Asio otus - autumn

Long-eared Owl

AGE – BEST CRITERIA:

In 1cy, 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 discernable, depending on the extent of the post-breeding moult of the individual.

1cy:

  • 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).

2cy+:

  • Uniformly post-breding 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.

2cy:

  • As 2cy+, but one or several juvenile SS still present in the arm, showing juvenile type barring, colour and wear.

3cy+:

  • As 2cy+, but one or several SS from last year’s post-breeding generation in the arm, showing adult type barring, colour and wear.

1cy October (male). Uniformly juvenile SS, lacking moult contrasts. The SS shows five bars (and a sixth bar is barely visible behind the GC tips). The bars are medium brownish and rather narrow, and the ground colour of the SS is rather warm yellowish brown. [8095536]

1cy October (female), showing variation. [8095523]

2cy+ November (male). SS are uniformly post-breeding, showing no moult contrast (if a moult contrast is present, the age may be able to specify to 2cy or 3cy+). The SS show four adult type bars (a fifth bar is just visible behind the tips of the GC), rather broad and dark blackish-brown. The ground colour of the SS is rather cold greyish-brown. [8095503]

2cy+ November (female), showing variation of the adult pattern in the warmer coloured female wing. [8099937]

2cy October. Birds with less extensive moult of remiges show moult contrasts in the arm. The unmoulted SS3-4 and SS7-9 are of typical juvenile type, showing five or six narrow bars, in contrast to the surrounding SS showing adult pattern with four broad bars. [8096064]

2cy November (female). This bird shows a largely unmoulted juvenile arm, and most SS are worn and slightly bleached. The single adult type S (in the mid-arm) shows adult pattern with four broad bars. [8094737]

3cy+ October (male). Birds showing moult contrast in SS, and where the old (worn) generation shows adult type pattern (similar barring as the adjacent fresh feathers) are possible to specify as 3cy+. Note that wear have made the unmoulted SS paler yellowish-brown. [8095398]

3cy+ October (female), showing variation. Note that some SS in the outer part of the arm are still growing, creating a difference in length of feathers of the same fresh post-breeding generation, [8095969]

1cy October (male). Juvenile central RR (R1) generally show neat bars close to tips. The bars may be rather wide (as shown here), but some show distinctly thinner bars, [C82395]

1cy October (female), showing variation. Note neat bars close to tip of R1. [8095516]

3cy+ October (male). Post-breeding R1 generally show less neat bars, and instead a more vermiculated pattern, close to tip. [8095398]

2cy+ October (female), showing variation. [8095966]

More Asion otus:

Ageing spring
Moult
Sexing autumn and spring

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