Studies of the White Pelican in South Dakota: Reproductive Biology of Wild Populations and Effects of Polychlorinated Biphenyls and DDT on the Behavior of Penned Birds

The learning behavior of penned white pelicans (Pelecanus erythrorhynchos) was studies 2 August to 5 October 1972 using a swimming pool – Y-maze apparatus in an operant conditioning experiment. The experiment consisted of three consecutive phases: trial-and-error learning, extinction, and relearning. Three groups of nine pelicans each were studied: a polychlorinated biphenyl (PCE) treated group, a DDT, DDD, DDE treated group, and a Control group. The object of this study was to determine the effect of PCB and DDT, DDD, DDE on the learning ability of penned white pelicans. Control, PCB, and DDT groups of penned white pelicans learned to respond to a positively reinforced stimulus in an operant conditioning experiment. Learning performance, in terms of response rates and response latency, improved over time in the three groups. Repeated trials without reinforcement (extinction) had the primary effect of reducing the total number of responses per treatment group while the proportion of responses to the previously reinforced stimulus remained high. Response recovery was rapid when positive reinforcement was reintroduced (relearning), and the proportion of response to the reinforced stimulus remained high through termination of the study. Variation among birds within each treatment group was manifested by a complete failure to respond by some birds, rejection of reward and decline in performance by others, and fluctuation in performance over the study by several individual birds. The only significant difference among groups was found in the extinction phase of study, in which the DDT group exhibited a greater resistance to extinction than the Control and PCB groups (P\u3c0.01), and the Control group exhibited a greater resistance to extinction than the PCG group (P\u3c0.01). It was concluded that consistent differences in learning ability among treatment groups were not demonstrated, but the inconclusive nature of the results indicates that further studies of the effects of environmental contaminants on learning behavior are warranted. During the summer of 1973 a survey was conducted to locate white pelican nesting colonies in South Dakota. Four colonies were located in northeastern South Dakota: Sand Lake National Wildlife Refuge, Brown County; Piyas Lake, Marshal, County; North Drywood Lake, Roberts County; and Grass Lake, Coddington, County. A fifth colony was located at Lacreek National Wildlife Refuge, Bennett County, in southwestern South Dakota. The 1973 breeding population for South Dakota was estimated at 3,664 pelicans, with the five colonies contributing a total of 1,832 nests (or breeding pairs). An estimated 1,894 young were produced resulting in a production rate for the state of 1.03 young per breeding pair. The Lacreek colony contributed 65.5 percent of the breeding pairs and 69.5 percent of the production to the state total and had the highest rate of production (1.10 young per breeding amongst the five colonies). The North Drywood lake colony had the colonies located in northeastern South Dakota. The Sand Lake Refuge colony had a much lower breeding population, production, and production rate than the other colonies. An intensive study of the nesting colony at Sand Lake was conducted in 1973 to determine nesting effort and success of white pelicans using the island and to observe behavior pattern of nesting birds, Twenty-nine pelican nests were established in the colony. Eggs in 16 nests hatched, nine nests were abandoned prior to hatching and six nests were destroyed and/or abandoned due to raccoon (Procyon lotor) predation and disturbance. It was estimated that 57 eggs were laid in the 29 nests (mean=1.95), and 28 eggs hatched in the 16 successful nests. Thirteen young survived to flight stage for a survival rate of 0.23 juveniles per egg over the 99-day period from start of incubation to fledging. Rate of production as 0.45 young fledged per breeding pair. It was conclude that maintenance of a viable nesting colony of pelicans at Sand Lake may not be possible if the number of breeding pairs and their rate of production continues at the level found in 1973. Recommendations for managing white pelican colonies include maintenance of islands by controlling bank erosion, creation of islands, protection of islands from human disturbance and mammalian predation, and annual monitoring of pelican breeding populations and productions