Let's Talk About Birds: Steller's sea eagles
This is one of a series presented by the National Aviary, which works to inspire respect for nature through an appreciation of birds.
As sleet pelted the National Aviary one wintry afternoon, our African penguins and bald eagles sought cover and warmth for the long evening ahead. But our Steller's sea eagles did not. Rather than retiring to their shelter safe from the cold wind and soaking rain, both birds perched high in their exhibit, wings spread wide, to bathe. To a warm-blooded human, this seems crazy. But for some birds, a Pittsburgh wintery mix is just another day in paradise.
The heaviest eagle in the world, the Steller's sea eagle sports a chocolate brown body with white tail and shoulders. It is equipped with a large bright yellow beak and matching feet. Like most raptors (hawks, eagles, falcons, owls), females are roughly 33 percent larger than their male counterparts. On average, a female Steller's can weigh between 15 and 20 pounds; the male weighs between 11 and 13 pounds.
As the name suggests, these sea eagles live along coastal areas of northeastern Russia, where they eat freshly caught (and some dead) fish. Here, the summers are cool, usually in the 50- to 60-degree range. However, in their wintering lands in northern Japan, a daytime temperature in the low 20s is considered warm. So how do Steller's sea eagles stay warm during these colder times of the year?
The answer is adaptation. A bird that flies has adapted so that most of its muscles are close to the center of its body to support the wings in flight. This is helpful because working muscles produce heat. But flying in cold weather is not the best use of the bird's energy resources. So, other activities such as shivering and digesting food also causes these muscles to work hard and create enough warmth for the bird.
However, creating heat doesn't help if the bird cannot maintain it. Short fluffy downy feathers cover a bird's body, keeping the generated heat close to the skin and the cold air out. As one of the largest eagles in the world, the Steller's sea eagle has no shortage of downy feathers to stay warm. Feathers cover their entire bodies, except their beaks and feet. The beak and feet are mostly bone and tendon, which do not need a large supply of blood. Because no blood vessels are close to the surface, there is little heat loss from these parts of the body.
Steller's sea eagles can live to be more than 20 years old and reach maturity at about 5 years of age. These birds are considered vulnerable due to overfishing, accidental poisoning and climate change. The National Aviary is home to two Steller's sea eagles: Kodiak, a 7-year-old male, and Aleutia, a 10-year-old female. Kodiak and Aleutia are part of a captive breeding program to ensure the future of the species.
Our Stellar's sea eagles are happy to watch you from the comfort of their outdoor digs, and you can watch them from the comfort of our indoor viewing area. Beat the cold by visiting the National Aviary daily from 10 a.m-5 p.m. Use the information at www.aviary.org to plan your visit.
This is one of a series presented by the National Aviary, America's bird zoo. The National Aviary works to inspire a respect for nature through an appreciation of birds.
First Published January 23, 2013 12:00 am