11th September

What had seemed like a carbon-copy day destined to maintain the rest of this week's pattern of pulses of visible passage but precious little on the ground, today suddenly veered off into the rarity realms at midday with the discovery of a Western Bonelli's Warbler in private gardens at Southwell. Hitherto, Meadow Pipits had been the morning's feature, with a flurry of 300 or more through the Bill in quick time after dawn; 300 House Martins, 250 Swallows, 72 Yellow Wagtails and 47 Siskins also passed by along with lower totals of a selection of other wagtails, pipits and finches. The season's first Goldcrest dropped in at the Bill but grounded migrants were otherwise only very thinly spread and included nothing of particular note beyond the lingering Little Stint at Ferrybridge.

A sizeable group of Bluefin Tuna lingered off the Bill for a while during the morning.

Seven of Portland's eight Western Bonelli's Warblers have occurred in autumn with previous arrival dates in this season spanning extremes of 10th August and 9th September, so today's bird becomes the latest ever © Pete Saunders:

It was a really busy bird, constantly on the move and always twitching/flicking its tail and wings © Martin Cade:

You get the impression from some reports these days that it's barely worth seeing a silent bonelli's warbler: the two species can be so similar in plumage that unless a call's heard the record's never going to get anywhere. Fortunately, today's bird was extremely vocal and could be instantly clinched as being a Western...

...as a reminder of just how utterly different the commonest call of an Eastern is here are a few calls from the bird at Avalanche Road in 2009:

To our ears the usual call of a Western Bonelli's isn't that unlike some Willow Warbler calls and maybe the issue in getting to clinch an otherwise quiet Bonelli's sp is making sure you don't inadvertently hear a background Willow Warbler and so assume you're on a Western Bonelli's. Today's bird was calling so much that there was no doubt where the call was coming from and on a sonogram the individual call-notes can be seen to be bang on the nail for Western Bonelli's:

By something of a coincidence, yesterday we had a copy of Identifier Les Oiseaux Migrateurs Par Le Son arrive; by way of advertising what looks to be a great resource (rather than infringing the author's copyright!) here's a scan from there of the sonograms of typical Willow and Western Bonelli's calls: