Powder

For birds, leading a near-water lifestyle and eating mainly fish, powders are especially necessary ( gray heron in the photo)

Powders are areas on the body of some families of birds covered with feathers of a special structure (the so-called "powder feathers"). These feathers, as they grow, constantly break off and crumble onto microscopic scales, forming a very fine powder. Feathers are rubbed with the resulting powder to prevent them getting wet and sticking ^[1] .

Powders in the heron family are most developed. The basis of the heron's diet is fish, the mucus of which, falling on feathers, can lead to their bonding, therefore, the powder from representatives of this family reaches a special development. However, powders are also found in other families of birds - parrots , bustards , toucans , in which the presence of powders compensates for the underdeveloped coccygeal gland (the body that produces the oily secretion by which the bird lubricates plumage). In general, in all birds with developed powders, the coccygeal gland largely loses its functions, and sometimes it is completely absent ^[2] .

An elongated and serrated claw of the middle finger of a gray heron, designed for applying powder on feathers

The powder of the bird formed during the breaking off of feathers is transferred from the powders to the body with its beak and then all feathers are lubricated uniformly. Heron do this with the help of an elongated and serrated claw of the middle finger. However, the functions of powders have not yet been fully explored. Experts emphasize that for a long time almost no attention was paid to the study of this organ ^[3] .

In herons, powders are located on the chest, in the lower back, and are located on the inner surface of the hips. The number of powder feathers in a gray heron is approximately 150 pcs / cm², in a great white heron - 156, in a red heron - 105, in a small white heron - 412, in a heron - 74. It has been established that the size of powder feathers in herons varies by season ; thus, in a gray heron in spring mating, their length is 24 mm, in winter - 32 mm. The great white heron in summer attire has a feather length of 22 mm, in winter - 42 mm. The seasonal increase in the length of powder feathers in winter can be due to the need to reduce heat transfer, as well as to a lifestyle that is more tied to water than the rest of the time. Small herons, which fly away for wintering to places with a warm climate (small white heron, yellow heron , red heron), did not show an increase in powder feathers in the autumn period. Thus, the presence of powders in herons is an important adaptation not only to the near-water lifestyle, but also to seasonal changes in weather conditions, especially in species nesting in cold areas ^[3] .