Study shows link between health and size of social group

Date: November 14, 2019

Source: Anglia Ruskin University

A new study has found that crows living in large social groups are healthier than crows that have fewer social interactions.

The research, led by Dr Claudia Wascher of Anglia Ruskin University (ARU), has been published this week in the journal Animal Behaviour.

Dr Wascher and her colleagues studied a population of captive carrion crows over a six-year period. They monitored the behaviour of the crows in different sized groups and measured friendship by ranking the birds using a sociality index.

At the same time, they studied the crows' droppings to measure for the presence of coccidian oocyst, a gastrointestinal parasite that can represent an important health threat for birds.

Increased exposure to parasites and disease transmission is considered as one of the major disadvantages of group living. This new study, however, shows the opposite effect.

The researchers found that crows with strong social bonds, living with more relatives, and in larger groups, excreted a significantly smaller proportion of droppings containing parasites than less sociable crows.

The study did not find a connection between health and the crow's dominance within the group, but found that male crows (33%) were slightly more likely to carry the parasite than females (28%).

Dr Wascher, Senior Lecturer in Biology at Anglia Ruskin University (ARU), said: "Crows are a highly social bird and we found that crows with the strongest social bonds excreted fewer samples containing coccidian oocyst, which is a common parasite in birds.

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Hue of Barn Swallow Breast Feathers Can Influence Their Health

Aug. 21, 2013 — A new study conducted at the University of Colorado Boulder and involving Cornell University shows the outward appearance of female barn swallows, specifically the hue of their chestnut-colored breast feathers, has an influence on their physiological health.

It has been known that in North American barn swallows, both males and females, those with darker ventral feathers have higher reproductive success than those with lighter colors, said Cornell Senior Research Associate Maren Vitousek, who led the new research while a postdoctoral researcher at CU-Boulder. Although there is evidence that breast feather color is significantly influenced by genetics, melanin-based plumage color like that in barn swallows also has been tied to social status and even to circulating testosterone, she said.

The new study showed that both naturally darker barn swallow females and those with artificially darkened breast feathers also had lower levels of oxidative damage, which could ultimately make the birds healthier. Oxidative stress results when the production of harmful metabolites known as free radicals exceeds antioxidant defenses in the birds, which can lead to DNA, protein and fat damage in the birds, said Vitousek.

"Intriguingly, females whose feathers were darkened to resemble 'attractive' birds rapidly adopted the physiological state of darker birds, decreasing their level of oxidative damage," said Vitousek. "These results suggest the appearance of an individual may be an under-appreciated driver of physiological health."

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