Went to Amwell at dusk hoping to see the Great White Egret that roosted there yesterday. No such luck. Did see a Bittern and a Barn Owl whilst waiting. Then at dusk, two Bitterns circled the reedbed quite high. They made a sound I’ve never heard (described in BWP as a nasal ‘kau’). Apparently this is often performed before migration. Then, when almost dark, one of the birds flew strongly and high North-East. Presumably it had left for the summer.
