Double trouble for the plover
The double ringed plover Charadrius bicinctus, which was included in this year’s Red List update from Least Concern to Near Threatened, is one of the more unusual migratory waders in the South Pacific. Rather than migrating to Australia for its summer and flying south from breeding areas in the northern hemisphere each year, it is unique in that it breeds in New Zealand in the southern summer and then flies west across the Tasman Sea in the fall towards Australian coasts visit and winter months.
At least a portion of the population does so – those birds that breed in the highland rivers of New Zealand’s South Island – while those that breed elsewhere in the Shaky Isles make local movements and do not cross the Tasman.
Like most waders, double ringed plovers nest on the ground and lay their eggs in a scratch in the sand on coastal beaches or further inland between pebbles on shingle banks in braided streams. Birds that breed in both habitats are each exposed to their own threats. These plovers that nest on coastal beaches face the threats so many beach nesting birds face, with disturbance topping the list. Incubating birds are easily disturbed by beachgoers or their dogs who get too close. The eggs are often accidentally crushed by being stepped on or run over by recreational vehicles, and even if not crushed, the eggs or chicks can be left unattended for too long and at the mercy of the elements or predators such as seagulls and domestic cats.
Plover that nest in the highlands are less prone to failure, but experience more predation, mainly from introduced mammalian predators, including hedgehogs, roosters, and cats. In addition, their breeding areas can be overgrown with invasive weeds such as marram grass on beaches and lupins on river banks, making these locations unsuitable for breeding.
The bird is a target species in Australia’s migratory shorebird action plan, which promotes the protection of wetlands.
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