Sunday, 1 August 2010

Chicks Ahoy

The number of chicks is growing daily at the moment, with typically one or two new hatches each day. The chicks are born covered in a layer of down and, unusually, replace this with a second set of downy feathers, before the true feathers begin to grow. Having two sets of down is a unique characteristic of tubenoses and penguins. The bill is well-developed already and the ‘tubes’ (nostrils) on top of the bill are a distinctive characteristic of the tubenoses.

Downy-feathered chick at about 10 days old 
 Due to the poor visibility and accessibility of many stormie nests, detecting a hatch is often not easy. The adult sits tightly on the chick for the first few days. The hatched egg shell may be visible, providing evidence that a chick has hatched. Typically a chick can be heard calling before it is seen.

Chicks are brooded by an adult for maybe 7 to 10 days; after this, the chick is left alone while both parents spend the majority of their time feeding offshore. Once a chick is left alone for the first time, the chick is removed the chick from the nest to weigh and measure it. This will be repeated every 5 days allowing us to monitor chick growth and development. The rate of development can indicate the environmental conditions that the parents or chick are experiencing; for example, slow growth may reflect low food availability or could be related to disturbance experienced by the chick in the nest.

Retrieving a chick from a nest site in a dry-stone wall

Weighing a chick
 A chick may be fed only every 2-3 nights, so its weight fluctuates dramatically depending on when it received its last feed. Weight can thus not tell us as much about growth, so, at first, the length of the tarsus (knee to ankle) is measured which reflects skeletal growth. Once the skeleton is fully grown, at about 30 days old, the feathers will be beginning to grow in and the wing chord will be measured to monitor development further.