Wednesday, December 06, 2017

Crested lark vs Thekla Lark ID Guide

Thekla's  vs. Crested Larks in Spain an ID Guide

Possibly the most widespread and common lark species to be found in Costa Blanca   
Both Thekla's Lark and Crested Lark occur over much of the warmer parts of Spain, and frequently both species can be found in the close company of each other. Surprisingly, relatively little has been said about the separation of this difficult species pair: In fact, the possibility of misidentification of one species for the other has frequently been played down, simplified or largely ignored.
Many birders who come to Spain question me about field separation of Crested and Thekla Larks so much so that this is probably the single most often asked question.

So here I am attempting to summarise what can be said about the field identification of these two species in Spain. Or rather to express my own opinion about the criteria that are most valid for separating Crested and Thekla's Lark in the field.

Crested Lark

Crested Lark

Often in the cultivated countryside. Very common along coastal areas. Heavy in appearance and during the autumn and winter has brown coloured mantle and wings, although this can pale significantly with the onset of spring and summer. Crested Lark is longer billed and the top edge of its upper mandible curved throughout its length, though more steeply towards the tip, and a straight or slightly concave bottom edge to its lower mandible; and hooked at the tip
A  pale, not white, supercilium, indistinct and varied streaking to the upper breast. Song diagnostic also has a distinct 3 syllable call in the ascending.

Crested Lark

Thekla Lark

Thekla Lark

In my opinion bill shape and length is probably the single and most important  (although not infallible) feature. Comparatively speaking. Thekla Larks have shorter, stubbier, more triangular bills, while face patterns of Thekla Larks usually have a more contrasting face pattern, with “spectacles” and a  white supercilium and eye-ring, with heavy black streaking to upper and medium breast and a more “open” expression.  

Thekla Lark

General plumage colouration: if you see a very grey contrasting looking bird then it is almost certainly a Thekla Lark. The problem is that not all Thekla Larks are greyish, as this is a feature that largely depends on wear and local variation and time of year.

Outer tail feathers: apparently the Thekla Lark has more rufous and more contrasting outer rectrices Its difficult to see and it’s not something that I look for to separate this species.

Underwing: Thekla Larks have greyer underwing coverts than Crested Larks, but just how often do you think you will be able to check that out in the field?

Crest: a rather useless criterion in my own opinion. It depends too much on the wind, attitude, moult, individual variation and observer bias.

Voice: difficult to tell apart, even with experience. Both songs are similar, although Thekla's Lark’s is more melodious, less imposing and lower-pitched, with less tendency to imitation than Crested Lark. 

Distribution: there are large tracts of land where only one species (usually Crested Lark) occurs, which is a good initial indicator if you are familiar with the species’ local distribution.

Habitat: this is a good indicator, although beware of “microhabitats”. Thekla Larks usually prefer less “agricultural” landscapes, and more often observed in broken, stony terrain with scattered bushes. 
I use this method:   First Look at the length of the bill? Is it stubby- Dagger-shaped or long and curved top mandible? Next: I look at the facial pattern? Does it have a white supercilium and eye-ring or is it pale, not clear and drab looking dirty? Next: the streaking on the breast? Is it bold and pronounced more at the centre? Or pale and thin.   

Thekla's Lark

Last, but not least: is the bird perched on a bush or a pile of rocks, or is it a ground hugger? In the former case, there is a very good chance that it will be a Thekla Lark!

Thekla's lark

Reliable identification generally requires close views or photographs, it is necessary to base the identification on a combination of features.
some birds I just can't be ID, as the views are just not good enough to reliably say one way or another.

Crested Lark

Hope it helps

Bryan Thomas

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