Nature Blog: nesting Wrens


CAT’s resident naturalist Rennie on nest-building wrens.

This is a great time of year to observe bird behaviour without too much effort, as lots of them a busy courting and nest building, tending to be so preoccupied with these activities that they don’t take too much notice of us and lose some of their wariness. Also, the trees are not yet in leaf so all the hectic avian comings and goings are easier to watch.

A couple of days ago Roger (CAT’s gardener) and myself noticed a wren outside the staff lunch room. He was busily collecting moss from one of the tree stumps and flying off to the back of the solar display building and disappearing under the eaves where it was obviously constructing a nest.

Wrens’ nests are beautiful structures made out of twigs, grass and mosses in a complete ball shape with just a tiny hole at the front for access. They blend into the background so well they can be extremely difficult to spot. The wren (dryw in Welsh) is unusual in that it is the male bird who builds the nest – in fact, he will often build several nests -and then proudly shows them off to his chosen female who selects the best one in which to set up home. She will then sometimes tweak it up a bit with a few blades of grass or some twigs before concentrating on egg laying and rearing her brood.

The male helps with feeding the young but also will do the rounds of his other nests keeping them in good condition, and often installing a second or even third female in them. Wrens often raise a second brood and will usually move to another nest to do this as the nests for some reason seem to get heavily infested with parasites to the extent where it can be a severe health hazard to the young. Obviously, the more nests the male can build the more successful he will be in passing on his genes in the form of lots of healthy offspring.