The saber-tooth cat snarls
and lunges towards a pack of dire wolves. The big dogs are closing
in with hopes of having seconds on a ground sloth carcass the lioness has
extracted from the goo and killed. A few small La Brea Caracaras scamper
in from behind to try to grab bites but squeal away as the big cat skids
|Patiently perched on a nearby juniper snag, a Merriam's
Teratorn dries its wings in the early morning sun. This gigantic carrion
vulture weighs 40 pounds and has a wingspan of 12 feet. Soon many individuals
of several species of condors and eagles, then a few Occidental Vultures
as well as mammalian scavengers, will stealthily circle down for last dibs
on bone marrow, skin or gristle. This is a place of dark termination.
But then a White-crowned Sparrow sings from a nearby rabbitbrush thicket
above a gopher snake probing the lodge of a dusky-footed woodrat. A California
Thrasher scratches in leaf litter on the shoulder of a well worn camel
It is a typical late-Pleistocene morning at the tar pits - 15,000 years
ago on the coastal plane of Southern California. It is also a birder-naturalist's
dream: the best of two epochs.
La Brea Caracara
Birds through Time
Earth's fossil record of "birds"
dates back 150 million years, to the Jurassic Period. Paleontological artifacts
that old are often a hard call between avian and reptilian. The first known
birds (like Archaeopteryx) were lizardy with long, branched, feather-like
scales along the trailing edge of the "wings." Animals from this
far back are only ancestors of living forms, each one entirely unique from
all birds here today.
The extinct Fragile Eagle
|Later, through the Cretaceous Period, bird skeletons such as Hesperornis
(a flightless, loon-like bird) and Icthyornis (a strong, flying predator)
are more easily identified as such, and by the Miocene Epoch in middle
of the Tertiary, about 60 million years ago, true birds were becoming common.
Skeletal and impressed remains appear more like the birds we see today,
and by the end of the Tertiary (1,000,000 years ago) all but four of the
orders of birds now living, and about half of the families, are known to
have been present.
The Pleistocene Epoch persisted up until 14,000 years ago - just prior
to the Recent Epoch in which we now live. Many avian fossil bits from the
Pleistocene are identical to what is here now and are members of the same
When not molested by geologic upheaval (or the arrival and over-success
of Homo sapiens), a species of bird may go 30 or 40 thousand years before
it passes naturally into time. From the fossil records, avian paleontologists
have projected that perhaps 150,000 species of birds have lived on Earth
since the Cretaceous Period. Given that there are only about 1800 documented
prehistoric species and that they are mostly big ones, we can deduce that
smaller and more fragile kinds were not saved... even in the most perfect
Very few passerines (perching birds) have been found previous to the
Pleistocene deposits in Southern California due, in part, to the fact that
the shelf-life for their dainty skeletons is short no matter how tight
the packaging and, more, to the surmisal that, of all birds, they are the
most recently evolved.
In the Miocene Epoch, much of California (and other portions of North
America) were under waters of what is now the Pacific Ocean, and many fossil
deposits from now-interior localities of the state contain mainly, or exclusively,
seabirds! The earliest California birds are from this epoch.
Sulids (boobys) of six species were common, while cormorants were rare.
Miocene tubenoses include three shearwaters, a storm-petrel, and an albatross.
The Diatomite Shearwater (compacted, single-celled diatom mud held the
imprints of many fossils in Southern California) was the size of a Black-vented
but had shorter wings and longer legs. It was abundant. The Miocene Albatross
was smaller even than a Black-footed, and the Hubb's Storm-petrel had big
feet. Single leg- and foot-bone imprints of the Dubious Auklet are similar
to those of a Rhino. An old lake bed near Barstow gave up bones of a flamingo-like
bird that also occurred in Idaho. The only Miocene landbirds are a quail
(genetically different from anything today) and three hawks - two extinct
buteos and Miohierax stocki, different from any present-day raptor.
The next epoch, the Pliocene, was similar to the Miocene both in the types
of birds (mostly seabirds) and in the inundation of California's lowlands.
Some interesting finds from the Pliocene are two species of extinct loons;
a grebe intermediate in size between a Horned and a Red-necked; Mancalla,
the Flightless Auk; fewer Sulas and more cormorants; and the big Kern Vulture,
most closely related to the current King Vulture.
The Grinnel Eagle
The Pleistocene Epoch, alias the Ice Age,
is that era when periodic glaciation came further south and to lower altitudes
then it does today. Earth, however, was not frozen solid, and some areas,
even in North America, were spared glacial penetration. Lowland California
was such a place.
It is no surprise that the fossil record of birds is best represented in
the Pleistocene, because it is relatively modern and because birds had
evolved (perhaps to their peak) during that time. The huge fossil record
in California, the finest in the world, is a surprise and is mostly attributable
to beds of soft tar that seeped from within the ground, forming pits. From
three spots in Southern California, Rancho La Brea, McKittrick, and Carpenteria
more that 140,000 individuals of over 130 species of birds have been exhumed
from their tarry tombs and catalogued into museum collections. Including
birds from several other Pleistocene sites, the number of California species
is more like 180, and of these about 30 (including the recently extinct
Passenger Pigeon) have no living descendants.
The avifauna of the Pleistocene was very large and diverse. It is thought,
there may have been 2000 more species, worldwide, than there are today.
Among the more outrageous of these in California, the Sinclair Owl was
a Bubo larger than a Great Gray. The Incredible Teratorn was a meat eater
30% bigger than the huge Merriam's Teratorn; its wingspan was 16 feet (excessive
"pishing" would not have been a good idea at this place). If
this seems tame by present-day standards, consider the teratorns' relative
from South America, Argentaris magnificens: with a 23-foot spread, it was
the largest known bird able to fly! The Asphalt Stork of Pleistocene California
was slightly more petite than the present-day Jabiru. It is curious that
only one Brown Pelican and three individual gulls have been located; these
kinds must have evolved and flourished elsewhere and recently come to California
The tar pits attracted and swallowed-up large numbers of animals, including
many mammals and waterfowl. It is possible that some of these were entrapped
because they were attracted to pools of rainwater that formed on the surface
of the tar. Others, especially
mammals and reptiles, no doubt walked right into it, perhaps at night.
Some must have died on the edges or pulled themselves free only to be whacked
by a predator. Because of the abundant death, predators and carrion eaters
were very common, and many of them also became fatally stuck in the goo.
Two-thirds of all the birds of the tar pits were birds of prey. Specimens
of Bald (170) and Golden (900) eagles suggest they must have been abundant,
and five extinct eagles are also represented. Several scavengers, most
now extinct, were common. Turkey Vulture was very rare. Conversely, of
nine owl species recovered at La Brea, eight are living today. Only Strix
brea (like Spotted Owl but bigger) is no longer with us. Most of the landbirds
recovered are those we see commonly in California today - but it would
have been nice to get a look at Pipilo angelensis, the L.A. Towhee.
One hundred years ago virtually nothing was known about prehistoric
birdlife, and now 1800 species have been identified worldwide. The Western
Field Ornithologists' 1996 official Field List of California Birds contains
592 species, including eight introduced and three extirpated. (In the U.S.
this total is second only to Texas.) Given that California's inventory
of extinct species is superb, wouldn't it be nice to know the numbers of
all the local bird species, not just those that still exist?
(Above: The fossilized remains of
Howard, Hildegarde, 1962. Fossil Birds, Science Serioes
53, Los Angeles County Museum of Natural History.
Stock, Chester, 1956. Rancho La Brea: A record of Pleistocene
Life in California, Science Series 37, revised 1992 by John M. Harris,
Los Angeles County Museum of Natural History.
Webster, Richard, 1979. "Birding the Tar Pits: 12,000
BC." Western Tanager Volume 45. Number 10, Los Angeles Audubon Society.
We want to thank Kimball L. Garret and Jean Brandt for
sending copies of relevant printed material; Loye Miller and John Merriam
for beginning in 1907, the long and gloppy job of exhuming and identifying
thousands of creatures from the pits, and Hildegarde Howard and Alden Miller
for completing the job. Thanks to Cathy McNassor and other personnel at
the Los Angeles County Museum of Natural History for providing photographs
of fossil skeletons.
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