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Browsing by Author "Mannan, R. William"

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    Preventing Raptor Electrocutions in an Urban Environment
    Dwyer, James F.; Mannan, R. William (Raptor Research Foundation, 2007)
    Electrocution of raptors on poles supporting overhead electric lines is a cause of concern in the United States. Techniques for modifying (i.e., retrofitting) potentially lethal poles to reduce electrocutions have been applied in rural areas to poles most likely to be used by raptors. However, raptors also live in urban areas, and criteria for selecting poles to retrofit in towns and cities may differ from those in rural areas. We assessed the effectiveness of using nest sites of Harris's Hawks (Parabuteo unicinctus) in Tucson, Arizona, U.S.A., as a means to focus proactive efforts to retrofit potentially lethal poles. Specifically, we investigated: (1) whether poles close to Harris's Hawk nests were more likely to cause electrocutions than more distant poles with the same configuration; and (2) whether retrofitting poles within 300 m of nests reduced electrocutions in treated areas. We assessed the number of electrocutions before and after retrofitting by searching for electrocuted hawks at a sample of poles. In 2003, we found 23 electrocuted Harris's Hawks within 300 m of nests. The proportion of poles that electrocuted a juvenile Harris's Hawk remained relatively constant from 0 to 300 m from nests. Poles 201-300 m from nests were more likely to electrocute subadult and adult hawks than were poles <200 m from nests. Prior to retrofitting poles, we detected 1.4 electrocutions per monitored nest. After about half of the potentially lethal poles within 300 m of nests were retrofitted, we detected 0.2 electrocutions per nest. For Harris's Hawks in Tucson, risk of electrocution was at least partially related to the proximity of nests to potentially lethal poles. This relationship also may hold for other medium- to large-bodied raptors nesting in urban environments. We recommend that all potentially lethal poles within 300 m of the nests of urban-nesting raptors be retrofitted through the addition of insulation, or through increased spacing between conductors.
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    Return Rates of Aluminum Versus Plastic Leg Bands from Electrocuted Harris's Hawks (Parabuteo Unicinctus)
    Dwyer, James F.; Mannan, R. William (Raptor Research Foundation, 2009)
    Ecological research programs investigating dispersal, migration, habitat selection, social structure, survival, reproductive success, and population size depend on the ability to identify individual study animals on multiple occasions (Bibby et al. 2000). Leg bands often are used to facilitate the identification of individual birds and more than one million birds, including numerous raptors, are marked annually in North America with aluminum leg bands (USGS 2008). In the United States, aluminum is also used in overhead electric systems because of its strength, low resistance, long life, and relatively low cost (APLIC 2006).