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RECOMMENDED BUFFER ZONES AND SEASONAL RESTRICTIONS <br />FOR COLORADO RAPTORS <br />Tolerance limits to disturbance vary among as well as within raptor species. As a general rule, <br />Ferruginous Hawks and Golden Eagles respond to human activities at greater distances than do <br />Ospreys and America Kestrels. Some individuals within a species also habituate and tolerate human <br />activity at a proximity that would cause the majority of the group to abandon their nests. Other <br />individuals become sensitized to repeated encroachment and react at greater distances. The tolerance <br />of a particular pair may change when a mate is replaced with a less tolerant individual and this may <br />cause the pair to react to activities that were previously ignored. Responses will also vary depending <br />upon the reproductive stage. Although the level of stress is the same, the pair may be more secretive <br />during egg laying and incubation and more demonstrative when the chicks hatch. <br />The term "disturbance" is ambiguous and experts disagree on what actually constitutes a disturbance. <br />Reactions may be as subtle as elevated pulse rate or as obvious as vigorous defense or abandonment. <br />Impacts of disturbance may not be immediately evident. A pair of raptors may respond to human <br />intrusion by defending the nest, but well after the disturbance has passed, the male may remain in the <br />vicinity for protection rather than forage to feed the nestlings. Golden eagles rarely defend their nests, <br />but merely fly a half mile or more away and perch and watch. Chilling and over heating of eggs or <br />chicks and starvation of nestlings can result from human activities that appeared not to have caused an <br />immediate response. <br />A `holistic' approach is recommended when protecting raptor habitats. While it is important for land <br />managers to focus on protecting nest sites, equal attention should focus on defining important foraging <br />areas that support the pair's nesting effort. Hunting habitats of many raptor species are extensive and <br />may necessitate interagency cooperation to assure the continued nest occupancy. Unfortunately, basic <br />knowledge of habitat use is lacking and may require documentation through telemetry investigations or <br />intensive observation. Telemetry is expensive and may be disruptive so a more practical approach is to <br />assume that current open space is important and should be protected. <br />Although there are exceptions, the buffer areas and seasonal restrictions suggested here reflect an <br />informed opinion that if implemented, should assure that the majority of individuals within a species <br />will continue to occupy the area. Additional factors, such as intervening terrain, vegetation screens, <br />and the cumulative impacts of activities should be considered. <br />These guidelines were originally developed by CDOW raptor biologist Gerald R. Craig (retired) in <br />December 2002. To provide additional clarity in guidance, incorporate new information, and update <br />the conservation status of some species, the guidelines were revised in January 2008. Further revisions <br />of this document may become necessary as additional information becomes available. <br />