Deer numbers in the UK have gone up dramatically in recent years - and it's having a big impact on other wildlife.
It's thought there are around 2 million deer now - the highest it's been in the last 1,000 years.
Deer feed on things like bramble and leaves, used by other animals to make nests. Birds especially are suffering.
Conservationist Stuart Newson explains: "Species like nightingale - that's one species which relies on this habitat for nesting.
"Other species, willow tit for example, for feeding in.
"So removal of this habitat can have quite a big effect on those species which are dependent on it."