There are various reasons why you see white feathers in crows (or what looks like white feathers at a distance).
In short, there are 3 categories:
– “McDonald’s disease” / malnutrition: Half-white, spotted and white feathers in poor condition.
– Leucism / Albinism / Genetic problem with white feathers: White feathers, usually in good condition
– White pieces on the feathers that are normal when the birds are getting new feathers
McDonald’s disease is the one you see the most. Just as one should not just feed white bread to ducks, no bird (or human) should just eat white bread.
It gives a feeling of fullness, but you have not received enough nutrition.
For birds that are getting new feathers or that have recently hatched, this means that they do not get the nutrition that the body needs. French fries do not contain much nutrition either and also contain a lot of salt which is unhealthy.
It is unlikely that these birds will survive their first winter. The bad plumage deteriorates rapidly. This usually means that these birds will eventually no longer be able to fly.
They get easily soaked and therefore they can no longer keep warm.
They are also prone to predation and will most likely not be able to survive.
Leucism / Albinism (Genetic problem with white feathers )
The jackdaw in the picture above has white feathers, but these are not caused by malnutrition.
This can be a genetic problem, but there are more and more signs that the reason is old age! We still have a lot to learn! If any one knows of any research being done in this area, let me know!
How do you see the difference? If you can get close or enlarge the picture you take of a bird, you can see that the feathers look good even though they lack color.
|McDonald’s disease||Genetic problems (Leucism / Albinism)|
|The feathers are in good condition (even if they are white)||X|
|The feathers are completely white (no color differences)||X||X (Only if the bird has red eyes)|
|The feathers are partly transparent||X|
|The feathers are broken||X|
|The feathers are brittle||X|
|The feathers look damaged||X|
|The feathers change color when moulting (black and white –> black)||X|
Albinism causes a crow to turn completely white or sometimes caramel. It it very rare.
Such a crow will not grow old because it probably does not get the help it needs. If you see such a crow, make sure to find a corvid-friendly rehabber to take in the bird.
White parts that are normal during the period when the birds get new feathers
The white pieces / parts you see on the wing are keratin that is coming loose. When a bird gets new feathers, they come out as white spikes / sticks (as you can see at the bottom of the picture). They are called blood feathers because they have blood on the inside of the stem until they have grown fully. When the feather is fully developed, white pieces peel off (almost like dandruff), but the bird also removes the parts that are ready to come loose (usually not long after a bath)