Re: Willow Warbler?

I wasn't saying if a bird has the wrong leg colour it is not of that species. I'm saying that some may have the 'wrong' leg colour so therefore it is not an acceptable feature. I've seen  a few Pale legged chiffchaffs and many paler brown. Ive mentioned this already.

The point I'm making is, if a bird has a variable feature which overlaps with a variable feature of another bird, it cannot be use to separate them. If species A tended to have a blue head, but it was occasionally green and species B had a green head that was occasionally blue would you use head colour to separate them, even though you may be getting the wrong ID?

I am also confused by what you mean with 'percentage ID'?

Ok thanks and I agree overlapping features on their own can't be used singly to positively i.d. At some point, percentages have to be weighed up. Otherwise, there will be a lot of unanswered posts. Where the percentages lie is down to each individual.

ID isnt about what percentage of the people think it's species A, its about if it is species A or B. As S says, ID isnt a democracy.

Or have I just got confused about what you mean?

I mean percentage probability, not volume of people saying one thing or another. Obviously, if someone's in a minority of one, clearly that person needs to stand back and reflect. May not be wrong, but worth doing anyway. But, I mean if it's 1% chance of being A and 99% chance of being B, it's not ideal to say it can't be positively i.d'd imo.  

If there is a minority with pale legs, then it's not a reliable feature as you can be wrong.

Wing formula and PP aren't unreliable.

Willow Should have pale legs, so if it has dark legs (using that as a feature, even though most other things point to Willow) this cannot be a Willow!

Michael M

Willow Should have pale legs, so if it has dark legs (using that as a feature, even though most other things point to Willow) this cannot be a Willow!

Michael, as John said at the outset, it had pale legs. Based on what you said in the brackets, you're edging towards an opinion of willow :-)

I believe this is Willow, I was responding to SarahW's post :P

Hi-

overall impression - if I saw it in the field I'd say it's a Willow- it just looks like one  :)  Especially the facial expression

S

Robbo

p.s. what's probably most important, I suspect, is John L wants an i.d. that's as close to accurate as possible. I think there's consensus that it won't be 100% guaranteed, but I suspect he's only after a very good probability. I think a number of chiffchaff v willow warbler i.d photos, esp the single ones, are percentage i.d's anyway.

I think that the real problem here is that it really isn't always possible to give an ID - which is something that has to be realised with all wildlife. Sometimes you just have to be prepared to let a bird go as unidentified.

It is often possible to say that based on visible features there is, for instance, a 90%, 75%, or 60% chance that a warbler like this one is a Willow Warbler rather than a Chiffchaff, but that is really only a different way of saying that the bird can't be identified.

In this case the clean underparts, the extent of the pale bill base, and the pale(ish) brown legs are all features that tend to be seen more on Willow Warbler, but the solidly dark cheeks, obvious white crescent below the eye, and perhaps the relatively weak supercilium are more pro- Chiffchaff. In my opinion what can be seen of the wingtips is of no use for the ID at all; the shape of the wingtips, as in whether they look pointed or blunt, is not important, what matters is how long the projecting primaries are in comparison to the length of the tertials (which does mean that the wings of Willow Warbler can seem longer - but wing length is very difficult to judge, especially from the angle shown, and the primary projection cannot be seen in these photos).

Personally I would say that the identification of this warbler is probably tipped in favour of Willow based on what can be seen, but it is a close call and this identification is probably no more than 60% certain.

For comparison:

Chiffchaffs with brown legs (similar in colour to the bird in this thread) - 

http://birdguides.com/iris/pictures.asp?v=1&off=349792&r=1&st=0&q=0

http://birdguides.com/iris/pictures.asp?v=1&off=348986&r=1&st=0&q=0

Chiffchaffs with clean underparts (top two photos) - 

http://birdguides.com/iris/pictures.asp?mode=search&sp=136287&rty=0&r=1&v=0&off=349604

Dull Willow Warbler with dark looking legs - 

http://birdguides.com/iris/pictures.asp?v=1&off=353122&r=1&st=0&q=0

and a dull Willow Warbler with darkish legs, plain cheeks, and weak supercilium - 

http://birdguides.com/iris/pictures.asp?v=1&off=350432&r=1&st=0&q=0

All posted to Birdguides within the last 5 weeks.

Forget willow/chiefs, I'll be after Marsh/reed tomorrow!

Id say I'm Willow on this but agree with RoyW that we can't be 100% certain on this, and often we cannot ID birds.

You'll often see the expert birders are the first to say they can't ID the bird

You can't do wing formula in the field! And the Willows that have dark legs always seem to have pale feet! Never seen a Chiffchaff with pale feet...

SarahW

You can't do wing formula in the field!

But you can reliably assess primary projection (and wing formula can sometimes be checked on good photographs - but not often).

SarahW

And the Willows that have dark legs always seem to have pale feet! Never seen a Chiffchaff with pale feet.

What do you make of this one then?: