A simple hweet, a wave of migration

Chiffchaff (Bob Garrett)

Wherever I walked at the weekend, it seemed that each bush, tree and hedgerow contained a Chiffchaff. Not the disyllabic, shouty song that heralds spring and continued into July, but the softer “hweet” call used to contact each other while they moult, on migration and in scrubby desert around the Mediterranean where most British Chiffchaffs spend the winter. While we are quick to note the first summer migrants, it’s harder to know when you’ll hear your last unless you keep a careful record. It's one reason that I use BirdTrack, the bird sightings smartphone app, to maintain a list of every species I see and hear.

The Chiffchaffs I heard at the weekend – on Anglesey, Eryri and on the Llŷn – may be local breeders that are moulting their flight feathers before departing south, but other migrants with farther to travel are definitely on the move.

Each wetland I visited on Anglesey provided sustenance for Sand Martins by the hundred, with dozens of Swifts too. House Martins, on the other hand, can have chicks in nests well into September, and it was a thrill to watch a dozen feed on insects over the hillside above Llyn Dinas, where the National Trust is encouraging natural woodland regeneration. A family of Spotted Flycatchers – a Red List bird of conservation concern – were enjoying the invertebrate feast too.

More unusual sightings this week included a Sabine’s Gull drifting north on the sea from Bardsey, a Balearic Shearwater off Porth Ysgaden, and Storm Petrel, Arctic and Great Skua off Rhos Point, in the wake of last week’s strong winds.

The first Teal and Wigeons of winter were recorded on local Wetland Bird Surveys (WeBS), the scheme that monitors the fortunes of the UK’s waterbirds. A recent study led by the British Trust for Ornithology showed that by combining winter data across temperate countries, scientists could produce waterbird indicators to track numbers and breeding performance in the remote north, where surveys are impractical. Since Arctic areas are experiencing the greatest impact of climate warming, this approach might be the only way to track changes faced by the birds we share.