Migration routes, population status and important sites used by the globally threatened Black-faced Spoonbill (Platalea minor): a synthesis of surveys and tracking studies

Since Hume (1874) and Przheval'skii (Prejevalsky, 1879) independently described this species, the Xinjiang Ground Jay (Podoces biddulphi) has always been considered endemic in the basin of the Tarim River and its terminal, now dried-up, lake, Lop-nor. Przheval'skii named the species Podoces tarimensis on this belief, which is still supported by recent maps of recording locations (Ma, 2004; Ma and Kwok, 2004; Ma, 2011). These maps actually add the lower courses of independent tributaries of Lop-nor to the species' range, which is nevertheless still all within the Xinjiang Uygur Autonomous Region of China.

However, Ma (2011) points up a recent range expansion to the adjacent Qinghai and Gansu provinces, based on records in Collar et al. (2001) and Sun and Li (2009) respectively. The former finding is an unpublished single sighting M. Turton and G. Speight obtained near Golmud in Qaidam Basin in 1986 and still awaits confirmation. The latter concerns Dunhuang Xihu Nature Reserve, established along the course of the Shule River north of Dunhuang. A detailed map from A.M. Stein's 1906–1908 explorations (Sheet No.78 in Stein, 1921) shows this river, at those times richer in water, having an expansion named "Khara-nor" at about 40°28′N, 94°18′E, some 70 km west of presentday Xihu Village. A previous map in Przheval'skii (1888) reports the same lake with the alternative name of Khala-chi. In an expedition report first published in 1899, Przheval'skii's assistant P.K. Kozlov (Kozlov, 1963: 158) states: "Восточная граница географического распространения P. Biddulphi проходит чрез озеро Хала-чи, вблизи оазиса Са-чжоу.", i.e., "The eastern border of the geographic distribution of P. biddulphi intersects Khala-chi Lake, near to Sa-chow Oasis." Sachow means Dunhuang.

Kozlov's statement makes no reference either to observation or collection data, a possible reason for its having totally been overlooked till now. Therefore, Sun and Li's (2009) is an important finding, but more probably as a confirmation of the persisting presence of the Xinjiang Ground-jay in Gansu than a sign of recent range expansion to this province. Although this species rather than the other ground-jays may suggest the true desert bird because of more frequent occurrence on sand dunes, its nesting habits involve stands of desert poplars (Populus euphratica = P. diversifolia) and tamarisks (Tamarix spp.) (e.g., Ma, 2011). These plants are phreatophytes and thus, especially the poplars, are affected in their growth by the distance to groundwater (Gries et al., 2003). They take advantage of less deep groundwater under sandy, than under gravelly, surfaces, and thrive in periodically flooded areas. Maps in Stein (1921) show that desert poplars and tamarisks were widespread around Khara-nor Lake, but already at those times a salt-encrusted bare plain had formed a wide vegetation gap between this lake and Lop-nor. There are thus reasons to suppose that Dunhuang Xihu Nature Reserve hosts a relict, isolated population of the Xinjiang Ground-jay. The nearest recent sightings, on the east side of Lop-nor, do not reach 91°30′E (Ma et al., 2011).

The current desertification of Xinjiang, accelerated by destructive human activities and the irrational use of water resources, is adversely affecting the vegetation on which the Xinjiang Ground Jay depends (Li et al., 2004). If this species expanded its range as a consequence of such a rapid, in part man-dependent, desertification, it would be a very adaptable, not-threatened species. On the contrary, its ecology suggests the stenotopic species and, not far from its known range, apparently suitable habitats exist where it has never been recorded. The Ejina Basin in Inner Mongolia, where a formerly large lake has reduced its surface in historical times (Liu, 1992) and desert poplars still thrive on the sands, is an example. Ejina Basin is not separated from Tarim-Lopnor Basin by high ridges — Qaidam Basin is — or bare deserts, possible barriers for the Xinjiang Ground Jay; on the contrary, these basins are linked together by the tectonic depression of the Hexi Corridor and its river system. The wider-ranging Mongolian Ground Jay (Podoces hendersoni) is the only ground jay recorded in Ejina Basin (distribution map in Cheng, 1987) and the usual ground jay in Qaidam Basin, where a higher altitude results in a colder climate and more stunted vegetation, with few desert poplars. The two species have recently been found (Londei, 2011; Ma, 2011) where climate is not obviously different, but soil conditions may produce different vegetation. The current global climate warming, a possible reason for an observed eastward expansion of several bird species in Xinjiang (Ma, 2010), might favor the Xinjiang Ground Jay over the Mongolian Ground Jay by raising the groundwater level in the desert. Thus the former might expand its range, provided that well-preserved deserts were available. Research in border areas might make the ecology of the mutually exclusive Mongolian and Xinjiang Ground Jays better understood.

Acknowledgements

Alexander Andreev, Director of the P.K. Kozlov Memorial Museum, St Petersburg, kindly provided specifications about Kozlov's publications.