Jackdaw nests are the bane of a sweep’s life, and to be honest, most customers don’t like them much, as soon as they realize the problems they are going to cause. Blocked flues are very dangerous to humans, but it does seem as though jackdaws are immune to the problems associated with monoxide.
Nests in chimneys are almost always built by jackdaws. No other bird has such a love affair with the chimneys in our houses, and we are regularly called out to deal with the consequences.
They don’t like the more modern, post 1965 chimneys, as their nest twigs can’t easily grip in the smooth flues. They like the old inglenooks sometimes, where their construction has left suitable flat ledges, but by far and away their most favoured choice of residence is the 9” x 9” Victorian flues, and not just where a bend makes it easier. They are perfectly happy to build in the vertical flue runs as their rough surfaces allow the birds to set the basic foundations for their nests.
These are constructed from long, flexible twigs that the birds push down the flu in a ‘U’ shape. Now if the flue isn’t rough enough on the interior surfaces, the twig will get pushed out of the bottom, and we often get called to properties where there are a dozen or so twigs at the bottom in the hearth. Basically, the bird will try several times, and if it doesn’t succeed within a reasonable time period, it gives up.
On a successful site, the twig will generate enough resistance aginst being pushed that will satisfy the bird. Off it goes foe another and another, pushing each down against the others to build up a strong, flexible mattress foundation. This is of course where the problem lies, as the sweep’s brush can neither penetrate this or batter it apart, as the bow in the twigs causes them to resist such a push, and their points stuck against the wall stop them from moving up in the flue.
The correct technique is to use a solid ram on the top of the rods and keep battering away until it penetrates the nest entirely, loosening it. Once isn’t enough, and the process has to be repeated many times until the mattress is so loosened and disjointed that pieces of it start to fall down the flue, to where they can be removed.
The sweep can then resort to the brush to remove the rest of the twigs and finish sweeping the chimney.
Having got the nest out, it behoves the householder to get a properly designed birdguard onto the top of the pot, and to do so promptly.. Resist the advice of those who recommend hooded pots, as jackdaws LOVE these and can get in and out with no problems at all. The gurad should be made of stainless steel, and be attached to the outside of the pot. Never, but never use one that is hooked onto the inside of the pot.
Finally, make sure there is someone ready and waiting to fit the bird guard the minute the sweep has cleared the flue. A wait of just 24 hours, and you could be playing host to yet another nest!