Breeding biology of white-eared ground-sparrows (Melozone leucotis), with a description of a new nest type

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Ornitologia Neotropical





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We provide the first detailed description of the breeding biology of White-eared Groundsparrows (Melozone leucotis), a little-studied Neotropical songbird that inhabits thickets in Central America. Based on eight years of data collected from populations in the Central Valley of Costa Rica, we describe White-eared Ground-sparrows' nests, eggs, nest parasitism, parental behavior, and breeding phenology. Nests conformed to one of two general types: (1) a bulky structure of plant fibres with a coarse outer layer and a fine inner layer; and (2) a smaller, simpler structure made up of a platform of thin plant fibres placed on top of rocks. Nest of the former type were located in vegetation near the ground, whereas the latter type were constructed directly on the ground. This is the first description of the second nest type. Eggs had a white background with variable brown spotting. Eggs were laid in clutches of two or three. Parasitism by Bronzed Cowbirds (Molothrus aeneus) was severe; five often nests were parasitized, including two that were multiply parasitized with 6 and 7 cowbird eggs. Only females were observed incubating the eggs, but both sexes provisioned nestlings; only females were observed provisioning fledglings while males assisted in locating food. This species has a long breeding season, begins in March (late dry season), and continues until September (late rainy season). We provide the first formal description of the breeding behaviour of White-eared Ground-sparrows, from a genus of birds whose behaviour is poorly known in the tropics. © The Neotropical Ornithological Society.