Swallow-tailed gulls hunt most often under a new moon, when
fish come to the surface under the cover of darkness
Zooplankton, small fish and squid spend hardly any time at
the surface when there's a full moon. To protect themselves from their natural
enemies, they hide deeper down in the water on bright nights, coming up to the
surface under cover of darkness when there's a new moon instead. Scientists at
the Max Planck Institute for Ornithology in Radolfzell discovered that this
also influences the behaviour of swallow-tailed gulls (Creagrus furcatus), a
unique nocturnal species of gull from the Galapagos Islands. They fitted the
birds with loggers and wet/dry sensors which enabled them to see how much time
the animals spent at sea at night. Their findings show that the birds' activity
was greatest at new moon, in other words the time when the most prey was
gathered at the surface of the water. The cycle of the moon therefore also
influences the behaviour of seabirds.