The wrens came every evening in the very hard frost to keep warm in the swallows nest. Then they built their own on top.
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This is a remarkable observation. It's common knowledge that wrens roost communally in the winter but I don't think I've ever seen a photo of it before. As for the nest extension, as far as I know this unique. Note that from the date this is not a breeding nest, but a wintering one.
I am looking for the photo of them at night Around 7-or 8 would go in head first and all you could see was their tails sticking up.
It went down to -15 some nights this winter so its the only way they could survive. and yes they never nested in it.
When did the Wrens build their extension?
Male Wrens build several nests, and the female then chooses the one she wants to use. If this nest wasn't built until the spring it may have been a male showing off his DIY skills.
Id say you were right, Not sure about the exact date I think either March or April was when they built it.
outstanding! Rare (and good) shot of a well-known but seldom-seen behaviour.
Lat/Lng: 53.7, -7.2
OS grid ref: SA6144