In October-November 1992 the island of Mangaia, Cook Islands, was surveyed for Tanga’eo (Halcyon tuta ruficollaris). The Tanga’eo was found to be primarily a forest bird, preferring continuous forest canopy. Its abundance was influenced by forest type, extent, and degree of habitat modification. A number of potential threats to the survival of Tanga’eo were identified including habitat loss and disturbance by Common Mynas (Acridotheres tristis). A brief survey of rodents was carried out. Although the Tanga’eo population was estimated to have been between 250 and 450 birds, low numbers of birds in apparently suitable forest in the southwest of Mangaia indicate that further research is needed to determine population trends and conservation requirements.
The breeding behaviour of Tanga’eo or Mangaia Kingfisher (Halcyon tutu ruficollaris) on the island of Mangaia in the Cook Islands was investigated in 1992. Calls and breeding behaviour are described from a study of pairs and trios. At least six calls were distinguished. Clutch size appeared to be two eggs for pairs and three eggs for trios. Incubation time was between 21 and 23 days, while the fledging period was estimated at approximately 26 days. Both birds of a pair and all members of a trio excavated nest holes, incubated, brooded and fed the chicks. In trios with two males, both males courtship fed and copulated with the female, suggesting a polyandrous relationship. The breeding behaviour and relationship of trios, and the effects of Mynas on breeding success warrant further investigation.
We present new distributional data from the eastern South Pacific Ocean for the White-headed Petrel (Pterodroma lessonii), Kerguelen Petrel (P. brevirostris), and birds showing characters of the endangered Magenta Petrel (P. magentae). Extrapolation of density for White-headed Petrels suggests a pelagic population of 18,770 birds for the 10( x 5( block of subtropical surface waters between 27-37(S and 80-85(W (August 1995). Two Kerguelen Petrels were noted off Chile at around 40(30’S 74(50’W (August 1995). Three sightings of apparent Magenta Petrels between 28(44’S 72(40’W (March 1992) and 36(24’S 78(02’W (August 1995) are reported to alert observers to the potential occurrence of this species off South America.
Morphological comparison of the extinct Huia (Heteralocha acutirostris) with its closest known relatives suggests that the pronounced sexual bill dimorphism of the former evolved through selection on female, rather than male bill form. Because sexual selection acts predominantly on males, it cannot readily explain such dimorphism in a non-polyandrous species. Greater female divergence in foraging-related anatomy in a species in which males are the larger (and therefore presumably socially dominant) sex is, however, consistent with the hypothesis that sexual dimorphism can be an adaptation to reduce intersexual competition for food. Determining which sex changed most is a more rigorous means of establishing the evolutionary significance of sexually dimorphic traits than interpretation of current function.
Measurements of the lengths of fossil bones show that North Island Laughing Owls were appreciably smaller than South Island ones. Humeri and tarsometatarsi from the North Island were on average significantly shorter than those from the South Island. The regressions of humerus length and tarsometatarsus length on latitude were significant, and length and latitude were positively correlated. The North Island samples were too small to establish whether variation was clinal, and in the meantime the continued recognition of North and South Island subspecies seems warranted. KEYWORDS: Laughing Owl, Sceloglaux, fossil bones, geographical variation, subspecies.
Evidence of predation by kiore (Rattus exulans) on Little Shearwater (Puffinus assimilis haurakiensis) eggs was obtained on Lady Alice Island, Hen and Chickens Group, during the 1994 breeding season. A time-lapse video camera filmed a kiore removing a Little Shearwater egg from a nesting chamber. This egg was later recovered, showing signs of damage typical of rat predation. A kiore was also filmed breaking open and eating a punctured hen egg that had been placed in a shearwater burrow. Sixteen (55%) of the 29 nests monitored failed during incubation, and predation by kiore was the probable cause of failure for up to 75% of these nests.