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Raptors and "campo-cerrado" bird mixed flock led by Cypsnagra Hirundinacea (Emberizidae:Thraupinae)

Predadores aéreos e bandos mistos de aves, em campo-cerrado, liderados por Cypsnagra hirundinacea (Emberizidae: Thraupinae)

Bird mixed flocks including Cypsnagra hirundinacea and Neothraupis fasciata as species with sentinels were studied in "campo-cerrado" in order to investigate the possible relationship between alertness and the mixed flock leadership. This study was conducted from March to September 1996 and mixed flocks were observed on average for 2:30h. The time with sentinels were recorded for C. hirundinacea and N. fasciata. The sentinels of Cypsnagra hirundinacea performed most of the vigilance (time with sentinel was on average 42 ± 17%, 41 ± 17% of which by C. hirundinacea, whereas only 1.2 % by N. fasciata) and gave all the alarm calls recorded (54% of the encounters with raptors stimulated alarm calls). A relationship was verified between time with sentinel and the rate of encounters with raptor (ANOVA, F = 3.0, P < 0.05). The results of this study are an evidence for the anti-predatory function of mixed flocks, in campo-cerrado, and the alertness as a major feature of a leader species, since C. hirundinacea always led those flocks.

mixed flock; sentinel; Thraupinae; raptors; nuclear species


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