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structures can be more carefully sited, designed, and managed to minimize impacts. <br />However, the costs of some of these measures can be high and can vary greatly, but most <br />importantly the efficacies of many of these measures remain uncertain. Both the costs <br />and effectiveness of all of these measures can be better understood through <br />experimentation and careful scientific investigation. Post -construction fatality <br />monitoring should be an essential feature of any new building project. <br />Below is a listing of mitigation options, along with some notes and findings from the <br />literature. <br />Table 2. Window collision risk factors, their weightings based on the scientific <br />literature, and the level of risk introduced by the proposed project. <br />Collision risk to volant wildlife <br />Factor <br />Weighting <br />Added by project <br />Inherent hazard of structure <br />Universal <br />Some <br />Window transparency <br />Very high <br />Amply <br />Window reflectance <br />Very high <br />Amply <br />Black hole or passage effect <br />High <br />Likely <br />Window or fa ade extent <br />Very high <br />Amply <br />Size of window <br />High <br />Amply <br />Type of glass <br />High <br />Amply <br />Lighting <br />High <br />Amply <br />Height of structure <br />High <br />Amply <br />Orientation of fa ade <br />Unknown <br />Unknown <br />Structural layout <br />High <br />Amply <br />Context in urban -rural gradient <br />Likely high <br />Unknown <br />Height, structure and extent of vegetation near building <br />High <br />Amply <br />Presence of birdfeeders <br />Moderate <br />Unknown <br />Relative abundance <br />Uncertain <br />Unknown <br />Season of the year <br />Nons atial <br />Unknown <br />Ecology, demography and behavior <br />Uncertain <br />Unknown <br />Predatory attacks <br />Uncertain <br />Unknown <br />Aggressive social interactions <br />Uncertain <br />Unknown <br />Any new project should be informed by preconstruction surveys of daytime and <br />nocturnal flight activity. Such surveys can reveal the one or more facades facing the <br />prevailing approach direction of birds, and these revelations can help prioritize where <br />certain types of mitigation can be targeted. It is critical to formulate effective measures <br />prior to construction, because post -construction options will be limited, likely more <br />expensive, and probably less effective. <br />(1) Retrofitting to reduce impacts <br />(1A) Marking windows <br />(1B) Managing outdoor landscape vegetation <br />(1C) Managing indoor landscape vegetation <br />(iD) Managing nocturnal lighting <br />13 <br />