On Saturday evening whilst doing the Draycote roost John Judge suggested it was about time he/we went to have look at the 1st W/S Bonaparte’s Gull which has now been present for some time at Farmoor in Oxfordshire. Dan Watson had called that same evening keen to get out of the county and ‘actually see something’ the next day, so after work on Sunday instead of taking the sensible course of action and going home to deal with paperwork, I drove over to Dan’s and picked up a lift to Farmoor. I’m so pleased I did as the bird was constantly on view for the two or three hours we spent there and very close in the entire time. The Bonaparte’s spent much of its time gleaning insects from the surface but was also catching numerous fish.

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1 st W/S Bonaparte’s Gull, Farmoor Reservoir.

This behaviour was not lost on the Black-headed Gulls present which took to trying to steal a meal, providing ample opportunities to compare the two species. Whilst the quality of the following two images is poor they are worth including for illustrative purposes. Though the size difference is perhaps exaggerated here by the ‘flattened’ posture adopted by the Bonaparte’s, one which interestingly it seemed to utilise when being defensive and aggressive (which it was with surprising frequency given its smaller size and weight), it is nonetheless remarkable. As a result of these aggressive encounters the bird was vocal too, the peculiar high-pitched tern like call quite distinct from that of any gull regularly encountered in the UK. When no other birds were available for size comparison the tiny, short narrow bill was distinctive. Though the Bonaparte’s is at a poor angle in the shot below the darker tertials are obvious.

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1st W/S Bonaparte’s Gull and 1st W/S Black-headed Gull, Farmoor Reservoir.

The cleaner inner upper-wing of the Bonaparte’s is well illustrated here, the narrower, neater darker trailing edge and carpal bar and cleaner inner primaries combining to create a distinctive appearance. Black-head Gull of the same age typically shows a more extensive and more diffuse trailing edge to the wing and more extensive white in the primaries and outer greater primary-coverts resulting in a larger, cleaner white ‘wedge’ along the outer forewing.

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1st W/S Bonaparte’s Gull and 1st W/S Black-headed Gull, Farmoor Reservoir.

Photos taken at closer range and with more time to steady the camera show the spread wing pattern well. The clean underwing lacks the dark grey primaries typical of Black-headed Gull of the same age (see previous flight shot) but Malling-Olsen and the Collins Guide both warn of the potential for worn individuals to show rather translucent primaries (a photo of such a bird can be found in Gulls). These authors also point out that 1st W/S birds may be slightly smaller and I have certainly seen ‘runt’ Black-headed Gulls a few times in the Draycote roost and one bird with translucent primaries which gave me a scare during brief views at extreme range.

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1 st W/S Bonaparte’s Gull, Farmoor Reservoir.

The greater primary-coverts show an inverse pattern to that of Black-headed Gull in that they have dark bases to the outers but are otherwise pale whilst Black-headed Gull typically has white outers and dark centres to the inners.

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1 st W/S Bonaparte’s Gull, Farmoor Reservoir.

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1 st W/S Bonaparte’s Gull, Farmoor Reservoir.

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1 st W/S Bonaparte’s Gull, Farmoor Reservoir.

On the water the dark bill and extensive grey on the hind-neck and upper breast sides were obvious features but would be far harder to be sure of at range and in the failing light of a gull roost. Having said that we had originally gone to the wrong place and when Dan first picked the bird up across the width of the reservoir in the heat shimmer the latter feature was just about discernible. Black-headed Gull can show something similar and though typically less obvious in that species I have found its appearance exaggerated in poor light. The ear spot was also very neat and only a minority of Bonaparte’s Gull will develop a (blackish) hood in their first summer.

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1 st W/S Bonaparte’s Gull, Farmoor Reservoir.

There was no sign of tail moult although the extremely long tail-coverts overlaid the central tail feathers and sometimes gave the impression of replaced feathers.

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1 st W/S Bonaparte’s Gull, Farmoor Reservoir.

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1 st W/S Bonaparte’s Gull, Farmoor Reservoir.

Finally, and for no reason other than the fact that it was so pretty here are a couple more photos, long shots with a bit of background for ‘mood’.

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1 st W/S Bonaparte’s Gull, Farmoor Reservoir.

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1 st W/S Bonaparte’s Gull, Farmoor Reservoir.