Fossil Birds of Anza-Borrego Desert State Park
Birds of Ancient Southern California

The fossil record of Anza-Borrego Desert State Park preserves a diverse assemblage of birds that inhabited southern California during the Pliocene and Pleistocene. These fossils provide important evidence for ancient environments, climate change, and the evolution of North American bird communities.

Bird fossils are generally less common than those of mammals because their hollow bones are fragile and less likely to be preserved. Nevertheless, Anza-Borrego has produced an important record of fossil birds ranging from waterfowl and shorebirds to large terrestrial species and powerful birds of prey.

Birds in Ancient Anza-Borrego
During the late Cenozoic, Anza-Borrego supported a variety of habitats including rivers, lakes, wetlands, grasslands, and open woodlands. These environments provided homes for many different bird species.
Fossil birds occupied ecological roles similar to those seen today. Some were aquatic species associated with lakes and rivers, while others were terrestrial birds adapted to open landscapes. Predatory birds also played an important role in maintaining ecological balance within ancient ecosystems.

The diversity of bird fossils helps scientists reconstruct the habitats and environmental conditions that existed in southern California millions of years ago.

Giants of the Sky
Among the most spectacular birds known from the fossil record of southern California are the teratorns, giant soaring birds with wingspans far exceeding those of modern condors. These impressive scavengers and predators were among the largest flying birds ever to inhabit North America.

Fossils from Anza-Borrego contribute to our understanding of these remarkable birds and the ecosystems that supported them.

What Bird Fossils Tell Us
Bird fossils provide valuable information about:
  • Ancient habitats and climate
  • Wetland and river systems
  • Migration and dispersal patterns
  • Ecosystem diversity
  • Environmental change through time
Because birds often respond rapidly to environmental conditions, they are particularly useful indicators of past ecosystems.
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Explore a Fossil in 3D
Rotate, zoom, and examine this specimen from the Anza-Borrego Desert State Park collections.
Interactive 3D Model: Terror Bird beak
​Specimen Information
  • Catalog Number: LACM6747 V/26697
  • Element: Beak
  • Group: Palm Spring
  • Formation: Olla
  • Epoch: Pliocene
  • Age: Blancan and/or Irvingtonian
  • Locality: Fish Creek / Vallecito Creek
  • Scanned using Agisoft Metashape
  • Specimen © California State Parks. 3D model produced by the Anza-Borrego Desert State Park Paleontology Society.
Why Anza-Borrego Matters
Anza-Borrego Desert State Park preserves one of the most important late Cenozoic fossil records in North America. Although less abundant than mammal fossils, bird remains provide an important perspective on the changing environments of the Colorado Desert region.

Together with fossils of mammals, reptiles, fish, and invertebrates, fossil birds help create a more complete picture of ancient ecosystems preserved within the park.

Subsequent Discoveries
Since the publication of Fossil Treasures of the Anza-Borrego Desert, additional discoveries have expanded our knowledge of fossil birds in the park.

One of the most significant is the identification of the terror bird Titanis from the Olla Formation. Terror birds were large, flightless predatory birds that originated in South America and later dispersed into North America as part of the Great American Biotic Interchange.

The discovery of Titanis in Anza-Borrego represents one of the most remarkable bird fossils known from the park and demonstrates the continuing scientific importance of its fossil resources.

For more information, see the separate Titanis page on this website.

Fossil Record
The Anza-Borrego fossil record includes numerous bird taxa listed in Appendix Table 3 of Fossil Treasures of the Anza-Borrego Desert. These include water birds, shorebirds, birds of prey, and large terrestrial species preserved in Pliocene and Pleistocene deposits. The Anza-Borrego fossil record includes at least 40 bird taxa. This list is now out of date and does not include later discoveries such as Titanis. Contact us directly for an updated list.

Bird fossils recovered from the park include limb bones, skull fragments, vertebrae, and other skeletal elements that help document the diversity of ancient avifaunas in southern California.

Quick Facts
  • Class: Aves
  • Includes: Water birds, raptors, shorebirds, teratorns, and other fossil birds
  • Age: Pliocene and Pleistocene
  • Significance: Evidence of changing habitats and ecosystems
  • Notable discovery: Titanis terror bird from the Olla Formation
  • Location: Anza-Borrego Desert State Park, California
Learn More
Read Chapter 9 "The Fossil Birds of Anza-Borrego", in Fossil Treasures of the Anza-Borrego Desert for a detailed discussion of the avian fossil record of Anza-Borrego Desert State Park.