Pale Martin Riparia diluta in Mongolia

by Philip D. Round

While assisting Martin Gilbert and the Wildlife Conservation Society-GAINS (Global Avian Influenza Network for Surveillance) team in sampling waterbirds at Hunt Nuur, Saikhan soum, Bulgan aimag (northern Mongolia), I got a real surprise when checking the mist-nets set at the lake margin at 02:30h on 17 May 2008. Caught in a large-mesh net set for ducks was a single martin, that even my first cursory look indicated was a Pale Martin Riparia diluta – the first I have ever knowingly seen. It was roosted for the remainder of the night in a bag, and examined, measured and photographed in daylight, before release.


Pale Martin. © P. D. Round

Immediately obvious was the rather faint, blurred necklace at the junction of the throat and breast; and the blurring of the boundary between the dark ear-coverts and pale throat. The underwing coverts appeared only fractionally darker than the underside of the flight-feathers.

I was at the time unaware of, and consequently did not check, some of the other features separating Pale Martin R. diluta from Sand Martin R. riparia (outlined in Loskot 2006). But they include ear coverts that are paler, greyer than the crown in R. diluta (whereas only scarcely paler, and brown-tinged in R. riparia); a lighter-coloured short outermost primary, and more extensive tarsal feathering in R. diluta.

The wing measured 103 mm (maximum chord), the tail 50 mm and the tail fork only 5.5 mm—typically much shallower in this species than in races of Sand Martin. It weighed 13.0 g and had a fat score of 3 (after Bairlein 1995).



Pale Martin. © P. D. Round

When the bird was released, it flew off strongly heading north, calling as it left the hand. I was not primed to tape the bird on release, but the call sounded higher, more metallic and less dry and buzzy than that of Sand Martin.

While hirundines are usually diurnal migrants, one must presume that this individual had failed to find an overnight roost and kept going during the night.

Five races of Pale Martin breed from NW India to Central Asia, Transbaikalia and Siberia, largely overlapping with Sand Martin in this range. A further race, R. d. fohkienensis, breeds in central and southern China (Dickinson 2003).

References

Bairlein, F. 1995. European-African Songbird Migration Network Manual of Field Methods. Vogelwarte Helgoland, Wilhelmshaven, Germany.

Dickinson, E.C. (ed.) 2003 The Howard and Moore Complete Checklist of the Birds the World. 3rd edn. Princeton, New Jersey.

Loskot, V. M. 2006. Systematic notes on Asian birds. 61. New data on taxonomy and nomenclature of the Common Sand Martin Riparia riparia (Linnaeus, 1758) and the Pale Sand Martin R. diluta (Sharpe & Wyatt, 1893). Zool. Med. Leiden 80-5 (13), 21.xii.2006: 213–223.

Philip D. Round
Assistant Professor, Department of Biology,
Faculty of Science, Mahidol University,
Bangkok
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Note by A. Bräunlich:

The distribution of Pale Martin Riparia diluta in Mongolia is not well understood. The species apparently overlaps widely with Sand Martin Riparia riparia. Due to restricted knowledge of the field characters which distinguish the two species, it is very likely that quite often Pale Martin is erroneously noted down as the much better known Sand Martin. A post on the identification of the two species is in preparation: watch this space!