High-throughput sequencing reveals dietary segregation in Malaysian babblers

The coexistence of numerous species within a community results from how those species use available resources. Babblers are one of the major groups of Malaysian insectivorous birds, which frequently forage in dense vegetation cover and have a high level of sympatry. Therefore, examining the diet, prey selection and niche segregation of babblers can be challenging. In this study, we used high-throughput sequencing to investigate potential dietary overlap or segregation among 10 babbler species of the four genera of the family Pellorneidae and Timaliidae: Pellorneum, Malacopteron, Stachyris and Cyanoderma in central peninsular Malaysia. We tested the hypothesis that trophically similar species may differ in resource use to avoid competitive exclusion. We identified 81 distinct arthropod taxa from fecal samples, belonging to 71 families representing 13 orders, which were predominantly from 16 dipteran, 13 lepidopteran and 10 coleopteran families. Of all the prey taxa consumed, 45% were found to be distinct across the 10 babbler species, and less than 35% were shared simultaneously by three or more babbler species, indicating minimal dietary overlap. The black-throated babbler Stachyris nigricollis and moustached babbler Malacopteron magnirostre had the most generalist tendencies because they consumed a greater variety of prey taxa. Small dietary overlap values (Ojk) and a relatively wide range of food resources suggest that dietary segregation occurred among the studied babblers. The great diversity of prey consumed revealed the presence of dietary flexibility among the sympatric insectivorous birds, thus reducing any active dietary competition and facilitating the coexistence through niche partitioning.

Diet Diversity and Dietary Overlap of Two Sympatric Vulture Species in Hirpora Wildlife Sanctuary, Kashmir

Bird species that use similar resources are expected to use variant foraging approaches and segregate in order to minimize a possible competition among them. However, if they fail to attain this exclusion, competition results. We studied the diet composition and dietary overlap between two sympatric vulture species: Himalayan vulture (Gyps himalayensis) and Bearded vulture (Gypaetus barbatus), the two important avian scavengers of Hirpora Wildlife Sanctuary of Kashmir Himalaya. Analysis of pellets collected from feeding and roosting sites of these vulture species revealed a significant variation in their food consumption with Himalayan species consuming mostly larger dead mammalian species with higher frequency occurrence of 66.66% of Bubalus bubalus and bearded species the smaller dead mammalian ones with highest frequency occurrence of Ovis aries (83.82%). Diet spectrum of Himalayan vulture was more diverse (H’=1.97) than that of Bearded vulture (H’=1.64). The values of Berger-Parker index (Pimax) follows the reverse order of diversity with Pimax=36.2% for Himalayan vulture and Pimax =48.7% for Bearded vulture. There was very low dietary overlap between the two species (Ojk=0.466; C=0.457) which may favor their co-existence. The management of carrions of livestock and setting up of vulture restaurants is the need of the hour for the conservation of these scavenging birds which are facing high risk of extinction in Hirpora Wildlife Sanctuary.

Dietary Overlap between Native and Exotic Fishes revealed through Gut Content Analysis at Head Baloki, Punjab, Pakistan

An imminent threat to indigenous freshwater ichthyofauna is the introduction of alien fishes that can alter the behavior, population dynamics and native community structure. Thus, it is necessary to understand their feeding behaviour to avoid any unwanted incalculable loss. At sampling site, Head Baloki feeding habits both of native (L. calbasu, C. catla, L. rohita and C. mrigala) and alien (H. nobilis, H. molitrix, C. carpio, C. idella, C. auratus, O. aureus, O. niloticus and O. mozambicus) species were analyzed through frequency of occurrence and percentage by number from January 2017-December 2019. Results indicated that L. rohita remained herbivorous while L. calbasu, C. catla, C. idella and both C. carpio and C. mrigala were detritivore, planktivore, phytoplanktivore and generalist feeders, respectively. H. molitrix and C. auratus showed planktivorus and generalist feeding behaviour, respectively. Tilapia species enlisted as detritivores Whereas, H. nobilis was generalist feeder. Complex dietary overlap has been observed between different co-existing species. Current study has uncovered some surprising results where diet of O. niloticus was altered as detritus feeder. Change in feeding habit of alien fishes is the strategy to make them successful that is in line with current findings from freshwater ecosystem of Punjab, Pakistan.

Seasonal variation in the diet of two predators in an agroecosystem in southern–central Chile

In ecosystems, seasonal fluctuations in the availability of resources can promote effects on species with similar trophic requirements, increasing the probability of interspecific competition. This scenario becomes more evident in human–dominated landscapes where homogenization of space can contribute to the shortage of resources, modifying species feeding behavior to an uncertain degree. Understanding how these species modify their feeding habits within the context of habitat transformation is of special interest. We evaluated the diversity of prey and overlap for two predators, the chilla fox Lycalopex griseus and the barn owl Tyto alba, during three seasons in 2018 (winter, spring and summer). The study was based on the analysis of feces and pellets in a landscape with agricultural predominance in Southern–central Chile. We found the chilla fox had a generalist dietary profile, feeding on a broad spectrum of prey, with predominance of lagomorphs and, to a lesser extent, rodents. In contrast, the diet of the barn owl mainly consisted of small rodents, with little variation across seasons. Analyses of dietary overlap showed fluctuations during the periods surveyed, with a maximum value in winter and a minimum value in spring. Variations in the consumption of prey based on their size could facilitate their coexistence in the study area.

Breeding diets of the Little Eagle Hieraaetus morphnoides and Wedge-tailed Eagle Aquila audax in the Australian Capital Territory in 2011–2019

The diets of the Little Eagle Hieraaetus morphnoides and Wedge-tailed Eagle Aquila audax breeding sympatrically in the Australian Capital Territory during 2011–2019 were compared by analysis of pellets and prey remains (six Little Eagle territories and 13 Wedge-tailed Eagle territories; 69 and 49 collections for a total of 232 and 256 prey items, respectively). Little Eagles took 33% mammals (29% European Rabbits Oryctolagus cuniculus), 44% birds, 6% reptiles and 17% insects by number, and 65% mammals (62% Rabbits), 27% birds, 8% reptiles and <1% insects by biomass. Wedge-tailed Eagles took 59% mammals (23% Rabbits and 19% macropods), 38% birds, 1% reptiles, <1% fish and 1% insects by number, and 89% mammals (20% Rabbits, 38% macropods), 10% birds, and <1% reptiles, fish and insects by biomass. Indices of dietary diversity (Shannon Index and Standardised Food Niche Breadth) were 2.57 vs 3.07 and 0.19 vs 0.24, respectively; Geometric Mean Prey Weights (GMPW) were 164 vs 1392 g, but discounting a biased sample of insects in many pellets from two fledglings, Little Eagle GMPW was more like 340 g. Dietary proportions and some metrics for both species appear to have changed little since the preceding decade, although Wedge-tailed Eagle dietary diversity increased slightly and dietary overlap (80%) increased greatly, concomitantly with some pairs of Wedge-tailed Eagles replacing pairs of Little Eagles. Intraguild predation occurred, including Wedge-tailed Eagle predation on Little Eagles.

High Dietary Niche Overlap Between Non-native and Native Ant Species in Natural Ecosystems

Ants represent a highly diverse and ecologically important group of insects found in almost all terrestrial ecosystems. A subset of ant species have been widely transported around the globe and invade many natural ecosystems, often out-competing native counterparts and causing varying impacts on recipient ecosystems. Decisions to control non-native ant populations require an understanding of their interactions and related impacts on native communities. We employed stable isotope analysis and metabarcoding techniques to identify potential dietary niche overlap and identify gut contents of 10 ant species found in natural ecosystems in Aotearoa New Zealand. Additionally, we looked at co-occurrence to identify potential competitive interactions among native and non-native ant species. Ants fed mainly across two trophic levels, with high dietary overlap. Relative to other ant species sampled, two non-native ant species, Linepithema humile and Technomyrmex jocosus, were found to feed at the lowest trophic level. The largest isotopic niche overlap was observed between the native Monomorium antarcticum and the invasive Ochetellus glaber, with analyses revealing a negative co-occurrence pattern. Sequence data of ant gut content identified 51 molecular operational taxonomic units, representing 22 orders and 34 families, and primarily consisting of arthropod DNA. Although we generally found high dietary overlap among species, negative occurrence between a dominant, non-native species and a ubiquitous native species indicates that species-specific interactions could be negatively impacting native ecosystems. Our research progresses and informs the currently limited knowledge around establishing protocols for metabarcoding to investigate ant diet and interactions between native and non-native ant species.

Exotic Prey Facilitate Coexistence between Pumas and Culpeo Foxes in the Andes of Central Chile

Coexistence between species with similar ecological niches implies species must segregate along one or more niche axes to survive. Space, time, and trophic resources are regarded as the principal axes upon which species segregate. We examined segregation along these niche axes to determine mechanisms underlying coexistence between the two main predators, puma (Puma concolor) and culpeo foxes (Lycalopex culpaeus) in the Andes of Central Chile. We used occupancy modeling to examine space use and overlap, Kernel Density Estimation to determine temporal activity patterns and overlap, and analysis of prey remains in feces to assess diet breadth and similarity. We found high spatial overlap and positive associations between detection of the carnivores lending little support for spatial segregation. Similarly, we found high nocturnal, temporal overlap between pumas and foxes that matched peaks in activity of prey. In contrast, we found relatively low dietary overlap indicating niche segregation likely occurs along the dietary axis. The Puma diet was dominated by introduced, exotic hares and foxes appeared to shift away from hares to rabbits, small mammals, and seeds. Given that lagomorphs are the main dietary resource for pumas in particular, management decisions regarding the control or eradication of such exotic species could negatively affected puma survival.