Storrs L. Olson

Fossil Birds from the Hawaiian Islands: Evidence for Wholesale Extinction by Man Before Western Contact

Thousands of fossil bird bones from the Hawaiian Islands collected since 1971 include remains of at least 39 species of land birds that are not known to have survived into the historic period; this more than doubles the number of endemic species of land birds previously known from the main islands. Bones were found in deposits of late Quaternary age; most are Holocene and many are contemporaneous with Polynesian culture. The loss of species of birds appears to be due to predation and destruction of lowland habitats by humans before the arrival of Europeans. Because the historically known fauna and flora of the Hawaiian Islands represent only afraction of natural species diversity, biogeographical inferences about natural processes based only on historically known taxa may be misleading or incorrect.

Fossil evidence for a diverse biota from Kaua`i and its transformation since human arrival

Coring and excavations in a large sinkhole and cave system formed in an eolianite deposit on the south coast of Kaua‘i in the Hawaiian Islands reveal a fossil site with remarkable preservation and diversity of plant and animal remains. Radiocarbon dating and investigations of the sediments and their fossil contents, including diatoms, invertebrate shells, vertebrate bones, pollen, and plant macrofossils, provide a more complete picture of prehuman ecological conditions in the Hawaiian lowlands than has been previously available. The evidence confirms that a highly diverse prehuman landscape has been completely transformed, with the decline or extirpation of most native species and their replacement with introduced species. The stratigraphy documents many late Holocene extinctions, including previously undescribed species, and suggests that the pattern of extirpation for snails occurred in three temporal stages, corresponding to initial settlement, late prehistoric, and historic impacts. The site also records land-use changes of recent centuries, including evidence for deforestation, overgrazing, and soil erosion during the historic period, and biological invasion during both the Polynesian and historic periods. Human artifacts and midden materials demonstrate a high-density human presence near the site for the last four centuries. Earlier evidence for humans includes a bone of the prehistorically introduced Pacific rat (Rattus exulans) dating to 822 yr BP (calendar year [cal yr] AD 1039–1241). Vegetation at the site before human arrival consisted of a herbaceous component with strand plants and graminoids, and a woody component that included trees and shrubs now mostly restricted to a few higher, wetter, and less disturbed parts of the island. Efforts to restore lowland areas in the Hawaiian Islands must take into account the evidence from this study that the prehuman lowlands of dry leeward Kaua‘i included plants and animals previously known only in wetter and cooler habitats. Many species may be restricted to high elevations today primarily because these remote locations have, by virtue of their difficult topography and climate, resisted most human-induced changes more effectively than the coastal lowlands.

Unidirectional Spread of Secondary Sexual Plumage Traits Across an Avian Hybrid Zone

Theory predicts that traits under positive selection can rapidly cross a hybrid zone in spite of a substantial barrier to neutral gene flow between hybridizing taxa. An avian hybrid zone between Manacus candei (white-collared manakin) and M. vitellinus (golden-collared manakin) is reported here that displays an unusual pattern of noncoincident clines. Male secondary sexual traits of M. vitellinus have spread into populations that are genetically and morphometrically like M. candei. These birds have a lek breeding system in which male mating success is highly skewed, suggesting that sexual selection is driving male sexual traits across the zone.

mtDNA from fossils reveals a radiation of Hawaiian geese recently derived from the Canada goose (Branta canadensis)

Phylogenetic analysis of 1.35 kb of mtDNA sequence from fossils revealed a previously unknown radiation of Hawaiian geese, of which only one representative remains alive (the endangered Hawaiian goose or nene, Branta sandvicensis). This radiation is nested phylogenetically within a living species, the Canada goose (Branta canadensis) and is related most closely to the large-bodied lineage within that species. The barnacle goose (Branta leucopsis) is also nested within the Canada goose species and is related most closely to the small-bodied lineage of Canada geese. The peripheral isolation of the barnacle goose in the Palearctic apparently allowed the evolution of its distinctive plumage pattern, whereas the two Nearctic lineages of Canada geese share a primitive plumage pattern. The Hawaiian lineage of Canada geese diverged more dramatically, splitting into at least three species that differ in body size, body proportions, and flight ability. One fossil species, limited to the island of Hawaii, was related closely to the nene but was over four times larger, flightless, heavy-bodied and had a much more robust cranium. Application of a rate calibration to levels of DNA divergence suggests that this species evolved on the island of Hawaii in less than 500,000 years. This date is consistent with the potassium/argon-based age of the island of Hawaii of 430,000–500,000 years. The giant Hawaii goose resembles the moa-nalos, a group of massive, extinct, flightless ducks that lived on older Hawaiian Islands and thus is an example of convergent evolution of similar morphologies in island ecosystems.

Relationships of the extinct moa-nalos, flightless Hawaiian waterfowl, based on ancient DNA.

The extinct moa–nalos were very large, flightless waterfowl from the Hawaiian islands. We extracted, amplified and sequenced mitochondrial DNA from fossil moa–nalo bones to determine their systematic relationships and lend insight into their biogeographical history. The closest living relatives of these massive, goose–like birds are the familiar dabbling ducks (tribe Anatini). Moa–nalos, however, are not closely related to any one extant species, but represent an ancient lineage that colonized the Hawaiian islands and evolved flightlessness long before the emergence of the youngest island, Hawaii, from which they are absent. Ancient DNA yields a novel hypothesis for the relationships of these bizarre birds, whereas the evidence of phylogeny in morphological characters was obscured by the evolutionary transformation of a small, volant duck into a giant, terrestrial herbivore.

PREVALENCE AND DIVERSITY OF AVIAN HEMATOZOAN PARASITES IN ASIA: A REGIONAL SURVEY

Tissue samples from 699 birds from three regions of Asia (Myanmar, India, and South Korea) were screened for evidence of infection by avian parasites in the genera Plasmodium and Haemoproteus. Samples were collected from November 1994 to October 2004. We identified 241 infected birds (34.0%). Base-on-sequence data for the cytochrome b gene from 221 positive samples, 34 distinct lineages of Plasmodium, and 41 of Haemoproteus were detected. Parasite diversity was highest in Myanmar followed by India and South Korea. Parasite prevalence differed among regions but not among host families. There were four lineages of Plasmodium and one of Haemoproteus shared between Myanmar and India and only one lineage of Plasmodium shared between Myanmar and South Korea. No lineages were shared between India and South Korea, although an equal number of distinct lineages were recovered from each region. Migratory birds in South Korea and India originate from two different migratory flyways; therefore cross-transmission of parasite lineages may be less likely. India and Myanmar shared more host species and habitat types compared to South Korea. Comparison between low-elevation habitat in India and Myanmar showed a difference in prevalence of haematozoans.

Probable extirpation of a breeding colony of Short-tailed Albatross (Phoebastria albatrus) on Bermuda by Pleistocene sea-level rise

Albatrosses (Diomedeidae) do not occur in the North Atlantic Ocean today except as vagrants, although five species were present in the early Pliocene. No fossil breeding sites of albatrosses were known previously. The timing of extinction of albatrosses in the North Atlantic was likewise unknown. Deposits that formed near present-day sea level along the southeastern shore of Bermuda contain remains of a former breeding colony and include intact eggshells and bones of embryos, juveniles, and adults of Short-tailed Albatross (Phoebastria albatrus), a critically endangered species now confined to a few islets in the northwestern Pacific Ocean. These deposits are correlated with the middle Pleistocene Lower Town Hill Formation, which at other sites have a radiometric age of ≈405,000 years ago. This equates with the marine isotope stage 11 interglacial, which culminated in a rise in sea-level to >+20 m. Bones of a juvenile Short-tailed Albatross were also found in beach deposits at +21.3 m from this same interglacial. We interpret the extirpation of albatrosses on Bermuda as probably resulting from lack of nesting sites protected from storm surges over the little emergent land that remained at the height of the marine isotope stage 11 sea level rise.

Fossil counterparts of giant penguins from the north pacific.

New fossils of giant, flightless penguinlike birds have been found in late Oligocene and early Miocene rocks in Japan and in the state of Washington. These birds belong to the order Pelecaniformes, in the extinct family Plotopteridae, previously known by a single fragment of bone from California. Hindlimb and pelvic morphology is most similar to that of Recent anhingas, but the wing is paddlelike and remarkably convergent toward penguins and flightless auks. Both the Plotopteridae and the giant penguins became extinct by the middle Miocene, possibly because of competition from seals and porpoises.

Paleognathous Carinate Birds from the Early Tertiary of North America

Fossils newly discovered in the Paleocene and early Eocene of western North America document some of the oldest birds known from nearly complete skeletons. These were medium-sized carinates with powers of sustained flight but which had a paleognathous palate like that of the flightless ostrich-like birds and the tinamous. The fossils provide additional evidence that the paleognathous palate is probably primitive and therefore should not be cited as a derived character state to define the ostrich-like birds as a monophyletic group.

Neogaeornis wetzeli Lambrecht, a Cretaceous loon from Chile (Aves: Gaviidae)

The fossil bird Neogaeornis wetzeli was described as a new genus and species by Lambrecht (1929), based on a right tarsometatarsus collected in 1923-1924 by W. Wetzel from the Upper Cretaceous Quiriquina Formation of Chile. The specimen shows the laterally compressed shaft and retracted inner trochlea typical of birds that are highly specialized for foot-propelled diving. Consequently, Lambrecht (1929) compared this fossil with loons (Gaviiformes), grebes (Podicipediformes), and the Cretaceous diving birds Hesperornis, Baptornis, and Enaliornis. Lambrecht (1933) placed Neogaeornis, Enaliornis, and Baptornis in his order Colymbo-Podicipediformes, along with loons and grebes. This was preceded by the order Hesperornithiformes, containing only Hesperornis. Brodkorb (1963) placed Enaliornis in the Gaviiformes and Neogaeornis and Baptornis in the Podicipediformes, while maintaining Hesperornis in a different subclass. Not until the important work of Martin and Tate (1976) were the relationships among the Cretaceous and modern divers clarified. Martin and Tate determined that none of the Cretaceous divers were closely related to modern loons and grebes. Within the Hesperornithiformes, they recognized three families: Enaliornithidae for Enaliornis from the Lower Cretaceous of England, Hesperornithidae for Hesperornis from the Upper Cretaceous of North America, and Baptornithidae for Baptornis, a more primitive genus than Hesperornis, also from the Upper Cretaceous of North America. Without examining the holotype, they tentatively included Neogaeornis wetzeli in the Baptornithidae. The Hesperornithiformes are not otherwise known outside of North America and none of those yet found are younger than Campanian. The Gaviiformes are unknown outside the northern hemisphere and their fossil record extends only as far back as the late Eocene (Olson, 1985). The cosmopolitan Podicipediformes are unknown before the early Miocene (Olson, 1985). Thus Neogaeornis has considerable temporal and biogeographic importance regardless of its identity. After more than 60 years, a reappraisal of the type specimen is appropriate.