Firstly consult one of the many identification guides available (either in print or online). The Collins Bird Guide (HarperCollins) is particularly good. The RSPB bird identifier https://www.rspb.org.uk/birds-and-wildlife/wildlife-guides/identify-a-bird/ is also useful. Please do not contact the county recorder unless you can provide a full description, preferably with a photograph.

Much depends on the circumstances. Action is only required if there is a suspicion of crime or disease. In the event of a crime (usually shooting or poisoning) excellent advice is available at https://www.rspb.org.uk/birds-and-wildlife/advice/how-to-report-crimes/ In the case of disease follow the advice at https://www.rspb.org.uk/birds-and-wildlife/advice/how-you-can-help-birds/disease-and-garden-wildlife/ If waterfowl (swans, geese, ducks etc.) are found dead or multiple carcasses are discovered it should be reported to the Defra hotline on 03459 335577.

Open the windows or an exterior door (if present in the room) and move away. The bird will usually follow the light and escape.

Excellent advice is available at: 1. https://www.rspb.org.uk/birds-and-wildlife/advice/how-you-can-help-birds/injured-and-baby-birds/baby-birds/ 2. https://www.rspca.org.uk/adviceandwelfare/wildlife/orphanedanimals/babybirds

All ringed birds will have a metal ring with an address (the Natural History Museum in the UK) and a series of letters and numbers. Report the finding online at http://app.bto.org/euring/main/ with the grid reference. This link also covers colour-ringed birds.