Testing the roles of species in mixed-species bird flocks of a Sri Lankan rain forest

Abstract

Studies of mixed-species bird flocks have found that 'nuclear' species, those important to flock coherence, are either intraspecifically gregarious or are 'sentinel' species highly sensitive to predators. Both types of species are present in flocks of a Sri Lankan rain forest: orange-billed babblers (Turdoides rufescens Blyth) are highly gregarious, whereas greater racket-tailed drongos (Dicrurus paradiseus Linnaeus) are less so, but more sensitive and reliable alarm-callers. We hypothesized that flock participants would be attracted to the playback of both species more than to the clearly non-nuclear yellow-fronted barbet (Megalaima flavifrons Cuvier). Further, we hypothesized that insectivores would prefer babbler vocalizations, as babblers could facilitate their foraging in several ways. We found that the response of insectivores was three times greater during babbler or drongo playback, and eight times greater during playback of these two species together, than during barbet playback or silence. Insectivores did not show, however, any difference in their response to babbler as compared to drongo playback; omnivores and frugivores responded relatively equally to all treatments. Our results show that birds with high propensity to flock, such as insectivores, use the vocalizations of nuclear species to locate flocks and that a sentinel species may be as attractive as a highly gregarious species.

Response of tropical avifauna to visitor recreational disturbances: a case study from the Sinharaja World Heritage Forest, Sri Lanka

“…The sensitivity of individual bird species to visitor recreational disturbances seems to vary with the stratum/ layer of the rain forest usually occupied by bird species. Ashy-headed Laughing-thrush, Dark-fronted Babbler, Spot-winged Thrush and Tickell's Blue Flycatcher, found to be particularly sensitive to recreational disturbances, are all forest birds that usually occupy the understory and edges of jungle trails (Kotagama and Goodale 2004;Goodale and Kotagama 2005;Harrison and Worfolk 2011;Warakagoda et al 2012). As the intensity of human recreational disturbances increased, their presence near the trail declined significantly.…”

“…Layard's Parakeet and Sri Lanka Crested Drongo commonly occupy the canopy or the upper parts of the sub-canopy (Kotagama and Goodale 2004;Goodale and Kotagama 2005;Harrison and Worfolk 2011;Warakagoda et al 2012). As indicated by the results of our ANOVAs in Appendix 2, their abundance was found to be independent from the intensity of recreational disturbances at various distances from the trail.…”

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

“…For example, after observations of elevational gradients suggested interspecific interactions, playback trials were used to demonstrate interspecific aggression (Jankowski et al 2010). In an analogous manner, several studies have used the playback of a species' vocalizations to simulate that species' presence and then measured approaches by heterospecifics to determine the importance of that species to the community (Mönkkönen et al 1996), or specifically to other flocking species (Goodale and Kotagama 2005b;Goodale et al 2012;Cordeiro et al 2014). While these Fig.…”

Bird mixed-flocks and nuclear species in a tecoma savanna in the Pantanal

“…The points in which the playback trials were performed were at least 200 m from each other. This is an adequate distance to avoid the stimulation of the same birds from different points (Goodale and Kotagama, 2005), due to the small territory size (2-4 ha) of Neotropical passerines (Powell, 1989). Also, to avoid repeated stimulations of the same potential respondents, at a given transect, the playback trials were performed only during an observation period.…”

“…Taking in to account that different traits may explain the role of nuclear species (Goodale and Kotagama, 2005), and that in savannas, the nuclear species are the ones with greater sensitivity to the presence of predators (Alves and Cavalcanti, 1996;Ragusa-Netto, 2000, 2002, it is important to examine which traits potentially may be related to the existence of nuclear species in this savanna of the Pantanal. Therefore, in this study, we analyzed the structure and composition of bird mixed flocks in a tecoma savanna in the southern Pantanal.…”