Molecular scatology and high-throughput sequencing reveal predominately herbivorous insects in the diets of adult and nestling Western Bluebirds (Sialia mexicana) in California vineyards

Abstract

ABSTRACT Determining the ecosystem function of high-order predators is critical for evaluation of food web interactions. Insectivorous birds are abundant predators in many ecosystems yet because they forage upon small taxa, it remains largely unknown whether birds are providing ecosystem services in the form of pest control or disservices by preying upon predaceous arthropod species. We extracted DNA from noninvasive fecal samples of adult and nestling Western Bluebirds (Sialia mexicana) in California vineyards. Using universal arthropod-specific primers, we sequenced prey items via massively parallel sequencing on the Illumina MiSeq platform. Bluebirds consumed a broad diet comprising 66 unique arthropod species from 6 orders and 28 families. Aedes sp. (mosquitoes: Culicidae), a previously unknown prey, was the most common item recovered, occurring in 49.5% of the fecal samples. Ectoparasitic bird blowfly (Protocalliphora) DNA was found in 7% of adult and 11% of nestling samples, presenting clear evidenc...