Exposing migratory sparrows to Plasmodium suggests costs of resistance, not necessarily of infection itself. Issue 1 (23rd March 2018)

• Record Type: Journal Article
• Authors: Kelly, Tosha Ruth; Bonner, Simon Joseph; MacDougall‐Shackleton, Scott A.; MacDougall‐Shackleton, Elizabeth A.
• Is Part Of: Journal of experimental zoology. Volume 329:Issue 1(2018)
• Page Start: 5
• Page End: 14
• Publication Date: 2018-03-23
• Subjects: body composition -- migration -- parasitism -- Plasmodium -- radio telemetry -- song sparrow; Zoology -- Periodicals; Zoology; Animal Population Groups -- physiology; Zoology; Electronic journals; Periodical; Periodicals; 590
• DOI: 10.1002/jez.2151
• Languages: English
• ISSNs: 2471-5646

Abstract

Abstract: Migratory birds move through multiple habitats and encounter a diverse suite of parasites. This raises concern over migrants' role in transporting infectious disease between breeding and wintering grounds, and along migratory flyways. Trade‐offs between flight and immune defenses could interfere with infected individuals' migratory timing and success, potentially affecting infection dynamics. However, experimental evidence that parasitic infection affects migratory preparation or timing remains scant. We hypothesized that birds encountering hematozoan parasites shortly before migration incur physical costs (reduced body condition) and behavioral costs (delayed migration), due to the infection itself and/or to the demands of mounting an immune response. We experimentally inoculated song sparrows ( Melospiza melodia ) with Plasmodium shortly before fall migration. We monitored infection and body composition for 2 weeks after inoculation, and used radiotelemetry to track timing of migratory departure for another 7 weeks after release. Inoculated individuals that resisted infection had lower lean mass 12 days post exposure, relative to controls and infected individuals. This suggests trade‐offs between body composition and immune defenses that might reduce migration success of resistant individuals. Despite group differences in body composition prior to release, we did not detect significant differences in timing of migration departure several weeks later. Thus, malarial infection did not appear to incur detectable costs to body composition or to migratory timing, at least when exposure occurs several weeks before migration. This study is novel considering not only the costs of infection, but also the costs of resisting infection, in an experimental context. GRAPHICAL ABSTRACT: The first field experiment with controlled malaria exposure. We found different costs of resisting and tolerating malarial infection: Resisting decreases lean mass and weak evidence that tolerating might delay departure for migration.