Raptors and campo-cerrado bird mixed flock led by Cypsnagra Hirundinacea (Emberizidae:Thraupinae)
Data
2000-08-01
Autores
RAGUSA-NETTO, J. [UNESP]
Título da Revista
ISSN da Revista
Título de Volume
Editor
Instituto Internacional de Ecologia
Resumo
Bandos mistos de aves incluindo Cypsnagra hirundinacea e Neothraupis fasciata como espécies que vigiam por sentinelas foram estudados em campo-cerrado de março a setembro de 1996. O propósito desse estudo foi verificar a possível relação entre o grau de alerta de uma espécie e a liderança dos bandos. Durante as observações (em média de 2h30) foi quantificado o tempo vigiado por sentinelas de ambas as espécies. Os sentinelas de Cypsnagra hirundinacea realizaram a quase totalidade da vigilância (tempo com sentinela foi em média de 42 ± 17% do tempo, sendo 41 ± 17% vigiado por C. hirundinacea e 1,2% por N. fasciata), além de emitirem todos os chamados de alarme registrados (54% dos encontros com predadores aéreos estimularam chamados de alarme). O tempo vigiado por sentinelas nos bandos apresentou relação significativa com a taxa de encontro entre os predadores aéreos e os bandos (ANOVA, F = 3,0; p < 0,05). Esses resultados evidenciam a função antipredatória dos bandos mistos em campo-cerrado e que o grau de alerta é uma característica relevante em uma espécie líder, uma vez que esses bandos sempre foram liderados por C. hirundinacea.
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.
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.
Descrição
Palavras-chave
bandos mistos, Thraupinae, sentinelas, predadores aéreos, espécie nuclear, mixed flock, sentinel, Thraupinae, raptors, nuclear species
Como citar
Revista Brasileira de Biologia. Instituto Internacional de Ecologia, v. 60, n. 3, p. 461-467, 2000.