Geographic variation in phenological response and example trajectories of temperature and arrival date. Credit: Hurlbert AH, Liang Z (2012) Spatiotemporal Variation in Avian Migration Phenology: Citizen Science Reveals Effects of Climate Change. PLoS ONE 7(2): e31662. doi:10.1371/journal.pone.0031662
Bird migration timing across North America has been affected by climate change, according to a study published Feb. 22 in the open access journal PLoS ONE. The results are based on a systematic analysis of observations from amateur birdwatchers. This citizen science approach provided access to data for 18 common North American bird species, including orioles, house wrens, and barn swallows, across an unprecedented geographical region.
The researchers, led by Allen Hurlbert of University of North Carolina, Chapel Hill, found that the average arrival time for all species and all locations was shifted earlier by almost a full day for every degree Celsius of warming of the spring temperature, and some species shifted their arrival time by as much as 3-6 days per degree. These results highlight both the power of citizen science for obtaining data, and the potential important impacts of climate change on migration patterns.
"We now have a much better idea of which parts of the country are seeing big shifts in migration timing, and which species may be least able to adapt to the changing climate", says Dr. Hurlbert.
A team of researchers has found a key to the habitat puzzle for improving long-term survival of the endangered Florida Scrub-Jay.
New research published online today in The Royal Society's journal Biology Letters shows that "clustered habitat networks" are needed to maintain the genetic diversity of Florida Scrub-Jays, a species at risk of extinction with just more than 5,000 birds left in the world.
The new research reveals, for the first time, a direct connection between genetic variation of Florida Scrub-Jay groups and geographic distances separating patches of their favored scrub-oak habitat. Researchers analyzed DNA samples of Florida Scrub-Jays and evaluated how genetic differences between them were affected by the gaps of habitat in between them. They found that if habitat patches were separated by more than 2 to 3 miles, the distance was too far to permit free interbreeding – thereby resulting in more inbreeding within isolated groups. Inbreeding reduces genetic fitness, and raises the risk that an isolated population will blink out.
"We now know how to configure the stepping stones of scrub-oak habitat so they can link together Florida Scrub-Jay populations and maintain sufficient genetic diversity to promote long-term survival of the species," says John Fitzpatrick, co-author of the research and executive director of The Cornell Lab of Ornithology. "These research findings will be critical to a revision of the recovery plan for endangered Florida Scrub-Jays."
Fitzpatrick says the findings lay out, for the first time, a precise prescription for sustaining fragmented populations of an endangered species, and could be a model for other examples around the country. For Florida Scrub-Jays, that prescription is to maintain or restore networks of the bird's scrub-oak habitat so that individual preserves would be located within 2 to 3 miles of each other. Fitzpatrick says that because the Florida Scrub-Jay population is broken up into 10 distinct genetic units, these habitat networks would only need to be established locally within the 10 regions of individual populations, not across the bird's entire range in Florida.
"We are now revising the Florida Scrub-Jay Recovery Plan to create the geometry of habitat preserves needed within each of the 10 units of the Florida-Scrub Jay population," says Fitzpatrick, who also is a team leader for the group of government and university biologists working on submitting a revised Florida Scrub-Jay recovery plan to the U.S. Fish and Wildlife Service by year's end.
The Florida Scrub-Jay is the only bird found exclusively in Florida. It was added to the federal Endangered Species List in 1987, with a dwindling population down to less than 10 percent of its pre-settlement numbers. The high, dry, sandy scrub-oak patches where the bird lives and breeds exclusively have been prime real estate for Florida developers and for citrus farms. Today, only about 5 percent of the original scrub-oak habitat remains.
"The pizza is gone," Fitzpatrick says. "We're just trying to save the crumbs, so we can keep the Florida Scrub-Jay and a host of other scrub animals and plants in existence."
By beating their wings, Ruffed Grouse create a low thumping sound, often said to be felt more than heard. Listen to the sounds in a YouTube video narrated by Martha Fischer of the Cornell Lab of Ornithology.
Dicey weather could mean more marital strife for birds coping with climate change, study says
Larus michahellis. Credit: Constantine Alexander. All Rights Reserved
Married people may pledge to stay faithful through good times and bad, but birds sing a different tune — when weather is severe or uncertain, birds are more likely to stray from their mates, says a new study by researchers working at the National Evolutionary Synthesis Center and Columbia University.
The results could mean more marital strife for birds coping with climate change, the researchers say.
Divorce and infidelity are a normal part of life for most birds, which typically nest with one partner for a few months or years, but may have chicks out of 'wedlock' or move on to new mates between breeding seasons.
"Most apparently monogamous birds end up having multiple partners," said lead author Carlos Botero, who conducted the study while at the National Evolutionary Synthesis Center, and is now a postdoctoral fellow at the Initiative in Biocomplexity at North Carolina State University.
Botero and his colleague Dustin Rubenstein of Columbia University wanted to find out if bird divorce and infidelity were more or less likely in dicey climates.
To find out, they studied records of the mating habits of hundreds of bird species, focusing on species where males and females work together to raise their chicks — a large data set that included swallows, chickadees, blue birds, falcons, warblers, sparrows, ducks, geese and gulls.
For each species in their data set, they measured the rate of infidelity — defined as the fraction of nests containing chicks resulting from an 'affair' — as well as the rate of divorce, or the fraction of birds that changed partners between breeding seasons.
When they combined this data with temperature and precipitation records from weather stations near each species' nesting sites, they found something interesting — birds that breed in changeable climates were more likely to cheat.
Infidelity was more common in species that breed in areas with more dramatic seasonal swings between warm and cold. When seasons are severe, promiscuity may pay off as a way of increasing the genetic diversity of the chicks, Botero said. "Mating with multiple partners improves the chances that at least one chick will have the genes to cope with the variable conditions to come," he explained.
The effect was greater for divorce. Birds in unpredictable climates were more likely to cast off their current mate and seek a new partner for the next breeding season, even at the expense of losing valuable breeding time before they paired up again.
"The quality of a potential mate depends on the context," Botero explained. In the Galapagos Islands, for example, finches with bigger beaks are better at finding food during dry periods, when larger, drier, harder-to-crush seeds are more important, whereas finches with smaller beaks do better during wet periods.
The perfect partner during one set of conditions may be a so-so mate at another. But when the length, timing or intensity of annual weather cycles is less certain, it may be harder for a bird to predict, based on conditions during the courting phase, what conditions are likely to be like during the chick-rearing phase. "The more unpredictable the environment is, the more likely birds are to make mistakes [in picking a mate], and the more likely they are to divorce," Botero said.
What does this mean for birds coping with climate change?
"As a result of climate change weather patterns have become more unpredictable, and the frequency of extreme weather events has increased," Botero said.
Whether the findings apply to humans is still unknown, but in birds "we would expect marital strife will become much more common," he added.
The results will appear in the February 16th issue of PLoS ONE.
CITATION: Botero, C. and D. Rubenstein (2012). "Fluctuating environments, sexual selection and the evolution of flexible mate choice in birds." PLoS ONE.
The National Evolutionary Synthesis Center (NESCent) is a nonprofit science center dedicated to cross-disciplinary research in evolution. Funded by the National Science Foundation, NESCent is jointly operated by Duke University, The University of North Carolina at Chapel Hill, and North Carolina State University.
Global warming, extreme weather aggravate habitat loss
Rainbow-billed toucans like the one shown here normally are confined to lower elevations in Costa Rica, but global warming is allowing them to colonize mountain forests, where they compete with resident birds for food and nesting holes, and prey on their eggs and nestlings. Credit: Cagan Sekercioglu, University of Utah
Climate change spells trouble for many tropical birds – especially those living in mountains, coastal forests and relatively small areas – and the damage will be compounded by other threats like habitat loss, disease and competition among species.
That is among the conclusions of a review of nearly 200 scientific studies relevant to the topic. The review was scheduled for online publication this week in the journal Biological Conservation by Çağan Şekercioğlu (pronounced Cha-awn Shay-care-gee-oh-loo), an assistant professor of biology at the University of Utah.
There are roughly 10,000 bird species worldwide. About 87 percent spend at least some time in the tropics, but if migratory birds are excluded, about 6,100 bird species live only in the tropics, Şekercioğlu says.
He points out that already, "12.5 percent of the world's 10,000 bird species are threatened with extinction" – listed as vulnerable, endangered or critically endangered by the International Union for Conservation of Nature (http://www.redlist.org).
The resplendent quetzal (shown here) of Costa Rica’s highlands is one of the main victims of the rainbow-billed toucan’s move to higher elevations due to warming climate. The quetzal’s mountain forest habitat also is growing drier. The quetzal was venerated by the Mayas and Aztecs as the "god of the air" and is the bird most sought-after by birdwatchers visiting Costa Rica. Credit: Cagan Sekercioglu, University of Utah.
Şekercioğlu's research indicates about 100 to 2,500 land bird species may go extinct due to climate change, depending on the severity of global warming and habitat loss due to development, and on the ability of birds to find new homes as rising temperatures push them poleward or to higher elevations. The most likely number of land bird extinctions, without additional conservation efforts, is 600 to 900 by the year 2100, Şekercioğlu says.
"Birds are perfect canaries in the coal mine – it's hard to avoid that metaphor – for showing the effects of global change on the world's ecosystems and the people who depend on those ecosystems," he adds.
Şekercioğlu reviewed the scientific literature relevant to climate change and tropical birds with Richard Primack, a biologist at Boston University, and Janice Wormworth, a freelance science writer and ecological consultant in Australia.
Wormworth and Şekercioğlu coauthored the 2011 book, "Winged Sentinels: Birds and Climate Change." The new article is an updated condensation of that book and another 2011 book Şekercioğlu coauthored, "Conservation of Tropical Birds."
The review was funded by the Christensen Fund – which finances community-based conservation projects – the University of Utah and National Science Foundation.
Putting the Heat on Tropical Birds
Scientists expect climate change to bring not only continued warming, but larger and-or more frequent extreme weather events such as droughts, heat waves, fires, cold spells and "once-in-a-century" storms and hurricanes. Birds may withstand an increase in temperature, yet extreme weather may wreck habitats or make foraging impossible.
"The balance of evidence points to increases in the numbers of intense tropical hurricanes (though hurricane frequency could decrease overall)," Şekercioğlu and colleagues write. "This would predominantly affect tropical bird communities, especially species living in coastal and island habitats."
Şekercioğlu says it is difficult to predict how habitat loss, emerging diseases, invasive species, hunting and pollution will combine with climate change to threaten tropical birds, although "in some cases habitat loss [from agriculture and development] can increase bird extinctions caused by climate change by nearly 50 percent."
In addition, "compared to temperate species that often experience a wide range of temperature on a yearly basis, tropical species, especially those limited to tropical forests with stable climates, are less likely to keep up with rapid climate change."
The researchers say studies indicate:
Climate change already has caused some low-elevation birds to shift their ranges, either poleward or to higher elevations, causing problems for other species. Global warming helped rainbow-billed toucans move from Costa Rican lowlands to higher-elevation cloud forests, where they now compete for tree-cavity nest space with the resplendent quetzal. The toucans also eat quetzal eggs and nestlings.
Birds with slower metabolisms often live in cooler tropical environments with relatively little temperature variation. They can withstand a narrower range of temperature and are more vulnerable to climate change.
Climate change may spread malaria-bearing mosquitoes to higher elevations in places like Hawaii, where the malaria parasite can threaten previously unexposed birds.
Longer and less regular dry seasons and droughts expected during global warming may reduce populations of tropical birds that often time their breeding with wet seasons when food is abundant.
Şekercioğlu acknowledges that "not all effects of climate change are negative, and changes in temperature and precipitation regimes will benefit some species. … Nevertheless, climate change will not benefit many species."
Scenarios for Extinction
Venezuela's scissor-tailed hummingbird has an existing habitat of less than 100 square miles of humid mountain forest. It is currently considered threatened with extinction, and computer models of expected extinctions due to climate change indicate that this species will be among the most likely to go extinct by the end of the century if global warming continues. Credit: Cagan Sekercioglu, University of Utah
A 2008 study by Şekercioğlu and late climatologist Stephen Schneider calculated 60 scenarios of how tropical land bird extinction rates will be affected by various possible combinations of three variables: climate change, habitat loss and how easily birds can shift their range, meaning move to new habitat. Citing those estimates, the new review paper says that "depending on the amount of habitat loss, each degree of surface warming can lead to approximately 100 to 500 additional bird extinctions."
The Intergovernmental Panel on Climate Change has predicted 1.1 to 6.4 degrees Celsius (2 to 11.5 degrees Fahrenheit) of global warming of the Earth's surface by the year 2100, which Şekercioğlu's study converted into a best case of about 100 land bird extinctions and a worst case of 2,500.
He says the most likely case now is considered to be 3.5 C (6.3 F) warming by 2100, resulting in about 600 to 900 land bird species going extinct. These estimates are conservative because they exclude water birds, which are 14 percent of all bird species.
Because they don't travel far, "sedentary" birds "are five times more likely to go extinct in the 21st century than are long-distance migratory birds," says Şekercioğlu.
The review found:
Tropical mountain birds are among the most vulnerable to climate change. Warmer temperatures at lower elevations force them to higher elevations where there is less or no habitat, so some highland species may go extinct.
Climate change and accompanying sea-level rise pose problems for birds in tropical coastal and island ecosystems, "which are disappearing at a rapid rate," Şekercioğlu and colleagues write. Many such ecosystems already have been invaded by non-native species and exploited by humans.
Birds in extensive lowland forests with few mountains – areas such as the Amazon and Congo basins – may have trouble relocating far or high enough to survive.
Tropical birds in open habitats such as savanna, grasslands, scrub and desert face shifting and shrinkage of their habitats.
Rising sea levels will threaten aquatic birds such as waders, ducks and geese, yet they often are hemmed in by cities and farms with no place to go for new habitat.
Tropical birds in arid zones are assumed to be resilient to hot, dry conditions, yet climate change may test their resilience by drying out oases on which they depend.
More Research and Conservation Needed
To better understand and reduce the impact of climate change on tropical birds, Şekercioğlu urges more research, identification and monitoring of species at greatest risk, restoration of degraded lands, relocation of certain species, and new and expanded protected areas and corridors based on anticipated changes in a species' range.
"Nevertheless," Şekercioğlu and colleagues write, "such efforts will be temporary fixes if we fail to achieve important societal change to reduce consumption, to control the emissions of greenhouse gases and to stop climate change."
"Otherwise," they add, "we face the prospect of an out-of-control climate that will not only lead to enormous human suffering, but will also trigger the extinction of countless organisms, among which tropical birds will be but a fraction of the total."
After many years of decline, the bittern (Botaurus stellaris) is re-establishing itself in British wetlands. While its subtle brown plumage make it difficult to spot among reeds, its distinctive foghorn-like call or ‘boom’ is being heard again in Britain thanks to conservation efforts initiated by LIFE. In 1997, the population of bitterns had fallen to 11, and the project, ‘Bittern - Urgent action for the Bittern (Botaurus stellaris) in the UK’ (LIFE96 NAT/UK/003057) was launched to arrest the decline of this bird species, which before the Middle Ages was common in the UK. Its numbers fell first as a result of its desirability as a delicacy, then its interest to taxidermists, and finally the drainage of wetlands. By the end of the project, the beneficiary, the Royal Society for the Protection of Birds (RSPB), reported that numbers had recovered to 30.
A follow-up project, ‘Bittern - Developing a strategic network of SPA reedbeds for Botaurus stellaris’ (LIFE02 NAT/UK/008527) was carried out to expand the range of breeding sites and increase the number of areas suitable for dispersing young and over-wintering birds, The RSPB says that conservation of the bittern has been a “phenomenal success”. According to its monitoring report for 2011, there are now 104 booming male bitterns in Britain and a large increase in the number of nesting sites occurred in the past year (from 41 to 63).
But experts at the RSPB remain concerned about the negative impact of climate change. Rising sea levels could result in tides flooding key freshwater habitats, such as the RSPB site at Minsmere in Suffolk, thus making them unsuitable for the bittern. Droughts are another habitat threat. However, Grahame Madge of the RSPB, told The Guardian that the continued upturn in bittern numbers is “a very encouraging trend”.
Fast-evolving microbe lost a key chunk of its genome after jumping to new host
The house finch (Carpodacus mexicanus) is a common North American songbird. Photo by Geoffrey E. Hill.
A new study of a devastating bird disease that spread from poultry to house finches in the mid-1990s reveals that the bacteria responsible for the disease evolves at an exceptionally fast rate. What's more, the fast-evolving microbe has lost a key chunk of its genome since jumping to its new host, scientists were surprised to find. The missing portion contained the genes that made up the microbe's immune system, researchers report in the February 9th issue of PLoS Genetics.
When thousands of wild house finches started dropping dead from a mysterious eye infection in the Washington, DC, area in the winter of 1994, scientists were puzzled.
The birds had red, swollen, crusty eyes that left them unable to see or forage for food, until they eventually died from starvation or predation. Researchers soon identified the cause — a bacterium called Mycoplasma gallisepticum, a common cause of respiratory infections in turkeys and chickens that was previously known to infect only poultry.
By the time biologist Geoff Hill spotted his first sick bird in Auburn, Alabama, in 1995, the disease had spread through the eastern part of the continent, as far north as Quebec and as far south as Florida. "This was a devastating pandemic," Hill said.
Since its discovery, the epidemic has spread as far west as California, and is estimated to have wiped out hundreds of millions of birds. But scientists are still far from understanding how Mycoplasma gallisepticum gained the ability to spread to house finches — which diverged from chickens and turkeys some 80-90 million years ago — or what turned it into such a sweeping killer.
The red, swollen, crusty eyes in this house finch are the result of a highly-contagious infection caused by the bacterium Mycoplasma gallisepticum. Photo by Geoffrey E. Hill.
In a new study in the journal PLoS Genetics, researchers compared the genomes of a dozen strains of Mycoplasma gallisepticum sampled from infected house finches between 1994-2007, in the years following the initial outbreak. Using a technique called pyrosequencing, "we can measure evolution on very short time scales," said co-author Scott Edwards of Harvard University. Instead of studying the host switch years after it happened, the researchers are able to track it in real time. "We're catching the switch in the act," he added.
In both poultry and house finches, the microbe has been evolving at frightening speed, they report. "It's evolving anywhere from ten to 100 times faster than previous estimates for any other bacterium," said Harvard graduate student and first author Nigel Delaney.
But when the researchers compared the DNA sequences of the poultry strains with those sampled from house finches, they found something surprising — since making the switch, some parts of the parasite's genome have begun to break down.
Mycoplasma gallisepticum has a tiny genome to begin with, with less than 1000 genes, Delaney said. But rather than acquire new genes to help it outwit its new host, the parasite has gradually lost more than 50 genes — particularly those that make up the microbe's immune system.
Mycoplasmas are parasites, but they also have parasites of their own, including naturally occurring viruses called bacteriophages. "One of the main functions [of the genes that were lost] is to help guard Mycoplasma against the attacks of bacteriophages," Edwards explained.
"It was surprising to see a part of the genome that was assumed to be so important suddenly become unimportant," Delaney added.
It seems crazy, but "scientists have seen the same phenomenon before in HIV," said co-author Allen Rodrigo of the National Evolutionary Synthesis Center in Durham, North Carolina. When HIV infects a new host, it doesn't encounter the same threats, so it loses the specific immune defenses that protected it in its former host, Rodrigo explained. These original defenses may be expensive to maintain, Rodrigo said. Studies show that the HIV strains that lose them are able to reproduce more quickly and spread.
"It's similar to the 'use it or lose it' principle," Edwards added.
Mycoplasma gallisepticum can't be transmitted to humans. It can infect other backyard birds —including American goldfinches, purple finches, evening grosbeaks and pine grosbeaks — but none with the devastating consequences like those seen in house finches.
Researchers still don't know which genetic changes enabled the pathogen to reach epidemic proportions in house finches. But if the house finch strains have lost the genetic machinery that protected them in poultry, then reintroducing the parasites to the bacteriophages of their former hosts could be one way to control the disease, the scientists say.
Determining which specific bacteriophages those are, and whether the remnants of the Mycoplasma immune system still provide some protection against them, will take much more work.
"But this study shows that there's a third player that's important to understand this pandemic, which are the bacteriophages. Nobody's looked at that so far. This is the first observation that they seem to matter," Delaney said.
Other authors on the paper (in alphabetical order) include Susan Balenger of the University of Turku in Finland, Camille Bonneaud of the French National Center for Scientific Research (CNRS), Christopher Marx of Harvard University, Naola Ferguson-Noel of the University of Georgia, and Peter Tsai of the Bioinformatics Institute of New Zealand.
The findings will be published in the February 9th issue of PLoS Genetics.
CITATION: Delaney, N., S. Balenger, et al. (2012). "Ultrafast evolution and loss of CRISPRs following host shift in a novel wildlife pathogen, Mycoplasma gallisepticum." PLoS Genetics.
The National Evolutionary Synthesis Center (NESCent) is a nonprofit science center dedicated to cross-disciplinary research in evolution. Funded by the National Science Foundation, NESCent is jointly operated by Duke University, The University of North Carolina at Chapel Hill, and North Carolina State University.
This is a white-crowned sparrow. Photo courtesy of Douglas Nelson, Ohio State University
When mature male white-crowned sparrows duel to win a mate or a nesting territory, a young bird just doesn't get much respect.
Researchers found that older male white-crowned sparrows don't put much of a fight when they hear a young male singing in their territory – probably because the older bird doesn't consider the young rival much of a threat.
But a male sparrow will act much more aggressively if it hears a bird of the same age singing in a territory it claims as its own.
"These male sparrows assess an opponent's fighting ability based on age. And for a mature sparrow, a young male is just not going to scare them," said Angelika Poesel, lead author of the study and curator of Ohio State University's Borror Laboratory of Bioacoustics and the tetrapod division.
Poesel conducted the study with Douglas Nelson, associate professor of evolution, ecology and organismal biology at Ohio State and director of the Borror Lab. Their results appear online in the journal Biology Letters.
This study is one of the first to suggest that some birds use each other's songs – and not just plumage – to help determine a potential rival's age and thus threat level.
The researchers did the study in a migratory population of white-crowned sparrows that nested in a state park in Bandon, Oregon from 2008 to 2011. The researchers have been studying this population since 2005.
A male white-crowned sparrow, like many bird species, uses its songs to claim a nesting territory, win an appropriate mate, and sometimes to find additional females to mate with. Males will often attack and attempt to chase away other birds of the same species that sing in their territories.
In some species of birds, second-year males differ in their plumage and/or their songs from older, more mature birds. In white-crowned sparrows, second-year males have some plumage differences from older males. But this study focused on another difference: second-year males will often sing two or more versions of their species' song before they settle on the one that they will use the rest of their lives.
That means older white-crowned sparrows can tell a youngster by the fact that it will sing more than one version of the species song.
In this study, the researchers mapped out territories of 16 male white-crowned sparrows – eight of which had held territories at the park in previous years (identified by bands placed on their legs in previous years) and eight second-year males that had never held a territory there before.
The researchers placed a loudspeaker within the birds' territories and played recordings that suggested either a second-year bird or an older, mature bird had invaded their territory.
Several measures determined how threatened the birds were by what they perceived as an incursion into their territories.
If the male perceives the bird they hear as a greater threat, it will approach the loudspeaker more closely (to confront the rival), take more flights toward the speaker, and sing more songs.
Results showed that older birds didn't react as strongly when they heard a recording of a second-year bird than they did to one of an older male. In other words, when they heard the second-year male, they didn't approach the loudspeaker as closely, they didn't fly to the speaker as many times, and they didn't sing as often in response.
"Other research suggests that younger male birds are less successful at attracting females than older males. That means older males see these young birds as little threat to them and not worth a lot of attention," Poesel said.
But the study did show that second-year males that had established a territory did respond aggressively when they heard the recordings of other second-year males within their area.
"Another young male that is likely in search of a territory is seen as a strong threat and an equal competitor," she said. "They will elicit a strong, aggressive response from another young bird."
These findings suggest that some male songbirds use each other's song as a way to conduct a "mutual assessment" of each other as a potential rival.
"There's more likely to be a conflict when both of the birds see themselves as equal competitors," Poesel said.
"White-crowned sparrows aren't interested in picking a fight with another bird that is much stronger or weaker than themselves."
The research was supported by a grant from the National Science Foundation.
Tachycineta bicolor. Credit: John Benson, Madison WI
Imagine an environment filled with wind, storms, predators, noise, and limited food and shelter. Then imagine providing and caring for a tiny egg or peeping baby bird in those conditions. The tree swallow and most other wild birds face these stressful challenges on a day-to-day basis.
Virginia Tech biologists recently received a $705,000 National Science Foundation grant to study how these birds respond to stress as well as the behaviors that stress produces. The question driving the research: do stressed out birds make good parents?
Fran Bonier, research scientist in biological sciences, and Ignacio Moore, associate professor of biological sciences, study stress hormones known as glucocorticoids. These hormones are present in most living organisms, including humans, and levels become elevated when a stressful life event occurs, such as danger, injury, reproduction, or parenting.
Glucocorticoids are used to provide the temporary energy boost needed to outrun a bear, dodge a falling limb, or rescue a baby from danger, Moore explained. But he and Bonier are interested in what happens when organisms sustain longer periods of elevated glucocorticoids, such as when a soldier is deployed for six months in dangerous territory, or a tree swallow lives with limited resources for a long period of time.
For their experiment looking at tree swallows, Moore and Bonier partnered with Queens University in Kingston, Ontario, Canada, which operates a biological station that is home to many types of birds. The station provides boxes for the cavity-dwelling swallows to nest in, but otherwise, the birds live in a wild, natural habitat.
Bonier, stationed at Queens, takes blood samples from tree swallow mothers, which must be done within three minutes of human contact to get an accurate, base-line reading. During the next four years, she will compare the glucocorticoid levels in the birds' blood with their observable behaviors as parents. For example, at what level of stress will a bird abandon her young and focus on meeting her own needs? She will also conduct experiments in which she changes the birds' hormone levels, brood sizes, and blood parasite loads and then measures the effects on parenting behaviors.
The scientists predict that they will find one of several competing hypotheses to be true. One possible scenario is that there is no connection between glucocorticoid levels and bird parenting behaviors. In a second scenario, a mother's decision to cut and run will be based on the offspring's age and health—if it's older and healthy, the mother will sacrifice her own needs to increase her young's chance of surviving. A last possible scenario is that the mother will choose to invest in herself when conditions worsen.
The experiments could provide groundbreaking insight into the effects of stress on organisms, as well as the evolution of biological systems. The Tech researchers share the total $800,000 grant with Mark Haussmann, assistant professor of biology at Bucknell University, who will be measuring molecular markers of stress in the birds.
"The grant is going to dramatically change the scope or our research project, increasing our ability to answer important questions," Bonier said. Meanwhile, as part of the grant's outreach component she will offer annual public workshops on box-nesting birds in Ontario. Participants will learn how to build and maintain a nest box as well as identify nesting species.
Λίμνη Κουμουνδούρου: Ο ρημαγμένος υγρότοπος, μέχρι πριν από λίγο καιρό, δεν υπήρχε πουθενά. Αποτελούσε έναν τόπο φάντασμα, ένα σημείο no man's land, όπου απλώς έκλεινες τη μύτη σου και προσπερνούσες. Εδώ και πολλά χρόνια αποτελεί τη χαβούζα αποβλήτων των γειτονικών βιομηχανιών και το σουρωτήρι της υπερχωματερής των Αθηνών! Κι όμως αυτός ο τραγικός υγρότοπος, η λίμνη της Περσεφόνης, η λίμνη του πετρελαίου, αντιστέκεται και προσπαθεί να επιβιώσει μέσα σε μια ανελέητη επίθεση σοκάροντας μας με τη δύναμη και την αντοχή του. Η συλλογική προσπάθεια και η επιμονή 'δίνει' τα πρώτα θετικά αποτελέσματα για τη λίμνη ενσωματώνοντας την στους υγρότοπους της Αττικής! Από 'κει και πέρα πρέπει να διανυθεί ένας πολύ δύσκολος δρόμος μέχρι την απορρύπανση και ανάδειξή της. φιλοξενεί τον μεγαλύτερο πληθυσμό υδρόβιων πτηνών της Αττικής το χειμώνα! Επίσης μαζί με τον υγρότοπο του Σχινιά φιλοξενεί τις παγκοσμίως απειλούμενες βαλτόπαπιες.
