The moult and migration strategies of Lesser Sand Plover, Greater Sand Plover and Terek Sandpiper

Jackson, Colin

The moult and migration strategies of Lesser Sand Plover, Greater Sand Plover and Terek Sandpiper

Doctoral Thesis

2018

Publisher

University of Cape Town

Department

Department of Biological Sciences

Faculty

Faculty of Science

Abstract

Moult in birds is a critical yet often underrated component of a birds' annual life cycle together with breeding and migration. A good understanding of the moult strategy of a species is important for its conservation because key moulting grounds must be protected to allow this component of the life cycle to be undertaken. Lesser Sand Plovers, Greater Sand Plovers and Terek Sandpipers are among the least known of the commonly encountered long-distance migrant waders in Africa and Australasia. This is particularly true for the populations which spend the non-breeding season on the East African coast. This study aims to describe the primary moult strategies for the three species from five locations at different latitudes: south-eastern India, Kenya, South Africa, north-western Australia and southeastern Australia. Differences in moult strategy between species, age and latitude are highlighted and explanations are proposed for the differences in the light of the breeding behaviour, migration time and routes, food availability and local climatic conditions. Results from this study are combined with other moult studies on migrant waders to present hitherto undescribed patterns in wader moult strategies at a global scale. A synthesis is presented of published and available unpublished information about the different populations for the three study species, their distribution, status and migration strategies with a focus on those visiting the East African coast. The three species follow a similar basic moult strategy in adults where primaries are moulted soon after arriving on the non-breeding grounds. Immature moult strategies are more complex and differ between species and latitude. In general adults in all three species at the more northern nonbreeding sites start moult earlier than those travelling farther south probably as a result of greater proximity to breeding grounds. Lesser Sand Plovers have a relatively long duration of moult (152- 154 days) across all locations where data were sufficient; Greater Sand Plovers have a short duration (80 days) in India and similar, comparatively longer durations (132-134 days) at the other latitudes. The Indian site is used mainly by this species as a site to stopover and moult while on migration to more southerly non-breeding grounds. Terek Sandpipers in Kenya have a relatively short duration of moult (99 days) when compared to India and Australia (121-130 days) and tend to have a rapid start to moult which then slows down after the first few primaries are moulted. Young Lesser Sand Plovers in India mostly undergo a complete primary moult while in Kenya and Australia birds generally do not moult in their first year. First year Greater Sand Plovers mostly all undergo a complete primary moult irrespective of latitude. Terek Sandpipers in their first year do not moult in India in the north, mostly undergo a partial moult of outer primaries in Kenya on the equator, and do a complete moult in south-eastern Australia. The north-west Australian population was divided into two almost equal groups: those that undergo a complete primary moult, and those that only moult a few outer primaries. A difference in winglength between these two groups suggests that there may be two distinct populations involved, most likely originating from distinct breeding grounds. In-depth study is needed to confirm this. The overarching picture of moult in adult migrant waders is that at high latitudes moult starts early and is kept short. With decreasing latitude, the timing of moult is delayed with increasing distance from breeding grounds. In the tropics the lack of constraints of approaching harsh winter weather and long distances from breeding grounds allow species to adapt a wide range of moult strategies. As birds migrate farther south before they moult, constraints on time available to moult due to large distances travelled mean duration is reduced in order to fit it in. An upper limit in duration of moult in migrant waders irrespective of the size of the bird appears to be set at c. 160 days. Small birds have a wide variation in duration while as body size increases over 100 g, moult duration is necessarily longer. With harsh winters in the north, large waders are forced to migrate south in order to moult. This study suggests that irrespective of body size the 'gold standard' for duration of moult is around 120 days (four months). While timing of migration is relatively well-known for the three species in Australia, it was hitherto unknown that juvenile Lesser Sand Plovers delay in reaching Australia until February or March in contrast to all other migrant wader species where first years arrive in September/October. It is unknown where they stop en route or indeed why they delay in this way. All three species in Kenya peak at a maximum population in November and early December after which numbers reduce as birds start to depart for the breeding grounds. Resightings of colour-flagged Lesser and Greater Sand Plovers confirmed the north-western coast of India as an important stopover site for migrants heading to western China and Mongolian breeding grounds from Kenya. A review of country population estimates for the three species suggested non-breeding populations in Africa of 200,000 Lesser Sand Plovers, 25,000-35,000 Greater Sand Plovers and 115,000-200,000 Terek Sandpipers. Mida Creek is shown to be a key stronghold for non-breeding waders in Kenya and its importance for their continued conservation is thus confirmed.

Keywords

Zoology

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Collections

PhD / Doctoral

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