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<p>Most Neotropical buteonine raptors are characterized by two poorly understood traits: delayed plumage maturation (requiring multiple annual molt cycles to reach Definitive Basic Plumage) and complex social behavior (aggregation at specific sites and facultative cooperative hunting and breeding). Despite the ecological significance of these traits, comprehensive data on molt cycles, plumage sequences, and their connection to social behavior remain lacking for most species. To address these gaps, I analyzed the plumage of 139 photographed individuals and conducted behavioral observations of the bay-winged hawk (<i>Parabuteo unicinctus unicinctus</i>) across the Austral Temperate Region, identifying three key natural history traits crucial for its taxonomic reassessment. First, the bay-winged hawk reaches Definitive Basic Plumage after four annual molt cycles, with five distinct age classes: Basic I (≤ 8 months), Basic II (9–20 months), Basic III (21–32 months), Basic IV (32–44 months), and Basic V (≥ 45 months). Second, observations of three active nests—two in winter and one in spring—suggest year-round breeding. Third, mixed-age groups (five to eight individuals) were frequently observed soaring or perching together, with a trio forming an active nest, providing further evidence of social behavior. These findings challenge previous accounts of plumage sequence, breeding phenology, and social behavior in the bay-winged hawk within the Austral Temperate Region. Expanding fieldwork in tropical South America, where bay-winged hawk and Harris’ hawk (<i>Parabuteo unicinctus harrisi</i>) coexist, is crucial for refining the natural history and taxonomic reassessment of the <i>Parabuteo unicinctus</i> complex.</p>

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Framing the natural history of the bay-winged hawk (Parabuteo unicinctus unicinctus) for accurate taxonomic assessment

  • 期刊论文

  • 发表日期：

    2026年3月20日

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  • Matías A. Juhant

摘要

Most Neotropical buteonine raptors are characterized by two poorly understood traits: delayed plumage maturation (requiring multiple annual molt cycles to reach Definitive Basic Plumage) and complex social behavior (aggregation at specific sites and facultative cooperative hunting and breeding). Despite the ecological significance of these traits, comprehensive data on molt cycles, plumage sequences, and their connection to social behavior remain lacking for most species. To address these gaps, I analyzed the plumage of 139 photographed individuals and conducted behavioral observations of the bay-winged hawk (Parabuteo unicinctus unicinctus) across the Austral Temperate Region, identifying three key natural history traits crucial for its taxonomic reassessment. First, the bay-winged hawk reaches Definitive Basic Plumage after four annual molt cycles, with five distinct age classes: Basic I (≤ 8 months), Basic II (9–20 months), Basic III (21–32 months), Basic IV (32–44 months), and Basic V (≥ 45 months). Second, observations of three active nests—two in winter and one in spring—suggest year-round breeding. Third, mixed-age groups (five to eight individuals) were frequently observed soaring or perching together, with a trio forming an active nest, providing further evidence of social behavior. These findings challenge previous accounts of plumage sequence, breeding phenology, and social behavior in the bay-winged hawk within the Austral Temperate Region. Expanding fieldwork in tropical South America, where bay-winged hawk and Harris’ hawk (Parabuteo unicinctus harrisi) coexist, is crucial for refining the natural history and taxonomic reassessment of the Parabuteo unicinctus complex.