Über die Großgefieder-Mauser von Schleiereule und Waldkauz

Summary

Two Barnowls(Tyto alba), born in June 1957, were kept in a large aviary for several years. The process of wing and tail moult was closely followed and proved to be very complicated.

The first primary to drop in 1958 was the sixth (from within), which was followed after 46 days by the seventh. All the rest of the ten primaries were shed in 1959 and 1960. This was the sequence:

$$6\frac{{7 - 8 - 9 - 10}}{{5 - 4 - 3 - 2 - 1}}$$

The chronological rhythm of the proximal series (5 to 1) was independent from that of the distal series (7 to 10). In 1960 the third generation of primaries started to grow, beginning once more with the sixth and, in the same year, ending with the tenth; but the proximal series remained unaffected. At the end of 1960 the primaries were thus of different rank and age, some belonging to the third, others to the second generation. Some of the latter had grown in 1959, others in 1960.

The secondaries followed a sequence not essentially different from that of other owls(Strix, Athene); however, the moult of the first generation was very much protracted. It began in 1958 in ended in 1960. Some of the juvenile secondaries reached an age of three years.

The tail moult started in 1958 with the outer and innermost pair; the rest followed in 1959. No tail feathers were moulted in 1960.

With the Tawny Owl(Strix aluco) the moult is far simpler. Two birds taken from the same nest at the end of April 1959 moulted all ten primaries in 1960 following the descending mode, and practically all secondaries in the same sequence asAthene. The twelve tail feathers dropped within a few days.