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Résumé :
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Radio-tags are commonly used in studies of avian behavior and ecology, even though many studies have revealed negative impacts of radio-tags. Other studies of songbirds have revealed no negative effects of radio-tags on parental care, nesting success, or annual return rates. However, such studies have not addressed the potential physiological costs of carrying radio-tags or determined if such costs affect birds during the energetically costly molt period. Simultaneously investigating the behavioral, physiological, and fitness consequences of radio-tags is important for evaluating possible costs. We studied Wood Thrushes (Hylocichla mustelina) in northwestern Pennsylvania and used a repeated-measures design to determine if radio-tags affected parental care behavior and nesting success, and measured levels of plasma lipid metabolites (beta-hydroxybutyrate, free glycerol, and triglycerides) to evaluate physiological condition. We also examined the possible physiological effects of radio-tags during the energetically demanding period of molt in late summer. Radio-tags did not affect male or female feeding rates, nesting success, number of nesting attempts, number of eggs laid, fledging success, or hatching success, and we found no significant effects of radio-tag use on levels of plasma lipid metabolites of nesting females. During molt, Wood Thrushes with radio-tags had lower levels of beta-hydroxybutyrate and higher levels of trigylcerides, suggesting they were in better, not worse, energetic condition. Our results suggest that radio-tags do not have negative effects on the behavior or physiology of Wood Thrushes. Similar studies on a wider range of songbirds are needed before concluding radio-tags have little or no impact during the molting period.
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