Missing feather???

[Arthur Morris]

Hi All, Is this bird missing a primary on the near-wing or is the hand just separated from the rest of the wing feathers? Me thinks the latter...

If the latter, any idea why this happens? (Wind, change in flight pattern???)

[John Chardine]

Good question Artie. The bird is in primary moult, although it is showing an unusual pattern. Birds replace their primaries once a year because they would wear out otherwise. Primaries are critical flight feathers so the process is highly controlled, unlike body feather moult which proceeds on a "feather here, a feather there" basis. There are two general patterns of primary moult- drop them all at once and go flightless for a time (ducks do this), or lose them two at a time in a highly controlled and predictable way. Terns and many other species do the latter. Most species have 10 main primary feathers and they are numbered from the inside out. First to be lost is p1, and both wings lose their primaries at about the same time (so that the bird doesn't fly in circles!!). This tern has lost p1 and p2 from one wing but all 10 primaries are present on the other, which is unusual. Once p1 starts to grow in, p2 on both sides is lost, and on it goes until p10 ends the process for the year.

Moulting is an energetically costly process and some species cannot breed and moult at the same time. Terns can because they tend to feed inshore where food is relatively close by.

Does anyone have an image of a bird with the middle primaries missing?

[Juan Aragonés]

I totally agree with John here. As far as I can remember the moulting sequences are symetric in both wings and it is not common to see one bird losing two contiguos primaries on a wing while keeping all the feathers in the other wing. Maybe this bird is not moulting and the lack of feather is due to a different reason (i.e. the attack of a bird of prey, a fighting or the like)

[Blake Shadle]

Ok, this forum rocks! Great information John, thanks so much for taking the time to mark up the image :)

[Arthur Morris]

Agree on the great info so big time thanks John. Nobody told me you were supposed to count! <smile> This bird had young so Juan's explanation sounds plausible. I did know that they usually molt the same feather on each side...

[Roman Kurywczak]

I Just happened by here................this is so cool and well explained! Thanks John! Definitely my lesson for the day.

[John Chardine]

Roman- Please come back!


I Just happened by here................this is so cool and well explained! Thanks John! Definitely my lesson for the day.

[Susan Griffith]

John, great description of primary molting.

Great topic.

-Susan

[Julie Kenward]

This forum is fascinating! I suspect I'll be learning way more than anyone will ever want me to tell them about birds!

[Anita Rakestraw]

Me too, Julie! I just dropped in here for the first time and can't leave till I finish....