They are a rare freak of nature: Blackbirds with white plumage are often noticed in gardens and parks. According to Stefan Bosch from the nature conservation association Nabu Baden-Württemberg, house sparrows, jackdaws and carrion crows are also often affected. “Black bird species with white feathers are particularly noticeable and keep people busy.”
There are no exact figures due to a lack of systematic surveys. The proportion is probably in the lower single-digit percentage range. “An obvious accumulation in cities and settlements can be related to deficits in the food supply but also to the increased probability of observation,” explained Bosch. The “Pforzheimer Zeitung” recently reported on a spotted blackbird spotted in the city.
The so-called whites are generally not affected and behave in a manner typical of the species, according to Bosch. “However, they have an increased risk of not finding a mate or of being caught by a predator.”
Various causes
According to Bosch, the reason for white feathers is that black color pigments are missing. This could have various causes – such as hereditary factors, illnesses or nutritional deficiencies. In carrion crows and jackdaws, for example, white patches in the wing feathers were often due to nutritional deficiencies and were associated with poor feather quality. “These discolorations are more common and have been shown to be related to nutritional deficiencies, often in urban environments.”
According to the expert, if there is a genetic cause, birds often turn white as they get older. However, this phenomenon is very rare. Albinism is possible, but even rarer, in the bird world, in which all body parts are usually discolored and the blood supply to the back of the eye makes the eyes appear blood red.
Nabu about leucism report in the “Pforzheimer Zeitung”
