Mistletoe is a hemiparasite, meaning that it does absorb nutrients from the host tree, but it also photosynthesizes on its own. It is unusual for mistletoe to get such a stronghold on its host tree that it kills the tree, but it can weaken the tree, which makes it more susceptible to other parasites and diseases. It also adds to biodiversity in several ways. The most obvious is that it provides habitat for nesting birds and serves as a nectar and host plant for pollinators, but mistletoe has some other advantages: because it has green leaves and flowers in the winter, it provides a source of nectar and nutrition when those resources might be scarce. And most deciduous plants suck all the nutrients out of their own leaves to prepare for fall and dropping their leaves, mistletoe has an almost constant source of nutrition from their host plant. Which means they can drop green leaves, providing more nutrients to the forest floor. In Australia, a study showed that when mistletoe was removed from an ecosystem, 1/3 of the bird species disappeared. Not only those birds who consumed those seeds directly were affected: those who consumed insects from the forest floor that relied on the falling nutrients also suffered.