HERE’S ANOTHER RECORDING from the Waterways sound map made last Friday by the river Lea. The Lea remains London’s most industrialised minor river, even though most of the valley’s factories and paper mills have now disappeared.
Just north of the Cooks Ferry roundabout the Lea passes a collection of large waste recycling plants. A row of trees stands between them and the west bank of the Lea. Dozens of rooks had convened on the branches.
The rook’s efficient respiratory system absorbs atmospheric pollutants at a high rate. It expels them by hacking up rich gobbets of phlegm, accompanied by the rattling vocalisations you can hear in the recording.
On reaching the ground each phlegm-clot begins forcing a network of fine roots into the soil to extract trace nutrients such as cadmium and mercury. Meanwhile the clot becomes cold and firm to the touch as it swells into a puffball-like mass known as the sacculus. In time this ruptures and out crawls a new baby Londoner.