Shorebird conundrum

So, in terms of conservation, which of these shorebirds in the top row and bottom left and bottom centre is not quite like the others (the photo in the bottom right hand is a clue)? This quizz pertains to a newly published study that showed high survivability in 6 species of shorebirds at 9 breeding sites across the North American Arctic in 2010–2014: American Golden Plover, Dunlin, Semipalmated Sandpiper, Western Sandpiper, Red-necked Phalarope, and Red Phalarope with one important difference. The conclusion of the paper is that the main conservation concern may be at stopover sites or wintering sites, see: rhttp://www.bioone.org/doi/10.1642/AUK-17-107.1 ... scroll down to see the answer:
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This study looked at breeding and survivorship of six species: Western Sandpiper (top left), Dunlin (top centre), American Golden-Plover (top right), Semipalmated Sandpiper (bottom left), Red-necked Phalarope (bottom centre) and also Red Phalarope (not pictured). They showed good breeding success and high survivorship in all except the arcticola subspecies of Dunlin. So how does the arcticola Dunlin differ from the others? Well, it breeds in North America but it winters in Asia and uses the East Asian Flyway (all of the others stay within the Americas). Stop-over sites in the East Asian Flyway have deteriorated so drastically and there is so much habitat loss that it affects survivorship. This is a major problem not just for these Dunlin but also for many Asian shorebirds such as the Spoon-billed Sandpiper (the clue is the bottom right photo of a Dunlin beside a Spoon-billed Sandpiper, a photo that I took in South Korea). It goes to show that even if all is well on the breeding grounds, a species can encounter great danger elsewhere in its range (on migration or on the wintering grounds). It is important to remember this connectivity and its consequences when we talk about Canadian Species At Risk.