Asio otus - spring

Long-eared Owl

AGE – BEST CRITERIA:

 

Autumn criterias are still applicable. In 2cy, all SS are uniformly juvenile, and show juvenile type barring. Older age classes show (most or all) SS with adult type barring, and in c. 35% of the birds at Ottenby, two different generations of SS are present. Two to four age categories are discernible, depending on the extent of the post-breeding moult of the individual.

 

2cy:

  • Uniformly juvenile SS, lacking moult contrasts.
  • The barring of the SS is of juvenile type: 5-6 brownish and rather narrow bars visible above GC (use SS in the outer part of the arm).
  • Juvenile SS and PP have a slightly paler and warmer brown ground colour.
  • The bars in the distal part of R1 is rather neat (although varying in width).

3cy+:

  • Uniformly post-breeding SS, lacking feathers from last year’s (more worn) generation. Very slight contrasts (or differences in length) is sometimes seen, but this is caused by the three different moult waves in the arm.
  • The barring of the SS is of adult type: 4 (or sometimes 5) dark blackish-brown and rather broad bars visible above GC (use SS in the outer part of the arm).
  • Adult SS and PP have a slightly darker and colder greyish-brown ground colour.
  • The bars in the distal part of R1 is often rather diffuse and generally show a more vermiculated pattern.

3cy:

  • As 3cy+, but one or several juvenile SS still present in the arm, showing juvenile type barring, colour and wear.

4cy+:

  • As 3cy+, but one or several SS from last year’s post-breeding generation in the arm, showing adult type barring, colour and wear.

2cy May. Uniformly juvenile SS, lacking moult contrasts. The SS shows six bars, mediumn brownish and rather narrow. The ground colour of the SS is rather warm yellowish. [8095941]

2cy April (female), showing variation. [8095509]

3cy+ March (male). SS are uniformly post-breeding, showing no moult contrast (if a moult contrast is present, the age may be able to specify to 3cy or 4cy+). The SS show four adult type bars, rather broad and dark blackish-brown. The ground colour of the SS is rather cold greyish-brown. [8095938]

3cy+ April (female), showing variation. [8095956]

3cy April (male). Birds with less extensive moult of remiges show moult contrasts in the arm. This bird shows a largely moulted arm, but two SS are worn, paler and slightly longer. These unmoulted two SS are of typical juvenile type, showing five narrow and paler brown bars, in contrast to the adjacent adult type SS showing adult pattern with four broad and darker bars. [8095960]

3cy April (female). Another bird, showing three remaining juvenile SS (two intact and one broken), in contrast to adjacent adult post-breeding feathers. [8095958]

4cy+ April (female). Two generations of SS are present in the wing, and since the retained generation (older, worn and rather bleached feathers, from last year's post-breeding generation) is also of an adult type, the bird can be aged to 4cy+. [8097165]

4cy+ April (female). Similar to the previous bird, but this individual shows only one single retained SS, this being of an adult type generation. [8097164]

2cy May. Juvenile central RR (R1) generally show neat bars close to tips. The width of the bars may vary, and some are wider than shown here. [8095941]

2cy April (female), showing variation. Note neat bars close to tip of R1. [8095509]

3cy April (male). Post-breeding R1 generally show less neat bars, and instead a slightly more diffuse and vermiculated dark pattern, close to tip. [8095960]

3cy+ May (female), showing variation in the pattern of post-breeding R1. [8095940]

More Asio otus:

Ageing autumn
Moult
Sexing autumn and spring

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