Crested vs Thekla Lark - playing the odds (1 Viewer)

John Cantelo · Mar 19, 2011

There's been a lot of discussion recently about the identification of Thekla & Crested Lark. This has encouraged me to muse about the mechanics of bird ID. To a large degree, I concluded, birding is all about 'playing the odds'. Given a good, extended, close views there's usually little room to doubt about a birds identity. Even a distant group of 'marsh terns' in the UK can almost certainly be ID's as Black Tern; not 100%, but pretty darn close. The same birds observed in southern Spain could also be Black Tern, but are just (more?) as likely to be Whiskered Tern. It's all about playing the odds and thinking about probabilities.

Then again there are those species that almost always need a decent view to allow any degree of certainty. Telling Thekla Lark from Crested is one such example of this. However, even here it might be useful to 'play the odds' to make your ID more certain.

So with some trepidation I'm going to attempt to have a systematic look at the Thekla/Crested problem. I've tried to put the criteria in a heirarchy and weighted points according to my own experience. To this end I have attached a 'crib sheet' which may prove useful in provoking debate/clarifying ideas. Naturally, others will give a different weight to some features, but I hope this makes a good starting point. (Note that my comments refer to the situation in Iberia).

I've put a slightly fuller version of this on my web/blog (see below), but my photos are so poor that I hesitate to post them here. So I'm hoping that this post will encourage better photographers to post images here to highlight/clarify the points on my sheet. Please comment/refine my ideas - I don't claim omniscience and still find the odd bird I decide to 'walk away' from!,

John Cantelo · Mar 21, 2011

What? No responses?

I was rather hoping for some debate/argument on my take on this ID matter! Better still I had hoped that it might elicit some comparative photos showing these points.

In the absence of anything else I've posted two rather indifferent photos to illustrate just how distinct the bill shape can be. Incidentally, the Thekla in the photo had a rather poorly marked chest - similar to many Crested - so the bill shape (plus the location) was particularly useful,

Trystan · Mar 21, 2011

I have a few birds on my list which are there based on likelihood rather than solid identification.

I visit Spain regularly and still don't have much confidence seperating these two species but on balance, I'm confident that at least some have been Thekla.

In your opinion, as Thekla are more prone to perching up but less prone to being around built up areas, would a bird perched on a house roof in hilly country where the houses are new (i.e. formerly good thekla habitat) be more likely a Thekla or a crested lark?

Brian J Small · Mar 21, 2011

Comparative image posted on Surfbirds by Stephen Daly in Spain - http://www.surfbirds.com/media/gallery_photos/20110312055228.jpg

Brian S

John Cantelo · Mar 21, 2011

Brian J Small said:
Comparative image posted on Surfbirds by Stephen Daly in Spain - http://www.surfbirds.com/media/gallery_photos/20110312055228.jpg

Brian S

An excellent comparison - well worth a look.

Everyone 'sees' birds in a subtly different way, but for me judging bill shape is the single most important feature and, arguably, the most reliable one. Presumably, bill shape reflects feeding strategies. Feeding in 'softer' ground the Crested's longer curved bill might aid probing. Thekla, being habituated to 'harder' ground may have less use for probing but more for picking prey off hard surfaces.

It would be intesting to see photos of the degree of variation in the boldness of the chest streaking too.

Motmot · Mar 21, 2011

A typical crested from my home patch (end of September):

John Cantelo · Mar 21, 2011

Motmot said:
A typical crested from my home patch (end of September):

Thanks for posting your photos - as a matter of interest, what time of the year were they taken?

davercox · Mar 22, 2011

Re song: I agree re usual length of song, but your point about 'distinct notes' doesn't chime with my memories. Maybe I've been lucky, but so far I've always found Crested song very distinctive (short but definite phrase): and Thekla usually so (longer with less structure). I expect there are Theklas that sing Crested, though ...

Jane Turner · Mar 22, 2011

Nice one John. With less experience of them, in a Spanish context I think I elevate bill shape to a 4 on your scale and downgrade crest to a 2.

John Cantelo · Mar 22, 2011

davercox said:
Re song: I agree re usual length of song, but your point about 'distinct notes' doesn't chime with my memories. Maybe I've been lucky, but so far I've always found Crested song very distinctive (short but definite phrase): and Thekla usually so (longer with less structure). I expect there are Theklas that sing Crested, though ...

I put that 'more distinct notes' in inverted comas because I was struggling towards articulating what I felt -the phrase isn't quite right, but I can't think of a better way to say it. But then I admit that I find song, and even more so describing it accurately, very elusive. I'll have to listen to them again to be sure, but perhaps I mean that Thekla's is a bit more flowing and fewer sharp notes (whch tend to sound more distinct to me). Having said that I still often find them so similar that I'd hesitate to say which was which - for me it's often little more than a 'feeling' than a 'certainty', but, to repeat myself, my aural recall is poor so I'm pretty sure your sensitivity & descriptive powers trump mine,

John Cantelo · Mar 22, 2011

Jane Turner said:
Nice one John. With less experience of them, in a Spanish context I think I elevate bill shape to a 4 on your scale and downgrade crest to a 2.

Thank you Jane - coming from yourself, that's a compliment indeed!

In my origina draft I rated the bill higher than the chest streaks and crest as an ID feature. The later can be altered by wear or appear different due to angle/light and even the strength/direction of wind, but, given a good view, the bill's distinction is constant. I chickened out as I know friends of mine argue that other features are equally important/obvious/distinctive. As I said we all see birds differently and my starting point with Thekla is, when possible, always the bill. Having looked at a few more photos, I think you're right about the crest too - again I was possibly swayed b a friend who rates this feature highly!

Mark Etheridge · Mar 22, 2011

This is a Crested, although the angle of the head makes the bill look more like a Thekla due to foreshortening... my other shots of this bird (not so good) with the bill sideways on shows the curvature better. I hope this is a useful view of the chest markings on this specimen.

Taken 23 June 2010, La Mata reserve near Torrevieja, Alicante - typical Crested territory.:t:

Stephen Fletcher · Mar 22, 2011

I would agree with all your points, bill for me is the most deciding clincher, as colour, streaking, and crest size can be extremely variable in both, and habitat can also have a large crossover. For me, jizz is the most important factor, something extremely difficult to pick up on in a still image. Calls are very similar and close birds tend not to call much so picking out which one is calling/singing can be very difficult too. I have attached a few images, a couple of which are a bit contentious as to the actual specie.

Stephen Fletcher · Mar 22, 2011

Another 2 as it would only let me upload 5.

John Cantelo · Mar 22, 2011

Mark Etheridge said:
This is a Crested, although the angle of the head makes the bill look more like a Thekla due to foreshortening... my other shots of this bird (not so good) with the bill sideways on shows the curvature better. I hope this is a useful view of the chest markings on this specimen.

Taken 23 June 2010, La Mata reserve near Torrevieja, Alicante - typical Crested territory.:t:

Thanks Mark. Good photo of the chest and a timely warning not make a snap judgement on bill shape at such a dodgy angle.

Attached is my redraft of my original table - still imperfect, but going in the right direction I hope!

Motmot · Mar 22, 2011

Three bad images of a local Thekla from this morning

John Cantelo · Mar 22, 2011

Hmmm! Some interesting images there Stephen. Several look to me to be clear cut Theklas and one at least looks more like a Crested, but others look very tricky indeed! Any info on time of year? And, yes, I hesitate to be the first one to 'jump into the water' and say which one is which. I'll ponder a little longer on this!

John Cantelo · Mar 22, 2011

Trystan said:
I have a few birds on my list which are there based on likelihood rather than solid identification.

I visit Spain regularly and still don't have much confidence seperating these two species but on balance, I'm confident that at least some have been Thekla.

In your opinion, as Thekla are more prone to perching up but less prone to being around built up areas, would a bird perched on a house roof in hilly country where the houses are new (i.e. formerly good thekla habitat) be more likely a Thekla or a crested lark?

Sorry for being so slow to come ba to you on this. I think in a sense the issue is that built up areas are less prone to appear in Thekla habitat! However, I do tend to assciate Cresteds with railway sidings and semi-derelict urban land. I've seen Crested perch on buildings but not Thekla. Howeve, I'm sure this reflects the want of houses in Thekla habitat; I'm sure they'd treat buildings pretty much as they treat large boulders on which they may often perch!

Motmot · Mar 22, 2011

Mark Etheridge said:
This is a Crested, although the angle of the head makes the bill look more like a Thekla due to foreshortening... my other shots of this bird (not so good) with the bill sideways on shows the curvature better. I hope this is a useful view of the chest markings on this specimen.

Taken 23 June 2010, La Mata reserve near Torrevieja, Alicante - typical Crested territory.:t:

Could we see the other shots of this bird? Theklas can also be found at La Mata afaik

Stephen Fletcher · Mar 22, 2011

John Cantelo said:
Any info on time of year?

1: 10 Feb
2: 29 May
3: 21 Jan
4: 23 May
5: 25 April
6: 5 May
7: 28 Aug

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