Antioxidant-rich diet reduces stress response during bird migration

Date: June 18, 2020

Source: University of Rhode Island

A research team led by a University of Rhode Island ornithologist had birds fly in a wind tunnel to simulate migration and found that birds that consume dietary antioxidants before and during fall migration can reduce the endocrine stress response triggered by long-duration flights.

The results, published this week in the Proceedings of the Royal Society B, emphasize the importance of protecting habitat with an abundance of available berries containing antioxidants at migratory stopover sites.

"This reduction in the endocrine stress response may be a major benefit birds gain in fall by eating fruits at stopover sites during migration," said Scott McWilliams, URI professor of natural resources science, noting that many species of birds select berries containing anthocyanins, a type of dietary antioxidant present in purple-colored berries. "We know birds prefer certain berries that have lots of antioxidants."

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Tree swallow study: Stressful events have long-term health impacts

Date:  August 28, 2018

Source:  Cornell University

Little is known about how brief yet acute stressors -- such as war, natural disasters and terror attacks -- affect those exposed to them, though human experience suggests they have long-term impacts.

Two recent studies of tree swallows uncover long-term consequences of such passing but major stressful events. Both studies provide information on how major stressful events have lasting effects and why some individuals are more susceptible to those impacts than others.

"We aren't looking at humans in either of these studies, but this research certainly could have implications for how humans respond to stress," said Maren Vitousek, assistant professor in the Department of Ecology and Evolutionary Biology. "The basic way that most vertebrates respond to stress is quite similar. We often see similar things predicting stress resilience in humans and in other animals."

The first study was published in Proceedings of the Royal Society B. Vitousek is the paper's first author.

The researchers developed a new method for manipulating hormone levels in free-living birds: They dissolved a stress hormone (glucocorticoid) in a gel and put it on eggs in tree swallow nests. The females, the only ones who incubate, absorbed the hormone through their skin. They were given five separate doses for an hour each early in their reproductive periods.

After absorbing the hormone, females fed their offspring at lower rates once they hatched, which led to much smaller offspring compared to two types of controls (one type with gel but no hormone on an egg and the other undisturbed). The smaller offspring in turn had lower survival rates.

"The take-home message here is that the hormones that birds would be exposed to if they had a short-term stressor do have these long-term effects," Vitousek said.

The researchers also found that birds exposed to higher doses of glucocorticoid were more likely to endure lingering impacts, she said. This result suggests that individuals who naturally mount a stronger hormonal response to brief challenges may be at greater risk of suffering from lingering effects of stress, Vitousek said.

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Noise pollution causes chronic stress in birds, with health consequences for young

January 8, 2018, Florida Museum of Natural History

Birds exposed to the persistent noise of natural gas compressors show symptoms remarkably similar to those in humans suffering from post-traumatic stress disorder, new research shows.

In a study published this week in the Proceedings of the National Academy of Sciences, researchers found that adults and nestlings of three species showed multiple signs of chronic stress caused by noise pollution, including skewed stress hormone levels, possibly due to increased anxiety, distraction and hypervigilance. 

The study is the first to test the relationships between noise, stress hormones and fitness in animals that breed in natural areas with unrelenting, human-made noise.

Constant noise could be acting as an "acoustic blanket," muffling the audio cues birds rely on to detect predators, competitors and their own species, said study co-author Rob Guralnick, associate curator of biodiversity informatics at the Florida Museum of Natural History. Unable to discern whether their environment is safe, mother birds must choose between staying on guard at the nest and finding food for their young.

Read more at: 

More stress and lower survival rates for birds in young, managed forests

November 14, 2017

Birds experience less stress during the winter months when they shelter in old forests rather than in younger, managed plantations suggests new research. The study in Springer's journal The Science of Nature was led by Indrikis Krams of the University of Latvia and the University of Tartu in Estonia.

Forestry activities are increasingly causing the fragmentation and deterioration of old growth forests, and these affect the diversity of plant and animal species. In Northern Europe, for example, a decrease in old, natural forests has been linked to the population decline of many insect-eating forest bird species because their typical wintering and breeding habitats are disrupted. Having enough food to eat and being in good physical condition is crucial if birds are to survive cold spells and snow storms.

Krams' team focused on willow tits (Poecile montanus), a small type of insect-eating bird found widely throughout temperate and subarctic Europe and Northern Asia. During the non-breeding winter periods, willow tits flock together in coniferous trees to feed on arthropods such as insects and spiders. Previous research has shown that the canopies of mature coniferous trees contain more food than younger ones because arthropods prefer older branches that have more needles attached to them.

This study was conducted in south eastern Latvia in young, managed Scots pine plantations between 35 and 55 years old and unmanaged forests up to 155 years old of mostly Norwegian spruce. The 98 birds from different flocks included in the study were caught twice: once during mild conditions, and again when temperatures were very low. They were weighed and banded, and the researchers evaluated the amount of underskin fat and the condition of their breast muscles. Blood samples were taken immediately after the birds were caught, and then again twenty minutes later to ascertain the effect of being handled. This was done to measure the levels of the stress hormone plasma corticosterone (CORT) in the blood.

Read more at: https://phys.org/news/2017-11-stress-survival-birds-young-forests.html#jCp

Stress in the nest can have lifelong effect

Date: August 16, 2017

Source: The Norwegian University of Science and Technology (NTNU)

Summary:

Why do some sparrows hatch six chicks while others don’t hatch any? How does upbringing affect the remainder of their lives? Physiological stress in the nest can actually affect birds’ DNA and possibly their lifespan.

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Shorter telomeres reveal stress in migratory birds

August 3, 2016

The stress of birds' continent-spanning annual migrations, it appears, leads to faster aging and a potentially earlier death. A new study in The Auk: Ornithological Advances reveals that telomeres, structures on the ends of chromosomes that shorten with age, are shorter in migratory birds than in their non-migratory counterparts.

Migration lets birds take advantage of abundant food resources at high latitudes during the breeding season while escaping the region's harsh winters. However, it's also an enormous undertaking, and the benefits that birds gain from it come with a cost. Carolyn Bauer of North Dakota State University and her colleagues compared the telomeres—bits of non-coding DNA that shorten during cell division and stress—of migratory and resident birds from the same species, the Dark-eyed Junco. They found that the migrants had significantly shorter telomeres than birds that stayed put year-round, suggesting that the migratory birds were aging at a faster rate and that the stress of a migratory lifestyle may actually shorten birds' lifespans.

"Whenever our cells divide, we lose a little bit of DNA on the ends of our chromosomes, and telomeres are simply non-coding regions that act as 'protective caps," explains Bauer. Once they reach a certain threshold of shortness, the cell dies. Importantly, exposure to stress can also make telomeres shorten faster. For their study, Bauer and her colleagues collected blood samples from 11 migratory and 21 resident juncos in Virginia, using only first-year birds to ensure that any telomere differences were not simply due to age. "I've been interested in measuring telomeres since I was undergraduate at the University of Washington," says Bauer. "I remember my introductory biology professor lecturing about telomeres and how environmental stress could cause them to shorten."

Read more at: 

Urban bird species risk dying prematurely due to stress

LUND UNIVERSITY

Birds of the species Parus Major (great tit) living in an urban environment are at greater risk of dying young than great tits living outside cities. Research results from Lund University in Sweden show that urban great tits have shorter telomeres than others of their own species living in rural areas. According to the researchers, the induced stress that the urban great tits are experiencing is what results in shorter telomeres and thereby increases their risk of dying young.

Telomeres are located at the end of each DNA strand in the body's chromosomes, in both great tits and humans. The length of the telomeres can be described as a kind of age biomarker - short telomeres mean short life expectancy. According to the researchers, their study shows that the environment in which great tits grow up determines the length of their telomeres more than their genetics.

"Although there are advantages to living in cities, such as the access to food, they seem to be outweighed by the disadvantages, such as stress - at least in terms of how quickly the cells of the great tits age", says biologist Pablo Salmón who conducts research in the field of evolutionary ecology at the Faculty of Science, Lund University.

The researchers obtained the results by studying great tit groups of siblings. Half of the siblings grew up in the countryside, half in Malmö. After 13 days, blood was taken to measure the length of their red cell telomeres. Pablo Salmón and his colleagues had partly anticipated the outcome, but were still surprised when they saw how big the difference in the length of the telomeres was after only 13 days.

Read on ...

How crows keep their cool

Bird species with larger-than-average brains have lower levels of a key stress hormone, an analysis of nearly 200 avian studies has concluded. Such birds keep their stress down by anticipating or learning to avoid problems more effectively than smaller-brained counterparts, researchers suggest.

Birds in the wild lead a stressful life. Constantly spotting predators lurking in the trees or sensing dramatic changes in temperature is essential for survival, but can leave a bird on the edge of a nervous breakdown. Reading these cues triggers changes in the birds’ metabolism, particularly increases in the stress hormone corticosterone. A sharp release of the hormone within one to two minutes after a cue triggers an emergency response and prepares birds to react quickly to the threat. However, regular exposure to the dangers of the wild and, hence, to high levels of this hormone has serious health consequences and shortens life expectancy.

Not all birds respond to stress in the same way, however, notes Daniel Sol, an ornithologist at the Centre for Ecological Research and Forestry Applications in Cerdanyola del Vallès, Spain. He and colleagues for years have looked at the differences between big-brained birds, such as crows and parrots, and those with smaller brains, such as chickens and quails. The former survive better in nature and also are more successful at establishing communities in new environments.

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Kestrels, Other Urban Birds Are Stressed by Human Activity

May 10, 2013 — American kestrels, small colorful falcons often seen perched along roadways, are abundant in urban and agricultural areas. Shorter grass makes insects, snakes, mice and other prey more visible, and signposts, fences and telephone poles provide excellent perches. However a new study from scientists at Boise State University in Idaho shows that even species considered "tolerant" of human activity may be adversely impacted by human disturbance; Kestrels nesting in close proximity to roads and developed areas had elevated stress hormones and high rates of nest abandonment. The apparently favorable location, then, becomes an ecological trap. 

The peer-reviewed paper "Reproductive failure of a human-tolerant species, the American kestrel, is associated with stress and human disturbance," was published in the British Ecological Society's Journal of Applied Ecology(May 10, 2013). Boise State University graduate student Erin Strasser, now with the Rocky Mountain Bird Observatory, and Julie Heath, a professor in the Boise State Department of Biological Sciences and Raptor Research Center, conducted the research. 

Strasser and Heath conducted research along one of Idaho's major expressways, Interstate 84, and in suburban and rural areas south of the state's capital city of Boise. Since 1987, researchers from Boise State and the U.S. Geological Survey have monitored a number of nest boxes located along the area's roadways, in people's back yards, and in sagebrush-steppe habitat. 

In this study, Strasser and Heath were interested in understanding how human-dominated landscapes affect breeding kestrels, with particular attention paid to the link between disturbance, stress and nest failure. The two monitored the boxes to determine nest fate, and collected a small blood sample from adult birds. The researchers were looking at corticosterone levels, which indicate stress levels (the equivalent in humans is cortisol). Corticosterone can lead to behavioral and physiological changes that allow individuals to cope with stressful situations, while suppressing other activities such as reproduction. 

Continued: http://www.sciencedaily.com/releases/2013/05/130510102025.htm