Date of Award


Document Type


Degree Name

Master of Science


College of Arts and Sciences


Biology, MS

First Advisor

Gordon J. Atkins

Second Advisor

James L. Hayward

Third Advisor

Shandelle M. Henson


Daytime behaviors and occupancy patterns of Glaucous-winged Gulls (Larus glaucescens) have been described and can be mathematically predicted based on environmental factors. However, little is known about the nighttime behaviors of Glaucous-winged Gulls. I used trail cameras to study the daytime and nighttime colony occupancy patterns of Glaucous-winged Gulls on a breeding colony on Protection Island, Washington, USA. Early in the breeding season gulls desert the colony en masse during nighttime even after some gulls have initiated clutches. Using acoustic recording units to identify an acoustic cue that signals the onset of the coordinated nightly departures from the colony, I found that five to ten minutes prior to the nighttime departures the gulls engage in a bout of synchronous extended long-calling. The departing gulls form two large rafts at night to the north and south of the island, both of which get closer to the colony as the season progresses. As more gulls initiate clutches, a switch occurs such that all gulls remain overnight on the colony even though a majority of them have yet to initiate clutches. The first gulls to initiate clutches influence the transition from leaving to remaining on the colony at night through social facilitation.

Subject Area

Glaucous-winged gull--Behavior; Glaucous-winged gulls--Breeding; Gulls--Behavior; Protection Island (Wash.)


Included in

Biology Commons