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The metal flashing was shown to be effective but only under a narrow range of optimal <br />conditions. Factors such as: avian predators, understory growth, tree configuration, and <br />blowdowns all impacted the efficacy of this methodology. As shown in Figure 13 and 14, <br />metal flashing does not deter avian predators. Analysis of the scratch patterns (Figure 15) <br />revealed that the rapidly growing understory may also have aided raccoons and opossum in <br />breaching the flashing (Coulter 1995). Tree shape /configuration is also important to flashing <br />efficacy. For example, the active part of the colony is dominated by American Basswood <br />(Tilia Americana) which is prone to grow in clusters. These clusters, if close enough, can <br />also facilitate breaching the flashing. And finally, several large trees and many smaller limbs <br />were blown down over the course of the 2005 season. The damage inflicted upon the <br />flashing potentially opened up routes to the canopy, thus increasing the likelihood of <br />predation. Installation and <br />maintenance also required a large <br />amount of labor. <br />13 <br />Figure 13: <br />The hole in this Great Blue Heron eggshell was <br />pecked by an avian predator; most likely an <br />American Crow (Corvus brachyrhynchos). <br />Figure 14: <br />This video screen shot shows an adult Great <br />Horned Owl (Bubo virginianus) perched upon <br />an abandoned Great Blue Heron nest. Video <br />evidence suggested that this nest was raided by <br />a raccoon. The owl's use of this platform was <br />recorded numerous times. The pattern of <br />disappearance of nearby heron chicks may be <br />indicative of owl predation. <br />