Mixed-species flocks: an example of niche construction?

Abstract

Mixed-species flocks result from co-evolved relationships between participants: interspecific gregariousness that varies in strength in different species pairs or groups. Such inter-specific associations of birds are a characteristic of most avian communities, observed in diverse habitats from forests to grasslands, estuaries to the open ocean, worldwide in both high latitudes and in the tropics. We explore the consequences of mixed-species flocks in shaping the selective environment and discuss whether the participants in flocks should be identified as niche constructors. As a result of the decision to associate with other species, a bird alters its relationship with competitors; potentially gains access to resources; becomes safer from predators; and may change microhabitat use. The recurrent patterns in the behaviour of disparate unrelated species active in mixed-species flocks have led investigators to conclude that similar selective pressures have shaped their behaviour. However mixed-species flocks are variable in their characteristics, the birds active in them are diverse in form and behaviour, and the selective pressures that have shaped their propensity to join mixed-species flocks must be various. In forming mixed-species flocks, species with specialised roles at the centre of flocks are creating a complex social environment that represents an important biotic selective force shaping their own ecology and behaviour, and that of other species within the avian community. In this review we consider how the spectrum of inter-specific relationships in mixed-species flocks make them an interesting focus for further studies of niche construction by relocation.

Cultural niche construction of repertoire size and learning strategies in songbirds

“…The literature on niche construction in birds has focused primarily on foraging and nest-building behaviors (Tebbich et al 2001;Odling-Smee et al 2003;Jones et al 1996;Harrison and Whitehouse 2011). Previous models have explored various aspects of avian song learning and its evolution: the origin (Aoki 1989) and maintenance (Lachlan and Slater 1999) of vocal learning itself, the preservation of dialects (Planqué et al 2014), the restrictiveness of ''innate learning preferences '' (sensu Marler 1990;modeled in Lachlan and Feldman 2003), and the effect of the song learning program on song divergence and male dispersal (Ellers and Slabbekoorn 2003).…”

Observations of the under-described avifauna of the Mostardas Peninsula, Rio Grande do Sul, Brazil

“…We identified birds as associating in mixed-species flocks if observed foraging in the same immediate area, and when there was evidence of association in the form of calls and other signals (Hutto 1987;Harrison and Whitehouse 2011). During the rapid assessment we encountered four mixed-species flocks involving a total of 15 species.…”

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

“…Most obviously, they are often intraspecifically gregarious ; indeed many are cooperative breeders ). 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).…”

“…It occurs in many different kinds of ecosystems, including pelagic, wetland, and grassland systems, and in many different groups of birds including waterfowl, wading birds, and granivores (see review of Harrison and Whitehouse 2011). Most research, however, has concentrated on flocks in forested systems, for which there are flock descriptions from all continents other than Antarctica ( Fig.…”

“…A second and perhaps more difficult approach is to ask how flocks affect the overall bird community. A recent review (Harrison and Whitehouse 2011) argued that, in an evolutionary sense, the behavior of some species in mixed-species flocks has created unique ecological niches for other species. But the role of species in creating niches for others is also relevant in ecological time, to understand the importance of flocking to conservation.…”