Birds, such as jackdaws, often nest in chimneys, leading to potential blockages that can cause smoke to enter the room when using a fire. To address this issue, it is recommended to remove the nest is not in use and install a bird guard at the chimney's top. If you hear noises coming from the chimney, it may indicate a trapped bird or animal, typically a pigeon. In such cases, it is advisable to seek assistance to rescue the trapped creature and potentially take it to a vet.