The whooping crane (Grus americana), the tallest North American bird, is an endangered crane species named for its whooping sound. In 2003, there were about 153 pairs of whooping cranes. Along with the sandhill crane, it is one of only two crane species found in North America. The whooping crane's lifespan is estimated to be 22 to 24 years in the wild. After being pushed to the brink of extinction by unregulated hunting and loss of habitat to just 21 wild and two captive whooping cranes by 1941, conservation efforts have led to a limited recovery. As of 2011, there are an estimated 437 birds in the wild and more than 165 in captivity.