Recycling mine dumps... (39)
They are herbivorous, feeding solely on Spirulina plantensis, one of the blue-green algae growing within a very limited range of pH: 10.4 - 10.5. They are surface feeders filtering the top inch or two of water where the spirulina is to be found with the deep-keeled bill that is specialized for very fine food particles. They swim well and are able to forage over the complete surface of a lake (the "swim and skim" technique). The upper mandible is larger than the lower, but lightweight, and acts like a float, keeping the head at just the right level to allow the bill to sieve the top three centimeters of water, where the spirulina is found. Their filter-feeding mechanism is structurally and mechanically different from that of ducks but is convergent with that of the baleen whales, particularly the Right Whale.
They are Gregarious, with mass displays and breeding areas. The courtship display is characterized by group "marches". The displaying birds (usually a group of 5 or 10) hold the head and neck erect (the "alert" posture), call to one another, and move heads from side to side in a horizontal arc (the "head-flagging" display). This increases in tempo over several minutes. Others join the head-flagging group until twenty-five to fifty birds are displaying together. Often this is followed by "wing salutes” or marching displays where the flock rushes headlong for about fifty feet, does an about-face, then dashes back to the starting point. The display may be repeated five or six times. During these displays, many birds pair up. Pairs stand with necks fully stretched, beaks touching. Then they circle slowly, pivoting around the touching beaks, sparring and intertwining necks.
A single white egg is laid which both parents incubate for 28-30 days. Chick is fed a bright red secretion formed by glands in the upper digestive tract that is rich in blood. Parents know their own young by their voice and will feed no other. They fly in undulating lines, long neck and feet extended. Life span is 50 years.
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