Does niche-overlap facilitate mixed-species flocking in birds?

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 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.Zusammenfassung Die Ü berlappung von Nahrungsnischen zwischen vereinzelt anwesenden Arten und den Hauptarten in gemischten Schwärmen könnte sowohl zu Konkurrenz als auch zu Begünstigung führen. In dieser Untersuchung stellen wir die Hypothese auf, dass Arten der Kronenbereiche häufiger in Schwärmen vorkommen, in denen die Hauptarten in der im Kronenbereich Nahrung suchen und dass Arten mit größerer Nischenüberschnei-dung mit der Hauptart des Schwarms geringere Abflugraten zeigen. Zwischen 1998 und 2000 wurde in Nordosttaiwan schwarmbildendes und Nahrungsverhalten in Trupps von Grauwangenalcippen Alcippe morrisonia außerhalb der Brutzeit untersucht. Mit zunehmender Gruppengröße an Alcippen stieg das Höhenspektrum zur Nahrungssuche an, da mehr Alcippen in verschiedenen Baumstraten nach Nahrung suchten. Die Anzahl der Arten und Individuen der Begleitarten im Kronenbereich in einem Schwarm stieg mit zunehmender Gruppengröße der Alcippen mehr an als die der Unterholzarten. Je mehr die Höhe der Nahrungssuche Communicated by T. Friedl. Electronic supplementary materialThe online version of this article (

Foraging niche segregation in Malaysian babblers (Family: Timaliidae)

“…nigriceps . The hypothesis that vertical distribution is a determinant of bird species assemblage was suggested by [ 52 ] and has been widely tested [ 53 – 55 ]. The findings of the present study provide further support that vertical distribution is important in niche partitioning of bird species and probably led to sympatric babbler species assemblages.…”

Does mixed-species flocking influence how birds respond to a gradient of land-use intensity?

“…In most tropical forests, a significant percentage of the birds are found participating in flocks at any one time [41], with an average of 48% of individuals found in flocks in our region [33]. Mixed-species flocking can increase foraging efficiency (reviewed by Sridhar et al [6]), through social copying [49,50] and the use of other species as beaters by some fly-catching species [51]. Such flocking can also decrease predation risk through a variety of mechanisms, including risk dilution and alarm calling [7,41,52].…”

The structure of mixed-species bird flocks, and their response to anthropogenic disturbance, with special reference to East Asia

“…Many studies, especially on tit-led temperate systems, have shown that tits may change where they feed in trees (Morse 1970;Alatalo 1981;Alatalo et al 1985Alatalo et al , 1987Krams 2001;Jabłoński and Lee 2002) or their foraging technique (Pomara et al 2003) to avoid dominant species in flocks. At the same time, however, other studies have demonstrated that species might actually move their foraging location to be close to other species, particularly leaders (Latta and Wunderle 1996;Hino 1998;Hsieh and Chen 2011;Farine and Milburn 2013), and sallying species adjust their location to capture insects disturbed by gleaners (Satischandra et al 2007;Srinivasan and Quader 2012;Sridhar and Shanker 2014). Valburg (1992) described a primarily frugivorous species that was insectivorous in flocks.…”

“…This gregariousness makes them conspicuous in flocks, and the possibly kin-selected signals they use for intraspecific communication, especially those related to predation threats, can be eavesdropped on by other species Harrison and Whitehouse 2011). Nuclear species also tend to be generalists that range over a wide variety of foraging heights, and leaf-gleaning species that disturb insects as they move, making them attractive to follow for a wide-range of other species (Hino 1998;Hsieh and Chen 2011).…”