Birds have surprising gut microbiome composition

Each year, millions of birds crash into windows in cities along their migratory path, many of them losing their lives. Although window collisions are considered a major problem for a variety of species of birds, the bodies of these birds can often be a treasure trove of scientific information. 

In a recent study published in the journal Molecular Ecology, a team of researchers has analyzed fecal samples from 747 birds that crashed into Chicago buildings over a period of three years to investigate the composition of their gut microbiomes. The analysis revealed that the population of microorganisms in these birds’ guts are significantly different from that typically found in mammals.

“In humans, the gut microbiome – the collection of bacteria, fungi, and other microbes living in our digestive tracts – is incredibly important to our general health and can even influence our behavior. But scientists are still trying to figure out how significant a role the microbiome has with birds,” said Heather Skeen, a research associate at the Field Museum in Chicago.

In mammals, different species usually have their own signature arrays of gut microbes which help them digest food and ward off disease. According to DNA studies, these relationships often go back millions of years, with different species co-evolving with their microbiomes in a symbiotic relationship benefiting both the animal and their microbes. 

However, the situation seems to be highly different in birds. “Bird gut microbiomes don’t seem to be as closely tied to host species, so we want to know what does influence them. The goal of this study was to see if bird microbiomes are consistent, or if they change over short time periods,” Skeen explained.

The analysis of fecal samples from 747 birds that crashed into Chicago buildings, belonging to four common species of songbirds called thrushes – supplemented with additional samples collected from thrushes in their summer breeding ground in Michigan, Minnesota, and Manitoba – revealed that, unlike in mammals, the different bird species did not seem to have their own unique set of microbes. By contrast, their gut microbiome appeared to change from season to season and year to year. These findings suggest that birds’ microbiomes are more connected to the environment around them than in the case of mammals.

However, further research is needed to clarify how birds manage to properly digest food and have functional immune systems that can efficiently fight off parasites, if their microbiomes change so much in just a few months.

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By Andrei Ionescu, Earth.com Staff Writer

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