Their distinctive 'teacher teacher' call is synonymous with British gardens, but great tits are facing a big problem - climate change. As our springtime becomes warmer and begins earlier, peak caterpillar abundance is also shifting earlier. As a crucial food source for great tit chicks, this is cause for concern. In this episode of the Big Questions Podcast, we catch up with ecologist Dr Charlotte Regan, one of the scientists who monitors the Wytham Woods great tit population, which has been systematically studied since the 1960s.