It was nice to get back to Reculver today and we were blessed with an open sky and drier conditions. Great to see a Grey Plover, Pluvialis squatarola, together with Oystercatchers and Gulls on the rocky foreshore by Coldharbour.
I identified it as a Grey Plover by its eyespot, overall bulkiness, lack of colour, and the fact that it was solitary - I have only seen Golden Plovers in large flocks over the winter, and never seen birds on their own. The Grey Plovers have travelled further to get to these wintering grounds, generally nesting up towards the Arctic Circle, on tundra beyond the tree limit. A nearly cosmopolitan bird it is known as the black-bellied plover in America. Russian birds get as far as Australia and South Africa, Alaskan birds get as far as Central America.
In winter feeds as much by night as by day, perhaps defending feeding territories and maybe not the most highly mobile wader species on its wintering grounds.
The adults generally leave the breeding grounds, generally non-coastal wet tundra from July to September, and the juveniles follow September to mid-October. When they arrive they tend to end up on beaches by the winter - although I have seen them at Cliffe and Oare Marshes in good numbers earlier in the autumn, presumably birds still moving through on passage. Northward return passage peaks in May and breeding should start in May and June. In Europe this appears to be primarily coastal, with few birds crossing continental Russia, but in America migration may be more continental as birds appear to be able to use the Mississippi Valley as one return route. Young birds however may stay southerly for the first year, presumably moulting into breeding plumage.
There was an interesting piece of research from the Sivash lagoons near the Black Sea indicating that waders may be more limited in feeding opportunities by salinity, wind speed, direction and tide state than might initially appear to the human researchers. The organisms accessibility is often limited by their vertical distribution in the sediments themselves, the worms being highly mobile.
Australian summaries indicated that during the non-breeding season, Grey Plovers mostly eat molluscs (especially gastropods), insects and their larvae, crustaceans (especially crabs) and polychaete worms. Vegetation is very occasionally found in their stomachs. During the breeding season, they eat mostly insects, but may occasionally eat vegetation. The Grey Plover usually forages during the day, but sometimes also feeds at night, when up to 40% of food may be obtained. They usually locate prey by sight, with cues used including movement of water, sand or casts from the burrows of polychaete worms. They feed with a running, stopping and pecking action typical of many species of plovers, gleaning and probing the substrate. Bivalves are seized by the siphon and torn from the shell, while crabs are pecked apart. Main prey in French research on wintering grounds indicated main prey items of benthic worms such as Nereis diversicolor or Nepthys hombergii. However I often see them just standing about, and not appearing to feed very much at all, so maybe they are not all that desperate? This was true of the half dozen birds I saw on the 30th December at Reculver last Christmas. However, maybe I need to look more closely as well!
Prey items include Fiddler Crabs, Uca spp. In one study of feeding on these in Argentina this species fed in a similar way to American Golden Plovers, but waiting longer than that species until they ran at the crabs. Several times they
waited until crabs surfaced, capturing crabs very
close to their standing position (n = 15). Crabs
were always eaten entirely. The selectivity index showed that females were the preferred
prey, while unidentified items and males were attacked
at much lower proportion than their availablity.
This species was the only species that defended
its territories by singing displays and chasing
other conspecifics or American golden plovers
when their feeding area was approached. American golden plover had a cyclical use of the crab bed and the nearby intertidal, spending a variable time (range: 3-9 rain) in the Uca bed, moving to the lower intertidal, and then returning to the Uca bed "after a similar amount of time (range: 6-10 rain). It was unclear from the paper whether the Grey Plover shared this habit.
