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;, ,~l~) -' ~.t;-., , -" : a 1275 cms flow. More important are the velocity in the primary eddies close to the terrilories. Based on the prediction that debris fans will not be overtopped by a 1275 cms flow, velocities on the inundated surface of the reattachment bars (substrate for territory vegetation), are , anticipated to range from 0.33 to 0.84 mls. Velocities of this range may scour the face of the reattachment bar but are unlikely to scour the rear portions of the bar or the cohesive silt sediments. Predications are reinforced by observations of 6 return current channel marshes that agraded slightly but were not scoured after the 1980 spill. ? 1':' ~ 4. Assess the relative proportions of terrestrial and aquatic invertebrates in the southwestern willow flycatcher diet: As no detailed diet study has been conducted on the southwestern willow flycatcher in Grand Canyon, examination of previous southwestern willow flycatcher food habits, Grand Canyon invertebrate studies, and interviews with biologists found the species feeds on a number of insects, other invertebrates and some plant matter. Aquatic invertebrates such as snails and Tabanidae larvae have reported elsewhere, and similar taxa may contribute to the food base of the species here. Because the test flow will be conducted in late March, invertebrate populations will have opportunity to repopulate or even increase because of renewed plant vigor and regrowth. Also, because most insects have not emerged at time of the test flow, while there may be some reduction in fossorial species, most terrestrial invertebrate groups are not anticipated to diminish. -. f~ ,) If the test flow is successful, proposed critical habitat should be enhanced as the fluvial processes restore sediment from channel bottoms to the nearshore and areas above the mean high interim flow. The duration and magnitude of the test flow was devised in order to create enough velocity and force to move sand-sized sedimenland deposit that sediment before it has traveled too far downstream or the flow has eroded return current attachment bars and other substrates of woody riparian in the upper portion of the Grand Canyon where sediment supply is limited. The physical and biological features and constituent elements of the proposed critical habitat would be benefited in the long-term (in this case, perhaps 1 or 2 years after the test flow) while there might be short-term adverse effects due to high flows to some of the constituent elements through temporary reduction in cover near or habitat for terrestrial insects. These short-term Summarizing, the test flow will be conducted before territorial southwestern willow flycatchers have returned to Grand Canyon habitats so there will be no direct loss of nests or young. The timing of the flow approximates a hydrograph designed to restore a more natural dynamic process to the Grand Canyon ecosystem. Loss of woody riparian vegetation is not expected at nesting territories as the quantity and duration of flows do not exceed a level previously experienced that did not scour those habitats. Some loss of return current channel wetlands. marshes, and understory at nesting territories is anticipated if the test flow is successful; however, while not anticipated to reduce appreciable the breeding, nesting, and forage value of that habitat, this loss is unquantified. Some insect and other invertebrate populations that are a food resource for the southwestern willow flycatcher might be reduced immediately following the flow but might increase later in the season. Whether territories are more susceptible to brown-headed cowbird parasitism after the test flow is also not quantified. Biological and Conference Opinions Glen Canyon BeachlHabilal.Building Flows 2116196 23