Date of Award:

5-1-1977

Document Type:

Dissertation

Degree Name:

Doctor of Philosophy (PhD)

Department:

Biology

Department name when degree awarded

Life Sciences:Biology

Committee Chair(s)

Keith L. Dixon

Committee

Keith L. Dixon

Abstract

The purpose of this investigation was to examine different aspects of the social tendency among three age classes of House Sparrows (adults, first-year, and juvenals). The social preferences of these birds were studied in relation to: (1) different flock sizes of conspecifics and nonconspecifics; (2) the sexes of conspecifics; (3) the playback of conspecific vocalizations in the presence of flocks of conspecifics; and (4) abstract models displaying configurations considered relevant from House Sparrow plumage patterns of either sex. This investigation was undertaken at the Green Canyon Ecology Station, Logan, Utah from June 1968 to May 1969. These experiments were carried out in a large cross-shaped experimental chamber in which the test birds could freely choose among several stimulus situations. The outer segment of each arm of the chamber consisted of a detachable cage in which bird flocks of one species - ix (conspecifics and nonconspecifics) were placed. All responses were defined as social preferences shown by physical approach to the stimuli presented. A total of 1332 trials were run using 867 individual test birds. Certain aspects of the experimental apparatus and design were discussed as having possible influences upon the responses of the test birds. Within the limits imposed by the test apparatus, the responses of the test birds were uniform within the age classes. However, certain differences in social preferences occurred among the age classes. All three age classes of test birds, in different instances, showed a greater preference for those flocks containing the larger number of individuals (15-5 birds). For example, the juvenal and first-year birds demonstrated a greater tendency to approach the dull plumaged Pine Siskins, especially when these birds were present in larger numbers, than did adults. The first-year birds, unlike the adults and juvenals, showed a preference for the larger flocks in all experiments. The adult birds preferred the smaller flock of conspecifics to the larger flock of Pine Siskins, but always preferred the larger flock of conspecifics to the smaller flocks of conspecifics. Depending upon the nature of the stimuli presented, adult conspecific flocks comprised of both sexes were found to be attractive to all age classes. However, this tendency appeared to be least manifest in juvenals, somewhat intermediate in first-year birds, and most evident in adults. Juvenals showed a marked preference to approach adult females rather than males. Adults showed nearly equal tendencies to approach individuals of either sex, whereas the first-year birds were intermediate between juvenals and adults in this respect. These results suggest that the younger age classes are less specific, being attracted to any individuals possessing dull plumage characteristics. Thus, the progressive changes occurring in the number and nature of social associations as the maturation process proceeds, may be reflected in a parallel maturation of the social tendency. The playback of tape recordings of conspecific's vocalizations appeared to enhance the attractiveness of the flocks of conspecifics; however, due to stimulus confounding this observation deserves caution. The abstract models displaying contrasting stimulus patterns were more attractive to the test birds than plain models lacking such markings. The fact that the patterned models were found more attractive, coupled with the increased positive orientation of the test birds to the more detailed models within the apparatus, suggests that stimulus complexity may be important in eliciting approach. Overall, and excluding the experiments with abstract models, the social preferences of the first-year birds showed similarities to those of both juvenals and adults. Dissimilarities in social preferences were greatest among juvenals and adults. All test birds found the areas containing flock birds to be ultimately more attractive than the control areas which lacked birds. Test birds entering wings containing birds rarely left for other areas.

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