Third Bird Count
Environmental News Issue 9
A diverse collection of Barrier aviaphiles set out to count the Kotare.
Kingfishers or kotare are quite a feature of Great Barrier Island. Although they are neither rare nor endangered, many ornithologists, and other visitors, have commented on how abundant they seem to be on the island compared to the rest of New Zealand. The New Zealand species (Halcyon sancta) is a sub-species (vagans) of the sacred kingfisher of Australia, with eight slight variants throughout the Pacific. Our kingfishers are colourful and noisy, and were the most conspicuous bird in our last “5 minute bird count” survey at the end of September 2006. At that time they were re-establishing their nesting territories, abandoned for the winter trip to the coast, and a lot of penetrating kek-kek-keking was to be heard.
The third bird count was on January 25th. Twenty people turned out at dawn to gather the data. As they had all done the job before, it was fairly routine doing the “five minute counts” at the same locations. Kingfishers were again conspicuous, and we made a special effort to try to convert “heard or seen at 84% of all 5-min counts” into some real numbers.
The method was to count the occupied nesting holes in the banks along a known distance of road, then multiply up by the total length of road on the island. To this figure we could add some guesswork about the numbers nesting elsewhere. The idea was to get a “ball-park” estimate, not a true figure.
Between the five minute counts we cruised many kms of Barrier roads, looking for the characteristic kingfisher nest holes, counting them and classifying them as “active”, “possibly active” or “old, inactive”. Active nest holes were identified by the presence of droppings and the “churring” coming from them when they contained chicks. If some of the counting team thought this was an eccentric activity, and some drivers thought worse, some passing vehicle occupants and adjacent landowners clearly thought we were up to no good. Our results are summarised below:
Number of km counted: 34
Number of active holes found: 26
Number of possibly active holes: 16
Number of inactive 'old' holes: 359
What can we make of these results? We can certainly say that kingfishers seem to have a lot of ‘spare’ real estate, most of which never gets used by the family! Maybe holes are territorial marking by the pair—another way of saying “we own this bank”. We can now make a few “back of the envelope” calculations as follows:
Definite nests per km of road counted = 26/34 = 0.76 nests per km.
Possible plus definite nests per km of road = 41/34 = 1.21 nests per km.
Assuming total GBI road length is c. 70km (estimated from the map) these figures equate to 53 certain or 85 possible nesting pairs on the island’s roads. But there are many other nests, in the banks of creeks in the bush, in holes in trees, coastal cliffs, old road and path cuttings etc. These are more difficult to estimate! The details will be in my report, but using the above figures, and some estimates for the number of nests in other places, I come up with a figure of: 200 – 250 nesting pairs on the whole of Great Barrier in 2006/07. This could be an underestimate: there may be up to five hundred pairs.
So what? Why does it matter how many kingfishers are here?
Kingfishers are not at risk, on the Barrier or elsewhere. Although some eggs and chicks are predated by rats, adult birds seem well able to defend themselves and their nesting holes. Changes in relative abundance can be easily monitored by the 5-minute count technique, provided counts are carried out at the same place and season. Absolute numbers are important only if we are concerned with the genetic breeding pool, with measuring the impact of kingfishers on their prey or other ecological interactions. These latter deserve study because skinks are an important food item. Like moreporks, kingfishers eject the inedible bits – beetle wing-cases, crustacean carapaces, bones, fur and feathers – in pellets which are dropped below perches and nest-holes, so their diet can be quantified by anyone with a microscope - and patience.
Other bird count news:
THE ROBINS are doing well at Windy Hill with 23 banded fledglings and only one nest predated by rats and one by moreporks. Two Windy Hill robins have been identified at Mt Hobson and one down in Rosalie Bay, demonstrating how rapidly the island would be populated by robins if it wasn’t for predation by rats. Kaka also seem to have had a successful breeding season, with six chicks seen at Windy Hill, and at least one at Okiwi. Anecdotal information from several sources indicates that the kaka population has increased over the last decade – since we stopped calling them “buzzards”! Although there has been no influx of bellbirds to match that in 2005, at least one has been reported (Halema Jamieson—at Okiwi). The 2005 influx failed to establish—again demonstrating the significance of rat predation on small birds.
Following their success at the last bird count, Amanda Yates and Emma Hunt sat on the edge of Andy Oxborough’s swamp at Awana one balmy evening in February, and played the “crake tapes”. They were amazed to get several clear positive responses! I have spent every summer for 16 years within 100 metres of that swamp and never known for sure, until now, that spotless crake were there! Which just goes to show … something.
Acknowledgements: Thanks to all those who participated in the 5-minute counts again: Don Armitage; Jeff Campbell; Des Casey; Fenella Christian; Peter Edmonds; Emma Hunt; Halema Jamieson; Ezra Kendall; Maaka McCandless; Hillary McGregor; Joanne O’Reilly; Emmy Pratt; Dale Tawa; Bert Vowden, Duane Walker; Tahi Walker and Amanda Yates. I’ll be writing my third report on that to D.o.C (Biodiversity Advice Fund) soon and copies will be available.