Does niche-overlap facilitate mixed-species flocking in birds?
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ORIGINAL ARTICLE
Does niche-overlap facilitate mixed-species flocking in birds? Fushing Hsieh • Chao-Chieh Chen
Received: 19 April 2010 / Revised: 30 January 2011 / Accepted: 7 March 2011 / Published online: 27 March 2011 Ó Dt. Ornithologen-Gesellschaft e.V. 2011
Abstract Foraging niche overlap between attendant species and the nuclear species of mixed-species flocks may induce competition as well as facilitation. In this study, we hypothesized that canopy species would appear more frequently in flocks where nuclear species foraged in the canopy and that species with greater niche overlap with nuclear species would have lower departure rates. Flocking and foraging behaviors of flocks led by the Grey-cheeked Fulvetta Alcippe morrisonia were studied in northeastern Taiwan for two consecutive non-breeding seasons from 1998 to 2000. The foraging height spectrum increased with increasing group size of fulvettas because more fulvettas were found foraging across different strata. The number of species and number of individuals of canopy attendants in a flock increased more rapidly than understory attendants as the group size of fulvettas increased. The more the foraging Communicated by T. Friedl.
Electronic supplementary material The online version of this article (doi:10.1007/s10336-011-0678-1) contains supplementary material, which is available to authorized users. F. Hsieh Institute of Statistical Science, Academia Sinica, Taipei 11541, Taiwan Present Address: F. Hsieh Department of Statistics, University of California, 4232 Mathematical Sciences Building, One Shields Avenue, Davis, CA, USA e-mail: [email protected] C.-C. Chen (&) Department of Biomedical Science and Environmental Biology, Kaohsiung Medical University, 100 Shih-Chuan 1st Road, Kaohsiung 80708, Taiwan e-mail: [email protected]
height of an attendant species overlapped with that of the nuclear species, the lower its departure rate. Specifically, canopy attendant species that usually had a lower niche overlap with the nuclear species dropped out of the flock more frequently than understory attendant species. These observations indicate that foraging niche overlap between attendant species and the nuclear species may facilitate the formation of mixed-species bird flocks. It is therefore important to incorporate the role of positive interactions when trying to understand the formation and maintenance of biological communities. Keywords Alcippe morrisonia Attendant species Flocking behavior Nuclear species Positive interactions Timaliidae ¨ berlappung von NahrungsniZusammenfassung Die U schen zwischen vereinzelt anwesenden Arten und den Hauptarten in gemischten Schwa¨rmen ko¨nnte sowohl zu Konkurrenz als auch zu Begu¨nstigung fu¨hren. In dieser Untersuchung stellen wir die Hypothese auf, dass Arten der Kronenbereiche ha¨ufiger in Schwa¨rmen vorkommen, in denen die Hauptarten in der im Kronenbereich Nahrung suchen und dass Arten mit gro¨ßerer Nischenu¨berschneidung mit der Hauptart des Schwarms geringere Abflugraten zeigen. Zwischen 1998
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