Resident parasites influence appearance, evolution of barn swallows

JUNE 24, 2020

by Kelsey Simpkins, University of Colorado at Boulder

Barn swallows live almost everywhere on the planet, recognizable by their forked tail and agility in the air. Yet while they share these characteristics, these little birds often look slightly different in each place they live—with some so distinct they're splitting off to become new species.

Researchers at CU Boulder think that local parasites are influencing why barn swallows in Europe, the Middle East and Colorado are choosing their mates differently. Their new research, published in Evolution, finds that these parasites could be playing an important role in changing the traits displayed to attract mates early in the process of the creation of new species.

"It's possible we haven't appreciated just how important parasites might be in shaping the evolution of their hosts," said lead author Amanda Hund, who conducted the research as a doctoral candidate in the Ecology and Evolutionary Biology Department.

Every organism, including humans, has co-evolved with a unique community of parasites, that by definition live at the expense of their host. While they are not beneficial to us like many other microbes are, parasites have shaped our own immune system, pheromones and even our mate selection, previous research has shown.

Hund set out to characterize as many parasite communities as she could in barn swallows, to find out if they could be influencing their mate selection, and therefore the male birds' physical traits and the creation of new species.

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Feeding bluebirds helps fend off parasites

FEBRUARY 4, 2020

by University of Connecticut

If you feed the birds in your backyard, you may be doing more than just making sure they have a source of food: you may be helping baby birds give parasites the boot.

New research published in the Journal of Applied Ecology from UConn assistant professor of ecology and evolutionary biology Sarah Knutie shows that feeding bluebirds can have a significant impact on parasitic nest flies feeding on baby bluebirds.

Parasitic flies can be found in the nests of many bird species, and some can have significant impacts on nestling survival.

The flies lay eggs in the nests, and once the eggs hatch, the larvae feed on the blood of nestlings by drilling holes through the young birds' skin.

In the case of bluebirds, Knutie says it appears nestlings are generally tolerant of the flies, meaning they can sustain high loads of parasites but not suffer significant negative impacts on survival and growth. However, the parasite removes a lot of blood from the nestling, which could have lasting impacts.

"Bluebirds do not have a detectable immune response to the parasitic flies," says Knutie. "Since backyard bird feeding by humans is so popular, I was interested in how giving these birds food could influence their immune response against the parasite, and whether there is a particular time during the breeding season when supplemental feeding is most effective."

To perform the study, Knutie and her father set up 200 nest boxes in northern Minnesota. She followed each nest for the presence of bird eggs, and then, when the eggs hatched, fed some of the birds live mealworms.

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Parasites affect flight ability of wild seabirds, new study finds

Date:  May 30, 2018

Source:  University of Liverpool

A study led by the University of Liverpool and the Centre for Ecology & Hydrology (CEH) has found that parasites affect flight ability of wild seabirds, which may make it harder for them to raise chicks.

The researchers studied a population of European shags on the Isle of May National Nature Reserve, Scotland and measured how parasites affect energy levels and behaviour of individual birds, something which hasn't been done before in a wild population.

They used an endoscope to count individual worms in the birds' stomachs and miniaturised electronic tags recorded the movement and energy of the birds.

They then calculated the total energy used on each day, and the energy used for flying, diving and resting.

Researchers found that the total energy used per day did not depend on the amount of parasites, but females with higher levels of parasites had more costly flight and spent less time flying each day, presumably to avoid using too much energy.

Olivia Hicks, lead author of the study and a PhD candidate with the University's School of Environmental Sciences, said: "This is the first study to measure the impact of parasites on individual birds in this way

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Human-driven Change Good For Parasites But Bad For Birds In Argentine Forests

Wildlife Conservation Society

A new report by the Wildlife Conservation Society (WCS) and the Disease Ecology Laboratory of Instituto de Ciencias Veterinarias del Litoral, Argentina (ICIVET LITORAL, UNL-CONICET) shows that increases in precipitation and changes in vegetative structure in Argentine forests — factors driven by climate change and deforestation in the region — are leading to increased parasitism of young nesting birds by fly larvae (botflies) of the species Philornis torquans.

This great kiskadee chick was infected with botfly larvae. Credit: Dario Manzoli

In temperate and tropical areas of the Americas, wild bird chicks are the target of parasitic flies whose larvae burrow under the skin of the baby birds to feed, causing a disease known as subcutaneous myiasis. In the study, scientists examined the circumstances that drive the abundance of these parasites and found that slight changes in precipitation and vegetation structure, coupled with crowding of nests resulted in large increases in the number of parasites per chick.

The report, Multi-level Determinants of Parasitic Fly Infection in Forest Passerines, appears in the current online edition of PLOS ONE. Authors include Pablo Beldomenico of WCS’s Global Health Program and Director of the Disease Ecology Laboratory, and Dario Ezequiel Manzoli, Leandro Raul Antoniazzi, Maria Jose Saravia, Leonardo Silvestri, and David Rorhmann, all of ICIVET LITORAL, UNL-CONICET.

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