Yellowheads (Mohoua ochrocephala) have disappeared from many parts of the South Island. The northernmost self-sustaining populations now occur in Arthur’s Pass National Park, where we surveyed Yellowheads in the Hawdon River Valley during their breeding in 1983 and 1984. Survey techniques were developed for assessing Yellowhead numbers at low densities. In 1983, 11 breeding pairs were found in 500 ha of forest, and in 1984, 21 breeding pairs were found in 2900 ha. About 70% of the birds occurred as breeding pairs, and the rest were itinerant non-breeders and helpers at nests. Yellowheads were spread throughout the valley but were more common at low altitudes. Breeding pairs preferred red beech (Nothofagus fusca) forests. There is some evidence that the nationwide decline of the species is continuing in the Hawdon River Valley.
Yellowheads (Mohoua ochrocephala) were observed between November 1983 and May 1984 in the Hawdon River Valley, Arthur’s Pass National Park. Of 11 breeding pairs, at least three had a third adult associated with them. Three pairs were watched in detail, and two nests were found, both in holes in live beech trees. The maximum breeding range was 7 ha. Young fledged in late December, and so laying had occurred in early November and hatching in late November-early December. There was no indication of double broods or renesting. Family groups of adults and juveniles remained in their breeding ranges for up to 2.5 days after fledging and then ranged throughout the forest. Parental care continued for about 55 days. From mid- January family groups began to come together for several hours and flocks of up to 25 Yellowheads were seen. In April and May flocks of 6-12 Yellowheads were seen, the birds apparently remaining together all day. Yellowheads were often in mixed species flocks.
Spotless Crakes (Porzana tabuensis) and Marsh Crakes (Porzana pusilla) were studied by R. Lavers, April 1971-July 1972, and by G. Kaufmann, September-December 1982, at Pukepuke Lagoon, Manawatu. Eleven Spotless Crake nests were found. Eggs were laid between 30 August and 19 December. Earlier nests usually contained 3 eggs; later nests contained 4-5 eggs, and the eggs were larger. Copulation and major calls are described. One male incubated 40°/o, the female 60%, of the 35 hours observed. Eggs of 4 nests were eaten by predators. Two Marsh Crake nests were found, containing 4 and 6 eggs. Both nests were unsuccessful. Analysis of museum skins highlighted similarities in bill size and structure, suggesting that interspecific competition occurs.