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NUMBER 89 101
FIGURE 13.—Lower mandibles (left) and skulls (right) of Mergus spp. (dorsal views). Top to bottom: Mergus, species
undescribed (MNZ S30049, PRM sample #113/91) from Te Ana a Moe Cave, Te Whanga Lagoon, Chatham
Island; Mergus australis (BMNH 1904.8.4.3, male); Mergus serrator (MNZ 12707, female). Scale bar=30 mm.
see Figures 11-14), two rails, a snipe, the undescribed species
of Nestor (Figure 10), and the putative Chatham Island Sea-eagle.
Of the four other species rendered extinct on the Chathams
in pre-European times, the swan and the crow {Palaeocorax
moriorum) may have survived on the New Zealand mainland a
little longer. The New Zealand Little Bittern {Ixobrychus novaezelandiae)
survived on the mainland until early in the twentieth
century. The New Zealand Scaup {Aythya novaeseelandiae)
is the only one of this group of 13 species exterminated on
the Chathams that still survives on the mainland.
European settlement brought further problems for the survival
of the remaining Chathams avifauna; habitat destruction
continued as forest and scrub were cleared for farming, two
more species of rats, house mice, cats, and dogs were introduced,
and human hunting no doubt continued. The four endemic
species that became extinct between 1840 and 1906
were all of small size, three were flightless (and thus obligate
ground nesters), and even the bellbird was a weak flyer. There
can be little doubt their demise was hastened by a combination
of habitat destruction and predation. Adults would have
been particularly vulnerable to cat predation, and their eggs
and young vulnerable to rats. The Brown Teal {Anas chloro-
TABLE 4.—Extinction of Chatham Islands terrestrial and freshwater birds. Of
the 36 former breeding species, 13 were exterminated during the pre-European
era, and eight were exterminated during the European era; total extinctions=21
(58%). There are now 15 breeding terrestrial species (excluding historic colonists
and introductions) on the Chathams Islands.
Era
Pre-European
European
Total extinction (endemics)
Mergus, species undescribed
Pachyanas chathamica
Tadorna, species undescribed
Anas, species undescribed
Haliaeetus australis
Diaphorapteryx hawkinsi
Fulica chathamensis
Coenocorypha chathamica
Nestor, species undescribed
Gallirallus dieffenbachii
(1840)
Gallirallus modestus (1900)
Bowdleria rufescens (1900)
Anthornis melanura melanocephala
(\906)
Local extirpation
Cygnus sumnerensis
Aythya novaeseelandiae
Ixobrychus novaezelandiae
Palaeocorax moriorum
Botaurus poiciloptilus (1910)
Anas chlorotis (1915)
Anas rhynchotis (1925)
Falco novaeseelandiae (1900)
tis) and New Zealand Shoveler {Anas rhynchotis), which were
last seen in the Chathams in 1915 and 1925, respectively,
would seem to have been the victims of recreational hunting.