Tuesday, February 21, 2012

Eagles, Weather, and Feathers!

It was hard not to feel sympathy and concern for Mom last night as she lay in the nest after egg #2, rapidly disappearing under a blanket of snow. Fortunately, she had roughly 7,000 feathers to protect her from the weather.

Different sources provide different answers about how many things birds do with their feathers, but all of them agree that insulation is important. The snow piling up on Mom's back last night provided a clear picture of the insulative properties of feathers: Mom wasn't losing enough heat to melt the snow away from her back. I wish my roof was so efficient.

Feather Anatomy
Image courtesy Ask a Biologist: http://askabiologist.asu.edu/explore/feather-biology

There are two basic types of feather: vane feathers, which cover the birds exterior, and down feathers - looser, fluffier feathers underneath the vane feather. All true feathers are branched: they have a central rachis with rows of barbs on either side. However, down remains light and fluffy, which traps air and helps insulate the bird, while flight feathers hook together like a zipper, to form a continuous 'vane'. Personally, I think of it as dressing in layers: the vane feathers form a sort of 'overcoat' underlain by the soft, insulative down feathers. Given that snow also has insulative properties, Mom was quite warm and cozy under her blanket.

So how else do birds use their feathers? According to 'Ask A Biologist', they help birds fly, keep warm, control body temperature, provide weather protection, aid in swimming, diving and floating (waterbirds and piscivorous birds), snowshoe (Ruffed grouse), toboggan (penguins), brace, feel, hearing (owls, harpy eagles), making sounds, muffling sounds (owls), foraging, keeping clean, aiding digestion, constructing nests, transporting water, escaping from predators, sending visual signals, and camouflage. I think I'm jealous!

Since feathers do so many things, it is unsurprising that they come in more than one type.

Types of Feathers
Image courtesy Ask a Biologist: http://askabiologist.asu.edu/explore/feather-biology

The feathers we find dropped in the woods most often are tail and flight feathers. They seem the same but are actually a little bit different. Tail feathers are balanced evenly left and right of the rachis, while flight feathers have a wider and narrower side. This helps them cut through the air with very little drag. Of course, wing shape also influences flight, but that is for another post. The downy feathers that are good for warmth are shown on the far right. Semiplume feathers are also insulative and help water birds float (although some diving birds are more concerned with going deep - their feathers become waterlogged to help them sink). We think the bristle feathers, found around eyes, nostrils, and sometimes the mouth, help protect those sensitive areas. Filoplume feathers are can be found around the tail and flight feathers. They are thought to be used to sense when the flight feathers need to be maintained.

Although feathers seem light, all of them put together weigh roughly two or three times more than a bird's skeleton does. They also require a lot of maintenance. Most birds have a preen gland near their tails. This gland secretes oil which they spread over their feathers with their beaks. Preening helps remove dust, dirt and parasites from feathers and also aligns them properly. Even with care, feathers eventually begin to suffer damage and must be replaced through molting - an itchy-looking process that renders some birds (but not eagles) flightless. However, the benefits of feathers - flight, protection, insulation, display - far outweigh their costs. We sleep warm in our beds with the benefit of furnaces and blankets. All Mom and Dad need are their feathers.

For more information on feathers, I suggest this website: http://askabiologist.asu.edu/explore/feather-biology. I also took some information from Colin Tudge's book The Bird.

40 comments:

Greyfax said...

an excellent post - thanks very much

mommap321 said...

Thanks for the info. Always learn so much about the eagles from all of you.

Ennoval said...

Thank you for the "feather info!" Very interesting!! So happy momma eagle stayed warm..

Cabin Fever said...

Thanks for this... sharing with some homeschoolers I know who are fascinated with feathers and birds.

Sara said...

Great info Amy! Your right about the roof!

hlwdutch said...

Thank You, What a timely blog.

1fuzzydickens2 said...

oh yes. my heart dropped when i saw the snow covered mom. found your feather info interesting.

photofun said...

Great info on the feathers and the insulation properties. We always try to put human emotions on wildlife and they have handled this kind of weather a lot longer and better then we do! Thanks!

RonnieVA said...

As usual, well written, informative and most helpful! Now if we could get everyone to read the information.....

Penny said...

Thanks, Amy, for taking the time. I feel much better about mom weathering the storm last night after such exhausting work. I sleep warm & cozy under my feather bed of fluffy white goose down.

peggy said...

This is so cool! Thank you for all your hard work and dedication. I love the feather anatomy lesson too. Just moved to Virginia to hang for a short bit and have been so enthused by the eagle population along the Potomac River. Look forward to following along and have loved the videos! Thanks! peggy

Cathryn B said...

Thanks for all you do!!! This is so enlightening and educational!!! I would never have seen any thing as this in the city of Detroit, MI!!
Sincerely, Cathryn B

sherry said...

That makes me feel better...I knew the Good Lord would provide for this condition when he created the world and everything in it!!

Cece said...

Thank you RRP for educating us all about these beautiful creatures. This is my second year to monitor this nest and the information I've gained is priceless. Thank you ALL, for your willingness to share so much with all of us all over the world!

steffer48 said...

Amy as usual you are the best! Thanks, makes me feel so much better, I could hardly watch last night!

Shellie said...

Interesting...

steffer48 said...

Amy as usual you are greatest source of information! Thanks so much on info regarding feathers, was so hard to watch last night, but was confident that Mom had it all under control!

lrock700 said...
This comment has been removed by the author.
lrock700 said...

Thanks for the information.

deb71452 said...

WOW! I still feel bad for Mom but very grateful for all of the info and knowledge that mom, dad and eggs are actually quite safe and warm. Thank you.

Cherie said...

Yay!!! Time to blog on the eagles again!!!

Bud Gurl said...

Thanks for all of the time you take to keep us informed with "Eagle Information". This was so interesting!

MJ said...

Very well written - many thanks!

Harriett said...

Thanks Amy. Very informative.

Sharon said...

Thank you very much for doing this blog. It was forwarded to me. This Blog will go right up there with Roger Paw (covers NYC Hawks and Related Raptors), Bruce Yolton (another excellent one in the NYC area that deals with urban hawks/birds etc...

Robin said...

thank you so much for the info ... these eagles so touch my heart.

Lisa said...

Great post! Thank you for taking the time to put it together.

Cherie said...

2:07 AM CST and all appears well on the nest. No wind. Mom is hunkered down on the eggs but not tucked in.

Northern Builder said...

Eagle is a instinct bird nowadays.

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Patricia Chambers said...

This is a beautiful and very informative blog...thanks Amy!

Black Pearl said...

We have been watching the Eagles here in Louisiana and were curious after watching and reading about these in Iowa, about how often do they need to be fed while they are growing so much in the nest?

Cherie said...

The eaglets will be offered food several times a day. Last year Dad would come in with breakfast and feed them while Mom stretched her wings. Leftovers are offered as the eaglets let them know they are hungry. Dad usually brings in fresh food 3 times a day. Being across the street from a Fish hatchery helps!

sunshine said...

Outstanding post Amy. Very informative. Well written!

sunshine said...

Outstanding post Amy. Very informative. Well written!

Cherie said...

TRIPLETS!!!!!!!!!!!!!!!!!

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