Russell F. Reidinger

Conspecific individual recognition between starlings after toxicant-induced sickness

After feeding in the presence of a cagemate (Group S, n = 16), food-deprived starlings were intubated with the toxicant methiocarb (Group E, n = 8) or its nontoxic carrier, propylene glycol (Group C, n = 8). During the 4 days after intubation, the birds in Groups E and C were presented on 2 days with the Group S bird that was present during gavage (S+ bird) and on the other 2 days with another Group S bird (S− bird). Group E (but not Group C) birds were more agonistic toward S+ birds than S− birds, fed less in their presence, and were less likely to enter and perch in the same cage quadrant with them. A second experiment suggested that such differential behavior was probably not the result of behaviors exhibited by the S+ birds. Few calls were recorded in either experiment. Although acoustic signals might have been involved, we suggest that the starlings might have used visual cues to recognize individual conspecifics that were present during aversion learning.

The Relative Importance of Reinforced Versus Nonreinforced Stimuli in Visual Discrimination Learning by Redwinged Blackbirds (Agelaius Phoeniceus)

Redwinged blackbirds were trained to locate and peck apple slices in two discrimination problems with four times more training on one problem than on the other. The birds were then given transfer tests with the stimuli re-paired. Nonreinforced (S-) stimuli exerted greater control over behavior than did reinforced (S+) stimuli. We inferred that the blackbirds learned more about what to avoid than what to approach when searching for food in the two-choice situation. That inference is contrary to the notion that, by being alert to the visual cues which signal foods (i.e., S+ stimuli), birds can more successfully cope with irrelevant visual information encountered during foraging. Rather, being alert to cues which signal the absence of food (i.e., S- stimuli) may be relatively more important.

Rodenticide flavor characteristics assessed through generalization of conditioned flavor avoidance

Little information is available concerning the flavor qualities of toxicants or bait formulations. Using generalization of flavor avoidance learning (FAL) in Experiment 1, we investigated the flavor of alpha-chlorohydrin, alpha-naphthylthiourea, calciferol, scilliroside, and sodium (Na) warfarin as perceived by Sprague-Dawley rats (Rattus norvegicus). Scilliroside was apparently tasteless. For the other toxicants, FAL was observed. Alpha-chlorohydrin and alpha-naphthylthiourea avoidance generalized to «bitter» and «sour» flavors, calciferol avoidance generalized to «bitter» and «sweet» flavors, and Na warfarin FAL generalized to «bitter», «sweet», and «salty» flavors. In Experiment 2 we used generalization of FAL to examine the flavor of strychnine in agar or water. Strong FAL was observed, although avoidance generalization was narrower for strychnine in agar than in water. In Experiment 3 we examined FAL among alpha-chlorohydrin, alpha-naphthylthiourea, calciferol, strychnine, and Na warfarin. Flavor avoidance learning and generalization were obtained for some (but not all) rodenticides, and similarities among generalization profiles obtained in Experiments 1 and 2 did not predict generalization among the rodenticides, per se. We infer that toxicants can have complex flavors and are not only bitter or sour, as some have proposed. Applications of our findings may range from the empirical development of prebait formulations to the evaluation of bait enhancers and microencapsulation techniques