Summary of threats 



Harlequin duck population regulation appears to be a complex mechanism affected by a 

 number of factors. Potential human-caused threats to population viability in the Rocky Mountains 

 include both habitat degradation and direct mortality in breeding and wintering areas. 



A. Presence of threatened destruction, modification, or curtailment of the species habitat or range. 



Al. Riparian habitats 



Harlequin ducks use diverse riparian habitats for nesting, feeding, to provide security, and as 

 escape cover. Streambank and/or channel alteration may reduce the quality of these habitats by 

 eliminating or reducing both cover and food supply. 



Management considerations: channelizaton, damming, livestock grazing, brush removal, timber 

 harvest, gravel extraction, logjam removal, dredging, bank rip-rap, and road construction. 



A2. Water yield levels 



Harlequin duck productivity is inversely related to spring streamflows, particularly during the 

 nesting and brood-rearing periods in June and July (Kuchel 1977, Diamond and Finnegan 1993, 

 Reichel and Genter 1994, Cassirer and Groves 1994). High flow events during this period can reduce 

 or eliminate productivity. 



Harlequin ducks are closely tied to streams for feeding and protection from predators. Hens 

 with broods usually travel downstream from nesting areas during the brood-rearing period prior to 

 fledging. Dewatering of feeding and brood-rearing areas during the breeding period will render these 

 habitats unavailable to harlequin ducks and will likely directly negatively impact productivity. 



Management considerations: hydropower development, stream diversion or damming, timber harvest, 

 and road construction. 



A3. Water quality 



Sedimentation may fill interstitial habitat in and adjacent to streams (Roby et al. 1977) and 

 reduce the density of the harlequin duck food supply (macroinvertebrates) and alter species 

 composition. Sedimentation may also reduce the ability of harlequin ducks to find prey. Toxic 

 chemical pollution can also directly impact the harlequin duck food supply. 



Management considerations: road construction, timber harvest, livestock grazing, toxic chemical spills, 

 mining activities. 



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