Birds of Indian Subcontinent

Absence of Breeding Readiness in Neotropical and Long-Distance Migrant Landbirds during Spring Stopover

Publication Type:Journal Article
Year of Publication:1998
Authors:Jones, GA, Norment, CJ
Journal:The Condor
Date Published:1998
ISBN Number:00105422
Keywords:Calendula, Catharus, Catharus minimus, Catharus ustulatus, Corthylio, Corthylio calendula, Emberizidae, Hylocichla, Hylocichla minimus, Hylocichla ustulata, Regulidae, Regulus, Regulus calendula, Turdidae, Zonotrichia, Zonotrichia albicollis
Abstract:We investigated breeding readiness of selected migrant species captured at a known stopover site in western New York during the spring of 1995 and 1996. A total of 775 individuals representing 14 species were examined for outward physiological indication of male breeding readiness measured by relative size of cloacal protuberance. Only 2 of the 775 individuals exhibited a cloacal protuberance, both being captured in 1996; one Ruby-crowned Kinglet (Regulus calendula) and one Swainson's Thrush (Catharus minimus). Cloacal lavage samples were taken from 22 White-throated Sparrows (Zonotrichia albicollis) and 26 Swainson's Thrushes during the spring of 1996. None of the migrating individuals lavaged exhibited presence of cloacal sperm regardless of species, sex, time, or date of capture. Poor energetic condition was typical of these captured migratory landbirds. Depleted energetic stores may explain the lack of early sperm production in migrants at this stopover site.
Short Title:The Condor
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