Walks through a forest are often made all the more enjoyable by the chance to watch brightly coloured birds flit between the trees. But birds are not just mere inhabitants of forests – in some parts of the world, they are the key to the trees’ survival.

The Serengeti is one such place. Since 1950, around 70-80% of riverside forests have disappeared from this area. Fires seem to be a particular problem, opening large gaps in the canopy that forests can’t seem to recover from. To understand why Gregory Sharam from the University of British Columbia has been monitoring the density of the forests since 1966. From 1997-2006, he studied 18 particular patches at varying stages of decline.

During this time, as