Feathers – textures, patterns and growth

 

A spray of coppery plumes (aigrettes) lit by the sun and contrasted with the slate blue contour feathers and white body feathers of my favourite diminutive heron…the Louisiana Heron (Egretta tricolor).

♦

♦

Ever since my first view of the young wings of a Great Blue Heron chick I have been fascinated with the way they grow and that interesting parallel arrangement of the pretty blue sheaths from which the feathers emerge. They always remind me of an Indian headdress in design. So I thought this view deserved some explanation!

A bird’s wing is very similar in its skeletal structure to a human arm and is, in fact, a modified limb. If you keep your upper arms to your sides, rotate your forearm sideways away from your body at the elbow, then tilt your hand down at the wrist with your thumb up, that is pretty much what you see in the picture above of the juvenile great blue heron standing with wings lowered and tilted towards the sun (sunning posture). The blue sheaths you see on this young bird house the growing flight feathers. From the ‘forearm’ section grow the secondary flight feathers and from the ‘hand’ section grow the primaries. From the ‘thumb bone’ grow the feathers of the leading edge of the wing called the alula. You can see this in the above image as well.

Feathers grow from papillae or follicles (like bumps) arranged along the birds skin in traces called ‘feather tracts.’ Each of these follicles is supplied with a vein and an artery. The outermost layer of the papilla forms a protective sheath inside which a feather grows, tip first, outwards. These new structures are called ‘pin feathers’ for their straight and pointy appearance. They are also called’ blood feather’s at this stage of growth due to the venous and arterial supply while growing which will bleed if plucked or broken. Ultimately the sheath splits and falls off allowing the tightly bound feather to unfurl. Once the feather is fully grown the papilla recedes and dries up leaving a hollow shaft. The feather is not ‘alive’ at this point not needing a blood supply, although the follicle itself does keep a blood supply in the skin. The tip is the oldest part of the feather and the base the youngest.

A chick like this one is growing new feathers all at once, and so there are lot of pin feathers. Later on as feathers become worn out new ones will grow to replace them.  Sometimes when you see a bird preening it is to get rid of insects or parasites, but also the sheaths do not always fall off so easily. I am sure many times when I see birds flicking their beaks out along the feathers that they are pulling sheaths from new growths away. I understand at times they will do this for each other.

In between the blue sheaths you can see other pin feathers sheathed in white for other feather layers. Right now the wing or arm of the bird looks rather like an anatomical drawing as there is not much there but skin, muscle, bone, ligaments and young feathers. When fully feathered these wings will become beautiful and inspire the awe that birds always do when soaring. Our arms so similar and yet we can only dream of flying!!

♦

This illustration of a dove’s wing shows the wing bones and how the secondary feathers relate to the radius and ulna of the’ forearm’ and the primaries extend from the’ hand’ bones. Alula feathers you see attached to the ‘thumb’ at the leading edge of the wing.

♦

Below are the context shots of the nesting Louisiana Heron and the Great Blue Heron Chick.

♦

♦

I find the patterns of nature fascinating and beautiful. Natural forms, patterns and textures inspire everything from art to architecture to the clothes we wear!

♦

I did want to share the link to the blog of a wonderful and nationally acclaimed sculptress – Sandy Scott.  She specializes in sculpture and sketches of wildlife, especially birds. She has several posts on the anatomy of birds and bird wings with her own very clear drawings which she uses to teach how to accurately draw or sculpt them. Discovering her work was a treat for me so thought I’d share something found while learning more on this subject.

Judy

Advertisement

~ by Judy on April 3, 2014.