Yes - bird food does expire. However, there are a number of ways that you can keep it fresh for as long as possible. Firstly, the type of food plays a role: Seeds last longer than suet or nectar due to their lower moisture content. Secondly, make sure that you are storing the food correctly: it should be in an airtight container, in a cool place away from direct sunlight. Exposure to moisture can cause mould and harmful bacteria to grow, which can have negative effects on the health of birds. Overall, correct storage, good hygiene, and the type of food used are all factors that affect how quickly bird food expires.