Bonaparte’s Gull at Oare Marshes

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British Wildlife

14th July 2016

Bonaparte’s Gull Chroicocephalus philadelphia, as its scientific name testifies, is a North American species, and as ubiquitous as the similar black-headed gull Chroicocephalus ridibundus is here in Western Europe. A single Bonaparte’s turns up at Oare Marshes, and immediately the record is run out as an alert online; rarity is prized by many and, like many stormblown ‘Yankees’, the bird draws people to stand and scope. Bonaparte’s is small with a jet back head and bill with a delicately etched, white eye ring; the larger black-heads have a chocolate brown head and a red bill. Vive la différence!

Unaware of the rarity before us, a kindly birder informs us of its presence and guides us to the lone American tucked up in a distant flock of russet-coloured black-tailed godwits; all sitting out the high tide in the sanctuary that is the East Flood. Eventually it stretches and preens, then departs for the freshly exposed mud along Faversham creek. We walk the path round and after admiring the sea lavender Limonium vulgare that has turned patches of the saltmarsh a delicate mauve, find it walking the flats in the company of black-headed gulls. It has short legs but walks faster than the locals and crosses the mud along invisible lines and occasionally picks prey from the surface. The walking is constant-paced and ceaseless and there is surely some complex method to optimise the search. The little emperor is ignored by the others and is therefore entirely alone in the crowd. The locals tell us that this is the fourth summer running that it has turned up; so where then does it spend the rest of the year?

In North America, Bonaparte’s gull breeds in the northern taiga of Canada but winters all across the United States; it builds a nest up in a tree, which sets it apart from other gull species that tend to nest on the ground or cliff sides and, more recently, on buildings. This stranded individual is unlikely to get ever back home and build a nest in a tree but does not appear to be in any way concerned by the isolation and exile; unlike a more famous namesake who seethed with indignation while rotting away on St Helena.

The walk round the sea wall path runs past ‘pinging’ bearded tits Panurus biarmicus that zip over the reeds Phragmites australis and quickly disappear into the foliage on landing. A sedge warbler Acrocephalus schoenobaenus sings its dizzy rattle from a small bush before dashing back to cover. Cock reed buntings Emberiza schoeniclus sit atop bushes and swaying reeds to rap out uninspiring repetitions of ‘zreet’ and ‘trip’. A common carder bee Bombus pascuorum works a teasel Dipsacus fullonum head. The path sides are full of colour with the pink of willowherb and thistles in an annual competition with the yellow of St John’s worts and others; the insects are at their most abundant in the July sunshine and spoilt for choice.

In July, sedge warblers are laying down fat reserves, stored subcutaneously under wings and either side of the breastbone, to provide the energy to make a long haul flight all the way to West Africa; they fuel up, doubling their body weight, by gorging on mealy plum aphids Hyalopterus pruni; these spend the summer multiplying on the reeds before returning to winter on Prunus trees. This remarkable migration strategy is different to that of the morphologically similar reed warbler Acrocephalus scirpaceus, which is for some reason a much less adept, aphid eater and hence has to refuel on other species of insects in southern Europe in a hip-hop migration pattern to sub-Saharan Africa.

Back at the East Flood, the godwits are becoming restless on the ebb tide; waves of chattering sound are carried on the wind.  Eventually they lift and circle but don’t leave for the estuary. The birds are moulting wing feathers and many retain their rich red breeding plumage. They are, as ever, an elegant crowd.

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