Take oxpeckers. These brown birds can be found in Africa, clinging to the flanks of giraffes and antelope. They’re classically viewed as cleaners that pick ticks and blood-sucking parasites off their hosts. But they also peck at open wounds – a less helpful habit that stymies the healing process and increases the risk of infection. These birds crave blood, and they satisfy that craving in ways that either profit their hosts, or punish them.
