Microbial communities in hummingbird feeders are distinct from floral nectar and influenced by bird visitation

Abstract

Human provisioning can shape resource availability for wildlife, but consequences for microbiota availability and exchange remain relatively unexplored. Here, we characterized microbial communities on bills and faecal material of hummingbirds and their food resources, including feeders and floral nectar. We experimentally manipulated bird visitation to feeders and examined effects on sucrose solution microbial communities. Birds, feeders and flowers hosted distinct bacterial and fungal communities. Proteobacteria comprised over 80% of nectar bacteria but feeder solutions contained a high relative abundance of Proteobacteria, Firmicutes and Actinobacteria. Hummingbirds hosted bacterial taxa commonly found in other birds and novel genera including Zymobacter [Proteobacteria] and Ascomycete fungi. For feeders, bird-visited and unvisited solutions both accumulated abundant microbial populations that changed solution pH, but microbial composition was largely determined by visitation treatment. Our results reveal that feeders host abundant microbial populations, including some bird-associated microbial taxa. Microbial taxa in feeders were primarily non-pathogenic bacteria and fungi but differed substantially from those in floral nectar. These results demonstrate that human provisioning influences microbial intake by free-ranging hummingbirds; however, it is unknown how these changes impact hummingbird gastrointestinal flora or health.

The effect of toxic pyridine-alkaloid secondary metabolites on the sunbird gut microbiome

“…Of the limited number of studies on avian gut microbiomes, most were carried out on domestic birds like chickens, and turkeys 3 rather than on wild birds. Furthermore, only a few studies have examined the gut bacteria of passerine birds [5][6][7][8][9][10] . As far as we know, there are only three studies on gut microbiota of nectarivorous birds; (i) nitrogen-recycling in the gut of Anna's hummingbirds (Calypte anna) 11 , (ii) gut microbiota composition of the rufous-tailed hummingbird, (Amazilia tzacatl) 9 and (iii) comparison between the microbial communities on bills and excreta of Anna's hummingbirds and blackchinned hummingbirds (Archilochus alexandri) and their food resources (feeders and floral nectar).…”

“…As far as we know, there are only three studies on gut microbiota of nectarivorous birds; (i) nitrogen-recycling in the gut of Anna's hummingbirds (Calypte anna) 11 , (ii) gut microbiota composition of the rufous-tailed hummingbird, (Amazilia tzacatl) 9 and (iii) comparison between the microbial communities on bills and excreta of Anna's hummingbirds and blackchinned hummingbirds (Archilochus alexandri) and their food resources (feeders and floral nectar). 10 The importance of specific bacteria for digestive recycling in avian species with large ceca and well-developed gastrointestinal microbiotas has been documented 12 ; however, most nectarivorous and frugivorous birds have only vestigial ceca. For example, hummingbirds, arguably the most specialized avian nectarivores, have no ceca and perform extremely fast digestion throughout the entire digestive tract, which may limit colonization by bacteria 3,13,14 .…”

Nectar Microbial Diversity and Changes Associated with Environmental Exposure

“…The consistency of detection in nectar types indicates that members of the Proteobacteria are common members of these microbiomes. Nectar communities have previously been found to be dominated by Proteobacteria [58], also comprising the main phyla in three pollinator exposed floral species (Borago officinalis, Centaurea cyanus and Symphytum officinale) but not being detected in non-pollinator exposed 'bagged' flowers of the same species [59].…”

Characterizing the nectar microbiome of the non-native tropical milkweed, Asclepias curassavica, in an urban environment

“…Acinetobacter has been identified as a nectar specialist efficient at producing acid from the metabolism of both glucose and sucrose [80], two sugars commonly found in A. curassavica nectar [47]. Neokomagataea, formerly known as Gluconobacter, is also an acid producing nectar-dwelling bacteria [81,82]. Both of these bacteria have been shown to lower the pH of nectar [80,82], and exert priority effects on late arriving yeast nectar specialists, such as Metschnikowia reukaufii, [67,83] but their effect on Aureobasidium, a yeast generalist very commonly found in nectar [34,[77][78][79], that made up a large proportion of the fungal communities in the nectar samples in this study as well, is yet to be determined.…”