Thursday, 3 May 2012

Tawny Owl Ringing

We spent an evening recently ringing tawny owls with BTO (British Trust for Ornithology) bird ringer Richard Barnes.  Richard has been carrying out tawny owl nest-box surveys and ringing here at Gibside for over twenty years and has compiled lots of useful information in that time.  Although the boxes used are designed for tawny owls other species such as kestrels and stock doves take readily to them and grey squirrels can be a problem building their dreys inside them.

Young kestrels

Tawny owls usually lay two to four eggs with an interval of a few days between each and with incubation beginning from the first, when hatched, the chicks are all of a different age and size.  Competition for food means that in times of shortage only the largest chicks may survive and cannibalism can also occur with the smallest chicks being eaten.  We did on this occasion find one brood of four young, known from a previous check, which had been predated by an unknown predator or possibly cannibalised with only a single half-eaten chick remaining in the box.

Two tawny owl chicks and an egg hatching

As well as ringing chicks any adults caught by means of a net placed over the nest-box opening have their ring numbers recorded or have rings fitted if they have not been rung before.  In one box Richard was able to remove three chicks from under an unusually placid mother owl before lifting her out of the box to check her ring number.  On completion all three rung chicks along with the mother were replaced back into the box.

Young owl having ring put on

Richard with adult female owl

Young helper with owl chick

In total on the night we caught two adult birds and recorded and/or rung sixteen young chicks.

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