Foraging guild perturbations and ecological homogenization driven by a despotic native bird species

Abstract

Anthropogenic activities often cause specialized and fragmentation-sensitive species to be replaced by competitive commensal or invasive species, resulting in reduced diversity and biotic homogenization. However, biotic homogenization driven by increased dominance of a native species has rarely been investigated. Increased abundance of competitive species can have important consequences for assemblage dynamics including homogenization of foraging strategies and, potentially, ecological services. This study assesses how changes to bird assemblages due to the occurrence of an aggressive honeyeater alter the foraging profiles of avifauna in 400 woodland sites in nine study regions across eastern Australia, and explores the potential implications for ecological services. We compared beta diversity among sites with a high and low abundance of the aggressive Noisy Miner Manorina melanocephala. Shifts in ecological characteristics of bird assemblages of sites with high and low abundance of Noisy Miners, including mean and variation in niche position, bill length and body size, were explored. Sites with a high abundance of Noisy Miners were more taxonomically and ecologically homogeneous and had fewer species than sites with a low abundance of Noisy Miners. The mean niche positions of bird assemblages changed and were increasingly dominated by larger vertebrate feeders, granivores and frugivores as Noisy Miner abundance increased. The mean body size and bill length of the insectivore species present at a site increased with Noisy Miner abundance. This change in the bird community along with reduced diversity in foraging strategies implies a loss of the ecological functions provided by smaller-bodied species, potentially affecting plant dispersal and regeneration, insect herbivory and ultimately woodland resilience. Our study demonstrates a substantial shift in ecological profile over a broad geographical area as a result of a single native species.

Causes and Consequences of Behavioral Interference between Species

“…For example, in Australia, the native hyperaggressive noisy miner (Manorina melanocephala) attacks most other birds. The resultant population declines of other species led to M. melanocephala being identified as a reverse keystone species by virtue of its subcontinental-scale effect on entire avifauna assemblages [55][56][57].…”

“…For example, in Australia, the native hyperaggressive noisy miner (Manorina melanocephala) attacks most other birds. The resultant population declines of other species led to M. melanocephala being identified as a reverse keystone species by virtue of its subcontinental-scale effect on entire avifauna assemblages [55][56][57].Habitat Partitioning and Coexistence The altitudinal replacements examples (above) illustrate how aggressive interference could foster coexistence between species on a regional scale where, in the absence of interference, one species might expand its niche and drive the other extinct [17][18][19]. Similar outcomes are possible on a finer geographic scale when habitats occur in a mosaic of low-and high-quality patches.…”

The Influence of Avian Biodiversity and a Weedy Understorey on Canopy Arthropod Assembly

“…Further studies are essential to test whether there is an effect of seasons, climate and tree host species. The important role of avian predators in regulating insect community dynamics is emphasised in the current literature with correlated indirect effects on the host plant, such as dieback [26] [68] [72] [73]. However, a possible bias may be reflected here for publishing significant results, as suggested by Low and Connor [74].…”

“…[51] [60] [61], as well as data from studies on despotic avian species e.g. [26]- [28], have shown similar effects for canopy arthropods. Our results also showed that the assemblage of the insect canopy community was not significantly affected by bell miner presence.…”

Implications of vegetation clearing biases for the interpretation of landscape-scale species-area relationships

“…This may reflect the fact that Manorina honeyeaters often favour more productive areas , which may support more individuals and therefore more species through greater energy and resource availability (Storch et al, 2005;Watson, 2011). Furthermore, noisy and yellow-throated miners tend to have their strongest adverse effects on smaller birds, although they are also associated with increases in larger birds (Howes et al, 2014;Kutt et al, 2015). Thus, it may be that undesirable compositional differences such as site-scale homogenisation of bird communities arise as a result of Manorina occurrence (Howes et al, 2014;Kutt et al, 2015), but that landscape-level species richness may not necessarily be reduced in landscapes with many Manorina honeyeaters.…”