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98 SMITHSONIAN CONTRIBUTIONS TO PALEOBIOLOGY
able to Sceloglaux in Forbes' material in the Natural History
Museum, London. It seems that this record is a case of mistaken
identity. More recently (1993) I have examined a tarsometatarsus
from Forbes' collection upon which is written in Forbes'
distinctive hand "Sceloglaux, Ch.I., HOF." This specimen is
clearly attributable to Falco novaeseelandiae. Several other
bones of Falco have been recognized in Forbes' collection (see
Dawson, 1961b) and many more have been collected from the
Chathams in recent years, but none of Sceloglaux.
The Chatham Island Sea-eagle, originally described as Ichthyophaga
australis (Harrison and Walker, 1973) but removed
to Haliaeetus by Olson (1984), is a particular enigma, although
it seems prudent to list it among the indigenous Chatham Islands
birds until unequivocal evidence shows otherwise.
Housed in the Natural History Museum, London, is a collection
of about a dozen eagle bones found or otherwise acquired by
H.O. Forbes in the 1890s, and labelled as being from the
Chatham Islands. These bones, parts of four individual birds,
certainly belong to the genus Haliaeetus (see Dawson, 1961a;
Olson, 1984) and have been considered to differ somewhat
from any existing species (although I could not distinguish
them from bones of the Alaskan race of Bald Eagle, H leucocephalus
alascanus Townsend). There is reason to doubt that
these bones came from the Chathams (some other bones in
Forbes' collections are wrongly labelled) because it is extraordinary
that among all the hundreds of thousands of bones collected
subsequent to Forbes, not one of a sea-eagle has been recovered.
Even the appearance of the bones is unlike that of
other Chatham Islands fossils, as they seem to have a surface
texture more like that of modern material. Another element of
doubt about their authenticity is raised by a radiocarbon date
(NZA 1548, locality uncertain) obtained from one of the
paratypical bones (BMNH A3732). Depending on the calibration
given, an age as young as ca. 1836 AD can be calculated.
The enigma remains unresolved. Perhaps Forbes chanced upon
the only bones yet known of an endemic Chatham Sea-eagle, or
perhaps the bones are from an existing species, acquired as part
of Forbes' reference collection of modern specimens.
NOTES ON SELECTED EXTINCT SPECIES FROM THE
CHATHAM ISLANDS
Dieffenbach's Rail {Gallirallus dieffenbachii): This species
is closely related to the widely distributed Banded Rail {G.
philippensis) and is presumed to have evolved from the same
ancestral stock (Olson, 1975). The anatomical differences between
Dieffenbach's Rail and the Banded Rail (of which it has
previously been considered only a subspecies; see Turbott,
1990) indicate that they are separate species (pers. obs.). Only
one live specimen was ever collected, by Ernst Dieffenbach in
1840, who stated (1841:195) that the species "was formerly
very common, but since cats and dogs have been introduced it
has become very scarce" (see Forbes, 1893b). Dieffenbach's
Rail was flightless, weighed perhaps 340-400 g (about twice as
much as the Banded Rail, which is a capable flyer), and had a
rather dull plumage and a distinctly down-curved bill (Atkinson
and Millener, 1991). An inhabitant of forest and scrub, it
probably consumed a wide range of foods, including soil invertebrates
probed from soft earth, insects, seeds, and even eggs of
ground-nesting birds.
Chatham Island Rail {Gallirallus modestus): This diminutive
(body weight 50-70 g; Atkinson and Millener, 1991),
flightless species may have evolved from the same stock as Dieffenbach's
Rail (Olson, 1975). The type specimen was obtained
by H.H. Travers from Mangere Island in 1871, but Oliver
(1955:355-356) stated that "through the work of
collectors... aided by cats... [it] was exterminated about twenty-five
years after it was discovered." The bill of the Chatham
Island Rail is very long and delicate and must surely have been
used as a probe to capture small invertebrates in soft soil or leaf
litter. The only observations of its habits are those of Hawkins
(in Forbes, 1893b:532): "They nest in holes in the
ground... [and] live on insects, principally the sandhoppers
which travel into the bush a long way." Until recently, fossil
bones of the Chatham Island Rail had not been commonly
found, but they have now been recorded from Pitt and Mangere
islands and from the Te Ana a Moe Cave beside the Te Whanga
Lagoon on Chatham Island. From this one small cave, many
thousands of bones, representing hundreds of individual birds
(Table 3), have been excavated from sediments dating from
about 1150 years to almost 4000 years ago.
Hawkins' Rail {Diaphorapteryx hawkinsi): Fossil bones of
this species were first collected by W. Hawkins who sent them
to H.O. Forbes in 1892 (see Forbes, 1892a, 1892b, 1892c,
1893a). This large (body weight ~2 kg; Atkinson and Millener,
1991), flightless rail is so distinct from the Gallirallus group
that it is placed in its own genus. Its wings were greatly reduced,
its legs robust, and its toes elongate. Its long, decurved
bill may have been an adaptation for probing into soft earth for
soil invertebrates. No living specimen of Hawkins' Rail was
ever seen or collected by Europeans, but the substantial numbers
of its bones in Moriori middens indicates that it was frequently
hunted for food.
Chatham Islands waterfowl: The Chatham Islands formerly
supported a wide range of waterfowl, including the extinct
Chatham Island Swan and perhaps eight species of duck. The
Chatham Island Duck {Pachyanas, Figure 7) and Merganser
{Mergus, species undescribed, Figures 12-14) were flightless,
and several of the other species (e.g., the Chatham Island Shelduck,
Tadorna, species undescribed, Figure 11) show indications
of having been weaker flyers than their mainland counterparts.
All but the Grey Duck {Anas superciliosa) became
extinct in the Chathams following human settlement. The extinct
swan {Cygnus sumnerensis) would seem to have evolved
from the same stock as the Australian Black Swan, which was
introduced to the Chathams about 1890 and now flourishes on