{"id":{"repo_id":"montana-tech","oai_identifier":"oai:scholarworks.umt.edu:etd-2265"},"canonical_url":"https://search.dev.ndltd.org/etd/montana-tech/oai:scholarworks.umt.edu:etd-2265","repository":{"repo_id":"montana-tech","name":"Montana Technology","base_url":"https://scholarworks.umt.edu/do/oai/"},"display":{"title":"Hormonal Mediation of a Unique Behavioral Polymorphism in the White-throated Sparrow (Zonotrichia albicollis)","abstract":"In this body of work, I examine how testosterone (T) physiology mediates the life-history trade-off between mating effort and parental care in the White-throated Sparrow. This species exhibits a behavioral polymorphism that occurs in both sexes. White-striped (WS) morphs are more territorially aggressive, sing more frequently and seek more extra-pair copulations. Tan-striped (TS) morphs provision nestlings more frequently. Thus this species roughly illustrates the trade-off between mating effort and parental care. I examine T physiology on three levels: plasma titres, binding globulins and response to the social environment. I ask whether levels of T correlate with morph-specific behavior and does this relationship change with stage in the nesting cycle. I found that WS males have significantly higher plasma levels of T than TS males. This difference is small, but it persisted through the parental stage of the nesting cycle. This suggests that T may mediate differences in mating effort and parental behavior in males, but is likely not the only factor. Female morphs did not differ in plasma T, thus T does not appear to play a similar role in females. Next I ask how corticosterone binding globulin (CBG) modulates T action. I found that CBG binds over 90% of T and is an important modulator of T action in this species. However CBG capacity did not differ between morphs, nor did morphs differ in baseline levels of corticosterone (CORT, a stress hormone that competes with T for binding sites on CBG.) Therefore interactions with CBG and CORT do not affect T action differently in the morphs, and patterns of free T (T not bound to CBG) mirror patterns of total T. Finally I investigated how T physiology responds to a change in the social environment- the establishment of a dominance relationship. WS males exhibited aggression more frequently and tended to dominate TS males. Levels of total T, CBG, CORT and free T were not predictive of future dominance status. Nor did these measures show persistent changes once the dominance relationship was established. The response of T physiology to the formation of a dominance relationship did not differ between morphs.","abstract_html":"In this body of work, I examine how testosterone (T) physiology mediates the life-history trade-off between mating effort and parental care in the White-throated Sparrow. This species exhibits a behavioral polymorphism that occurs in both sexes. White-striped (WS) morphs are more territorially aggressive, sing more frequently and seek more extra-pair copulations. Tan-striped (TS) morphs provision nestlings more frequently. Thus this species roughly illustrates the trade-off between mating effort and parental care. I examine T physiology on three levels: plasma titres, binding globulins and response to the social environment. I ask whether levels of T correlate with morph-specific behavior and does this relationship change with stage in the nesting cycle. I found that WS males have significantly higher plasma levels of T than TS males. This difference is small, but it persisted through the parental stage of the nesting cycle. This suggests that T may mediate differences in mating effort and parental behavior in males, but is likely not the only factor. Female morphs did not differ in plasma T, thus T does not appear to play a similar role in females. Next I ask how corticosterone binding globulin (CBG) modulates T action. I found that CBG binds over 90% of T and is an important modulator of T action in this species. However CBG capacity did not differ between morphs, nor did morphs differ in baseline levels of corticosterone (CORT, a stress hormone that competes with T for binding sites on CBG.) Therefore interactions with CBG and CORT do not affect T action differently in the morphs, and patterns of free T (T not bound to CBG) mirror patterns of total T. Finally I investigated how T physiology responds to a change in the social environment- the establishment of a dominance relationship. WS males exhibited aggression more frequently and tended to dominate TS males. Levels of total T, CBG, CORT and free T were not predictive of future dominance status. Nor did these measures show persistent changes once the dominance relationship was established. The response of T physiology to the formation of a dominance relationship did not differ between morphs.","abstract_has_math":false,"creators":["Swett, Meredith Bettencourt"],"institution":"University of Montana","degree_name":"Doctor of Philosophy (PhD)","degree_level":null,"degree_discipline":null,"degree_department":null,"school":null,"contributors":[],"advisors":[],"committee_chairs":[],"committee_members":[],"year":2007,"date_issued":"2007-01-01T08:00:00Z","date_published":"2007-01-01T08:00:00Z","updated_at":"2026-07-24T03:14:30Z","subjects":["behavioral polymorphism","corticosterone","corticosterone binding globulin","testosterone","White-throated sparrow","Zonotrichia albicollis"],"languages":[],"rights":[],"rights_urls":[],"identifier_entries":[]},"links":{"outbound_url":"https://scholarworks.umt.edu/etd/1246","outbound_label":"Repository record","outbound_source":"dc:identifier"},"metadata_groups":[{"id":"people","label":"People","entries":[{"key":"dc:creator","label":"Author","values":["Swett, Meredith Bettencourt"]}]},{"id":"academic_context","label":"Academic Context","entries":[{"key":"dc:publisher","label":"Institution","values":["University of Montana"]},{"key":"dc:type","label":"Dc Type","values":["Dissertation"]},{"key":"thesis:degree_name","label":"Degree Name","values":["Doctor of Philosophy (PhD)"]}]},{"id":"subjects_keywords","label":"Subjects and Keywords","entries":[{"key":"dc:subject","label":"Dc Subject","values":["behavioral polymorphism","corticosterone","corticosterone binding globulin","testosterone","White-throated sparrow","Zonotrichia albicollis"]}]},{"id":"identifiers","label":"Identifiers","entries":[{"key":"dc:identifier","label":"Identifier","values":["https://scholarworks.umt.edu/etd/1246"]}]},{"id":"additional","label":"Additional Metadata","entries":[{"key":"dc:description.abstract","label":"Abstract","values":["In this body of work, I examine how testosterone (T) physiology mediates the life-history trade-off between mating effort and parental care in the White-throated Sparrow. This species exhibits a behavioral polymorphism that occurs in both sexes. White-striped (WS) morphs are more territorially aggressive, sing more frequently and seek more extra-pair copulations. Tan-striped (TS) morphs provision nestlings more frequently. Thus this species roughly illustrates the trade-off between mating effort and parental care. I examine T physiology on three levels: plasma titres, binding globulins and response to the social environment. I ask whether levels of T correlate with morph-specific behavior and does this relationship change with stage in the nesting cycle. I found that WS males have significantly higher plasma levels of T than TS males. This difference is small, but it persisted through the parental stage of the nesting cycle. This suggests that T may mediate differences in mating effort and parental behavior in males, but is likely not the only factor. Female morphs did not differ in plasma T, thus T does not appear to play a similar role in females. Next I ask how corticosterone binding globulin (CBG) modulates T action. I found that CBG binds over 90% of T and is an important modulator of T action in this species. However CBG capacity did not differ between morphs, nor did morphs differ in baseline levels of corticosterone (CORT, a stress hormone that competes with T for binding sites on CBG.) Therefore interactions with CBG and CORT do not affect T action differently in the morphs, and patterns of free T (T not bound to CBG) mirror patterns of total T. Finally I investigated how T physiology responds to a change in the social environment- the establishment of a dominance relationship. WS males exhibited aggression more frequently and tended to dominate TS males. Levels of total T, CBG, CORT and free T were not predictive of future dominance status. Nor did these measures show persistent changes once the dominance relationship was established. The response of T physiology to the formation of a dominance relationship did not differ between morphs."]},{"key":"dc:title","label":"Title","values":["Hormonal Mediation of a Unique Behavioral Polymorphism in the White-throated Sparrow (Zonotrichia albicollis)"]}]}],"canonical_facts":{"dc:creator":["Swett, Meredith Bettencourt"],"dc:description.abstract":["In this body of work, I examine how testosterone (T) physiology mediates the life-history trade-off between mating effort and parental care in the White-throated Sparrow. This species exhibits a behavioral polymorphism that occurs in both sexes. White-striped (WS) morphs are more territorially aggressive, sing more frequently and seek more extra-pair copulations. Tan-striped (TS) morphs provision nestlings more frequently. Thus this species roughly illustrates the trade-off between mating effort and parental care. I examine T physiology on three levels: plasma titres, binding globulins and response to the social environment. I ask whether levels of T correlate with morph-specific behavior and does this relationship change with stage in the nesting cycle. I found that WS males have significantly higher plasma levels of T than TS males. This difference is small, but it persisted through the parental stage of the nesting cycle. This suggests that T may mediate differences in mating effort and parental behavior in males, but is likely not the only factor. Female morphs did not differ in plasma T, thus T does not appear to play a similar role in females. Next I ask how corticosterone binding globulin (CBG) modulates T action. I found that CBG binds over 90% of T and is an important modulator of T action in this species. However CBG capacity did not differ between morphs, nor did morphs differ in baseline levels of corticosterone (CORT, a stress hormone that competes with T for binding sites on CBG.) Therefore interactions with CBG and CORT do not affect T action differently in the morphs, and patterns of free T (T not bound to CBG) mirror patterns of total T. Finally I investigated how T physiology responds to a change in the social environment- the establishment of a dominance relationship. WS males exhibited aggression more frequently and tended to dominate TS males. Levels of total T, CBG, CORT and free T were not predictive of future dominance status. Nor did these measures show persistent changes once the dominance relationship was established. The response of T physiology to the formation of a dominance relationship did not differ between morphs."],"dc:identifier":["https://scholarworks.umt.edu/etd/1246"],"dc:publisher":["University of Montana"],"dc:subject":["behavioral polymorphism","corticosterone","corticosterone binding globulin","testosterone","White-throated sparrow","Zonotrichia albicollis"],"dc:title":["Hormonal Mediation of a Unique Behavioral Polymorphism in the White-throated Sparrow (Zonotrichia albicollis)"],"dc:type":["Dissertation"],"thesis:degree_name":["Doctor of Philosophy (PhD)"]},"updated_at":"2026-07-24T03:14:30Z"}