Wednesday, 21 August 2013

Some notes on Thekla and Crested Lark identification in central and southern Portugal

Separating Teklas Galerida theklae and Crested Larks Galerida cristata is one of the trickiest ID problems for most foreign birders when visiting Iberia, and topics of discussion regarding this issue are common on online forums. A good example here, http://www.birdforum.net/showthread.php?t=206146 with most birds inicially identified as Crested Larks, and later correctly identified as Theklas.
Most Theklas depicted in birdguides are always typical birds, however what many dont realise is how variable this species could be regarding bill size and shape, breast marks, upperpart tone and habitat.
 Most of these traits should of course be looked for in the field, but keep in mind that Theklas could show strait lower bill mandibule, fairly long bills, to a certain degree fine breast streaking, and 1st primary 3mm shorter than the longest primary covert, overlapping at this point with Crested wich can show only a 2mm diference from the longest primary covert.

Sketches as shown in Svensson

 In some areas they live simpatrically like in Montado Holm Oak edges with artificial steppe (Castro Verde and Mértola in Baixo Alentejo, Portugal), and close views are needed to separete them, specially in early summer when most birds are worn and light conditions could be tricky. But as a general rule in contact zones, Crested Larsk are found often in heavy mobilized soils with intensive agriculture, and Theklas prefer the steppe like habitat with rock outcrops and some scrubland, where man intervention is less pronounced due to orography and aridity of soils.


Thekla and Crested Lark simpatric habitat in Baixo Alentejo:

[A] Crested Lark [B] Thekla Lark -  Baixo Alentejo, Portugal 2012

[B] Thekla Lark - Baixo Alentejo, Portugal Jul2012












Note the 1st primary longer than the longest primary covert, slightly rufous uppertail coverts, median coverts less worn than most Crested Larks in July and proeminant eye ring caractheristic of Thekla.
Note also the fine streaking on breast sides, at least for ilustrated Thekla standarts.

[B] Thekla Lark - Baixo Alentejo, Portugal Jul2012




The same ind., note the spiky crest resembling crested, but beware with worn birds. Crest starting from the mid crown unlike the common belief the Theklas crests start right from the forehead.

[B?] Thekla Lark - Baixo Alentejo, Portugal Jul2012
The same territory, but probably a second bird. Note the heavy marked upperparts and proeminent eye ring with rather long and decurved bill.
 
[A] Crested Lark - Baixo Alentejo, Portugal Jul2012
Crested Lark, note the very short 1st primary feather, obviouly shorter than the 3mm max shown by Thekla, long bill but quite similar to some Theklas, worn median coverts and sandy brownish rump and upper tail coverts with no contrast, poorly streaked breast sides typical of Crested Lark

   
Crested larks from the nearby simpatric area in Baixo Alentejo:

[1] Crested Lark - Baixo Alentejo, Portugal Jun2012









Less proeminant eye-ring, obvious long and decurved bill, very short 1st primary, worn median coverts and fine breast streaking on breastsides.

[2] Crested Lark - Baixo Alentejo, Portugal May2012
Eye-ring less proeminant, long and decurved bill with decurved lower mandibule, very worn median coverts, breastsides finnely streaked increasing towards the center of the breast and finally short 1st primary but overlapping with Thekla Lark.

[2 ]Crested Lark (the same ind. as above) - Baixo Alentejo, Portugal May2012

The 1st primary is quite obvious in this photo, and certainly overlapping with Thekla Lark measeruments, note also the obvoius absence of contrast in rump and upper tail coverts. Note the obvious contrast between lower scapulars and the other feathers on the back, unlike Thekla (see 2nd photo from the [B] ind.).
 
[3] Crested Lark - Baixo Alentejo, Portugal Jul2012

 Typical heavy billed Crested Lark, with typical worn plumage in July.

[3] Crested Lark Baixo Alentejo, Portugal Jul2012


[4] Crested Lark - Baixo Alentejo, Portugal Jun2012





[4] Crested Lark - Baixo Alentejo, Portugal Jun2012









Crested Lark with strong pattern and much less worn plumage, short 1st primary, long bill with strait lower mandibule but overlaping with Thekla, less proeminant eye-ring mostly under the eye socket and fine streaking on breastsides increasing towards the center. Bird photographed at no more than 100 meters from a small village in a open plain area, areas wich Crested larks are more prone to habit. The surrounding hilly habitat with rock outcrops and scrub was home for Theklas.

[5] Galerida cristata - Baixo Alentejo, Portugal Jul2012



Thekla lark, contact zone from the nearby simpatric area in Baixo Alentejo:
 
[6] Thekla Lark - Baixo Alentejo, Portugal Mar2013


Thekla lark, short bill slightly upcurved at the tip of the lower mandibule, conspicuous eye ring, fuller crest, and strongly marked breast and upperparts, long 1st primary but overlapping with Crested



Thekla lark, typical habitat in Baixo Alentejo:

[C] Thekla Lark typical habitat - Mértola, Baixo Alentejo, Portugal

Typical Thekla Lark habitat with dense Holm Oak Montado with some scrubland, on the margins of Guadiana River.
[C] Thekla Lark - Baixo Alentejo, Portugal May2012
Thekla Lark, identified by strong marked upperparts, long 1st primary and breast pattern, but note how the crest is spiky and not fan like starting in the begining of the crown, and how the slight upcurved bill tip in the lower mandibule seems strait and much better for Crested lark in the following pictures

[C] Thekla Lark - Baixo Alentejo, Portugal May2012
   
Theka Lark from a second visited contact zone in Baixo Alentejo:
 
[7] Thekla Lark - Amareleja, Baixo Alentejo, Portugal Mar2012

Typical Thekla regarding structure and bill size, but note the breast pattern resembling Crested creating a dark and well marked area in the center of the breast.

[7] Thekla Lark - Amareleja, Baixo Alentejo, Portugal Mar2012




 The same ind., note head and bill proportions and also proeminent eye ring.

Thekla Lark from a third visited contact zone in Beira Baixa:
Thekla Lark at Tagus Internacional  Park area, are quite commom mostly on hilly mediterranean scrubland with scattered  spontaneous Holm Oak wich margins the Tagus, the further we get from the river, higher is the predominance of Holm and Cork Oak Montados, with less scrubland, and higher is the predominance of heavy mobilized soils and cultures which Crested Larks prefers.

Simpatric habitat near Monforte da beira with predominance of Thekla Lark
















The simpatric area visited near Monforte da beira is deeply centered and surrounded by Thekla Lark typical habitat, and the later is the dominant species, however Crested Larks can also be found in low numbers, and both share the habitat with Short-toed larks and Calandra Larks.

Visited simpatric area with arid scrubland like habitat used for cattle to graze




[8] Thekla Lark - Monforte da Beira, Beira Baixa, Portugal May2013
Thekla Lark showing typical short and compact struture, with short bill and strait lower mandibule, fan like crest and proeminente eye ring, note tthe faintly marked breast pattern closely resembling Crested Lark.

[8] Thekla Lark - Monforte da Beira, Beira Baixa, Portugal May2013


[8] Thekla Lark - Monforte da Beira, Beira Baixa, Portugal May2013

 Strongly marked upperparts and overhall dark appearance,

[9] Thekla Lark - Monforte da Beira, Beira Baixa, Portugal May2013


[9] Thekla Lark - Monforte da Beira, Beira Baixa, Portugal May2013

[9] Thekla Lark - Monforte da Beira, Beira Baixa, Portugal May2013

 Note the more carachetereistic drop shaped marks on breast typical of Thekla


[10] Thekla Lark - Monforte da Beira, Beira baixa, Portugal May2013


Very difficult bird if not seen  properly, with weak streaking on breast resembling Crested Lark, long bill with strait lower mandibule, but note de very long 1st primary and upperparts were well marked like in most Thekla


[11] Thekla Lark - Monforte da Beira, Beira Baixa, Portugal May2013

 Typical Thekla individual,  however not all are like this....


[12] Thekla Lark - Monforte da Beira, Beira Baixa, Portugal May2013
Rather long and leggy appearance on this individual, breast pattern, proeminant eye ring and longer 1st primary. Well marked scaps and mantle, but note how median and lesser coverts shown already no contrast.
 


Thekla Lark, typical habitat in Sagres, Algarve:

[13] Thekla Lark - Sagres, Algarve, Portugal Oct2012

Typical Thekla individual regarding strutucture, grey upperpart tone greyer than in any population I have ever seen in Portugal, bill shape and size, and also breast pattern extending towards the the lower breast and flanks.
[13] Thekla Lark - Sagres, Algarve, Portugal Oct2012




Birds like this one are rather straightforward regarding their ID not only for foreign birder visitors but also for Iberian birders wich do not deal with Theklas across their entire distibution in Iberia.

Hybridization is often an explanation for Theklas, "Crecklas" and Crested Larks phenotypes, mainly because their seems to be a correlation between these intermediate caracheteristics and contact zones between both species, however these could reflect only  an ecological adaptacion to such habitats and hybridization was never found across thekla and Crested lark investigation on genetics.



Gillaume A. Crochet PA. Pons JM. Climate-driven diversification in two widespread Galerida larks. BMC Evolutionary Biology. 2008;8:32
Svensson L (1992) Identification Guide to European Passerines. Stockholm: Lars Svensson.
Svensson, L., Mullarney, K. & Zetterstom, Z. 2009. Collins Bird Guide. 2nd Edn. London.
van Duivendijk, N. 2010 Advanced bird ID Guide. The Western paleartic. London







1 comment:

Matthias Tissot said...

Muito bom post, obrigado.