Monday, November 25, 2019

Notes on Oystercatchers Haematopus ostralegus

Having recently moved to the bird-rich east coast of Yorkshire I see lots more Oystercatchers than I was used to seeing in south-east Notts. There were always Oystercatchers knocking about the gravel pits and the Trent basin but I generally gave them little regard. The other week I remembered from somewhere in the past that the white band across the throat and the neck-sides was indicative of winter adults as well as first year birds. I had not previously given this much thought but then I checked through recent photographs just to make sure that I was correct. Sure enough it is possible and easy to tell first year birds from adults and breeding adults from winter adults on obvious plumage/bare-part differences. Telling males from females however is more tricky: females have slightly longer and thinner bills than males but experienced observers can usually sex adults on this feature.
So what do we have then in the way of obvious plumage differences. Juveniles have brownish-black upperparts and wing coverts and they have dull pointed bills and dull greyish legs, brownish-red iris with on orangey orbital ring and no throat-band. They develop the white throat-band later in their first year as they enter first winter plumage. Adult winter/non-breeding birds also have the white throat-band but they lose the brownish colouration, becoming dull black, the bill is orange the legs are pink and the iris and eye-ring are red. Breeding adults lose the throat-band; the head, neck, breast and upperparts become glossy black. The rest of the plumage is white and there is a striking white wing bar across the upper-wing.

There are at least two birds entering first winter plumage in this shot. They can be aged by the dull bills and the white throat-band. The other birds are breeding adults.

Adult breeding Oystercatcher showing bright red iris and orbital-ring and bright orange bill. No throat-band.

Adult breeding Oystercatcher - no throat-band

Adult breeding Oystercatcher in flight - no white throat-band.

Adult non-breeding/winter Oystercatchers showing the white throat-band. These birds were all feeding at Filey Country Park.

Flight shots of adult breeding birds. Glossy black head, neck and upperparts, bright bare parts and no white throat-band.

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