Date of Award

4-6-2018

Document Type

Honors Thesis

Department

Biology

First Advisor

Shandelle M. Henson

Second Advisor

James L. Hayward

Abstract

A common source of reproductive loss in gulls is egg cannibalism. At a large Glaucous-winged Gull (Larus glaucescens) colony on Protection Island, Washington, cannibalism accounts for 55% of egg loss. Because cannibalism is a form of predation and birds have a highly developed sense of vision, I hypothesized that visible light coloration of Glaucous-winged Gull eggs plays a role in determining whether they are cannibalized. I used logistic regression to test whether egg fate was related to egg brightness, specific coloration, specific spot coverage, coloration relative to the most common coloration, and spot coverage relative to the most common spot coverage. The odds that an egg was cannibalized increased increased when an egg was more intensely red, more intensely green, and its green value was closer to the most common green value, and when its combined color value was closer to the most common combined color value. These results suggest that cannibals may prefer eggs with the most common coloration.

Subject Area

Glaucous-winged gull; Eggshells; Protection Island (Wash.); Sea birds--Cannibalism

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