Denver Zoo Map
July 3, 2014


By Jennifer Nixon, Denver Zoo Bird Keeper

Introducing this week’s feathered friend, Toano. He is a male bald eagle (Haliaeetus leucocephalus) that US Fish and Wildlife Service recovered from the wild in 2000 when he got West Nile Virus. His illness was severe enough that he would not have survived in the wild. After his rehabilitation he came to the Denver Zoo in 2002 and now he tells the plight of the bald eagle to everyone.

He eats many foods here at the zoo but his favorite is rats. He is also the more timid of our two eagles. He is typically found toward the back of the exhibit like in the picture above. Toano always waits for his female to eat first before he will eat. He is the quiet one and if one of them is vocalizing, it is most likely the female. You can see the size difference between him and the female named Oenone. As usual with birds of prey the females are larger.

You can visit Toano and Oenone at their current home in the exhibit across from the flamingo ponds next to the Andean condors.

Interesting conversation facts about the bald eagle:

  • Vocalizations of bald eagles are a shrill, high-pitched twittering. The usual depiction on TV is actually the call of the red-tailed Hawk.
  • Bald eagles have no vocal cords, the sound actually comes from the syrinx (bony chamber where the trachea divides to the lungs).
  • They have 4 times better vision than a perfect human eye.
  • Their feathers weigh twice the amount of their skeleton, made of hollow bones.
  • The oldest bald eagle on record was 48 years old in Stephentown, NY. Toano is at least 14 years old and Oenone is at least 34 years old.
  • Bald is actually a term meaning white, not bare.

The bald eagle was chosen in 1782 as the emblem because of its long life, great strength and majestic looks. Their species started declining in numbers in the late 1800’s. In 1940 the Bald and Golden Eagle Act started protecting them but they continued to decline. By the 1960’s the number of breeding pairs was lower than 450. In 1967 they were listed on the Endangered Species List and in 1972 DDT (one of the main reasons for the decline) was banned. By the 1990’s the numbers had increased to more than 4500 pairs and by 2007 there were around 10,000 pairs and they were taken off the Endangered Species List. The bald eagles are still protected by The Bald and Golden Eagle Protection Act and the Migratory Bird Treaty Act of 1918. Under the 1940 act it is still illegal to own any feathers or other parts of an eagle. Recognized Native American tribes can submit an application to obtain feathers and other items from the USFWS. This is a wonderful comeback by a species that is very close to the heart of most Americans and proof that when people take action a positive outcome can be accomplished for a species headed to extinction.

One of the main problems for the eagles was when DDT became the leading pesticide in the world. DDT concentration increases as it moves up the food chain. As the top animal in the food chain, Toano’s species is vulnerable to toxins as they become more concentrated. Plants and insects contain small amounts of DDT but rabbits eat many plants, and small birds eat thousands of insects, multiplying the effect within their tissues. Consuming numerous rabbits and birds, eagles accumulate greatly magnified DDT levels. The increased DDT levels caused thinning of the egg shells and increased the amount of eggs that broke in many bird of prey species, not just eagles. Unfortunately DDT does not excrete from the tissues of animals and is still in the food chain many years after it was banned. Other problems for bald eagles include: hunting, lead shot poisoning and habitat destruction all of which are illegal under their current protections. Even prohibiting habitat destruction that disturbs eagles falls under the current level of protection. Find more information visit or

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