Tuesday, May 19, 2020

Wrens in the garden

Wrens nest in our garden almost every year, and usually announce their presence with a loud burst of song that often takes me by surprise. This year they have a nest in an ivy-covered tree stump.

They tend to be quite secretive during the nesting season and spend a lot of time foraging close to the ground, but if I just sit quietly and wait they often become more confiding, allowing me to watch their foraging behaviour.

This year, for the first time, I've noticed their predilection for aphids. The underside of the leaves of our blackcurrant bushes are infested with greenfly and the wrens are constant visitors, picking off the insects with a beak that is akin to a pair of fine forceps. 

The individual food items may be tiny but they must have a high calorific value, because each aphid will be full of plant sap, which is predominantly sucrose.

I imagine that there may be other valuable prey amongst the aphids, including ladybird and hoverfly larvae. 

Being small and agile is an asset for a bird exploiting this food source, though I have also seen house sparrows visiting the blackcurrants for aphid snacks on several occasions.

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