I've visited Lady Musgrave Island in the Great Barrier Reef. It is covered with trees called "the grand devil's-claws", the seeds of which are barbed and sticky. The seeds stick to the wings of birds eating seeds, and so they can spread across islands.

However, a visitor to the island will soon notice lots of dead birds on the ground. There are no predators or scavengers, so the birds lay there decomposing.

Thus, the trees use the birds not only for reproduction, but also for food. It's a carnivorous forest out there on the reef.