In Love With Earth

You are here: Home Discover Blog Nature BRACKENDALE'S BALD EAGLES
Thursday, 26 December 2013 23:50

BRACKENDALE'S BALD EAGLES

It was January when I moved to Squamish and to Canada. A day after arriving, the first thing to do on that beautiful, crisp Saturday afternoon was to check out the local river trails.  With a bit of luck we would see those famous bald eagles...and we weren't disappointed. Walking beside the salmon spawning channels it felt like being in a wildlife documentary - rotting salmon carcases, eagles perched high and that unmistakable smell that is bizarrely gross and kinda cool at the same time (in a nerdy, discovering-nature kind of way). Yup, it was bald eagle season in Squamish.

Mature bald eagles perched on trees

The area around Brackendale and Squamish is the winter home for hundreds of bald eagles. These majestic birds are amazing to watch. Winter after winter it's difficult not to keep your eyes peeled for them, in the trees, in the sky or on the riverbed.

But I'm ashamed to say that eight winters in and I don't know much about them. Time to change all that!

 

Size Matters

Big, beautiful and bald?  Hmmm? It doesn't take a brain surgeon to see they're not bald. So where does the name 'bald eagle' come from? Turns out, the name comes from 'piebald', which is an old English name to describe black and white patched animals. Get close enough to them though and you can see they're not even black, but brown.  So let's settle on big, beautiful and brown.

They are found throughout North America, from its head to its tippie-toes - or from the Arctic to the Sonoran Desert in northern Mexico to be more precise. Despite being found from north to south and east to west, they are a species of sea eagle. Where's the sea in Manitoba or Utah I hear you ask. I had the same question. Seems they don't have to be close to the sea. Any large enough fish habitat such as a river or lake, or other wetland area such as a marsh, will be enough for them to survive.

Another interesting fact about their distribution relates to their size. Under Bergmann's Rule (which I had never heard of before), certain animals are known to be bigger the further away from the equator they get (the rule suggests that the body weight to body surface ratio changes to help control body heat). The smallest bald eagles live in Florida and the largest in Alaska.  

 

Body Beautiful

What words would you use to describe the bald eagle? Noble, intimidating, beautiful, lofty...would be some I'd use. With a wingspan of over six feet, when one soars overhead you can't help but stand and watch as it goes by.

A bald eagle lands in his nest and a head shot of a bald eagle (separate image)

Left: A bald eagle approaches his nest in Alaska. Right: Getting up close and personal. Photo credits

Like other raptors, they are honed to perfection. An adult eagle's skeleton is so lightweight that it only totals half the weight of the feathers. Its 7000 feathers have different functions for flying and body heat control. In flight, its efficient and strong wing shape lets it soar and glide on thermals, reaching speeds of up to 70 km/hour. Its white tail acts as a rudder in flight too. Those powerful talons are formidable for prey. The eagles can swoop down and grab a fish from the water then take off again to enjoy their meal somewhere safe. They puncture the fish with their hind talons and hold on to the body with the front talons. 

 

Beady Eyes

To me it is their eyesight that is the most fascinating. It's sometimes easy to forget that many animals have better eyesight that us humans. Bald eagles have eyesight about five times better than ours - that is, they can spot a mouse (for example) five times farther away than we could. They can also focus on two areas at the same time...how handy would that be...and are also thought to have the ability to zoom in on something too. That poor wee mouse doesn't stand a chance!

Like many birds they can also see in the ultraviolet range of light. This comes in useful when tracking urine trails of rodents or other mammals as those fluoresce in this light range. All in all, the bald eagle's eyes are perhaps its most useful tool.

 

Family Ties

Bald eagles are generally the faithful kind. They mature into adults at 4 to 5 years and can live up to about 20 years in the wild. If they can they will mate for life, only 'moving on' in the event of one partner dying or if they have trouble mating. They're also the 'homey' type. They will reuse their nest for as many years as possible. Each year they add to the nest making it bigger and bigger. In fact, the largest known birds' nest in the Guinness World Records is a bald eagle nest, at almost 3 metres wide and 6 metres deep. The mind boggles!

They are also good parents. Both male and female will take turns incubating the eggs which hatch after about five weeks. After that both mom and dad keep a close watch as the eaglets gain confidence and grow. By about twenty weeks they are fledged and by about twenty eight weeks they will leave 'home', ready to fend for themselves.

The juvenile eagles are recognizable for their brown/white feathers and brown beak. Only on maturity do they change colour. In other words, any eagle you see with a white head/tail and a yellow beak is at least four or five years old.

Two bald eaglets in a nest and a juvenile bald eagle perched on a branch

Left: "Who're you looking at?" Bald eagle chicks in Alaska. Right: A juvenile eagle looks quite menacing perching on a branch. Photo credits

They may be family-minded, but they are not socially-minded. They will defend large territories of several hundred acres and it is only during breeding or winter feeding that they will share their personal space.

 

Feeding Time

Here in Squamish we tend to only see bald eagles eating dead fish, but they are adept hunters. During summer months when the salmon aren't spawning, they will hunt fish, birds and small mammals. They are not, as we know, afraid of scavenging carrion, or pinching food from others - a technique with the catchy title of kleptoparisitism. 

Bald eagles in the south are resident year round. Those in the north migrate during winter. This isn't for warmth, but to access food, for when their fish habitats are frozen, they must go in search of food elsewhere. This is why we get hundreds descending on the Squamish and Cheakamus Rivers between November and February. Hundreds also flock to the Harrison River and many other rivers on BC's south coast and Vancouver Island. They come from all over the Pacific Northwest in search of salmon - chum salmon being their general favourite. 

Squamish River from Eagle Run Dyke

Squamish River in January from Eagle Run Dyke. Much of the land to the west (left) of the river is Brackendale Eagles Provinical Park 

As well as unfrozen water and a feast of spawning salmon, these spots offer another of the eagles' much sought after needs - forests of mature, tall trees in which to perch high. If you've ever tried to photograph them without a good zoom lens, you'll know just how damn high those branches are too.

Feeding on the annual salmon runs are important for their winter survival. A good run is good news for the eagles and vice versa. Like bears though, sadly too many bald eagles are discovering local landfills, preferring the on-demand access to food scraps, that of course come with toxins and nasty particulates. Only human intervention will stop this in order to preserve the natural law and order of the food chain, and to protect the health of these wonderful animals.

 

And so, as another eagle season in Squamish peaks, I can more confidently say that I understand these big, beautiful birds a bit better. I hope you do too.

---

To find out more - the Brackendale Art Gallery is the home of the Brackendale Winter Eagle Festival and Count

 

Photo credits
Eagle landing: Dave Menke/US Fish & Wildlife Service, public domain
Eagle head shot: Thermos, licensed under Creative Commons
Eaglets in nest: Dave Menke/US Fish & Wildlife Service, public domain
Juvenile eagle: Ken Thomas, public domain
All others: © Diane Mitchell

Sources include:

American Eagle Foundation

Bird Studies Canada

National Eagle Center

What if Humans Had Eagle Vision?

Last modified on Monday, 31 March 2014 03:34