The color of flamingo feathers is determined, to some extent, by their diet; apparently the mixed diet of the local variety doesn't give their coat the bright color of the Yucatan or other populations. They feed by sucking in water through their bill and passing it through sieve-like plates to filter out the small shrimp and water-boatmen of their diet, much like a baleen works for a whale. During the abnormally warm-water El Niño years 1982-1983, the flamingo population suffered heavily from reduced food sources, and many of their nests were drowned by higher water levels. Flamingos are thought to reach sexual maturity at about five years, and a lifespan of about 15 years; their population in the Galápagos is quite vulnerable.