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<p>The white-tailed hawk (<i>Geranoaetus albicaudatus</i>), found across the Americas, is well-suited for studying spatiotemporal patterns due to its conspicuous soaring behavior, preference for open areas, partial migratory habits, and delayed plumage maturation (five age classes). Here, we investigate overall abundance and seasonal shifts in age class abundance across the Gran Chaco/Espinal and the Cerrado. We also examine single-season abundance and age class distribution in the Amazon Basin and Guianan Savanna. Our analysis is based on systematic surveys spanning 692&#xa0;h and 20,755&#xa0;km in 138 roads (193&#xa0;h, 5,840&#xa0;km in 42 roads during the austral winter, and 499&#xa0;h, 14,915&#xa0;km in 96 roads during the austral summer). We found that: (1) overall abundance increased during the austral summer, with a 3.7-fold increase in the Gran Chaco/Espinal and a 1.6-fold increase in the Cerrado compared to the austral winter; (2) in the Gran Chaco/Espinal, age class distribution shifted from left-skewed (oldest class most abundant) in the austral winter to a slightly right-skewed, more even pattern (younger classes more abundant) in the austral summer, while in the Cerrado it remained left-skewed in both seasons; and (3) the Amazon Basin and the Guianan Savanna, surveyed in a single-season, exhibited a left-skewed distribution during the austral summer, similar to that of the Cerrado. This study establishes a crucial baseline for understanding spatiotemporal patterns at the age-specific level across South America, emphasizing the need for further research into age class distribution and its relation to the breeding phenology in the white-tailed hawk.</p>

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Large-scale spatiotemporal patterns in abundance and age structure of the white-tailed hawks in South America

  • 期刊论文

  • 发表日期：

    2026年8月3日

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  • Matías A. Juhant,
  • Juan I. Areta

摘要

The white-tailed hawk (Geranoaetus albicaudatus), found across the Americas, is well-suited for studying spatiotemporal patterns due to its conspicuous soaring behavior, preference for open areas, partial migratory habits, and delayed plumage maturation (five age classes). Here, we investigate overall abundance and seasonal shifts in age class abundance across the Gran Chaco/Espinal and the Cerrado. We also examine single-season abundance and age class distribution in the Amazon Basin and Guianan Savanna. Our analysis is based on systematic surveys spanning 692 h and 20,755 km in 138 roads (193 h, 5,840 km in 42 roads during the austral winter, and 499 h, 14,915 km in 96 roads during the austral summer). We found that: (1) overall abundance increased during the austral summer, with a 3.7-fold increase in the Gran Chaco/Espinal and a 1.6-fold increase in the Cerrado compared to the austral winter; (2) in the Gran Chaco/Espinal, age class distribution shifted from left-skewed (oldest class most abundant) in the austral winter to a slightly right-skewed, more even pattern (younger classes more abundant) in the austral summer, while in the Cerrado it remained left-skewed in both seasons; and (3) the Amazon Basin and the Guianan Savanna, surveyed in a single-season, exhibited a left-skewed distribution during the austral summer, similar to that of the Cerrado. This study establishes a crucial baseline for understanding spatiotemporal patterns at the age-specific level across South America, emphasizing the need for further research into age class distribution and its relation to the breeding phenology in the white-tailed hawk.