Aythya nyroca
English: Ferruginous Duck.
German: Moorente.
French: Fuligule nyroca.
Order: Anseriformes.
Family: Anatidae.
38-42 cm.
The Ferruginous Duck is easy to identify. Among the pochards, it is the only one with white undertail coverts and a general plumage in dark reddish-brown tones.
The adult male has overall dark reddish-brown tones. The dark brown (almost black) back contrasts with its white belly. On the other hand, the adult female has plumage with more subdued tones. Her back is completely brown.
It is possible to recognize 3 different ages:

Juvenile specimen: these individuals have plumage with quite dull overall tones. The undertail coverts are a dirty white color. The feathers on the head lack the reddish tones that will later stand out in older ages.

1st year/2nd year specimen: with retained juvenile feathers. The variability in molting between individuals is too high to obtain more concise data.

Adult specimen: in general terms, adult individuals have plumage in reddish-brown tones and completely white undertail coverts.
Ferruginous Duck undergo a complete postnuptial molt, acquiring eclipse plumage. This process usually ends in October. On the other hand, the post-juvenile molt is partial. In this process, only the body feathers usually change. All individuals undergo a partial prenuptial molt, in which they dress in breeding plumage.
Primaries: 10 per wing.
Secundaries: 15-16 per wing.
Rectrices: 14.
Link: http://blascozumeta.com/


Adult specimen:
Beak tip to pupil center:

Adult male specimen


1.- Right wing primaries. 2.- Primaries. 3.- Details of the tips of the primaries. 4.- Details of the primaries. 5.- Details of the tips of the primaries (P10-P6). 6.- Details of the tips of the primaries. 7.- Details of the primaries. 8.- Right wing secondaries (S1-S8). 9.- Secondaries (S9-S15). 10.- Right wing secondaries and tertials. 11.- Details of the tips of the secondaries. 12.- Details of the tips of the secondaries. 13.- Details of the tertials. 14.- Details of the secondaries. 15.- Details of the tips of the secondaries (S9 and S10). 16.- Primaries, secondaries and tertials. 17.- Difference between secondaries and tertials. 18.- Primary infra-coverts. 19.- Secondary infra-coverts. 20.- Right axillary feathers. 21.- Primaries, secondaries, and tertials. 22.- Primaries, secondaries, tertials. Primary coverts and greater coverts. 23.- Primaries, secondaries, tertials. Primary coverts and secondary coverts (G, M and L). Alulas. 24.- Primary coverts. 25.- Greater coverts. 26.- Alulas. 27.- Primary coverts. 28.- Greater, median, and lesser coverts. 29.- Details of the greater and median coverts. 30.- Details of the median and lesser coverts. 31.- Differences between primary and secondary coverts. 32.- Details of the primary coverts. 33.- Rectrices. 34.- Rectrices. 35.- Rectrices + uppertail coverts. 36.- Details of the tips of the rectrices. 37.- Details of R7. 38.- Rectrices + undertail coverts. 39.- Back feathers. 40.- Arrangement of the back feathers. 41.- Head feathers. 42.- Arrangement of the head feathers. 43.- Chest feathers. 44.- Right scapula. 45.- Right flank feathers. 46.- Ventral feathers.

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