The Wildlife and Countryside Act does not specifically define a ‘bird nesting season’, simply saying that if a nest is being built or contains eggs or young then it is active and therefore protected. While the breeding season is normally taken to mean between 1st March and 31st August (that’s according to the government’s website, other sources including the British Trust for Ornithology (BTO) say from 1st February), it’s important to note that some birds (especially some pigeon species) will nest all year round if conditions are right and eg Blackbirds and Robins have been found nesting in January. This is especially true of birds nesting in suburban gardens which because of the ‘heat island effect‘ tend to be warmer than the surrounding countryside. Species reacting to climate change will undoubtedly lead to earlier nesting as our winters become milder and food availability changes, making the concept of a set ‘season’ more redundant. It is not a defence, therefore, to use ‘outside the nesting season’ as an excuse. The law just says that ‘if a nest is being built or contains eggs or young then it is active and therefore protected’, and is not defined by the calendar.