Comparison of Surface Patterns on Cannibalized and Noncannibalized Gull Eggs
In a six-year study (Hayward et al. 2014a) we demonstrated that egg cannibalism in a glaucous-winged gull colony increases substantially in response to small increases in sea surface temperature due to El Niño events. We established that egg cannibalism accounts for most of the egg loss in a glaucous-winged gull colony. We now are in the process of focusing more closely on the behavior of individual cannibals, particularly as they determine which eggs to cannibalize. Finally, we are exploring the relationship between egg cannibalism and every-other-day ovulation synchrony, a process we discovered in recent years (Henson et al. 2010, 2011).
During the 2015 field season we plan to extend our understanding of the egg cannibalization process. One such extension will involve an examination of the characteristics of eggs selected by cannibals for cannibalization. Stoddard and Stevens (2010, 2011) and Stoddard et al. (2014) recently published innovative research on egg pattern recognition in birds. They have developed a software package called NaturePatternMatch which uses an algorithm that mimics visual and cognitive processes known to be involved in avian recognition. Stoddard has shared this software package with us. We plan to apply this software in a comparison of UV and visible light photographs between cannibalized and non-cannibalized eggs. Bird vision, it should be noted, is sensitive to both UV and visible light (Hart and Hunt 2007). Specifically, we wish to test the following hypothesis: Egg cannibals select eggs for cannibalization based in part on their surface pattern characteristics.