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

Abstract

Trophic niche partitioning is a mechanism that facilitates the coexistence of ecologically similar species by sharing their resource use. However, detailed information of the trophic niche in insectivorous birds is usually limited by the lack of accurate identification of consumed food resources. The use of DNA metabarcoding has proved useful for molecular identification of the taxa present in bird faecal samples. Here, we used this molecular technique to study the diets of six steppe passerine species distributed in two Special Protection Areas in central Spain, and to characterize the dietary niche overlap and the prey composition differences between bird species. In total, we distinguished 112 diet items, covering 39 arthropod families of 13 orders. Although significant dietary differences existed in prey species composition, our results indicated a 74% overlap in steppe bird dietary niche, mostly due to high consumption of abundant arthropod prey such as beetles, grasshoppers and spiders in the breeding season by all bird species. The lowest overlap was found for the dietary niches of the Greater Short‐toed Lark Calandrella brachydactyla and Dupont's Lark Chersophilus duponti, a scarce and threatened species, which appeared to be the species with the most distinct dietary niche within the community. Our results make a significant contribution to the knowledge of shrub‐steppe bird diets and their trophic interactions, indicating that some extent of interspecific resource partitioning occurs in the study area, notably between Dupont's Lark and the Greater Short‐toed Lark. Our study demonstrates the value of DNA metabarcoding in the assessment of passerine diets and provides useful ecological results for the design of biodiversity conservation programmes in the increasingly scarce and threatened steppe habitats.

Increased density of conspecifics caused niche contraction in a multispecific passerine assemblage

“…However, the moderate niche overlap between pairs of species observed in our study could also be explained if potential competitors coexist under nonlimiting resources, and consequently, do not need to segregate their use of resources (Chase & Leibold, 2009; Soberón, 2007). In this line, Barrero, Ovaskainen, et al (2023) suggested that food might not be limiting at the bird densities observed in these Iberian steppe sites, despite the high dietary niche overlap found in the same study area (Zurdo et al, 2023).…”

“…They show discreet behaviors, have cryptic plumage and long slender legs adapted to their walking habits, and nest on the ground, where they suffer high levels of predation (Su arez et al, 2009). They are territorial species with a socially monogamous mating system and have an insectivorous diet (Zurdo et al, 2023), at least during the breeding season and for feeding chicks (de Juana, 2005). Ecological similarities among these bird species, as well as the simplicity of the landscape, suggest that these species could experience moderate to high levels of interspecific competition in habitat utilization at the microscale.…”

DNA metabarcoding revealed how time and space do matter -sex does not- in the dietary variation of the endangered Dupont’s Lark

“…We removed every taxa not belonging to Animal kingdom, as well as mammals (human), birds and internal parasites (phyla Nematoda and Platyhelminthes). We also excluded taxa not considered as potential prey items (mites, ticks, springtails [14, 38]). We finally removed MOTUs representing less than 1% of the total number of dietary reads [50] to avoid incorporating false positives resulting from tag-jumping events, and samples with less than 100 dietary reads as they were considered to have failed (negative PCR controls and some Dupont’s Lark samples).…”

“…Diet can also vary among individuals of the same population due to intrinsic factors, such as sex, reproductive status or age [8, 13, 14]. Indeed, sex-related differences on birds’ diet have been typically attributed to morphological and behavioral differences [15, 16], but also to differing nutritional demands during the breeding season due to distinct reproductive roles [17].…”

Nest Features and Nesting Niche Segregation in Five Iberian Steppe Passerines

“…Nests were located and geo-referenced during the breeding season (from mid-March to late-July, covering the complete reproductive period of the species, both resident and migratory), between 2016 and 2019, either by chance while performing other field work (see for example Barrero et al ., 2022; Barrero et al ., 2023; Zurdo et al ., 2023) or after an active search, i.e observing adults showing breeding behaviour (i.e., carrying construction materials or food). Nests or eggs were not handled to avoid increasing predation rates, which are high in these systems (Gómez-Catasús et al ., 2021; Yanes & Suárez, 1995).…”