We have all heard the expression “As Light as a Feather!” But how much does a feather actually weigh?
I invite you to investigate Bird Feathers with us this month!
In some areas, you are asked not to collect bird feathers so please check your local park rules before collecting any feathers for this investigation. If you’re unable to gather feathers most craft supply stores will have feathers for sale that you can use. Or take your investigation outside and do it on-site.
Gather your feathers and talk about similarities and differences. Take time to measure the length of each feather. Talk about the shape. Take notice of the patterns on each feather. If you have a microscope look at the feather and see if you can describe the barbs/barbules. Sketch your findings into your nature journal and identify which bird they came from and what kind of feather you have collected. You can find a helpful image on the Cornell Lab Bird Academy web page to help you decide what type of feathers you have gathered.
It is hard to weigh feathers because they are so light. A typical feather can weigh as little as 0.008 grams for a down feather and up to 10 grams for a flight feather of a large bird. Because they are so light it is helpful to think about the weight of the feather compared to the body weight of the bird. When we compare like this we are using proportion and percentages.
Take for example the Cassowary. This bird is native to North-eastern Australia and New Guinea. It is a large flightless bird. Its feathers are unique. The feather structure is less dense than flight birds, and the rachis or ‘stem’ on the feather is more exposed. It gleams in the sunlight giving the Cassowary an iridescent black glossy coat. The bird is large with heavy clawed toes and a ‘helmet’ structure on its head. A Cassowary can weigh up to 72kg. It is estimated that 5-7% of this weight is feathers. Doing the math we can estimate that the total amount the feathers weigh would be between 3-6kg.
If we look at another bird, one that is not so heavy, with thick feathers, we might find that the percentage of feathers compared to body weight is a lot more. I’ve put together a table below, using some comparisons that I was able to find. You can use these for your children to work out some featherweights. There is also a worksheet to download.
| Bird | Feathers | Total body weight |
| Arctic Tern | 4-6% | 100-125g |
| Wedged-tailed Eagle | 5-7% | 3-5 kg |
| Emperor Penguin | 10% | 30 kg |
| Peacock | 30-35% | 4-6 kg |
If your children enjoy investigating math with nature, they may enjoy these books
