Lesser snakelark consists of two species - petsitterbank

Lesser snakelark consists of two species

A recent article suggested treating the lesser short-toed lark as better than two different species, with the following position [11 December] adopted by the IOC World Bird List.

Larks live mainly in open habitats, where the need for cryptic camouflage has resulted in few morphological differences. Recently, genetic and vocal data have shed light on considerable cryptic diversity in the family, and the number of recognized lark species has increased by nearly 30% over the past six decades.

The lesser snakelark complex, which includes the closely related sandlark and the Asiatic snakelark, is a widespread group distributed across the Palaearctic and North Africa. Because of the morphological similarities, the taxonomy of the taxon has historically been hotly debated, with up to 16 recognized forms distributed from the Canary Islands to northeast China.


Lesser snakelarks of the Canary Islands belong to the nominate rufescens clade, now subdivided as Mediterranean short-toed lark (Brian Harrison).

A study by Ghorbani et al (2020), who analyzed the molecular data of the lesser snakelark complex, revealed four distinct lineages within the complex that separated 1.6 to 3.2 million years ago, with the sandlark embedded in the lesser snakelark complex. The authors point out that the species would instead be treated better than four (namely the hey clade, Raytal clade [Sand Lark], sanitized clade, and the Cheleensis and leucophea clade [Asian Short-toed Lark]), although it was recommended that additional data be requested before a formal taxonomic revision should be undertaken.

The latest paper from Alstrom et al (2020) confirms the work of Ghorbani et al (2020) supported by mtDNA, morphology, and bioacoustics, as well as nuclear DNA, song flights, geographic distribution, habitat, and bioclimatic data. The paper suggests that the complex is best recognized as four species, the treatment of which is outlined below.

Mediterranean short-toed lark Alaudala renovated

Contains sanitized, appetite, irrelevant

Distribution: Southern Europe, Canary Islands, North Africa and Iberia through the Levant to western Iraq.

Turkestan short-toed lark Alaudala heinei

Contains hey, aharonii, persica

Distribution: Ukraine and Central Turkey across Central Asia to southern Mongolia and southern Afghanistan.

Asian short-toed lark Alaudala cheleensis

Contains Cheleensis, Tuvinica, leucophea, kukunoorensis

Distribution: Cheleensis and Tuvinica from northern Mongolia and eastern China; leucophea and kukunoorensis from central Kazakhstan to north-central China.

sandlark Alaudala Raytal

Contains Raytal, krishnakumarsinhji, adamsi

Distribution: Coastal Iran to south-central Myanmar.


Breeding distribution of Little Lark and Asiatic Snakelark (grey) and Sandlark (beige), with genetic samples labeled. From Ghorbani et al. (2020) (Wiley Online Library).

In terms of plumage characteristics alone, Mediterranean and Turkestan short-toed larks are considered extremely similar, differing mainly in hey overall less rufous-colored than sanitized, with average thinner chest stripes. Asiatic snakelarks have lighter, less blackish-brown remiges and rectrices than their sister taxa, and on average significantly more white on the outermost tail feather.

Sandlarks vary most in plumage and are characteristically thin and faintly striped on top. It is believed that the sandlark’s greater morphological differences are the result of adaptation to their unique habitat; sandy riverbanks and sandy seashores.


The study found that the sandlark is embedded in the lesser short-toed lark (Mital Patel) complex.

In particular, Mediterranean and Turkestan short-toed larks have been found to differ in song. The Mediterranean short-toed lark’s song is a short, rapid succession of simple tones, sometimes arranged in trills of varying length. In contrast, the Turkestan Short-toed Lark’s song sounds more musical, slower and more complex, with a higher proportion of complex, tonal, more elongated tones and longer rattling tones.

Although they occur in well-defined areas elsewhere in their range, Mediterranean and Turkestan short-toed larks are considered parapatric (perhaps even sympatric) along the Turkish-Syrian border.

In December 2020, the IOC World Bird List (worldbirdnames.org) accepted the proposal to separate the Turkestan short-toed lark from the Mediterranean short-toed lark, in line with the recommendations in Alström et al (2020), and the new taxon was added to IOC version 11.1.

Genetic analyzes have revealed several other examples of passerines with relatively similar distributions that exhibit unexpectedly deep genetic differences, including the lesser whitethroat and gray shrike complexes. Recent studies have also shown cryptic biodiversity in another close relative – the greater snakelark – with the Mongolian snakelark being shown to be more closely related to the Hume’s lark.

Status in UK and North West Europe

This recent split means that there are now two species in the lesser snakelark complex found in the western Palearctic, and their extreme similarity in plumage characteristics alone is likely to cause severe identification problems in migratory birds outside their usual range. In Spain, the Mediterranean lark is considered largely sedentary, while in North Africa it is resident to dispersed and perhaps nomadic; In contrast, the Turkestan short-toed lark is considered migratory in much of its range.

Placed in Category A on the British List, the Lesser Snakelark has only one record, a one-day individual at Portland, Dorset on 2 May 1992. While we have to await the next edition of the British List (McInerny et al 2017), it’s worth pondering the implications of this recent breakup. an account British Birds (Dickie and Vinicombe, 1995) noted that a Mediterranean short-toed lark from Spain or North Africa seemed most likely for the Portland record, but that the possibility of vagrancy by the more migratory Turkestan short-toed lark should not be ruled out.

It seems likely that the only British record not photographed will struggle to be classified as either a Mediterranean or Turkestan short-toed lark, reducing the British list by one and joining the bevy of records not identified at the species level and which are not included in the systematic list.

references

P Alstrom, J van Linschooten, P Donald, G Sundev, Z Mohammadi, F Ghorbani, A Shafaeipour, A van den Berg, M Robb, Aliabadian, M., Wei, C., Lei, F, Oxelman, B., and Olsson, U. 2020. Approaches to delimiting multiple species applied to the birdlark genus Alaudala. Molecular Phylogenetics and Evolution 154: 2021, 106994.
Dickie, I and Vinicombe, K. 1995. Lesser Short-toed Lark in Dorset: new to Britain. British Birds 88:2, 593-599.
Ghorbani F, Aliabadian M, Zhang R, Irestedt M, Hao Y, Sundev G, Lei F, Ma M, Olsson U, and Alström P 2020 Densely sampled phylogenetic analyzes of the lesser short-toed lark (Alaudala renovated) – Sandlark (A Raytal) species complex (Aves, Passeriformes) reveal a cryptic diversity. Zoological Script 49:4, 427-439.
McInerny C, Musgrove A, Stoddart A, Harrop A and Dudley S 2017. The British List: A Checklist of Birds of Britain (9th edition). ibis 160:1, 190-240.

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