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Movement patterns of Sanderling (Calidris alba) in the East Asian–Australasian Flyway and a comparison of methods for identification of crucial areas for conservation

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Abstract

Most migratory shorebird populations around the world are in jeopardy, none more so than those of the East Asian Australasian Flyway (EAAF). In order to preserve these highly mobile species detailed understanding of their use of fuelling and resting sites along the flyway is required. In this study we used light-level geolocators and new analytical tools to reveal individual breeding locations and detailed migration routes of 13 Sanderlings (Calidris alba) that spend their non-breeding season in South Australia. We then used these individual migration routes to identify the timing and location of important stopping areas and compared this with assessments based on leg-flag resightings and count data. During both northward and southward migration Sanderlings were found to make extensive use of five major areas distributed along the Chinese coastline, the Yellow Sea and the northern end of the Sakhalin Peninsula. Insights gained from these individual migration routes highlighted inherent biases in only using count and resighting data to identify important fuelling and resting sites along the flyway. These findings suggest that individual movement data may therefore be crucial to effective conservation planning of shorebirds in the EAAF and elsewhere in the world.
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... While light-level geolocators have long been deployed to provide an understanding of a range of animal movements, it is over the last 10 years that they have been used on a number of shorebird species to track migratory movements and identify breeding, stopover, and wintering areas (Bridge et al. 2011, Tomkovich 2016, Lisovski et al. 2016a). These devices measure and store ambient light levels which can be used to determine latitude and longitude when the data are downloaded. ...
... We used the template-fit method described in Lisovski et al. (2016a) to estimate the positions of the breeding sites. The level of accuracy of the estimated breeding sites is 100-300 km Lisovski et al. (2016a). ...
... We used the template-fit method described in Lisovski et al. (2016a) to estimate the positions of the breeding sites. The level of accuracy of the estimated breeding sites is 100-300 km Lisovski et al. (2016a). ...
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The tracking of birds using light-level geolocators has become a relatively frequent technique in the study of migratory shorebirds. The geolocator program, commenced in Australia by the Victorian Wader Studies Group in 2009, has provided insights into many of the strategies and outcomes of the species studied. The most numerous of these studies have been on the Ruddy Turnstone Arenaria interpres. While an increasing number of these are multiple tracks for the same bird, there are relatively few with field sightings to enable supporting calibration and confirmation of computed locations, hence the value of the sightings in Newcastle of Ruddy Turnstone with leg flag WMA described in this paper. The migrations of this bird, described over three consecutive years, show southward tracks over the Pacific Ocean and stopovers in Newcastle on its return journeys to King Island (Tasmania). Information regarding breeding locations and incubation characteristics are also described.
... Our data also suggest that the birds need to obtain resources for migration and other annual cycle stages (e.g., molt) in these countries. A similar migration pattern of the little ringed plover has been reported in the local population of Sweden 28 and in other small shorebirds in the EAAF, such as sanderling 34 and ruddy turnstone 8 . However, the migration routes and wintering areas of the six plovers we studied had less variability compared with the Swedish population, which showed a variety of migration routes among seven studied plovers. ...
... However, the migration routes and wintering areas of the six plovers we studied had less variability compared with the Swedish population, which showed a variety of migration routes among seven studied plovers. In addition, the migration routes and distances of the two plovers with complete migration data were similar in autumn and spring, as has been reported in sanderling 34 . The birds' small body size may restrict their selection of favorable stopover sites, with the sea acting as an ecological barrier. ...
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To maintain and recover populations of migratory waders, we must identify the important stopover sites and habitat use along migration routes. However, we have little such information for waders that depend on inland freshwater areas compared with those that depend on coastal areas. Recent technological developments in tracking devices now allow us to define habitat use at a fine scale. In this study, we used GPS loggers to track both spring and autumn migration along the East Asian-Australasian flyway of the little ringed plover (Charadrius dubius) as birds moved to and from their breeding grounds, gravel riverbeds in Japan. The birds we tracked overwintered in the Philippines and made stopovers mainly in Taiwan and the Philippines. The most important habitat during the non-breeding season was rice paddy fields. Our findings imply that changes in agriculture management policy in the countries along the migration route could critically affect the migration of waders that depend on rice paddy fields. To maintain populations of migrant inland waders that move within the East Asian-Australasian flyway, it is necessary not only to sustain the breeding habitat but also wetlands including the rice paddy fields as foraging habitat for the non-breeding season.
... Light-level geolocators accordingly do not track daily finescale movements and provide only "inexact" approximations of the general migratory route [70,71]. Furthermore, location estimates may be even less accurate at high altitudes during summer [71], especially if they are not analysed in a sophisticated way [72,73]. To assess the accuracy and precision of the location estimates, many studies apply ground truthing in breeding areas or wintering grounds. ...
... Since most songbird species probably encounter favourable feeding habitats along their migration route on a regular basis, the drive to accumulate large energy stores and extensively build up muscles before departure is generally less pronounced than in waders, for example. In the latter group, the occurrence of the first migratory fuelling period and extensive muscle development before the first migratory flight is a common phenomenon [129,130] because these species often migrate over long distances to reach the next favourable stopover area, e.g., [72,131]. Zhao et al. [22,132] minimized this issue in waders by estimating the partial speed of migration. ...
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... (b) The feedback process between individual stopover duration and population dynamics processes such as sex differences and a mixture distribution of migratory tactics. Males often migrate earlier than females in the northward migration to occupy the best breeding territories (Kokko et al., 2006;Newton, 2011), and some individuals might abort migration without making any breeding attempt (Lisovski et al., 2016;Shaw & Levin, 2011). However, as the lack of individual-identified information on both timing, energy reserves and migrating trajectory, we chose to ignore them in this model. ...
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... However, taking more population-specific and connectivity-based approaches to conserving Dunlin on the EAAF would require a more detailed understanding of subspecific migration patterns and site use than is currently available. To address this knowledge gap we recommend a coordinated effort that combines deploying tracking devices at breeding sites to quantify subspecies' use of migration routes (e.g., Bridge et al. 2011, Kays et al. 2015, Brown et al. 2017 with the collection of morphological measurements, genetic samples (Gates et al. 2013, Miller et al. 2015, and flock counts at nonbreeding sites to quantify subspecies' use of nonbreeding areas (e.g., Lopes et al. 2006, Lisovski et al. 2016. Collectively these efforts would provide the greatest opportunity to scale our understanding of Dunlin space-time dynamics from dozens of individuals to entire populations, and ultimately enable more effective conservation efforts for Dunlin on the EAAF , Barter 2004, Bowlin et al. 2010. ...
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