The cold, wet spring has left berries, fruits and nuts ripening late, making life difficult for birds, mice and voles that rely on them for food, experts have said.
The RSPB said there were reports from parts of the country of late-ripening autumn foods in the countryside and gardens.
The cold, wet spring could be to blame as plants did not get the necessary conditions to develop or produce fruit at the right time, the wildlife charity suggested.
Plant charity Plantlife said some species at its Ranscombe Farm reserve in Kent appeared to have been pushed back by the cold start to the year.
Plantlife's Richard Moyse said: "There's a great crop of blackberries here, which is good for birds, dormice and other wildlife, but blackberries flower in summer, and it is spring-flowering species, such as blackthorn, that may have suffered from the absence of bees and other pollinators in the cold and wet spring. Sloes have certainly been hard to find this autumn."