Olson • THE EXTINCT HAWAIIAN GENUS CIRIDOPS 
669 
presence on Hawaii and Molokai would make 
probable, the birds were probably confined to 
lowland habitats. 
Fossils of Cirulops, apparently referable to C. 
anna on Molokai, were found in the Moomomi 
Dunes (Olson and James 1982) where suitable 
forest habitat was probably adjacent at the time of 
deposition, whereas no fossils of Ciridops were 
found in the dune deposits at Iho Point, a 
particularly isolated locality in a harsh, arid part 
of the island where probably only beach scrub 
habitat was able to persist. Given that Ciridops 
was definitely present on Molokai, it seems likely 
that a representative of the genus would have been 
on Lanai as well, although on that island the fossil 
record is scant (Dove and Olson 2011) and as yet 
includes no passerines. 
On Oahu, a species of Ciridops is fairly 
abundantly represented in the sinkhole deposits 
in the southwestern part of the island at Barbers 
Point. The bill and hindlimb bones appear to be 
somewhat shorter than in C. anna and it should 
perhaps be recognized as a separate species but 
has not yet been named (James and Olson 1991). 
The fossil species Ciridops ienax James and 
Olson (1991) was described from the Makawehi 
dune deposits in southeastern Kauai, where the 
diversity of species of various passerines indicates 
the presence of adjacent dry lowland forest. Yet not 
one bone of Ciridops ienax has yet been found in 
the Quaternary lake deposits excavated at Malta'u- 
lepu. about 2 km to the east of the Makawehi 
dunes, despite a great abundance of fossil material, 
including hawks and owls, and the exceptional 
diversity of species and quality of preservation 
(Burney et al. 2001). This suggests a rather strong 
habitat avoidance by Ciridops ienax. Although 
Prilchardia palms were present and abundant at 
Maha'ulcpu. the flora was extremely diverse, 
including several species of trees now restricted 
to upland localities where they are evidently relicts. 
The overall impression of the environment at 
Maha'ulaepu is a diverse, moist, closed-canopy 
forest. Therefore, the habitat preference of Ciri¬ 
dops may have been for drier, more open habitat in 
which Prilchardia grew in monospecific stands. 
Ciridops ienax may be the most primitive species 
of the genus because of its apparently less 
specialized hindlimb elements. Kauai is the oldest 
of the islands on which Ciridops was know to occur, 
suggesting that the genus may have originated there 
and spread eastward with the formation of the 
younger islands of the main Hawaiian chain. 
The available evidence suggests that one form or 
another of Ciridops probably occurred throughout 
all the main I lawaiian Islands, although confirming 
iis presence on Maui would certainly he desirable. 
The fossil record also shows that potential avian 
predators occurred throughout the range of Ciri¬ 
dops. The extinct, long-legged, bird-eating owls of 
the genus Grallistris arc known from Kauai. Oahu, 
Molokai, and Maui, but apparently did not occur on 
Hawaii (Olson and James 1991). The presence of 
fossils of Ciridops in the deposits on Kauai. Oahu, 
and Molokai is almost certainly attributable in 
whole or in part to those owls and bones of 
Ciridops were found in what was clearly an owl 
pellet on Molokai (Olson and James 1982). The 
Hawaiian Hawk UJuteo solitarius) of the island of 
Hawaii is known from bones of the same or very 
similar species from Molokai. Oahu, and Kauai, 
and small forms of Circus adapted tor catching 
birds are know n from fossils on Molokai and Oahu 
(Olson and James 1991). Thus, the species of 
Ciridops. like the other small passerines that shared 
their habitat, w-ould have had to have as keenly 
evolved predator-avoidance behavior as any of 
their mainland ancestors. 
Assuming a close, if not totally dependent, 
relationship between Ciridops and loulu palms 
( Prilchardia ). we may extrapolate more about the 
probable inter- and intraisland range and habitat 
preferences of the birds, albeit with a certain 
degree of circularity, based on information on 
Prilchardia from Hodcl (2007). The apparent 
diversity of Prilchardia is centered on the 
Hawaiian Islands, although there are scattered 
outliers in Fiji, Tonga, Cook Islands, and the 
Tuamotus whose distribution suggests there were 
probably widespread human-caused prehistoric 
extinctions elsewhere in Oceania. The nominal 
23 species in the Hawaiian Islands consist almost 
entirely of allopatric populations most of which 
are severely restricted in range and now often 
consist of only a few' living individuals. Specific 
characters are extremely variable and are usually 
only useful for defining species when used in 
combination. Only three species occur on more 
than one island and all of those occur on Maui 
Nui. which included the combined islands of 
Maui. Molokai, and Lanai during lowered sea 
levels of glacial periods. 
Prilchardia occurs naturally now on all the 
main Hawaiian Islands except the small, ecolog¬ 
ically devastated island of Kahoolawe. and also on 
the remote island of Nihoa. The plants may occur 
