In my blog on Florida Eagles, I made mention of blood feathers. A reader, ‘B’, wondered about those blood feathers. I realized then I needed to clarify the matter. So, let us take a short look at feathers – what they actually do – and in that discussion I will clarify the ‘blood feathers’.
What are feathers? Sibley says “that the precursors to feathers were not scales but bristle like hollow structures” that evolved into what we know today as a ‘feather’. Feathers are made out of keratin, the same material used for human fingernails and toenails as well as the beaks or bills of birds.
There are seven different types of feathers. They are the wing, the down, the contour, the fail, the semiplume, bristle, and filoplume.
The down feathers have hardly any shaft. You will recall the soft down that Daisy rubbed from her chest to line her nest. You can see it in the image below. This soft down helps to insulate the birds by trapping air.
The contour feathers help give the bird its colour and shape. Contour feathers cover the birds everywhere except for the beak, its legs and feet. They are the outer covering of the bird and you are probably more familiar with them than any other type of feather. These feathers overlap. You can see these overlapping feathers on Daisy in the image above.
Flight feathers are on the wing and the tail of the birds. It is easy to get confused. Some people separate and say tail and wing to distinguish the parts of the bird where the flight feathers grow. Tail feathers help the bird with flying. They help it to change direction – similar in function to a rudder on a boat. These broad flat feathers help the bird to fly along with those on its wings.
The image below is of a Turkey Vulture. It is still flying – and is alive – despite the fact that it is missing one leg and some of its wing (flight) feathers.
Here is a great diagram showing the primary, secondary, and tertiary wing or flight feathers. The Vulture above is missing some primaries as well as secondary feathers.
In the image below you can see the tail feathers clearly. You can also see the overlapping contour feathers.
The function of the wing or feathers is to support the bird so that it can fly precisely to its destination. Here is an example of a flight feather.
The central hollow shaft attaches to the bird at the calumus. In young birds, such as eagles, this shaft is filled with blood and is called a Blood feather. When the feather has completed growing, the blood vessels regress.
If a flight feather is broken – the tail or the wing – before it is fully grown, blood will flow. Normally, the blood of birds will coagulate just like humans and there is no risk to the bird. However, it is possible for birds, such as eaglets, to bleed to death by a simple broken feather. This is especially true if the bird has been exposed to rodenticide. Rodenticide stops blood from coagulating. In the case of the Captiva Eaglets, the elder was flapping its wings and jumping and broke a blood feather causing it to bleed to death. It had been exposed to rodenticide by a dead rat being brought to the nest.
There have been instances when birds have had to have emergency treatment because they have bled so much when a feather was broken. These are emergencies and the blood needs to stop flowing. Cornflour (cornstarch) and icing sugar can be applied to the site of the break. Both will help to coagulate the blood. If you have pet birds this is something to know if you raise little ones.
Here is an excellent article on all things feathers!
The feathers are ever so important for the birds. Indeed, the feathers are absolutely essential for the bird’s survival. You will see them constantly conditioning their feathers by preening them. The feathers wear out and have to be replaced. Some birds molt twice a year to change the colour from breeding to non-breeding. Others molt only once a year. Molting uses up a lot of energy so birds generally molt during the warmer times of year such as summer. Some birds replace a few feathers at a time. Geese and ducks actually molt all of their flight feathers at once which means that for several weeks until they grow in, they cannot fly. Some of you will have seen Cardinals or Blue Jays molting their feathers. Their heads often look like they have a disease. Our favourite Red-tail Hawk molts after the nestlings have fledged. The running joke is that Big Red becomes Big Blond as the colour of her feathers goes from a deep rich auburn red to a paler strawberry blond of blond during the late summer and early fall.
So, to be clear, birds will not bleed to death once their feathers have fully grown in and there is no blood in the shaft. One way to help reduce the number of blood feather deaths or any deaths of our raptors is to ban rodenticide.
For American Bald Eagles, we use the change in the colour of their plumage to tell us what age the birds are. When all of the eaglets from the nest fledge, they will look like the raptor in the top left. In 2020 (I think I am right), there was a 4 year old Dad at the DNR nest in Minnesota. This was unusual. Normally the adults that are breeding are 5-6 years of age and have that distinctive pure white head.
Thank you for joining me this evening. I hope that you are all well. I look forward to seeing you again soon.
Thank you to the following for their streaming cams where I took my screen captures: Sea Eagles@Birdlife Australia Discovery Centre Sydney Olympic Park and the WRDC Bald Eagle nest in Miami.