Bird guards are designed to protect chimney flues from birds, as well as squirrels, leaves and rain.
Why install a bird guard? Birds can nest in live chimneys, which presents a serious carbon monoxide hazard, as well as being a cause of damp in the chimney breast for dead or redundant chimneys. Rather than block off a chimney if there is a nest in it, it is recommended that the chimney is cleared and a suitable bird guard is installed.
Tip: bird guards need to be suitable for the property and chimney it will be fitted to, so it is important to ensure that you consider the design, finish and material used.