Saturday, April 23, 2022


 I didn't know.

Recently I read an article published by the Audubon Society regarding bird migration that left me wide-eyed and amazed.  

I was curious about migration, especially the hummingbirds.  I have a friendly running competition with a friend in  Redmond.  What follows our greetings is an inquiry as to hummingbird sightings.  He usually wins and I am convinced  it is because his location is warmer than mine.

Anna's Hummingbird in Winter
I did have one hummingbird at the feeder the first week of April, as did my friend.  Was it the Anna hummingbird known to spend winters in Central Oregon or was it someone passing through?  It was a quick stop and in the blink of an eye, it was gone, no time to get a good look to identify.

After reading the Audubon article I learned what an incredible, wonderous journey migration is.  At summer's end, birds eat excessive amounts of food for two weeks to store enough fat for migration.  They gorge themselves on high-energy berries and fruits loaded with carbohydrates and lipids that are stored as fats.  That is another reason why it is important to grow native plants that produce the lipid-rich berries birds need.

Ruby-throated Hummingbird
Humans rely primarily on carbs for endurance activity.  Thinking back to our family and their sport activities, whenever they had a meet or a game it was high carb meals.  For birds, fat makes sense as it is lighter and less bulky than carbs and protein.

Ruby-throated hummingbirds are best known for packing on the grams.  Most double their weight before starting on their trip.  Some gain close to half that in four days.

The metabolism of the hummingbird is one of the highest of any animal on earth.  They require the equivalent of over 150,000 calories every day to power their fast-moving heart and wings, which can beat 1,000 to 3,000 times per minute.  That fat is burned in a steady release of energy to make a 2,000 mile journey that many Ruby-throated hummingbirds make twice a year.

All that fat on a bird's small frame must be distributed properly.  To do so, many birds are able to shrink and grow their internal organs.  An example is the Bar-tailed Godwit, one of the world's most intense migrators. 

Bar-tailed Godwit
The Godwit will fly from Alaska to New Zealand, a trip of 6,800 miles each fall.  The bird will absorb into their body 25 percent of the tissue comprising their  liver, kidneys, and digestive trach.  This happens through a natural cellular process called autophagy, which means "self-eating" in Greek.

What about sleep?  During migration, a neurological shift triggered by the changing season forces birds to adapt to nocturnal habits and sleep less.  Swainson's Thrushes migrate from Central and South America to northern Canada and Alaska, enter a sleep-like state for nine seconds at a time.  They keep one half of their brain awake to avoid predators or mid-air collisions while the other half rests.

Swainson's Thrush
And the rest of the story---once birds reach their destination, they need to regain their organ functions and shape and refuel their fat stores.  It is an urgent task.  As soon as they reach their breeding ground, they need to find a mate, build a nest, produce and raise young chicks, all the while taking care of themselves.  If they can't get food within a couple hours after landing, they can starve to death.  Birds on an average need to restore between 17 and 23 percent of their body weight in fat upon arrival and also account for protein and water loss depending on their species and migratory pattern.

There is still an unanswered question for me--Where do hummingbirds nest?  I go on a quest every summer looking, but have yet to find one.

According to the International Dark-Sky Association, April 15-May 18 is the key spring migration dates for Central Oregon.  Turn your outside lights off if possible.  Light pollution can cause birds to become disoriented resulting in collisions with buildings.

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