14th September

A lovely clear, sunny and warm day - initially with a brisk north-easterly blowing - brought forth a host of overhead passage but also caused some frustration with neither of the morning's oddities lingering: an Ortolan Bunting headed straight through into the wind over the Obs and shortly afterwards a Tawny Pipit was flushed from the Crown Estate Field and was likely also heading off when it was heard calling nearby shortly afterwards; further local quality at the Bill came in the form of 2 Avocets through on the sea and a Marsh Harrier leaving to the south overhead. The bulk of visible passage was hardly quanified, with the totals of 100 Yellow Wagtails, 30 Grey Wagtails, 12 Tree Pipits, 5 Grey Herons and a Short-eared Owl through over the Bill being just the main interest amongst a far heavier passage of hirundines and Meadow Pipits in particular. Maybe not surprisingly grounded migrants weren't exactly numerous, even if variety was a little better than in recent days; the first few migrant Stonechats of the season did merit a mention at the Bill. The Avocets aside, 2 Sooty Shearwaters, a Balearic Shearwater and a Teal were of note off the Bill. Elsewhere there were 21 Bar-tailed Godwits and a Knot at Ferrybridge.

Immigrant moth interest increased in tandem with the increase in overnight temperatures following yesterday's thunderstorms; however, there was perhaps a feeling that in another year such seemingly promising conditions would have come up with plenty more in the way of both numbers and rarities than proved to be the case on this occasion. The night's highlight was the first island record of Boxworm Moth Cydalima perspectalis at Weston; immigrant totals included 26 Silver Y, 24 Rush Veneer, 19 Rusty-dot Pearl, 13 Diamond-back Moth, 2 Convolvulus Hawk-moth and singles of Vagrant Piercer, Gem, Vestal, Hummingbird Hawk-moth and Pearly Underwing at the Obs. Other strays included singles of Portland Ribbon Wave (most likely an immigrant, since indigenous specimens are very rarely recorded at the Obs), Latticed Heath and Oak Hook-tip at the Obs, whilst another arrival of Western Conifer Seed Bugs saw at least 6 trapped in moth-traps around the island.

The chief prize (...although we're not sure that the topiary community would describe the occurrence of this pernicious pest of their works as a prize) from overnight mothing was the island's first Boxworm Moth from Duncan Walbridge's trap at Weston; despite having been on the British scene since 2007, the south-westward spread from the Home Counties of this Asian adventive hasn't exactly been rapid - has there been more than just one other Dorset record so far? - so, particularly bearing in mind the prevailing conditions, it may be that this first island occurrence comes as a result of immigration from France where the species is apparently also well established in places © Martin Cade