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Journal of Ornithology

, Volume 160, Issue 1, pp 165–172 | Cite as

Testing for sentinel coordination in Smooth-billed Anis (Crotophaga ani)

  • Jing Sheng Hing
  • Gregory Schmaltz
  • James S. QuinnEmail author
Original Article

Abstract

Sentinel behaviour has been widely described, but whether or not it is coordinated among group members requires careful examination. The Smooth-billed Ani, Crotophaga ani, a joint-nesting cooperatively breeding bird, appears to have a sentinel system; however, it is unknown whether that vigilance is coordinated, the defining feature of sentinel behaviour. We followed social groups during two breeding seasons to observe and time their individual sentinel bouts. We then tested for coordination by quantifying the observed and expected proportions of time during which (1) no sentinel was present during observations, and (2) two or more sentinels were present. The majority of social groups spent less time than expected, under the coordination hypothesis, with at least one sentinel, indicating evidence against coordinated vigilance. This was significant for social groups observed in 2015, but not in 2002. Across both years, temporal overlap in sentinel behaviour between two individuals occurred significantly less than expected under the coordination hypothesis. This study contributes to a gap in our knowledge of sentinel behaviour and suggests that Smooth-billed Anis lack organized vigilance, possibly due to low within-group relatedness and group instability.

Keywords

Sentinel behaviour Vigilance coordination Cuckoo Cooperative breeding Coordination hypothesis 

Zusammenfassung

Gibt es eine Wachtpostenkoordination bei Glattschnabelanis ( Crotophaga ani )?

Wächterverhalten wurde bereits vielfach beschrieben, ob es jedoch auch zwischen den Mitgliedern einer Gruppe koordiniert wird, bedarf sorgfältiger Prüfung. Der Glattschnabelani (Crotophaga ani), ein sozialer, gemeinschaftlich nistender Vogel mit kooperativem Brutverhalten, scheint ein Wachtpostensystem zu besitzen. Es ist jedoch nicht bekannt, ob das Wachverhalten auch koordiniert wird, was ein Definitionskriterium für ein echtes Wachtpostenverhalten wäre. Über zwei Brutzeiten hinweg verfolgten wir die sozialen Gruppen, um deren individuelle Wächterphasen zu beobachten und jeweils deren Dauer zu messen. Anschließend testeten wir auf eine Koordination des Verhaltens, indem wir die beobachteten beziehungsweise erwarteten Zeitanteile verglichen, zu denen a) kein Wachtposten zum Beobachtungszeitpunkt anwesend war oder b) zwei oder mehr Wachtposten zugegen waren. Die Mehrzahl der sozialen Gruppen verbrachte weniger Zeit als zufällig zu erwarten mit mindestens einem Wachtposten, was gegen eine Koordination des Wachverhaltens spräche. Für die im Jahr 2015 beobachteten Gruppen war dies signifikant, für die in 2002 allerdings nicht. Diese Untersuchung liefert einen Beitrag zur Schließung der Wissenslücke über das Wachtpostenverhalten und deutet darauf hin, dass es bei Glattschnabelanis kein organisiertes Wächtersystem gibt, möglicherweise aufgrund niedriger Verwandtschaftsgrade innerhalb der Gruppen und von Gruppeninstabilität.

Notes

Acknowledgements

This work was supported by an NSERC Discovery Grant to J.S.Q., a travel grant from the McMaster Biology Department to J. S. H., and a grant from the Natural Science and Engineering Research Council to G. S. Procedures in this study were approved and conducted under McMaster University Animal Care permits (AUP 05-07-40, AUP 09-07-25). We would like to thank Susan Silander, Oscar Diaz, Joseph Schwagerl, Fernando Rodriguez, Mariano Gonzales, Dennis Corales, Kirsty Swinnterton, Giselle Burgos, and James Padilla at the Cabo Rojo National Wildlife Refuge, as well as Fred Schaffner for logistical support. We would like to thank Josh Robertson, Zeke Smith, Morgan Parks, Lilla Barabas, and Adrienne Boon for their help in the field. We are also grateful to the staff at Finca Altamira for granting us access to their lands. We would also like to thank Ben Bolker for statistical advice. Last but not least, we thank Chris Guglielmo and two anonymous reviewers whose comments improved earlier versions of the manuscript.

Supplementary material

10336_2018_1584_MOESM1_ESM.pdf (95 kb)
Supplementary material 1 (PDF 94 kb)

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Copyright information

© Dt. Ornithologen-Gesellschaft e.V. 2018

Authors and Affiliations

  1. 1.Department of BiologyMcMaster UniversityHamiltonCanada
  2. 2.University of the Fraser ValleyAbbotsfordCanada

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