.org
and go to “Research Publications”. |
