Birds are vertebrates, with a backbone and skeleton, although some of the bones are hollow to keep the bird light. Their forelimbs have the same bones as the human arm, but they are highly modified to form the structure for wings. Some of the bones in the wrist and fingers are fused together for extra strength.
Like mammals, birds are endothermic, or warm blooded, but they are the only animals that have feathers. The feathers are made of keratin. Each feather has a stiff, hollow center shaft with hundreds of side branches, called barbs. Each barb has two rows of side branches, called barbules. This structure allows air to gather in the feathers, making them lightweight and keeping the bird’s body heat from escaping.
All birds lay eggs with hard, waterproof shells, which they create nests for. A nest may be just a scrape in the sand or an elaborate structure of twigs, leaves, and other gathered materials. Birds incubate their eggs until they hatch. The parents continue to care for their young, bringing food to the nest site as needed. The chicks of some bird species, like chickens, are already covered with down and can start finding their own food. They are called precocial. Other chicks, like robins, hatch with no feathers and are helpless, depending on their parents to feed them. They are called altricial.
There are more than 9,800 known species of birds. The smallest is the male bee hummingbird, which is 2.25 inches (5.7 centimeters) long and weighs only 0.056 ounces (1.6 grams). Its body is the size of a large bumblebee! The largest bird is the ostrich, which can weigh up to 340 pounds (154 kilograms). The bird with the most feathers is the tundra, or whistling, swan, which has more than 25,000 feathers. The bird that flies the fastest is the peregrine falcon: 117 miles per hour (188 kilometers per hour) in a steep dive.
Visiting the San Diego Zoo and the San Diego Zoo Safari Park helps support a managed breeding program for an endangered little bird that lives on one island in the whole world. The San Clemente loggerhead shrike program is supported by San Diego Zoo Global in collaboration with the U.S. Navy to increase and support the wild population of these songbirds. The shrike is about the size of a mockingbird but is a tough survivor that hunts for mice and lizards.
The program is run on the undeveloped, Navy-owned San Clemente Island off the coast of Southern California. Our population managers strive to maintain good genetic diversity, resulting in healthy animals that can survive and breed in the wild upon release. Since 1999, this program has released about 30 to 40 captive-bred birds each year, and the wild population has grown from only 5 breeding pairs in 1999 to over 50 breeding pairs in 2006. 2008 was a banner year; the wild population successfully fledged more chicks than any previous year. By 2011, the breeding population numbered more than 170 shrikes! More than 70 percent of the wild breeding pairs are release birds or their descendants.
Since the Hawaii Endangered Bird Conservation Program began in 1994, almost 1,000 chicks, representing 14 of Hawaii's most threatened bird species, have been raised at our Keauhou and Maui bird conservation centers. In an effort to prevent extinction and promote the recovery of the wild populations, more than 780 birds have been reintroduced into protected habitat throughout the Hawaiian Islands, including 222 puaiohi (a small thrush from the island of Kauai), and 442 nene (Hawaiian goose) to augment existing populations on the Big Island, Maui, and Kauai, as well as establishing a new population on Molokai.
But Hawaiian birds continue to face to major challenges. The alala (Hawaiian crow) is extinct in the wild, and the entire population numbered only 20 birds in the early 1990s. Thanks to our successful captive breeding program, the alala population currently numbers more than 100 birds, and we are making plans to reestablish the wild population in the next few years. We are also continuing captive breeding programs for palila and Maui parrotbills, with the aim of incorporating the release of captive-bred birds in a multi-faceted approach to avian conservation. Finally, environmental education programs continue to play a key role at both our bird facilities.
Working with Mexican partners, the California Condor Recovery Program is working to restore the California condor to Baja California, Mexico. At our field release site, researchers continue to study habitat use, foraging, social groupings, behavior, and condor ranging by GPS tracking. Researchers also address some of the challenges to free-flying condors, such as lead poisoning and ingesting microtrash.
In 2007, one of the birds from the program ventured up to San Diego County, and researchers continue to monitor the birds as they further explore the region, carefully watching the patterns of potential breeding pairs to see if they begin to nest and produce a chick. Today, you can watch a condor chick grow on Condor Cam!