Surveys of eleven species of wild and zoo birds and feeding experiments in white-tailed eagles reveal differences in the composition of the avian gut microbiome based on dietary habits between and within species.

The composition of the gut microbiome varies due to dietary habits. We investigated influences of diet on the composition of the gut microbiome using the feces of 11 avian species, which consumed grain-, fish- and meat-based diets. We analyzed gut microbiome diversity and composition by next-generation sequencing (NGS) of 16S ribosomal RNA. The grain-diet group had higher gut microbiome diversity than the meat- and fish-diet group. The ratio of Bacteroidetes and Firmicutes phyla was higher in the grain-diet group than in the meat- and fish-diet groups. The grain-diet group had a higher ratio of Veillonellaceae than the meat-diet group and a higher ratio of Eubacteriaceae than the fish-diet habit group. To clarify the influence of diet within the same species, white-tailed eagles (Haliaeetus albicilla, n=6) were divided into two groups, and given only deer meat or fish for approximately one month. The composition of the gut microbiome of individuals in both groups were analyzed by NGS. There were indications of fluctuation in the levels of some bacteria (Lactobacillus, Coriobacteriales, etc.) in each diet group. Moreover, one individual for each group which switched each diet in last week changed to each feature of composition of bacterial flora. The above results show that the composition of the gut microbiome differ depending on diet, even within the same species.

Mapping the collision risk between two gull species and offshore wind turbines: Modelling and validation.

Promoting the use of renewable energy and conserving biodiversity are conflicting issues that need addressing. While the development of offshore wind facilities/turbines is accelerating, many seabirds have been exposed to collisions with wind turbines. We must identify high collision areas and avoid the construction of wind turbines in these spaces to reduce these conflicts. One solution is to develop useful finer scale sensitivity maps. In this study, we created a fine-scale map of collision risk by spatial modelling using information from bird flights at sea and explored the relative importance of each geographic variable relevant to the risk. Between 2016 and 2019, we collected 3D-location data from 117 black-tailed gulls (Larus crassirostris) of three colonies in two areas and 21 slaty-backed gulls (L. schistisagus) of four colonies in one area of northern Hokkaido, Japan. The spatial models that explain the occurrence of M-zone flight, which is the flight within the heights of high collision risk (20-140 m height), were constructed at a 1 km mesh using a random forest algorithm, a machine-learning tool. The model satisfactory predicted the spatial distribution of M-zone flights using geographic variables and species (correlation coefficient: 0.57-0.94), although data had some degrees of variation between species, years, colonies, and areas. Our model can be applied to other regions, as long as we have general topological information and the locations of colonies and harbors. The distance to the breeding colony and the nearest harbors were important, and the collision risk was 6-7 times higher within 15 km from the colonies and 5 km from harbors. Black-tailed gulls used different sites for foraging and commuting between years, whereas slaty-backed gulls used relatively consistent sites. These variations between species and among years suggest that collecting bird data over multiple years is necessary and effective for creating a generally applicable sensitivity map.

The relationship between pink salmon biomass and the body condition of short-tailed shearwaters in the Bering Sea: can fish compete with seabirds?

Seabirds and large fishes are important top predators in marine ecosystems, but few studies have explored the potential for competition between these groups. This study investigates the relationship between an observed biennial change of pink salmon (Oncorhynchus gorbuscha) biomass in the central Bering Sea (23 times greater in odd-numbered than in even-numbered years) and the body condition and diet of the short-tailed shearwater (Puffinus tenuirostris) that spends the post-breeding season there. Samples were collected with research gill nets over seven summers. Both species feed on krill, small fishes and squid. Although the mean pink salmon catch per unit effort (in mass) over the study region was not related significantly with shearwater's stomach content mass or prey composition, the pink salmon biomass showed a negative and significant relationship with the shearwater's body mass and liver mass (proxies of energy reserve). We interpret these results as evidence that fishes can negatively affect mean prey intake of seabirds if they feed on a shared prey in the pelagic ecosystem.