Scruffy Buzzard

[Phoebe]

There were two Buzzards flying over my house and this one seemed a little scruffy. What do you think? Is it just moulting or could it be a juvenile?

[FUDGEY]

Either or.

[Picidae]

Originally Posted by FUDGEY

Either or.

er, no, not exactly.

It's not a juvenile. It's moulting it's flight feathers among other things!

[ron1863]

It looks like a juvenile to me.

[Picidae]

Originally Posted by ron1863

It looks like a juvenile to me.

why?

The moult strategy indicates a bird at least in it's 3cy

Juveniles (by which I presume you both meant a bird born this year) do not moult their flight feathers in the first year. In the second year summer they only moult primaries. The picture shows a bird in active serial moult of the secondaries, with some already replaced. Fresh inner primaries. Active moult of the retrices. Other than the moult strategy which reveals it's age, for all intents and purposes plumage wise, it's indistinguishable from an adult.

[RoyW]

I can't entirely agree with Picadie on this one. It is certainly not one of this years young, because of the active moult of the primaries, secondaries and retrices (tail). But IMO it is a 2nd, not 3rd calendar year bird - ie. fledged last summer. It is not one of this years young because the flight feathers grow before they fledge (and then only some of their body feathers are replaced before the following spring/summer).
As for whether the bird is a 'juvenile' some people would refer to it that way until it has moulted into its first adult plumage - but immature or 2nd (or 3rd) calendar year is surely preferably. Some of the unmoulted wing feathers are juvenile ones (with a less broad and distinct dark trailing edge compared to the newly grown ones) and the tail contains juvenile feathers (without the broad dark terminal band of an adult, which can be seen on the growing feathers).
Some, but typically not all, of the primaries and secondaries are replaced by Buzzards in their second year, with the outer primaries and some secondaries (the last ones in each moult section) typically retained until the 3rd calendar year when there is a full moult of all flight feathers.

Roy.

[Picidae]

Originally Posted by RoyW

...it is a 2nd, not 3rd calendar year bird - ie. fledged last summer. .. Some of the unmoulted wing feathers are juvenile ones (with a less broad and distinct dark trailing edge compared to the newly grown ones) and the tail contains juvenile feathers (without the broad dark terminal band of an adult, which can be seen on the growing feathers).

Hi Roy

The pic on the link to me looks better for a 2cy bird than the subject bird ... The even edge to the trailing wing indicates no existing serial moult/ie. same generation feathers, but the bird is in active primary moult. Also note the streaked breast pattern and streaked underwing coverts, very worn outer primaries and moult of the faded brown inner primaries all indicative of a 2nd summer bird which doesn't show in our pic:

http://www.surfbirds.com/blog/upload...lanza/7266.jpg

Juveniles moulting to first adult only moult the inner primaries, all other flight feathers are retained in the 1st summer.(2cy)

Cf. our Buzzard above: IMO moulting into its 3cy Autumn - note the transverse spotting (rather than streaking). The bird is a very pale morph, they often have less distinct trailing edge to wing and a more diffuse terminal band. Pale feathers also wear much faster than dark ones which, given the state of overall wear on this bird, goes some way to explain the apparent lack of any terminal banding on tail. Trailing edge will also always get paler as feathers get more worn at any age. Also note the new primary coverts growing on the underwing. Buzzards (unlike many other raptors) regularly retain their outer primaries until the 3rd Summer. This time of year, it's still in active moult so actually probably has a way to go before it finishes/or suspends this year's moult.

But that's my twopence worth! You may be right, I certainly don't have the expertise to argue the toss with you to any length!

(With regard to ''juvenile'', I agree it's interchangeable, however, in the way it was meant in the OP and subsequent post, I was trying to clarify the difference between what most members would regard as a juvenile bird ie. hatched this year, and subsequent moults into first and second adult plumage since it was clear, it couldn't be a 1cy bird from the state of feather wear/moult.)

[diggleken]

All very technical and accurate - Hopefully in some clarification, if we use generally accepted wisdom, but partic Svensson and Zetterstrom et al in Collins Bird Guide, they define juvenile as a young, fledged bird wearing its first set of true feathers (juvenile plumage) but which has not yet moulted any of these feathers.
It is a bit more complicated from there on as there are also definitions for post-juvenile, young, immature and sub-adult, which meld a bit, besides the following on 1st winter, 1st summer etc etc.
Great fun, but I suspect we all know pretty much what we mean..........?
Cheers
Ken

[Phoebe]

Thanks guys for all the replies I didn't expect such technical information. I will have to keep reading the replies to get to understand what you mean

[RoyW]

Hi Phoebe,

I'll try and make it a little bit clearer!
The flight feathers (wings and tail) of juvenile birds all grow at the same time and are fully grown when they leave the nest (Ducks and some other birds are exceptions in that they leave the nest as soon as they hatch).
This means that your bird is not a juvenile that has recently fledged because there are feathers at different stages of growth visible. When the bird needs to replace the feathers they would become flightless if they moulted all the flight feathers at once, so they are moulted and regrown in specific orders (again depending on species) - this is what Picadie refers to as serial moult.

Different species moult at different ages/times of year, with large species often keeping some of their first feathers for several years. Because the bird you photographed is in serial moult it is at least 1 year old (and may even be 2 years old) so would usually be referred to as an immature or sub-adult, or by terms such as 2nd calendar year or 2nd summer, in order to distinquish it from this years young (which are 'true' juveniles, and as they have just hatched are in their 1st year).

Any clearer?

Roy.