Date of Award


Document Type

Honors Thesis



First Advisor

Shandelle M. Henson


Protection Island, Washington hosts a large colony of Glaucous-winged gulls (Larus glaucescens). These birds are known to exhibit every-other-day egg-laying synchrony in dense areas of the colony in response to egg cannibalism, which is the main source of egg loss. Here we present an equilibrium analysis of a discrete-time animal behavior model for egg laying. We use Jury Conditions to find the stability criteria for the equilibrium as a function of the colony density and show that a 2-cycle bifurcation occurs when the equilibrium loses stability. The 2-cycle pattern in egg laying becomes increasingly synchronous as the colony density increases. We also show that egg-laying synchrony benefits the colony by allowing more eggs to survive cannibalism.

Subject Area

Glaucous-winged gull; Sea birds--Eggs; Sea birds--Behavior; Protection Island (Wash.)

Creative Commons License

Creative Commons Attribution-No Derivative Works 4.0 International License
This work is licensed under a Creative Commons Attribution-No Derivative Works 4.0 International License.


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