Lesser scaup Aythya affinis, medium‐sized black and white diving ducks, were collected at Arkansas baitfish farms during November‐December 1999 (N= 33), January‐February 2000 (N= 39), and March‐April 2000 (N = 22) to determine seasonal differences in their diet and their relative impact to baitfish production. The mass of gastrointestinal contents was used to determine the proportion of each diet item relative to all items recovered during stomach analyses. Chironomids were the primary food item recovered. Ten of 94 (10.6%) scaup contained identifiable fish biomass. Fish bones and otoliths were found in an additional 14 scaup (14.9%). All fish remains were identified (via otoliths) as those commonly produced at Arkansas baitfish farms (Cyprinidae). Other diet items (ranked by proportional mass) were vegetative seeds, snails, insects, crayfish, and other aquatic worms (class Oligochaeta). Scaup diets were similar among collection periods, between males and females, and between juvenile and mature ducks. We estimated the economic impact of lesser scaup to baitfish production based upon estimated duration of ducks at farms, the proportion of ducks containing fish, and scaup energetic requirements. Provided estimates of scaup abundance and the cost of bird harassment at a particular farm, economic thresholds (i.e., fish replacement cost as a function of scaup predation) will facilitate cost‐effective decisions regarding bird damage management at Arkansas baitfish aquaculture facilities.

— We conducted foraging observations, food habits studies, and producer surveys to determine the foraging behavior and monetary impact of great blue herons Ardea herodas, great egrets A. alba, and little blue herons Egrerra caerulea foraging at Arkansas baiffish farms. Although great egrets captured most baitfish/minute, captures/strike were nearly identical among the three wading bird species. American gizzard shad Dorosoma cepedianum, goldfish Carassius auratus, and giant water bugs Hemiptera: Belostomatidae were collected from the gastro‐intestinal tract of great blue herons. Only golden shiners Noremgonus crysoleucas and goldfish were found in great egrets. We found dragonflies Odonata, golden shiners, green sunfish Lepomis cyanellus, and water bugs in little blue herons. In contrast to other birds collected, snowy egrets E. thula were found to contain mosquito fish Gambusia affinis. Among 2,742 teleost otoliths recovered from collected great blue herons, great egrets, and little blue herons, most otoliths belonged to the Cyprinidae family (including the baiffishes). Surveyed farm managers use various auditory and visual stimuli to disperse fish‐eating birds from their farms. Surveyed baitfish farmers suggested that the average cost of their annual bird harassment program was $11,580 at relatively small farms (< 202 ha) and $104,560 at relatively large × 202 ha) baitfish aquaculture facilities. We estimated the replacement cost of baitfish consumed by wading buds based upon their daily food requirements, the food habits of herons and egrets at baiffish farms, the hypothetical abundance of wading birds at a particular baitfish farm (relative to survey results), the duration of herons and egrets reported by farm managers, and current baitfish market values.