Trophic niche similarities of sympatric Turdus thrushes determined by fecal contents, stable isotopes, and bipartite network approaches

Abstract

An ecological niche has been defined as an n‐dimensional hypervolume formed by conditions and resources that species need to survive, grow, and reproduce. In practice, such niche dimensions are measurable and describe how species share resources, which has been thought to be a crucial mechanism for coexistence and a major driver of broad biodiversity patterns. Here, we investigate resource partitioning and trophic interactions of three sympatric, phylogenetically related and morphologically similar species of thrushes (Turdus spp.). Based on one year of data collected in southern Brazil, we investigated niche partitioning using three approaches: diet and trophic niche assessed by fecal analysis, diet and niche estimated by stable isotopes in blood and mixing models, and bipartite network analysis derived from direct diet and mixing model outputs. Approaches revealed that the three sympatric thrushes are generalists that feed on similar diets, demonstrating high niche overlap. Fruits from C3 plants were one of the most important food items in their networks, with wide links connecting the three thrush species. Turdus amaurochalinus and T. albicollis had the greatest trophic and isotopic niche overlap, with 90% and 20% overlap, respectively. There was partitioning of key resources between these two species, with a shared preference for fig tree fruits—Ficus cestrifolia (T. amaurochalinus PSIRI% = 11.3 and T. albicollis = 11.5), which was not present in the diet of T. rufiventris. Results added a new approach to the network analysis based on values from the stable isotope mixing models, allowing comparisons between traditional dietary analysis and diet inferred by isotopic mixing models, which reflects food items effectively assimilated in consumer tissues. Both are visualized in bipartite networks and show food‐consumers link strengths. This approach could be useful to other studies using stable isotopes coupled to network analysis, particularly useful in sympatric species with similar niches.

Interannual patterns of avian diseases in wild New Zealand avifauna near conservation areas

“…and Passer spp. species (Bosenbecker & Bugoni, 2020) are known reservoirs of avian malaria in New Zealand (Filion et al, 2022; Howe et al, 2012; Tompkins & Gleeson, 2006). By constantly altering the landscape towards agricultural lands around conservation areas, humans have contributed to increased colonization by these species in those localities.…”

“…Therefore, it is vital to improve our understanding of the pressure exerted by this disease on this iconic species. Additionally, biotic interactions with populations of generalist introduced birds well suited for disturbed environments, such as Blackbird ( Turdus merula ), Song Thrush ( Turdus philomelos ) and House Sparrow ( Passer domesticus ) (Bosenbecker & Bugoni, 2020), might enhance the risk of infection in Yellow‐eyed penguins. Indeed, populations of those species have been shown to have high prevalence of avian malaria, potentially acting as reservoirs for the disease and enabling spill‐over towards penguin populations (Howe et al, 2012; Tompkins & Gleeson, 2006).…”

Anthropogenic landscape alteration promotes higher disease risk in wild New Zealand avian communities

“…While the low overall prevalence of infection was unexpected, as many more species are known to be infected by avian malaria ( Plasmodium spp.) in New Zealand (see review by [ 26 ]), it is not entirely surprising, as true generalist species, such as Turdus species [ 47 ], are known to be active reservoirs of vector-borne diseases [ 2 ]. The strong phylogenetic signal observed is also in contradiction with what has been observed in other systems, as larger scale studies have shown that Plasmodium spp.…”

Dietary niche overlap and resource partitioning among six steppe passerines of Central Spain using DNA metabarcoding

“…Species coexistence and competition for resources over evolutionary time contribute to shape the configuration of communities (Leibold et al 2004). Food niche partitioning is one of the main mechanisms through which many species limit interspecific competition (Schoener 1974, Kent & Sherry 2020, and therefore dietary niche overlap studies are of paramount importance for understanding community structure and the coexistence of ecologically similar species (Vieira & Port 2007, Orłowski & Karg 2013, Arrizabalaga-Escudero et al 2018, Bosenbecker & Bugoni 2020). An abundance of food resources may lead to high dietary niche overlap between species, but when foraging resources become less abundant, trophic niche overlap is expected to decrease as interspecific competition becomes stronger (Cody 1974, Schoener 1982.…”