Breeding ecology of the Little Tern 2: The first few days

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Most of the newly hatched chicks can be grouped into two main groups. They can be hatched helpless, with eyes closed, naked or sparsely covered with down, in which case they are altricial. On the other hand they can be hatched with their eyes open, covered with down and can soon walk or swim, then they are precocial.

The chicks of the Little Tern (Sterna albifrons) are neither altricial nor precocial – they are semi-precocial. Although the chicks can move about within a few hours after hatching and are covered with down the next day, they are hatched with their eyes closed and partially covered with down (above). The advantage here is that the chicks do not need total parental care in a habitat that is exposed and dangers lurks at every corner.

By the second day the chicks are fully covered with down (above). They lie motionlessly and await the calls of their parents. When the parents are nearby and no threat seems to be around, they pop out with gaping mouths, sometimes chirping (below). At any instance of danger, they remain motionless again.

Otherwise they prop up and open their beak when they hear the calls of their approaching parents (above). The parents feed them non-stop, having no time to preen themselves after splashing in sea water to refresh. The chicks find comfort having the parent close by (below).

The days of the adult involves warming the chicks, protecting the chicks from the environment and feeding the chicks. Feeding usually take the form of broken down fish parts since the chick cannot swallow. Feeding is rotational and also cycles between the chicks.

Input and images by Dr Jonathan Cheah Weng Kwong.

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