Giant, fruit-gulping pigeon eaten into extinction on Pacific islands


Date:
July 22, 2020
Source:
Florida Museum of Natural History
Summary:
A large fruit-eating bird from Tonga joins the dodo in the lineup
of giant island pigeons hunted to extinction.



FULL STORY ==========================================================================
A large fruit-eating bird from Tonga joins the dodo in the lineup of
giant island pigeons hunted to extinction.


========================================================================== Fossils show that Tongoenas burleyi, a newly described genus and species, inhabited the Pacific islands for at least 60,000 years, but vanished
within a century or two of human arrival around 2,850 years ago.

Unlike the dodo and the extinct Viti Levu giant pigeon of Fiji,
however, T.

burleyi could fly. This canopy-dwelling species co-evolved with
fruit-bearing trees in the mango, guava and chinaberry families, acting as
an essential forest cultivator by spreading seeds to new locations. The
size of a large duck, Tongoenas burleyi was likely capable of swallowing
fruit as big as a tennis ball, said study lead author David Steadman,
curator of ornithology at the Florida Museum of Natural History.

"Some of these trees have big, fleshy fruit, clearly adapted for
a big pigeon to gulp whole and pass the seeds," Steadman said. "Of
the fruit-eating pigeons, this bird is the largest and could have
gulped bigger canopy fruit than any others. It takes co-evolution
to the extreme." The absence of T. burleyi from the Tongan islands
could threaten the long-term survival of local trees that depended on
the pigeon as a seed transporter, said study co-author Oona Takano,
a doctoral student at the University of New Mexico.

"T. burleyi provided an important service by moving seeds to other
islands," said Takano, who was previously a research assistant at the
Florida Museum.

"The pigeon species on Tonga today are too small to eat large fruits,
which imperils certain fruit trees." When Steadman first found
T. burleyi fossils in a cave on the Tongan island of 'Eua, he was
immediately impressed by their size: The bird was about 20 inches long,
not including the tail, and weighed at least five times as much as the
average city pigeon.



==========================================================================
"I said, 'Oh my God, I've never seen a pigeon that big,'" Steadman
said. "It was clearly something different." Once he and archaeologist
David Burley of Simon Fraser University -- who is also the species's
namesake -- began excavating charred and broken remains of T. burleyi at archaeological sites, "we knew it was another human-caused extinction," Steadman said. "Pigeons and doves just plain taste good." Columbids, the family that includes pigeons and doves, had few predators or competitors
before people reached the Pacific islands, he said. The region was devoid
of primates and carnivores such as cats, dogs and weasels, and hawks
and owls were absent from many islands. The birds flourished in this
nurturing environment, diversifying over the past 30-40 million years.

Today, the Pacific islands are the global epicenter of pigeon and dove diversity, with more than 90 species, ranging from fruit doves as light as
a handful of raisins to the turkey-sized, ground-dwelling crowned pigeon
of New Guinea. But the number and distribution of birds in the region
is a shadow of what it once was, Steadman said. Tonga's four remaining
species of pigeons and doves represent less than half of the islands'
historic diversity.

"This is another example of how looking at the modern fauna doesn't
yield a complete picture of a region's diversity," he said.



========================================================================== Steadman and Takano analyzed the features of columbid hindlimbs, dividing
them into three groups: tree-dwelling species, ground-dwellers and those
that live both on the ground and in trees. Pigeons and doves that spend
most of their time in the canopy tend to have shorter legs, more suitable
for perching and gripping in high winds. Those that forage for seeds on
the ground have longer legs adapted for walking and running. Birds that
flit between the understory and the forest floor have legs that are a
blend of the characteristics of the other two groups.

The researchers found surprising agreement between the groupings based on
leg characteristics and molecular data: In other words, canopy-dwelling
pigeons tend to be more closely related to one another than to birds in
the other two groups.

"Given that there are 350 species of pigeons and doves, people might
suspect these big changes in lifestyle evolved independently many
times," Steadman said. "But right now, we don't have evidence that
it happened more than once - - at least in the tropical Pacific."
The relatively short hindlimbs of T. burleyi mark it as a canopy-dwelling species. Steadman hypothesized the species featured the bright, even
gaudy, plumage of other pigeons that live in treetops, where intense
colors provide better camouflage than the muted browns and grays of
pigeons that live on the ground.

The researchers dedicated the study to the memory of W. Arthur "Art"
Whistler, whose expertise in West Polynesian botany was unsurpassed,
Steadman said.

Whistler died from COVID-19 in April.

"There wasn't a plant on Fiji or Tonga that Art didn't know, including
all of the pigeon-dispersed fruits," Steadman said. "He was a true plant
nerd and complete salt of the earth. He always made time for people."

========================================================================== Story Source: Materials provided by
Florida_Museum_of_Natural_History. Original written by Natalie van
Hoose. Note: Content may be edited for style and length.


========================================================================== Journal Reference:
1. David W. Steadman, Oona M. Takano.

A new genus and species of pigeon (Aves, Columbidae) from the
Kingdom of Tonga, with an evaluation of hindlimb osteology of
columbids from Oceania
2. . Zootaxa, 2020; 4810 (3): 401 DOI: 10.11646/zootaxa.4810.3.1 ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2020/07/200722163236.htm

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