CURWOOD: Its Living on Earth. Im Steve Curwood. [MUSIC: BIRDNOTE THEME] CURWOOD: The way animals behave is a constant source of fascination for some observers and an interest for scientists. And as Mary McCann explains in todays BirdNote, careful observation can help solve mysteries. [GULL CALLS] BIRDNOTE/GULLS BEAKS http://birdnote.org/show/little-red-spot-gulls-bill[/embed] The Little Red Spot on a Gulls Bill [Bugling calls of Glaucous-winged Gulls] MCCANN: You may have noticed on a trip to the shore or at a waterfront restaurant where gulls gather that many gulls have a bright red spot near the tip of their otherwise yellow bills. Herring Gull (Photo: mongolito404; Courtesy of BirdNote) [BUGLING CALLS OF GULLS] MCCANN: Behind that red spot lies a considerable tale thats t-a-l-e! MCCANN: In the mid-20th Century, Dutch scientist Niko Tinbergen studied nesting Herring Gulls. He noticed that newly hatched gull chicks were fed by their parents only after they pecked at the adults bills [BEGGING CALLS OF YOUNG GULLS] MCCANN: Tinbergen devised experiments that varied the shape and coloration of the adults bill. It became clear that the red spot on the adult gulls bill was a crucial visual cue in a chicks demands to be fed, and thus its survival. A mature Herring Gull looks out over the water. (Photo: Timelapsed; Courtesy of BirdNote) [BEGGING CALLS OF YOUNG GULLS] MCCANN: Tinbergen also made the case that the chicks attraction to the red spot on the bill was instinctive. This conclusion came at a time when there was furious debate among experts about whether such behavior was learned or innate. MCCANN: Tinbergens gull research helped lay the groundwork for the science of animal behavior, and in 1973 earned him a Nobel Prize. And it all started with that little red spot. An adult Herring Gull displays its iconic red spot. (Photo: roamingwab; Courtesy of BirdNote) [BEGGING CALLS OF YOUNG GULLS] MCCANN: Im Mary McCann. ### Written by Bob Sundstrom Bird audio provided by The Macaulay Library at the Cornell Lab of Ornithology, Ithaca, New York. Calls of Glaucous-winged Gulls recorded by A.A. Allen. Begging call of Glaucous-winged Gulls recorded by E.S. Booth. Herring Gulls recorded by Martha Fischer. Producer: John Kessler Executive Producer: Dominic Black 2014 Tune In to Nature.org October 2014 Narrator: Mary McCann Herring Gull chicks peck at an adult in the hopes of a meal. (Photo: Tony Morris; Courtesy of BirdNote) CURWOOD: Youll find photographs of gulls and their red spots - at our website, LOE.org. [BEGGING CALLS OF YOUNG GULLS]