Does it make sense to speak to birds, to explain to them in a calm tone what is expected of them? When it comes to crows, probably. Carrion crows recognize the voice of the people they have become acquainted with, even if they hear that voice through a recorder. It was recently demonstrated by researchers at the Konrad Lorenz Forschungsstelle near Vienna.
Crows react more laconic to familiar human voices than to the sound of unfamiliar people. The researchers were quite excited about it, but anyone who has had a tame crow or jackdaw in the past already knew this. Also that crows often understand where you want to go.
Something strange going on
Let this be said in advance. A resident of the Amsterdam Rivierenbuurt sent a video of a young black crow with which something strange is going on. The video shows how the animal is dozing on the handlebars of a bicycle until it has to be put into use. At a friendly request, he hops over to the handlebars of another bicycle. Immediately after landing, it stretches considerably, which is called ‘wing-stretching’ in jargon, and it turns out that a large part of the flight feathers, the primary feathers, are not black but partly white.
It’s not clear what that sudden stretching means. Literature makes a mess of that. Many birds combine the wing stretch with a ‘leg stretch’, the stretching of a leg on the same side, and that is often regarded as a pleasant ‘comfort movement’. We humans also know that comfort, just like dogs and cats. A sudden wing stretch without a leg stretch can actually be a so-called displacement activity, an abrupt, more or less illogical action by a nervous animal in a conflict situation. Such as: flee or attack. A bird can suddenly start grooming its feathers violently. The problem is that the crow from the Rivierenbuurt showed a two-sided wing stretch and that is of course not with a two-sided leg stretch. Whether he was at ease or nervous: unknown.
There is more to say about those weird white flight feathers. The ‘partial albinism’ that seems to be visible in the young crow became in 2018 in British Birds discussed by Hein van Grouw. Van Grouw, formerly affiliated with the Naturalis Museum in Leiden and since 2009 at the Natural History Museum in Tring (in Hertfordshire, England), has been working for decades with deviant colors and unexpected whitishness in the feathers of birds. Deviating white spots in the plumage always have to do with deviations in the appearance of the dark pigments eumelanin or phaeomelanin. These can arise in many different ways – Van Grouw gave an overview in 2013 – and usually have a hereditary component: the trait is then passed on to the offspring according to fixed rules. Partial albinism does not exist because partial albinism does not exist. You’re albino (and can’t make melanins) or you’re not, but you’re not half.
Bread, fries and other waste
The white patches on the River Crow’s quills are not the result of some genetic defect, but are the result of poor nutrition. It is a phenomenon that occurs more and more in large cities: the parent crows feed the young bread, chips and other waste that lacks the proteins that crows need. Crows mainly live on animal material such as eggs, birds, insects, worms, snails and carrion. They extract the amino acids tyrosine and lysine from this, which are indispensable for the production of eumelanin. The white pieces code for the growing period when the food supply was incomplete. (The chick’s feathers grow in sync.)
The feathers with white pieces are also usually weaker than unaffected feathers, which reduces the birds’ chance of survival: they cannot fly well with them. Many do not make it to the end of their first year. But with a slight infestation and full nutrition, full recovery can occur, then normal black feathers appear in the second year of life after the spring moult.
What you call a mixed message. So I called Van Grouw to dot the i’s and cross the t’s, but that didn’t make it any more fun. He explains that the video shows not a freshman but a sophomore crow, which you can tell from the color of the other feathers and that of the eyes. The fact that he still can’t fly and falls through his legs regularly is a bad sign. The bird has had it worse than other crows. “Can’t I hear him cough? Then he also has trachea mites. It is a sick animal that would not survive in nature. It’s best but…”, but that’s enough.
If the chances of survival are so poor then the question is why the crow is not already dead. A visit to the Rivierenbuurt provides the answer: the cheerful hopscotch has more human friends than you think possible. They come from far and wide to give him complete food, and recently he also received organic lamb from France. Tensely one follows his clumsy flying exercises. Waiting for the moult.