Conservation ecology of kea - Kea Conservation Trust website

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• From daily survival rates, the proportion of nests fledging at least one chick was 51% (95% CI = 34-73%). • The probability of nest contents (i.e. eggs or chicks) disappearing decreased with increasing slope at the nest site. • Nest predation did not increase in the breeding season following full beech mast- seeding in 1995, when stoat (Mustela ermina) numbers were beginning to rise. • 37 different adult kea (8 females and 29 males) were radio-tagged. Most of these were monitored for more than one year, giving a total sample of 89 kea-years (19 female and 70 male). • Five deaths of radio-tagged adults occurred, giving an adult survival rate of 93% (SD = 2.8%). All five deaths were of adult males. • Adult females had to be captured at their nests because they seldom visit the skifield. This was time consuming and we sometimes had difficulty recapturing these females when their transmitter batteries went flat after two years (transmitters with 5-year batteries only became available toward the end of the study). We therefore settled with colour-banding females rather than radio-tagging them. • Five adult females had been colour-banded prior to their nest contents disappearing. All five were confirmed alive after their nest contents had disappeared. • Uncertainty about the fates of the other 6 adult females whose nest contents disappeared led to an estimated annual adult survival rate of 82%. • Productivity around the skifield was 0.33 female chicks per adult female per year. • Population modeling showed that a change in adult survival has roughly four times the impact on population growth as a proportional change in any other parameter. • 11 fully-grown nestlings were radio-tagged in 1997 and 7 were radio-tagged in 1998. A third cohort of 9 will be radio-tagged in1999. • Of the 11 nestlings radio-tagged in 1997, 10 signals were obtained during the tracking flight a year later. Follow-up tracking on the ground showed that 8 of the nestlings had survived their first year, 1 had died, and one had dropped its transmitter. This yields a fledgling survival rate for 1998 of 89% (95% CI = 70 – 100%). vi
• The radio-tagged one-year-olds led us to four flocks of kea which contained unmarked one-year olds, indicating that breeding was probably widespread among kea in the hinterlands in 1997. Conclusions Kea nests appear to be relatively immune to predation from introduced mammals. The nest survival rate was significantly higher than that observed among kaka nests in an adjacent forest, where only 2 of 20 nests found over a period of 11 years fledged chicks (Wilson et al. 1998). A possible explanation for the relationship between slope and nest failure is that predators tend to avoid very steep sites. This could occur because predators probably never learn to hunt in very steep places in beech forest because few prey animals are found there. Kea nests occurred at a very low density (one nest per 4.4 km 2 ) and other stoat prey (rodents and large invertebrates) are probably more abundant on gentler slopes. Nesting in spring may also afford kea some protection from predation by stoats, particularly following beech mast seeding, as stoat numbers are normally low until January-February. With the data at hand we can only speculate about the reasons for the low predation rate. Our results agree with a previous study of kea nesting at Arthur’s Pass, where no evidence of significant nest predation was found (Jackson 1963). Since most kea habitat is similar to that found within Nelson Lakes and Arthur’s Pass, it seems likely that kea nesting success rates and adult survival rates are high throughout their range. The dynamics of our study population are driven largely by adult survival. This is typical of populations of long-lived animals with low-reproductive output (K-selected species). A decrease in the adult survival rate will cause a much more rapid decline than a proportionally similar decrease in any other parameter. A rapid decline in kea numbers would, therefore, most likely be caused by inflated adult mortality. We found that survival of radio-tagged adults was high (93%) and adult females seemed to escape being killed during the few nest predation events that we observed. Since adult survival was high and a reasonable number of chicks were fledged, this population is unlikely to be vii
Page 1 and 2: WWF-NZ Final Report Conservation ec
Page 3 and 4: There are two possible explanations
Page 5: Study site and methods • The stud
Page 9 and 10: in the hinterlands. Adult female su
Page 11 and 12: Wilson, P., Karl, B., Toft, R., Beg
Page 13 and 14: Timing of the breeding season .....
Page 15 and 16: Chapter 2 List of tables Table 1. S
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Page 19 and 20: Bond, A. D., Wilson, K.-J., Diamond
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Page 25 and 26: Locating and monitoring nests We fo
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Page 29 and 30: Nest density The density of kea nes
Page 31 and 32: Beech seedfall and stoat abundance
Page 33 and 34: Nest site topography Nest sites wer
Page 35 and 36: Table 2. Model-fitting summary for
Page 37 and 38: Predation of adult females in their
Page 39 and 40: independent and stoat numbers becom
Page 41 and 42: could help to explain the differenc
Page 43 and 44: Lebreton, J.-D., Burnham, K. P., Cl
Page 45 and 46: 3. Kea (Nestor notabilis) populatio
Page 47 and 48: technology now enable detailed stud
Page 49 and 50: Parameter estimates Productivity We
Page 51 and 52: transmitter was buried under two-me
Page 53 and 54: Nest survival We previously estimat
Page 55 and 56: Pre-adult survival Of the radio-tag
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Kea population dynamics We chose no
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could result in a downgrading of th
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O'Donnell, C. F. J. 1996. Predators
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the Nelson Lakes study site. Most o
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