The Unknown Owl of Pleistocene Georgia

A few scraps of bone found at just 2 fossil sites in Georgia indicate a now extinct species of owl, larger than any present day owl species, used to live in the region.  Starrs Olson compared a mandibular symphysis discovered on Ladds Mountain, Bartow County with those from a great horned owl (Bubo virginianus), a snowy owl (Nyctea scandiaca), and a great gray owl (Strix nebulosa).  On a human the mandibular symphysis is the cartilage in the front dimple of the chin that connects the left jaw bone with the right jaw bone, but on a bird it’s the lower bill.  The unknown species of owl’s lower bill was significantly larger than those from the extant largest species of owls.

Marshall Forest

Photo comparing the mandibular symphysis of the unknown Pleistocene species with those from the 3 largest species of extant owls.  It’s the largest lower bill, suggesting this extinct species was larger than any North American owl species still extant.

David Steadman examined all the bird fossils excavated from Kingston Saltpeter Cave, also located in Bartow County, and he came across 2 unusually stout tarsometatarsii from juvenile owls that didn’t match the measurements from any known species of owl.  The tarsometatarsi is a bird’s equivalent of an ankle bone.

Tarsometatarsii from vultures and condors.  I couldn’t find any photos on the web of owl tarsometatarsi.

Those 2 specimens from Kingston Saltpeter Cave either belong to the same species that Starrs Olson examined, or they belong to yet another unknown extinct species.  Neither paleo-ornithologist was willing to describe a new species based on such scant evidence, even though it’s fairly certain a large unique owl did exist here during the Pleistocene.  This case reminds us of why the La Brea Tar Pits are of such value to science.  A different extinct Pleistocene owl also used to live in the American southwest.  It’s known as the Brea owl and was recently given the new scientific name Oraristrix brea.  At least 23 individual Brea owls became trapped in the tarpits, leaving scientists with many specimens to examine.  But if it wasn’t for the tarpits, there’s barely enough evidence to recognize this animal as a species because just a few fossil specimens of this owl have been found at 2 other sites in Arizona and Mexico.

The unknown Georgia species was likely a spectacular bird that would have impressed any human who had a chance to see it.  Like most large predatory birds, it probably lived in low population densities.  Let’s assume an average of 1 individual lived per 10 square miles, and that an average owl’s lifespan was 3 years.  Let’s also assume this bird had a limited geographical range of about 60,000 square miles ( the area of present day Georgia).  And suppose this animal existed as a species for 1 million years.  I did the math: 1.8 billion individuals of this undescribed species of owl lived on earth, and the only evidence we can find is a lower bill and a couple ankles.  Moreover, there’s no evidence at all of its immediate evolutionary ancestor.  My calculations show just how low the odds of an organism becoming a fossil can be, especially for a forest bird that successfully can avoid dying in a flood when the possibility of being covered by sediment and preserved is higher.  No Pleistocene fossils of ivory-billed woodpeckers or Carolina parakeets have ever been found either, though parakeet fossils from the Pliocene have been unearthed in Nebraska.

Scientists are interested in finding more fossils of this owl.  Besides earning the honor of naming a new species, they want to unravel the possible evolutionary relationship between this large owl, and the extinct giant Cuban owl (Ornimegalonyx), a flightless owl that served as top predator there until its extinction when man disrupted the environment.  The unknown Georgia owl was probably not flightless because it would have faced too much competition from large mammalian predators.  Its shorter, stouter legs suggest it was also not likely a ground dweller, like the Brea owl of the southwest.  Nevertheless, it undoubtedly was at least a fearsome predator as the 3 large owls below.

Great horned owl with captured skunk.  The great horned owl is the heaviest extant species.  They’ve been known to prey on tom cats and they regularly prey on skunks, squirrels, rabbits, turkeys, and grouse.

The lower bill of the unknown extinct species was 25% larger than that of this species, the great gray owl.  If the overall body proportions were the same, than the extinct Pleistocene owl of Georgia was probably about 25% larger  than this species as well.

Snowy owls have been known to attack small house dogs.  The extinct Pleistocene species that used to live in Georgia was also likely a fearsome predator of small mammals.

What caused the extinction of this mystery owl?  I believe a large fearless owl living in low population densities was easily overhunted by men.  According to George Leonard Herter, owl meat is as white and flavorful as chicken.  They reportedly have large drumsticks.  There’s also the possibility that this owl scavenged meat for part of its diet, and the extinction of the megafauna reduced its food supply.  Or this owl may have had a narrow ecological niche that disappeared at the end of the Pleistocene.  Whatever the reason for its extinction, it’s a shame that we know so little about this animal.

References:

Campbell, Kenneth; and Zbigniew Dochinski

“A New Genus for the Extinct Late Pleistocene Owl Strix brea (Aves: Strigiformes) from Rancho La Brea”

Australian Museum of Natural History 62 (1) 2010

Olson, Starrs

“A Very Large and Enigmatic Owl from the late Pleistocene at Ladds”

Special publication of the Carnegie Museum of Natural History 1984

Steadman, David

“Fossil Birds from Kingston Saltpeter Cave, Bartow County, Georgia”

The Late Pleistocene Record of Kingston Saltpeter Cave, Bartow County, Georgia edited by Joel Sneed and Larry O. Blair

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4 Responses to “The Unknown Owl of Pleistocene Georgia”

  1. Jose White Says:

    There are some 220 to 225 extant species of owls, subdivided into two families: typical owls (Strigidae) and barn-owls (Tytonidae). Some entirely extinct families have also been erected based on fossil remains; these differ much from modern owls in being less specialized or specialized in a very different way (such as the terrestrial Sophiornithidae ). The Paleocene genera Berruornis and Ogygoptynx show that owls were already present as a distinct lineage some 60–57 mya ( million years ago ), and, hence, possibly also some 5 million years earlier, at the extinction of the non-avian dinosaurs . This makes them one of the oldest known groups of non- Galloanserae landbirds. The supposed ” Cretaceous owls” Bradycneme and Heptasteornis are apparently non- avialan maniraptors .

  2. The Rodent Fossils Found in Kingston Saltpeter Cave | GeorgiaBeforePeople Says:

    […] Kingston Saltpeter Cave served as a roost for at least 3 species of owls, including screech (Otus asio), probably a long-eared (Asio sp?), and a very large unknown extinct species (Strigidae sp?).  See https://markgelbart.wordpress.com/2013/04/22/the-unknown-owl-of-pleistocene-georgia/ […]

  3. Night Sounds of the Pleistocene | GeorgiaBeforePeople Says:

    […] I’d also be sure to hear owls, perhaps even the unknown extinct species only known from 2 ankles and 3 lower bills found at the Kingston Saltpeter Cave and Ladds fossil sites (See:https://markgelbart.wordpress.com/2013/04/22/the-unknown-owl-of-pleistocene-georgia/) […]

  4. I Lured a Barred Owl (Strix varia) to My Yard | GeorgiaBeforePeople Says:

    […] Barred owls have probably been the most common owl in southeastern North America for millions of years.  Their fossil remains are more abundant than any other species of owl in the fossil record of Florida, the southern state with the most Pleistocene-aged sites.  Barred owl fossil remains have been found in at least 10 sites in Florida.  The smaller screech owls (Otus asio) are the next most abundant owl in the fossil record, having been excavated from 8 sites in Florida and 1 in Georgia.  The larger great horned owls have been found in just 5 Florida fossil sites.  Fossil remains of the long-eared (Asio otus) and the short eared owl (Asio flammeus) total just 4 sites in Georgia and Florida.  Fossil remains of burrowing owls (Athene cuniculara) were abundantly found but at just a single site in Florida.  There was a poorly known extinct species of owl living in Georgia during the Pleistocene that has yet to be named as a species.  (See:https://markgelbart.wordpress.com/2013/04/22/the-unknown-owl-of-pleistocene-georgia/) […]

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