COMPLICACIONES DE LOS TRATAMIENTOS A TENER EN CUENTA EN AP.-

India. Adult Lesser Sand Plovers arrive in south-eastern India in August with first years arriving a

month or so later (Cramp and Simmons 1983, Balachandran and Hussain 1998). Counts carried out over three years in the Gulf of Mannar, south-eastern India, showed markedly large numbers of birds in September/October (up to 13,000) and again in January/March (more than 10,000) with relatively few (maximum less than 4,000) in November/December (Balachandran and Hussain 1998) suggesting the location is used as a stop-over site for moult during southward migration and for fattening during both south- and northbound migration than as a continuous non-breeding area for the whole season. Where the birds move on to from the south-east of India is uncertain. Both atrifrons and pamirensis occur in south-eastern India but, of the two, only atrifrons occurs farther south in Sumatra and Indonesia (Hirschfield et al. 2000). It is possible that birds cross the Indian Ocean to reach there, a distance of c. 1,800 km which well within the capability of a long-distance waders to fly without stopping (Minton et al. 2011). There is a lack of ring recoveries from south- eastern India to date to help understand patterns; this represents an opportunity for further research.

Australia/South-east Asia. Most birds of the nominate and stegmanni races pass south through

Japan, the Yellow Sea, south-east Asia and reach Australia between July and September. Arrival in northern Australia begins from late August through to October (Cramp and Simmons 1983,

Marchant and Higgins 1993, Department of the Environment 2016). The northern and north-eastern coastlines form an important staging area for migrants heading farther south. Birds stop here for a week to ten days as suggested by evidence in the south-eastern corner of the Gulf of Carpentaria

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from observations of colour-flagged waders, albeit of other species such as Red Knot Calidris canutus (Roger Jaensch pers. comm.). After a stop off to fatten up, birds continue to south-eastern Australia with the earliest arriving at the end of August with main arrival in September and latest through to November and even December (Marchant and Higgins 1993), C.D.T. Minton pers. comm.). Large numbers (c. 10,000 or 6% of the estimated flyway population) of mostly mongolus stopover on foraging grounds in South Korea on southward migration (Moores 2006, Rogers et al. 2006) from where it is likely they fly non-stop to their non-breeding grounds.

Northward migration from the southernmost non-breeding grounds is thought to start as early as February; however, the main departure, particularly from the northern part of the non-breeding grounds, occurs in April and continues into May with an earlier ‘wave’ of departure in March (Marchant and Higgins 1993, Department of the Environment 2016). Northward migration passes through Wallacea in February and April-June where the species is mainly found on passage (White 1975). On the Bohai Sea (mouth of the Huang He river) and the Yellow Sea numbers appear to peak towards the end of April and early May (Zhu et al. 2000, Barter and Riegen 2004) and birds are seen on the Korean peninsula in April and May where large numbers occur presumably fattening for the last leg of their migration to the northern breeding grounds (Moores 2006, Department of the Environment 2016).

As expected, adult birds precede first years in their migration timing, usually by several weeks. But in north-western Australia ringing showed that adults arrive in September, and that first-years must delay somewhere en route because the first juvenile birds arrive in January and the majority delay arrival until March and April. The evidence for this is that during 35 years of ringing, 679 Lesser Sand Plovers were ringed of which 136 were first years. Of these, only one first year Lesser Sand Plover was caught between August and January compared to 170 adults. Seven were caught in January, four in February, 47 in March and 55 in April (Fig. 2). Further research is needed to understand why the first years delay their arrival so substantially. Segregation by age occurs in other wader species, but is rarely as large as this. For example, juvenile Red Knots Calidris canutus rogersi reach the non- breeding grounds in New Zealand at the beginning of their second year (Minton 2003). The reasons for the delay are unknown and where they stop between leaving the breeding grounds in July and arriving in north-western Australia in March is also unknown.

One possibility is that foraging conditions in north-western Australia are suboptimal during these months for Lesser Sand Plovers to be able to support the larger population of both adults and young. Between July and November conditions are dry in north-western Australia with average monthly precipitation ranging from 1 – 8 mm (Chapter 1, Fig. 2c). The main rainfall occurs in January and February which may only then stimulate good production of the invertebrates the sand plovers feed

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on. Considering therefore, the enormous distances to be covered (these are mainly mongolus birds that breed up to 9,000 – 10,000 km away) and the possible lack of good feeding in north-western Australia, in the light of competition for resources by experienced adults, young birds may delay their arrival by stopping for longer at some stop-over sites along the migration route and only time their arrival when foraging conditions have improved. Ideally young birds would be ringed at breeding or stop-over sites and recovered between August and December—or better still to have satellite transmitters placed on juveniles on the breeding grounds to learn their migration route and timing. Otherwise trapping and ageing birds at stop-over sites to the north during August to

December would also give an indication of the first year migration strategy. Many of the first year birds remain on the non-breeding grounds over their first boreal summer and are aged as sub-adults come August (Fig. 2).

The Middle East. In contrast to the eastern populations, most surveys and fieldwork in this area have

been undertaken during the boreal winter (Eriksen 1996), with some surveys during the northward migration and only a few during the southward migration, and then mostly towards the end, in September/October. Thus knowledge of arrival dates in the region is weak (Keijl et al. 1998, Klaassen and de Fouw 2008). Cramp and Simmons (1983) considered Lesser Sand Plovers to arrive in

“southern Arabia” from early to mid-August which corresponds with arrival dates in East Africa (Fogden 1963). Large numbers spend the non-breeding season in the region (see above) and birds appear to be late in departing for breeding grounds compared to other species such as the similar Greater Sand Plover (Keijl et al. 1998).

Cramp and Simmons (1983) gave the departure from non-breeding grounds as ‘the first half of April’ with breeding grounds of pamirensis reoccupied mid-April to early May. However most evidence from work carried out over the past 40 years suggests Lesser Sand Plovers migrate notably later than other species with a migration peak through United Arab Emirates in late April/early May (Keijl et al. 1998). This relatively late departure date (with birds still present on 18 May) from the Arabian Gulf is logical in the light of the species’ breeding grounds at high altitude where the phenology of

temperatures and snow cover are comparable to the high arctic; the late timing of the thaw results in conditions becoming favourable for breeding at a later date than would be anticipated for the latitude.

East Africa. At the Mida Creek study area, small numbers of Lesser Sand Plovers between April and

the end of June consisted of non-breeding sub-adult birds, remaining behind when the adults returned to the breeding grounds (Fig. 3). A clear increase in numbers from mid-July marked the main arrival of adult Lesser Sand Plovers, and continued through to the end of August. A small reduction in numbers at the end of September suggested that some birds were in passage and

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moved farther south. From early October numbers increased sharply with the arrival of first year birds, an arrival which continued through to peak in the second half of November with a density of c. 6 birds/ha (Fig. 3).The proportion of juveniles in the samples trapped while ringing over 27 years supports this with an increase in percentage of juveniles present from 0% in August, 10% and 16% in September and October respectively to 27% in November after which the percentage is stable until adults start to depart in April (Fig. 4). The departure for the return migration was relatively late. Numbers decreased by c. 15% during December to February but most birds remained until the first half of March at which point there was a rapid departure, the majority of adults having departed by the first week of May (Fig. 3). There was an early influx of birds in July and August. A likely

interpretation of this is that it consisted of adults which had failed to breed and left breeding grounds early. The main arrival of adults is in September, and juveniles arriving only in November through to December.

The counts at Mida Creek confirmed Lesser Sand Plovers as present throughout the year in Kenya including during the breeding season in June and July. These non-breeding birds are generally first years that remain on non-breeding grounds during their first boreal summer and only return to breed at two years of age (Pearson and Britton 1980, Cramp and Simmons 1983, Marchant and Higgins 1993, del Hoyo et al. 1996).

The pattern of arrival and departure at Mida confirms previous observations. The main adult arrival period is in September and there is a late departure for breeding grounds (Fogden 1963, Pearson and Britton 1980). There have been two recoveries of ringed birds from Mida Creek that further support these observations, one on the Pakistani coastline on 3 September 1985 (ringed 12 December 1982) confirming the late southward migration to Kenya and similarly for the return an adult found on the coast at Modhava, western India on 22 May 2016 that was ringed on 20 January 2013 (Jackson 2016), (Table 5).

The decrease in numbers during November (Fig. 3) may reflect a departure of birds on passage moving farther south, however retrap histories of birds ringed in August–October suggested that at least a certain proportion of birds that arrive in this period remain throughout the non-breeding season (Table 3). Furthermore, a gap in the data collection during this period is likely to have had an effect on the results shown. Further fieldwork is needed to obtain a better dataset to reveal the full patterns of Lesser Sand Plover arrivals and departures on Mida Creek, for all age categories. This fieldwork would involve both regular ringing and regular surveys.

South of Kenya, information on arrival and departure dates is scanty. In Dar es Salaam, Tanzania, Harvey (1974) noted the main arrival of Lesser Sand Plovers was mid-September with a peak in October. Thereafter numbers dropped and there is no sign of a return migration with birds just

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dwindling in number as adults leave for breeding grounds. Baker and Baker (2016), however, noted that large flocks of birds are occasionally recorded on return passage.

There are a small number of inland records of Lesser Sand Plover in Africa (Dowsett 1980). It is a vagrant to the interior of Africa, and it is almost exclusively a coastal species during the non- breeding season, confined mostly to the shorelines of the Indian Ocean between the tropics (Hayman et al. 1986, del Hoyo et al. 1996).