Page 432 - Hand rearing birds second

425

26

Gulls­and Terns

Meryl Faulkner

Natural History

Laridae (gulls and terns) are represented in North America by 25 species of gulls, including two
called kittiwakes; and eighteen species of terns, including two called noddies. Gulls and terns are
closely related to skuas, jaegers, and skimmers, and are grouped in the order Charadriiformes.
Gulls and terns are colonial breeders nesting on the ground, on and around beaches, marshland,
and abandoned salt works. Some gull species nest on rocky cliffs, but some species also may nest
on manmade structures such as hotel, apartment, and office building roofs in many coastal cities.
Nests may be a shallow scrape or structure lined with grass, twigs, pebbles, and debris. Incubation
typically lasts 21–27 days, depending on species.
Gull and tern chicks are semi-precocial. They hatch with their eyes open, are covered with down
and able to walk, but remain at or near the nest for the first 2 or 3 weeks. Depending on the species,
chicks fledge at 21 days (Least Tern) to 42 days (Western Gull), but are fed by parents for additional
time. In the case of Western Gulls, this may last for 11–12 weeks post-hatch.
Although both gulls and terns have webbed feet and have waterproof plumage, only gulls swim
and float on the water for extended periods of time. Terns have shorter legs and smaller feet and do
not spend any extended time paddling. Adult gulls and terns eat fish; however, gulls are more likely
to take invertebrates and human refuse, particularly if not feeding young or if environmental con-
ditions change and fish are scarce.
Gulls and terns range in weight from the 40 g Least Tern to more than a kilogram in larger gulls.
Young terns and gulls are fed primarily fish of the appropriate size on the day of hatching by the
parent. Least Terns feed their chicks fish approximately twice an hour. Western Gull males feed
chicks every 2–3 hours, with females feeding every 3–4 hours by the fledging period. Fish is offered
whole by terns, but gulls regurgitate a bolus of food such as small fish or shrimp into young chicks’
mouths or drop larger fish onto the ground for chicks older than 10 days to pick up (Pierotti and
Annett 1995; Thompson et al. 1997).

­ Criteria­for Intervention

Terns and gulls may be brought to rehabilitators by state or federal agencies in cases where endan-

gered or threatened species have been disturbed at nesting sites and the young abandoned. In addition,

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.