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Gastornis roamed Arctic in the Eocene (free pdf)

Ben Creisler

A new paper in open access that may be of interest:

Thomas A. Stidham & Jaelyn J. Eberle (2016)
The palaeobiology of high latitude birds from the early Eocene
greenhouse of Ellesmere Island, Arctic Canada.
Scientific Reports 6, Article number: 20912 (2016)
http: // www.nature.com/articles/srep20912

Fossils attributable to the extinct waterfowl clade Presbyornithidae
and the large flightless Gastornithidae from the early Eocene (~52–53
Ma) of Ellesmere Island, in northernmost Canada are the oldest
Cenozoic avian fossils from the Arctic. Except for its slightly larger
size, the Arctic presbyornithid humerus is not distinguishable from
fossils of Presbyornis pervetus from the western United States, and
the Gastornis phalanx is within the known size range of mid-latitude
individuals. The occurrence of Presbyornis above the Arctic Circle in
the Eocene could be the result of annual migration like that of its
living duck and geese relatives, or it may have been a year-round
resident similar to some Eocene mammals on Ellesmere and some extant
species of sea ducks. Gastornis, along with some of the mammalian and
reptilian members of the Eocene Arctic fauna, likely over-wintered in
the Arctic. Despite the milder (above freezing) Eocene climate on
Ellesmere Island, prolonged periods of darkness occurred during the
winter. Presence of these extinct birds at both mid and high latitudes
on the northern continents provides evidence that future increases in
climatic warming (closer to Eocene levels) could lead to the
establishment of new migratory or resident populations within the
Arctic Circle.