Why Jackdaws can cause havoc in a chimney

Well, it may disappoint the RSPB, but Jackdaws most certainly are not a sweep’s best friend, nor are they particularly the friends of the people whose chimneys they build nests in.


Normally you would assume that any bird rash enough to build a nest in a working chimney would soon expire from monoxide poisoning, but Jackdaws do seem bullet proof.  I have taken a nest full of chicks out of a chimney.  The householder’s family had nearly died from monoxide poisoning due to the chimney being blocked, but the chicks were fat and in excellent health.


Jackdaws like chimneys, and if you have a nest in your chimney, it is a given that it will have been built by a jackdaw.  No other bird has quite such a love affair with our flues.


While they seldom are found in modern, post 1965 chimneys (though you will find a few) their favourite flues are the Victorian constructions.  These tend to have rough internal surfaces, and corners to aid in keeping the nests up there.  While such bends are easy to build in, and the horizontal surfaces of the big inglenooks are also easy, most of the nests are situated in comparatively straight flues.  Their trick to making this work is also the item that makes them so hard to shift.


The main constructional material of the nest are springy twigs that are flexible enough to bend well.  The jackdaw takes hold of the twig in the middle and proceeds to work its way down the flue until it feels adequate resistance from the twig being pushed down.  If the lining is too smooth, the bird wil keep pushing down until the twig falls out the bottom.  It will repeat this for a number of times, until giving up on the chimney as a bad deal.


As soon as a twig lodges, off goes the bird for another one which is pushed down until it lodges against the first, then another, and another until a dense mat of ‘U’ shaped twigs has  been built up.   This is the foundation on which the rest of the nest is constructed, and it is this foundation that is such a problem to the sweep.  The U of each twig won’t easily move when struck by the brush, and the brush itself can’t penetrate.


The usual technique is to put a battering ram on the end of the rods and give the nest hell.  The game is to loosen the mass of the nest by passing the ram through it repeatedly until the core starts to break up and fall down the flue.  Eventually enough falls to allow the brush through, and with that the sweep is able to dislodge and remove the twigs that are left.


Once the nest is removed, it is VITAL to get a properly designed birdguard onto the pot the same day.  Leave it 24 hours and the birds will have started to rebuild it.  Within a very short period, (sometimes just 24 hours,) there can be enough new material in the flue to block it off a second time.  The best advice is, have someone standing by to fit the birdguard the minute the sweep hascleared the flue.

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