Today I bumped into a chap called Tony Fulford from the zoology department at Cambridge. He had got wind of the fact that we have a lot of willow warblers and chiffchaffs at Paxton Pits, and they don't all sing from the same hymn-sheet! Working here and in the Gambia, he has discovered that willow warblers react to chiffchaff calls by repeating them. Basically, they are bilingual. So are they hybrids? It doesnt look like it to me, but the two species are very similar.
Chiffchaffs sing from tall trees while willow warblers use lower bushes, but both nest on the ground and look very similar. Our willow warblers generally winter in West Africa while chiff chaffs winter around the Mediterranean, but they overlap in all respects. We tell them apart by leg colour, wing length and of course, song. But it's not that simple.
As part of his study, he has ringed one of our birds and measured it up. It's pure willow warbler but it's bilingual.
"Attached are photos of the wiffwaff. Note the emargination to the 5th primary. The 2nd primary was noted to be approximately as long as the 6th. So typical WILWA wing. The wing chord was 68mm and weight 9.4g - typical for male WILWA but way off for a CHIFF. Curiously the bill has a slight hooked overgrowth."
"This was a rather tentative bird compared with some I've encountered. As usual in response to both WILWA and CHIFF playback it stop singing while it searched for the source but once the playback had stopped it resumed with a rather quiet chiff-chaffing. After a minute or two it was back in full swing with its usual half-half song."
Ypu can hear our willow warbler here:
https://paxtonpits.podbean.com/e/willow-warbler-at-paxton-pits/
His new ring number is EJE 495. Ypu can hear our willow warbler here:
https://paxtonpits.podbean.com/e/willow-warbler-at-paxton-pits/
