EXPLORACIÓN FÍSICA.-

The Lesser Sand Plover is a poorly known long-distance migrant wader. It breeds in central and north-eastern Asia from the Pamir Mountains in Kyrgyzstan and Tajikistan in central Asia east in a broken distribution to the Chukotsky Peninsula in the north-east with breeding also recorded in Alaska (Cramp and Simmons 1983, Hirschfield et al. 2000, Delany et al. 2009).

Five races of C. mongolus are recognised: three form the more westerly breeding ‘atrifrons group’ which includes C. m. pamirensis Richmond, 1896, C. m. atrifrons Wagler, 1829 and C. m. schaeferi de Schauensee, 1938 and the remaining two the easterly-breeding ‘mongolus group’ containing C. m. mongolus Pallas, 1776 and C. m. stegmanni Portenko, 1939 (Cramp and Simmons 1983, Hirschfield et al. 2000). All five races are migratory, flying south from the breeding grounds to spend the boreal winter along the coastlines of East Africa, south and east Asia and Australia (Nielsen 1971, del Hoyo et al. 1996, Hirschfield et al. 2000) (Fig. 1). Due to the difficulty in separating the different races of Lesser Sand Plover when in non-breeding plumage, it has been difficult to identify exactly where each of them migrate to in the non-breeding season. From a careful analysis of museum specimens, however, pamirensis migrates south-west to spend the non-breeding season in India, the Middle East and south to the East African coastline (Cramp and Simmons 1983, Hayman et al. 1986,

Hirschfield et al. 2000). Birds reaching north-western Australia are mostly from the ‘mongolus group’ and are considered to belong to the larger and paler nominate race (Barter 1991, Barter and Davies 1991, Hirschfield et al. 2000) which breeds east and north of Lake Baikal. Lesser Sand Plovers reaching south-eastern Australia are also thought to belong to the ‘mongolus group’ but consist mainly of the stegmanni sub-species (Barter and Davies 1991) which breeds in Kamchatka, north eastern Russia.

The breeding grounds of the Lesser Sand Plover are rarely visited by ornithologists. Consequently, there are no estimates of population sizes. Likewise surveys on most of the non-breeding grounds are few and far apart. However, I have attempted to make estimates for each race from the available data.

C. m. pamirensis Richmond, 1896, is slightly larger than atrifrons. It breeds in montane valleys,

elevated tundra and mountain steppe in an arc from Tien Shan in Xinjiang, north-western China west to the Pamir Mountains in Kyrgyzstan and Tajikistan and south-east to western Kun Lun in southern Xinjiang. The current “official” Wetlands International estimate of the global population of this

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subspecies, on which the 1% criterion of 1,250 birds for Ramsar wetland status is based, is 100,000– 150,000 birds (Hirschfield et al. 2000, Delany et al. 2009, Wetlands International 2016).

The majority of pamirensis appear to spend the non-breeding season on the Indian coastline

(estimated at 100,000) with c. 50,000 in the Middle East and along the East African coastline (Cramp and Simmons 1983, Hirschfield et al. 2000, Delany et al. 2009). Counts of up to 1,470 Lesser Sand Plovers have been made at Khor Dubai in January and similarly high numbers in the northern Spring at the end of April which, when extrapolated, gave estimates of almost 20,000 birds present during the Spring (Keijl et al. 1998). Similar large numbers were estimated for 200 km2 _{of intertidal flats}

along the Saudi Arabian coastline in January/February where over 3,000 Lesser Sand Plovers were counted giving an estimate of 28,000 birds (Zwarts et al. 1991). The north-eastern shores of the Arabian Gulf on the Iranian coastline have an estimated 2,500–5,000 birds (Scott 2010). Along the eastern coastline of the Middle East, 8,800 were counted for the whole coast of Oman excluding Barr al Hikman where 9,000 were counted the same year (2008) (Green and Harrison 2008, Klaassen and de Fouw 2008). Added up, this suggests a total in the Middle East of 70,000–80,000 birds. However, in 2013, 72,378 Lesser Sand Plovers were counted at Barr al Hikman by de Fouw et al (Wetlands International 2014) and in January 2016 even more, 123,000 birds (de Fouw in press). The explanation for this large increase in numbers in recent years is not understood. Such a large and rapid increase cannot possibly be the result of greatly improved breeding success. More likely it is a shift of a population from somewhere else where perhaps the non-breeding grounds have been destroyed, e.g. by development as has been a threat all around the Gulf of Arabia (Aspinall and Hellyer 2006). It would be necessary to survey other key sites around the Gulf to ascertain whether birds have indeed moved to Barr al Hikman from elsewhere in the Middle East—or have come from farther afield such as the Indian or Pakistan coastline. Thus, assuming this is a shift of birds rather than a previously undetected population, the total figure for this area lies in the region of 70,000– 80,000.

Along the East African coast, little is known about Somalia (T. Dodman pers. comm.) but evidence points towards there being little area of suitable habitat (muddy sand flats), and the Lesser Sand Plover population is unlikely to exceed 5,000–10,000 birds. In Kenya up to 1,400 have been counted across several wetlands on one weekend survey in the Watamu/Malindi area of the north coast with a single maximum count at Mida of 1,264 in 2010 (pers. obs.); a count of 2,340 was recorded at the Tana River Delta basin in 1993 (Bennun and Njoroge 1999) but subsequent counts at this location have not exceeded 160 (pers. obs.). On the Kenyan coast south of Mombasa, (Pearson 1984) counted 700–800 and estimated a total of 1,000–3,000 birds from Malindi south to the Tanzanian border. These surveys are not necessarily representative of the Kenyan population; however, given what is known, it is likely to be in the region of 6,000-8,000 birds. The maximum count at Mida Creek

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of 1,264 therefore made up c. 15–20% of the Kenyan population. In its non-breeding range, Lesser Sand Plovers are strictly coastal and tend to prefer tidal mud and sandflats, hence Mida Creek is an optimum location for it (see site description, Chapter 1).

In Tanzania no counts have been made that surpass the 1% criteria for the biogeographical regional population (1,250) with a maximum of 722 counted on the Rufiji River Mouth (Nasirwa et al. 2001). While recognising that there is a bias in the number of observers in the north, the majority of

Tanzanian records come from the northern section of the Tanzanian coastline but with the comment ‘large flocks are sometimes seen during return passage’ (Baker and Baker 2016). This is in contrast to Harvey (1974) who recorded larger flocks of up to 200 in the southward migration with ‘little

evidence of a return passage’ and only small flocks during the main boreal winter period. Lesser Sand Plovers have been recorded regularly as far south as Durban and counts of almost 500 have been made in southern Mozambique (Dodman et al. 1999, Parker 1999), but concentrations of this size appear to be the exception and not the rule with Greater Sand Plover being markedly more common in general (Parker and de Boer 2000, Oschadleus and Lotz 2004, Wilson 2009). Borghesio and Gagliardi (2011) recorded relatively large numbers of Lesser Sand Plover in Quirimbas National Park, Mozambique, compared to Greater Sand Plover. However, they noted the difficulty of differentiating the two species and investigation with others familiar with the area suggest that in fact Greater Sand Plovers outnumber Lesser Sand Plovers (M. Wilson pers. comm.). This is certainly the pattern with other surveys from Tanzania south. There are, nonetheless, many estuaries along the Tanzanian and Mozambique coastline which have never been surveyed and thus the possibility of undiscovered concentrations of birds cannot be ruled out. Current knowledge, however, indicates that this species is relatively uncommon along the Indian Ocean coastline south of Kenya. An

estimate for the Tanzanian and Mozambique coastline, therefore, lies in the region of 5,000–10,000 birds.

Its status in the Malagasy region is unclear due to uncertainty regarding correct separation with Greater Sand Plover Charadrius leschenaultii. However small numbers are known to reach Seychelles (Cramp and Simmons 1983) and it would appear that the species is widespread along coasts

throughout the region (Safford and Hawkins 2013) though unlikely to be numerous. A first estimate would put the total number at 1,500-2,000 birds.

Altogether, therefore, with the 100,000 estimated for India and Pakistan, up to 80,000 for the Middle East and probably in the region of 25,000 for the East African coast, a global estimate for the population of the race pamirensis would be 200,000 birds. This is at least 50,000 more than was taken as the estimate by Delany et al. (2009).

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C. m. atrifrons Wagler, 1829, is a small, dark, short-billed subspecies that breeds south and east of

pamirensis in the Himalayas and southern Tibetan plateau with a global population estimated at 100,000 (Hirschfield et al. 2000, Department of the Environment 2016) or 120,000–150,000

(Wetlands International 2016). It spends the non-breeding season from Sindh in Pakistan east along the Indian coastline, around the Bay of Bengal, and south and east to Sumatra (Cramp and Simmons 1983, Balachandran and Hussain 1998, Hirschfield et al. 2000, Department of the Environment 2016) where it is probably the commonest wader along the Indian coastline (Ali and Ripley 1988). An estimated 40,000 birds of this race occur in the East-Asia Australasian Flyway focused around the Bay of Bengal, Malaysia, Thailand, and western Indonesia (Bamford et al. 2008).

C. m. schaeferi, mongolus and stegmanni population estimates. The total population for Lesser Sand

Plover including all subspecies for the East Asian–Australasian Flyway was estimated to be a minimum of 130,000 birds (Bamford and Watkins 2005). However figures provided by Wetlands International (2016) suggest a much smaller population of 68,000 birds. With many threats to staging and non-breeding grounds along this flyway, this probably indicates a real decline in overall numbers. Due to the difficulty in distinguishing between subspecies in the field in non-breeding plumage, however, the following are estimates.

C. m. schaeferi de Schauensee, 1938, is a larger, paler, long-billed subspecies that comprises the

eastern part of the ‘atrifrons group’ of C. mongolus. It breeds from southern Mongolia through Qinghai to eastern Tibet and the other adjacent provinces of China, and spends the non-breeding season from coastal Thailand to the Greater Sunda Islands with concentrations such as 5.8% of the biogeographical population estimated to spend the non-breeding season in Malaysia (Wei et al. 2006). There is a suggestion that some might regularly visit northern Australia as well. The global population is estimated at 25,000-100,000 (Lane 1986, Hirschfield et al. 2000, Bamford et al. 2008, Wetlands International 2016, Wiersma et al. 2016b).

C. m. mongolus Pallas, 1776, is a paler race that breeds from Lake Baikal in inland eastern Siberia

and northern Mongolia, through the Russian Far East to the Verkhoyansk mountain range. It spends the boreal winter from Taiwan to Australia and together with stegmanni forms the non-breeding population of Lesser Sand Plovers found in Australia (Cramp and Simmons 1983, Lane 1986, Department of the Environment 2016). The global population has been estimated at 25,500 (Wetlands International 2016) and 40,000 (Bamford et al. 2008). Frequently mongolus population estimates are combined with stegmanni to be 25,000-100,000 since estimates have only been made on the non-breeding grounds where in non-breeding plumage, the two races are inseparable in the field. 20,000 were estimated (Watkins and Royal Australasian Ornithologists’ Union 1993) to spend the boreal winter in Australia of which 84% are considered to occur in Queensland in the north-east

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(Minton 2006). The rest are expected to spread out between China, Philippines, Indonesia and Papua New Guinea (Bamford et al. 2008).

C. m. stegmanni Portenko, 1939, is a darker, short-legged race that breeds in north-eastern Russia,

especially around Kamchatka, on the northern Kuril and Commander Islands and on the Chukotski Peninsula. It spends the boreal winter from southern Ryukyu Island and Taiwan south to Australia where it mixes with the nominate race. This is likely to be the race that migrates to south-eastern Australia, although the non-breeding population there is small; the population in Victoria was estimated to be 100 birds by Barter and Riegen (2004). It has subsequently declined and is considered to be 10 birds in 2016 (C.D.T. Minton pers. comm.). The population size for this

subspecies is unknown but is considered together with mongolus to number in the region of 25,000- 100,000 birds (Cramp and Simmons 1983, Hirschfield et al. 2000, Bamford et al. 2008, Department of the Environment 2016, Wiersma et al. 2016b). Wetlands International (2016) suggested a population of 13,000, based on expert opinion.