In humans and other animals, lead exposure in infants and young animals affects anatomic, physiologic, behavioral, and intellectual development. Yet it is largely unknown whether the effects occur gradually or are more pronounced if exposure occurs at particular stages. In this article we examine the effects of temporal differences in lead exposure on early behavioral development in herring gulls (Larus argentatus). We randomly assigned 64 1-2-day-old gull chicks to one of four treatment groups to receive a lead acetate dose at age 6 days (100 mu g/g) or 12 days (50 or 100 mu g/g), or to receive matched volume saline injections on the same days. Behavioral tests were performed at 2-5-day intervals to examine locomotion, balance, righting response, thermoregulation, and visual cliff. Flight behavior was examined at fledging. Results were compared with previously studied exposures at 2, 4, and 6 days of age. Righting response and balance were disrupted immediately after exposure, regardless of the timing of exposure. Thermoregulatory, visual cliff, and individual recognition behavior were more affected by exposure at 2-6 days, and there was little effect with exposure at 12 days. These results confirm the existence of critical periods for certain behaviors to lead exposure in developing herring gulls.
