One of Autumn’s remarkable seasonal changes is the migration of honeyeaters flying North for the winter from March to May. Look up in the early morning, and you may glimpse this season’s honeyeater migration. Their migration route depends on the availability of flowering plants, rainfall, or bushfire damage. We may wave goodbye to honeyeaters, but new feathery friends will fly in for the season like the robins.
Many shorebirds make Australian beaches their home in summer, as the days begin to shorten in Autumn, migratory birds like the Godwit and Curlew prepare for an extraordinary 25,000 km return journey to the Arctic to breed. Shorebirds need energy to make this flight over the oceans, so they will constantly eat to store up reserves for the journey. If you visit to wave goodbye, be careful not to disturb their feasting as their lives depend on it.
Birds have the amazing ability to fly gracefully with strength. The Peregrine falcon can slice through the air in a dive as fast as 300 km/hour making it the world’s fastest bird.
But have you wondered how birds defy gravity? To understand the mechanics of flight, we must dabble with physics. There are four forces a forward-moving object must overcome to move through space: weight, lift, thrust, and drag.
Thrust is a force pushing the object forward.
Drag is the friction holding the object back.
When thrust is stronger than drag, a bird can move forward.
The weight of an object pushes it downward.
Lift is the upward force allowing the subject to become airborne.
When lift is stronger than gravity, a bird can fly.
The bird’s physical design of body and wing is essential to create lift. The wing bone is the shape of a comma on its side; the top of the wing curves upwards then tapers down towards the back. This shape creates more surface area on the top of the wing than on the underside. Air always tries to equalize its pressure over a surface. To do this, the air will stretch like a sock to cover the top of the wing while losing pressure. This causes different air pressures on either side of the wing. A bird creates lift when there is lower air pressure above the wing. This is known as the Aerofoil Effect. When the bird flaps its wings in a forward circular motion it creates thrust.
A Bird’s bones are hollow making them lightweight.
Fun Fact
Feather colours and patterns have fascinated people for centuries. The Ancients like the Aztecs took bird feathers to adorn their robes and headdresses. Feathers have been used as writing tools, and placed on the butt of an arrow to increase accuracy.
While feathers contribute to a bird’s ability to fly, they are also used for protection from the elements. Feathers are oiled by glands in the skin, and because feathers overlap, rain runs off the bird keeping it dry. Many birds have a thick undercoating of down feathers on their breast. Birds incubate their eggs against the Brood Patch and snuggle over their young keeping them toasty. Down feathers are especially dense and they are used in pillows and doonas.
A feather is slender with a tapering central shaft. The bottom of the shaft is called a quill. It is hollow and slides into the bird’s skin. Even though the shaft is light, it is strong. The upper part of the shaft is the rachis from where many small barbs branch. The barbs then branch into smaller barbules with hooks that interlock with the hooks of the barb next to it forming a web.
There are 7 types of feathers:
Wing or Flight feathers are big feathers that are windproof, strong, and lightweight. The rachis is not central to the feather as it sits off to one side.
Tail Feathers are similar to wing feathers except the rachis is in the centre. They are arranged in a fan shape and used for steering or stopping.
Contour Feathers cover a bird’s body. The zipped feather tips overlap creating a weatherproof coat while the fluffy ends keep the bird cozy. Contour feathers display the patterns and colours of bird species.
Semiplume Feathers have a central rachis but have fewer links and the feathers are more fluffy creating insulation beneath contour feathers.
Down Feathers trap heat close to the body. They are the softest, and fluffiest of the feather types. The rachis is short and the feather is loose without hooks.
Filoplume Feathers have a simple structure much like a cat whisker. They sense the position of contour feathers.
Bristle Feathers protect a bird’s eye, nose, or face. It has a simple rachis and is without barbed branches.
Use the resources below to explore and examine feathers!
Please check park rules before collecting feathers.
Examine a feather. Rub the outside edge of the vane downward and watch the hooks disengage and the branches tear apart. Now stroke the branches upward and notice how the hooks reknit like a zipper. This is what happens when a bird preens itself.
Go walkabout to spot feathers. Who could the owner of the feather be? Can you name the feather type? Download the Feather Types Notebook pages below.
But those who hope in the Lord will renew their strength. They will soar on wings like eagles; they will run and not grow weary, they will walk and not grow faint.
Homeschooling is a gentle amble for me since four of my five children have graduated. I share my joy with things beautiful, good and lovely with my grandchildren where I live contently with hubby in rural South Australia.
