Hazards to kea (Nestor notabilis) at rubbish dumps

Abstract

Kea (Nestor notabilis, Gould) are attracted to rubbish dumps where they forage. The aim of this study was to quantify the hazards kea face by their foraging at rubbish dumps. In quantifying these hazards I hoped to establish whether rubbish dumps were detrimental to kea populations. I concluded that rubbish dumps do not pose a threat to kea populations, but may pose a threat to individual kea.

The research consisted of field and laboratory work. The field work took place at Halpin Creek dump, Arthur's Pass. The aim of the field work was to investigate diurnal and seasonal attendance patterns of kea at the dump and seasonal changes in their body condition. Kea were monitored for signs of disease, injury or lead poisoning. Monitoring methods included observation, physical assessment and analysis of samples of their blood. Necropscopic and toxicological analysis was carried out on kea from seven sites to establish whether the kea showed evidence of lead, zinc, arsenic or organochlorine pesticide poisoning. These kea had been found dead or were killed illegally.

As in previous studies of kea at sites occupied by humans, it was found that a greater proportion of male than female kea were banded at Halpin Creek dump. Re-sighting data suggested that certain adult male kea habitually foraged at the dump, whereas younger male kea forage at the dump until they disperse in their second summer. This may mean that, in the long term, dumps have a greater impact on certain adult males than on younger kea or female kea.

The age of a kea did not appear to have an influence on the amount of time that it spent at the dump. However, the amount of time individual kea spent at the dump varied considerably within and between seasons. More kea were observed at the dump in winter than in summer and they spent greater time at the dump in the winter than in summer. Thus, the importance of the dump to kea varies apparently between individuals, and according to different times of the year.

Using measurements from 252 kea from seven locations a measure of body condition that was independent of age and sex was developed. Kea that foraged at sites where anthropogenic food was freely available had higher body condition scores throughout the year than kea that foraged at sites where such food was limited. The difference in body condition scores for the two groups of kea was probably attributable to the amount of fat reserves. However, obesity did not appear to be a major problem for kea that forage on anthropogenic food.

Two of the 11 kea tested for lead toxicity at Halpin Creek dump were suffering from subacute lead poisoning. Kea that had been found dead or found killed illegally were analysed for lead, zinc, arsenic and organochlorine pesticide toxicity. A kea found at Otira dump and another from Bottle Flat, a non dump site, both probably died of lead poisoning. Another kea from Fox Glacier rubbish dump may have died of lead poisoning had it not been shot. There was no evidence of arsenic or organochlorine pesticide poisoning in any of the kea tested and evidence of zinc toxicity was inconclusive. The source of lead in the kea tested was not identified; it could not be concluded that the lead came from dumps.