The alligator has no bird friend. You're thinking of the crocodile, whose pal the plover helps keep the smile of a crocodile clean. The plovers aren't suicidal. The truth is, the relationship between the crocodile bird and the crocodile is symbiotic; each getting a benefit from being strange bedfellows.
The bird widely known as the "crocodile bird" is correctly called an Egyptian plover, or Pluvianus aegyptius. It lives in parts of Africa, frequently around tropical rivers and human activity. This tiny bird grows to about 7 to 8 inches long and weighs less than 3 ounces. You might think the little bird is either brave or stupid. But there's a method to what appears to be madness. The plover routinely sticks his head in a croc's mouth and lives to tell the tale.
So why do these little plovers do it? Why so glib about their health and safety? The crocodile bird, despite the fact that it acts like a dental hygienist, is merely enjoying a good meal. After the crocodile eats a large animal, such as an entire cow, he suns himself on the banks of the river with his mouth open. Crocs swallow their prey whole, but bits of meat gets stuck between their teeth anyway, and they can't very well floss.
Crocodiles cannot sweat through their skin like humans can, or through their paws like dogs. To dissipate heat, they bask on the banks with their mouths open. The plover comes along and, using his sharp little beak like a toothpick, removes the bits of meat from between the crocodile's teeth. This feeds the plover and removes parasites from the croc's mouth.
The plover serves as a security alarm system for the crocodile. If, while in the croc's mouth, the plover senses danger from an oncoming animal, she screams and flies away. This behavior alerts the crocodile to the imminent danger, so he can slide into the water and out of harm's way as well. In this way, the plover keeps her source of free food safe for future use -- a service the croc, no doubt, appreciates regardless of the motive.
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