. Ecological and behavioural evidence for the systematic status of New Zealand oystercatchers : (Charadriiformes: Haematopodidae) . TIME IN SECONDS Fig. 8. Sound spectrograph of a segment of the social piping vocaHzation of a Chatham Islands Oystercatcher. This spectrograph was made from a segment of spectrograph E in Figure 8 (above the second marker), at a tape speed of 7Vi inches per second over a frequency range of 160-16,000Hz. their pair-bonds throughout the year and drive of! any intruding birds. The courtship behaviour and pair formation of the Chatham Islands Oystercatcher is unkn
. Ecological and behavioural evidence for the systematic status of New Zealand oystercatchers : (Charadriiformes: Haematopodidae) . TIME IN SECONDS Fig. 8. Sound spectrograph of a segment of the social piping vocaHzation of a Chatham Islands Oystercatcher. This spectrograph was made from a segment of spectrograph E in Figure 8 (above the second marker), at a tape speed of 7Vi inches per second over a frequency range of 160-16,000Hz. their pair-bonds throughout the year and drive of! any intruding birds. The courtship behaviour and pair formation of the Chatham Islands Oystercatcher is unknown. The copulatory behaviour of the three New Zealand species of oyster- catcher is identical. Copulation is usually, but not always, preceded by specific posturing. The male posture involves a stealthy approach, with the head drawn between the shoulders and held to one side of the body. This hunched- up attitude is accentuated by a general lowering of the body, and by depressing and fanning the tail. Responsive females assume a passive posture, raising the body higher above the ground than is usual and at the same time erecting the tail feathers above the horizontal. The male mounts from behind and during coition maintains balance by flapping his wings. Occasionally, in all species, copulations occurred in which the male did not adopt the pre- copulatory posture, but either walked up to the female and mounted or flew onto her back from a short distance. Webster (1941 a) noted that copulation of American Black Oystercatchers did not involve any special preliminary ceremony, the male commonly flying onto the female as described above. The maintenance of pair-bonds throughout the year by Variable Oyster- catchers is probably related to their copulatory behaviour. I have observed pairs copulating in the winter months of May, June and July, and since it is extremely unlikely that these copulations could have resulted in fertilization of ova (and may not have involved transference
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