Birds, Conservation

Identification of Sand Martins in southern India

Abhinand Chandran 

Introduction

Sand Martins (Genus: Riparia) are passerine birds (Family: Hirundinidae) closely related to swallows (Genus: Hirundo & Cecropis) with brown body and shorter tail, without any white spots which is commonly seen in Crag-martins (Genus: Ptyonoprogne). Three species occur in India: The resident Grey-throated Martin (Asian Plain Martin) Riparia chinensis, migratory Common Sand Martin (Sand Martin, Bank Swallow) R. riparia and Pale Martin (Pale Sand Martin) R. diluta (Praveen et al., 2018). Sand Martin breeds in the Holarctic and winters in Africa through Middle East, south Asia to Indonesia and south America while Grey-throated Martin is a resident and race indica of Pale Martin is probably a resident augmented with migrant population (Rasmussen & Anderton, 2012). Though state checklists of Kerala (Praveen, 2015) and Karnataka (Praveen et al., 2016) listed Grey-throated, reports of Sand and Pale Martins from Kerala were not considered due to the difficulties in identification and separating them to species level.

Here I attempt to separate the Sand Martins from Pale Martins by analysing the morphological features using pictures in public domain with the help of Schweizer et al. (2018). I also try to establish that there were several records of Martins in Kerala that are almost certainly Sand Martins. There may be several photos in private collection that has not been analysed here.

Taxonomy

The taxonomy of Sand and Pale Martins is complex, both R. diluta and R. riparia were treated conspecific (Table 1). R. riparia split from R. diluta around 3.07 Mya (millions of years ago). Despite having wide zone of overlap, their mixed colonies were observed without any evidence of interbreeding. Molecular analysis clearly separates them as two species. They differ in mitochondrial and nuclear DNA data. No clear separation between the subspecies of R. riparia and R. diluta was found in morphometric analysis. Different taxa of R. diluta are morphometrically similar, though they show strong genetic differences.

On current evidence Schweizer et al. (2018) has synonymised several currently recognised races of both Pale and Sand Martins with other known subspecies. They treated the race eilata of Sand Martin as a synonym of race shelleyi. The paler race innominata which breeds in Iran and southern Central Asia, morphologically similar to Pale Martin, is also included in the nominate form of Sand Martin. Also the validity of subspecies gavrilovi and transbaykalica are questioned and they included in the nominate for Pale Martin. Table 1 shows the details of subspecies of Sand and Pale Martins.

Identification

Riparia martins are often found within the group of swallows and it will create problem in separating them from juvenile swallows. A juvenile Barn Swallow Hirundo rustica (Fig: 1) is overall duller in appearance with darker upperparts and buffy rufous forehead and throat while Riparia martins shows brownish upperparts, lack any colour difference on forehead. Except Grey-throated, others show paler throat and white half collar. A juvenile Streak-throated Swallow Petrochelidon fluvicola can be distinguished from martins by heavily streaked throat and breast, finely streaked flanks, rufous brown head and glossy mantle. Structurally a martin looks smaller and slimmer compared with a juvenile swallow. When it comes to identification of regionally occurring Riparia martins, Grey-throated Martin shows pale greyish-brown throat and lacks any breast band (Fig: 2) while the other two martins shows white throat with breast bands. Identification of Sand and Pale Martins are further complicated. In morphometric analysis, characters like size, structure, wing length, tail length, tail fork etc. shows no clear separation between the different subspecies of Sand and Pale Martins and show similarity in plumage features. Smaller and paler individuals of R. r. shelleyi resemble R. diluta in some aspects. R. d. tibetana is the largest and darkest subspecies of Pale Martin which resemble a R. riparia. Based on Table 1 in Schweizer et al. (2018), the main morphological differences of different subspecies of Sand and Pale Martins are tabled (Table 2) below. X indicates character is present while (X) indicates there is some variation in the presence of this character. It must however be cautioned that all these characters are rather variable and no identification should be made based only on one or two characters.

Observations and
Discussion

First photographic record of a Sand/Pale Martin from Kerala was from Vembanad by Tim Inskipp & Sathyan Meppayur on December 2006 (Sashikumar et al., 2011). After that Riparia Martins have been photographed at least ten times from different wetlands of Kerala. I made an attempt to analyse the photographs available in public domain with the help of above table (Table 2). During morphological analysis of the photographs from south India, it was observed that wintering martins showed dark brown upperparts with strongly contrasting breast bands. Based on the current range statements (Rasmussen & Anderton, 2012), the most likely taxon that would occurs in southern India are nominate race of Sand Martin and tibetana race of Pale Martin. The identification keys of birds normally observed in south India are listed in Table 3. Observations with photographs showing sufficient morphological features are given in Table 4 (wing length which cannot be assessed using photographs was not considered here). I provide a list of photographs from my collection of the bird I recorded from Kadamakudy on 13 November 2014, illustrating some of the points that confirm the identification (Fig: 3-7). Additional photographs from other observers are used to illustrate further identification details (Fig: 8-10).

Based on the above analysis, at least on five occasions in Kerala and two occasions in Karnataka the Riparia martins wintering showed features that match well with the nominate race of Sand Martin. Hence, it is recommended that Sand Martin be included in the list of birds of Kerala and Karnataka. Remaining reports, with insufficient photographs to analyse the morphological features, can be considered as Sand/Pale Martin. As identification of martins is a complex process, extreme caution must be taken while identifying them. Birds in moult may show intermediate plumage, colour shade and tail fork depth may vary, breast band can be ruffled and may show diffuse borders. In most cases more than half of the tarsi are unfeathered and there are chances that tarsal feathers may wear off. It is always recommended to provide sufficient photographs showing as many views as possible that can be useful for establishing and the identifying the birds.

Acknowledgements

My sincere gratitude to Praveen J. for encouraging and guiding me for writing this paper and commenting on an earlier draft. I would like to thank Dilip K.G., Govind Vijayakumar, Harikumar Mannar and Premchand Reghuvaran for providing photographs. I am extremely grateful to all who has uploaded their observations online.

 

References

  • Chandran, A., 2014. Website URL: https://ebird.org/ebird/view/checklist/S21727728 [Accessed on 19 July 2018]
  • Clements, J. F., Schulenberg, T. S.,  Iliff, M. J.,  Roberson, D.,  Fredericks, T. A.,  Sullivan, B. L., and Wood, C. L., 2017. The eBird/Clements checklist of birds of the world: v2017. Website URL:  http://www.birds.cornell.edu/clementschecklist/download/ . Accessed on 18 July 2018.
  • Karingamadathil, M., & Jameela, P., 2017. Website URL: https://ebird.org/view/checklist/S44296767  [Accessed on 19 July 2018]
  • Mannar, H., 2017. Website URL: https://ebird.org/ebird/view/checklist/S33616701 [Accessed on 19 July 2018]
  • Praveen, J., 2015. A checklist of birds of Kerala, India. Journal of Threatened Taxa 7(13): 7983–8009; http://dx.doi.org/10.11609/JoTT.2001.7.13.7983-8009
  • Praveen, J., 2017. Website URL: https://ebird.org/india/view/checklist/S35434142 [Accessed on 19 July 2018]
  • Praveen, J. Jayapal, R. & Pittie, A., 2016. A checklist of the birds of India. Indian BIRDS 11: (5&6): 113-170
  • Praveen J., Subramanya, S., Raj, Vijay Mohan 2016.. A checklist of the birds of Karnataka. Indian BIRDS. 12: (4&5): 89–118
  • Prince, M., 2008. Website URL: https://ebird.org/view/checklist/S19421971 [Accessed on 19 July 2018]
  • Rasmussen, P. C., & Anderton, J. C., 2012a. Birds of South Asia: the Ripley guide: field guide. 2nd ed. Washington, D.C. and Barcelona: Smithsonian Institution and Lynx Edicions. Vol. 1 of 2 vols. Pp. 1–378.
  • Rasmussen, P. C., & Anderton, J. C., 2012b. Birds of South Asia: the Ripley guide: attributes and status. 2nd ed. Washington, D.C. and Barcelona: Smithsonian Institution and Lynx Edicions. Vol. 2 of 2 vols. Pp. 1–683.
  • Reghuvaran, P., 2017. Website URL: https://ebird.org/india/view/checklist/S40129724 [Accessed on 19 July 2018]
  • Sashikumar, C.;Praveen J.,;Palot, Muhamed Jafer;Nameer, P. O. 2011. Birds of Kerala: status and distribution. 1–835. DC Books. Kottayam, Kerala.
  • Schweizer, M., Liu, Y., Olsson, U.,Shirihai, H., Huang, Q., Leader, P.J., Luis Copete, J., Kirwan, G.M., Chen, G., Svenson, L., Contrasting patterns of diversification in two sister species of martins (Aves: Hirundinidae): the Sand Martin Riparia riparia and the Pale Martin R.diluta, Molecular Phylogenetics and Evolution (2018), doi: https://doi.org/10.1016/j.ympev.2018.02.026
  • Surendran, A., 2017. Website URL: https://ebird.org/ebird/view/checklist/S33364722 [Accessed on 19 July 2018]