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Shearwaters and Petrels

Tracy Anderson

Natural History

Shearwaters are part of the family Procellariidae that includes shearwaters and petrels, which are
in turn a part of the order Procellariiformes that includes the “tubenoses” – albatross, fulmars,
petrels, and storm‐petrels. This chapter was written using knowledge and experience from the rais-
ing of Wedge‐tailed Shearwaters (Ardenna pacifica) and Newell’s Shearwaters (Puffinus newelli)
and the post‐fledging care of Hawaiian Petrels (Pterodroma sandwichensis) at Save our Shearwaters
(SOS) in Hawaii, USA.
Shearwaters and petrels are long‐lived species that reproduce slowly. It takes 3 to 6 years to reach
breeding maturity. They then lay a single egg and it takes both parents to raise the chick to fledging
age. Fledging takes place at night, and shearwaters and petrels provide no post‐fledge parental
care. During the first week or so post‐hatch, they go through a “guard phase” when at least one
parent is present and brooding the chick. Following that, the chick is able to thermoregulate and
both parents go to sea to forage, leaving the chick unattended in the burrow during the day.
Foraging strategies during chick rearing differ from species to species and can even differ between
populations of the same species, depending on food availability. Generally, Procellariiforms have a
bimodal foraging strategy that has one parent doing shorter feeding trips closer to the colony and
the other doing a lengthier trip to more productive waters. Hawaiian Petrels do a short/long trip
where one parent can be at sea for 21 days or so and fly nearly to Alaska and back to take advantage
of the rich feeding areas in the North Pacific. The other parent does shorter feeding trips closer to
the main Hawaiian Islands (Raine et al. 2017). Wedge‐tailed Shearwater’s foraging strategy appears
to depend on the colony’s proximity to productive waters, with birds adopting a bimodal (or dual)
strategy when areas of high productivity are “at‐distance” (Congdon et al. 2005) and a unimodal
strategy when productive waters are close by (Baduini 2002). Due to the different strategies and the
distances the parents must fly to find food, Procellariiform chicks may go without provisioning for
several days and then receive meals from both parents on the same night. In one study it was deter-
mined that Hawaiian Petrels were fed 70% of their total food during the first half of the nesting
period (Simons 1985). There is conflicting evidence regarding the “desertion period” just prior to
the chick’s fledge. Some parents desert entirely 1 to 2 weeks prior, while others continue to provide
food up to when the chick leaves (Simons 1985). There is evidence that this is determined by the
chick itself, as some will start to refuse food while others will continue to beg, which may correspond

Hand-Rearing Birds, Second Edition. Edited by Rebecca S. Duerr and Laurie J. Gage.
© 2020 John Wiley & Sons, Inc. Published 2020 by John Wiley & Sons, Inc.