Sentinels in Saltator atricollis (Passeriformes: Emberizidae)
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Data
2001-05-01
Autores
Ragusa-Netto, J. [UNESP]
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Editor
Instituto Internacional de Ecologia
Resumo
Estudei a existência de sentinelas em S. atricollis em campo-cerrado, nas estações reprodutivas de 1994-95 e 1995-96. Os grupos de S. atricollis continham de dois a sete indivíduos (N = 25). Os sentinelas vigiaram os grupos (média ± dp) por 62% ± 9% do tempo, sendo que a maioria dos turnos de vigilância durou de menos de um a seis minutos (em alguns casos se extenderam por mais de 30 min.). Dois ou mais sentinelas vigiaram simultaneamente, em média, apenas 3,2% do tempo vigiado. Os sentinelas comumente emitiam chamados de contato quando iniciavam e/ou terminavam um turno de vigilância. O tamanho dos grupos não apresentou relação com o tempo vigiado. Por outro lado, a taxa de encontros entre predadores aéreos e grupos influenciou significativamente o tempo vigiado. A habilidade dos sentinelas em perceber predadores provavelmente apresenta uma função relevante, conferindo vantagens antipredatórias aos grupos dessa espécie.
I studied the existence of sentinels in Saltator atricollis in a 'campo-cerrado' (Brazilian savanna) during the breeding seasons of 1994-95 and 1995-96. Groups of this species consisted of two to seven birds (N = 25). Sentinels were present (mean ± sd) 62% ± 9% of the time, and most sentinel bouts lasted from less than one to six minutes (although in some occasions for more than 30 min.). Overlap of two or more sentinels occurred on average only 3.2% of the time with birds on guard. Sentinels commonly gave contact calls in the beginning and/or at the end of a sentinel bout. The group size had no effect on time with sentinels. However the encounter rate between raptors and groups significantly influenced the time guarded. The results of this study suggests that the ability of sentinels to detect predators may play a central role as an anti-predator device.
I studied the existence of sentinels in Saltator atricollis in a 'campo-cerrado' (Brazilian savanna) during the breeding seasons of 1994-95 and 1995-96. Groups of this species consisted of two to seven birds (N = 25). Sentinels were present (mean ± sd) 62% ± 9% of the time, and most sentinel bouts lasted from less than one to six minutes (although in some occasions for more than 30 min.). Overlap of two or more sentinels occurred on average only 3.2% of the time with birds on guard. Sentinels commonly gave contact calls in the beginning and/or at the end of a sentinel bout. The group size had no effect on time with sentinels. However the encounter rate between raptors and groups significantly influenced the time guarded. The results of this study suggests that the ability of sentinels to detect predators may play a central role as an anti-predator device.
Descrição
Palavras-chave
Emberizidae, campo-cerrado, predadores aéreos, vigilância, sentinelas, Emberizidae, Brazilian savanna, raptors, alertness, sentinels
Como citar
Revista Brasileira de Biologia. Instituto Internacional de Ecologia, v. 61, n. 2, p. 317-322, 2001.