Bluebird

March 19, 2012, 7:45 AM

A Spring Sprung Too Soon Is a Death Blow to Butterfly

By JOSIE GARTHWAITE

Carol L. BoggsAn early snow melt can cause a cascade of negative effects on the Mormon fritillary butterfly.

Early snow melts caused by climate change could deliver a mighty one-two punch to the delicate Mormon fritillary butterfly, shrinking the insect’s favored nectar supply, killing caterpillars and causing a steep population decline, a new studyin the journal Ecology Letters finds.

In all, the researchers report, the combined effects of two consecutive years of early snow melt explained as much as 84 percent of the variation seen in the fritillary’s population growth rate between 1980 and 2005.

“It is very unusual for research to uncover such a simple mechanism that can explain almost all of the variation in growth rate of an insect population,” one of the study’s co-authors, David W. Inouye, a biology professor at the University of Maryland, said in a statement.

The deadly power of an early snow melt has to do with the particulars of the butterfly’s life cycle. During the first summer of a female fritillary butterfly’s life, she lays eggs and dies. Caterpillars from these eggs spend the winter without food and become adult butterflies the following summer.

The adult butterflies eat nectar, mostly from the aspen fleabane, which blooms from mid-late July to mid-late August — the peak of the fritillary flight season. The number of eggs laid has been found to depend upon how much nectar the fritillary consumes, according to laboratory experiments cited in the journal paper.

By analyzing decades of data on fritillary populations, aspen fleabane blooms and snow melt dates in the Colorado Rocky Mountains, scientists discovered that one early snow melt can throw these phases out of whack. Working out of the Rocky Mountain Biological Laboratory, Dr. Inouye and the the study’s other author, Carol L. Boggs, found that two consecutive years of early snow melt and frosts at the beginning of the growing season make matters worse for the fritillary.

That is because early season frosts can kill both young caterpillars and aspen fleabane buds. As snow begins to melt, signaling winter’s end, the caterpillars and fleabanes enter a development stage in which they are poorly equipped to survive frost. If flower buds are killed off early in the season, that means less nectar will be on tap for each butterfly come summer, which in turn leads to fewer eggs. So the adults are eating less and laying fewer eggs, while the next generation is being struck down by frost.

Dr. Boggs and Dr. Inouye considered more than 30 years of records on the first day of bare ground, and the number of aspen fleabane flowers blooming in seven wildflower plots in the Elk Mountains of Colorado. They analyzed the annual population density of male fritillaries during nine pairs of sequential years between 1980 and 2005.

Estimated population densities during that time spanned two orders of magnitude, ranging from just 28 males per hectare (2.47 acres) in 1985, apparently due to a severe snowstorm in late June, to nearly 4,500 males per hectare in 1980. More often, the researchers found fewer than 2,000 fritillary males per hectare.

The road is not getting any easier for the Mormon fritillary, said Dr. Boggs, a professor of biology at Stanford.

“We already can predict that this coming summer will be a difficult one for the butterflies,” she said in a statement, “because the very low snowpack in the mountains this winter makes it likely that there will be significant frost damage.”

 

February 7, 2012, 8:07 AM

Crossed Fingers for a Threatened Butterfly

By JIM WITKIN

Stuart WeissThe Bay checkerspot butterfly, which conservationists are trying to reintroduce in Edgewood Park in Northern California. The insect is viewed as a poster child for the harmful effects of nitrogen on biodiversity, which could be even more profound than the impacts of global warming.

If you stand with your back to the sun and inspect the place on the ground where your shadow is cast, you might spot the tiny larvae of the threatened Bay checkerspot butterfly.

“It takes some practice,” said Stuart Weiss, a conservation biologist from the Creekside Center for Earth Observation. “But when you see a little black object that stays black, that’s usually a checkerspot.”

Dr. Weiss explained the technique as we hiked through the grasslands ofEdgewood Park, a 500-acre nature preserve on the San Francisco peninsula where I have been volunteering.

To reintroduce the checkerspot to the park, Dr. Weiss and his team placed 4,000 larvae, or caterpillars, here last winter. Over the next several weeks, he and several volunteers whom he refers to as “checker spotters” will be searching their shadows for signs of success: a new batch of larvae, descendants from last year’s transplants, that will be transformed into thousands of bright orange and black spotted butterflies in late March.

While the work may seem tedious, especially for an insect whose adult life as a winged butterfly spans a mere 10 days, the study of this tiny creature has far broader implications. The checkerspot, Dr. Weiss explains, “has become the poster child for the effect of nitrogen on the environment.” The impact on California’s biodiversity could be even more profound than that of global warming, many scientists say.

Vehicle exhaust from nearby Interstate 280 deposits up to 15 pounds of nitrogen per acre each year in the park. The interstate runs along the park’s western border, carrying more than 100,000 cars between San Francisco and San Jose on a busy day.

Nitrogen from car exhaust fertilizes the soil just as common lawn fertilizer does and favors faster-growing nonnative plants. “It’s a matter of competitive ability — the nitrogen-rich soil produces a very strong growth response in annual grasses, like Italian ryegrass,” Dr. Weiss said. “They thatch over and smother native plants.”

As native plants disappear, so do the native species like the Bay checkerspot that depend on them. “When you continue to dump nitrogen into the atmosphere, it has all sorts of negative impacts on the ecosystem, on human health, on the air you breathe and the water you drink,” Dr. Weiss said.

The Bay checkerspot once thrived at Edgewood but has not been seen here since 2002. Since then, an aggressive program of mowing and weeding has helped keep invasive plants in check and restore the native grasslands.

Using grant money from the San Mateo Parks Foundation to finance the work, Dr. Weiss and his team collected 4,000 Bay checkerspot larvae last winter from Coyote Ridge park in San Jose, the only remaining habitat for the species. They carried the larvae to Edgewood and placed them over 20 acres on the west side of the park, where its favorite meal, the native California plantain, is plentiful.

During this year’s hunt, which runs throughout February and March, the team hopes to find 4,000 new larvae. A lot depends on the weather conditions, Dr. Weiss said. A wet winter and a cool spring are ideal, as sufficient moisture in the soil helps extend the lifespan of the plants that support the larvae and adults.

Ultimately, the project will be counted a success if 2,000 adults are observed flitting among the wildflowers in late March. Once the adults appear, over the course of about 10 days, they will feed on nectar from the wildflowers, mate, lay their eggs on the native plantain and then die. The annual cycle begins again.

Based on early counts of larvae, Dr. Weiss is optimistic about this year’s outcome, although he expects it will take additional cycles to re-establish the butterfly at Edgewood.

The checkerspot is not the only threatened species that occupies his time. In a remote corner of the park, he points to a few square meters of ground that hold the only known remaining patch of the San Mateo thornmint, an endangered annual wildflower. The plant has also fallen victim to invasive Italian ryegrass, its population dwindling to a few hundred plants by 2008.

Thinning the nonnative grasses and carefully replanting thornmint seeds has brought the population back to nearly 3,500 plants. He is hopeful that the plant has reached critical mass and may now come back on its own without his continuing intervention.

Although the tiny thornmint has not attained the celebrity status of the Bay checkerspot, Dr. Weiss says that nurturing the species is important work. “It’s an utterly unique form of life and we shouldn’t let it go extinct on our watch,” he said.

Jim WitkinStuart Weiss, a conservation biologist,  demonstrating the technique of “shadow hunting” to find Bay checkerspot caterpillars in the grass. Interstate 280 is in the background.  

 

pulling focus

OBSERVATORY

Jumping Spiders Focus Like a Camera to Hunt

By SINDYA N. BHANOO

Published: January 30, 2012

Jumping spiders do not weave webs. Instead, they jump about and then pounce on their prey. For this reason, depth perception is very important to their survival.

E

Science/AAAS

A jumping spider's eyes show how far to pounce by sharpening the prey and blurring the background.

Now Japanese researchers have discovered that the spiders use an unusual technique to estimate how close or far away an object is.

The technique, called image defocus, involves blurring out objects in the distance while keeping closer ones sharp. Jumping spiders are the only animals known to use it, but a camera with a good lens demonstrates the same principle — keeping a person’s face sharp in the foreground while blurring out the trees in the background.

Takashi Nagata and Mitsumasa Koyanagi of Osaka City University and their colleagues write about the jumping spiders in the current issue of Science.

The researchers studied each of the four layers of the retina in one of the spider’s eyes. They found that green light is never in focus in one of the layers, and that in another layer it is always in focus.

“So the spider seems to capture a sharp image and a blurry image and compare the information to estimate the distance of an object,” Dr. Koyanagi said. Depending on whether a fly, for instance, looks blurry or sharp, the spider can decide how far to jump.

“It’s done in real time, so studying this may help develop better computer vision,” Dr. Koyanagi added.

 

What I want...

Earthly Delights | The Slug and the Squirrel Terrariums

DESIGN

 |

By MADISON SHIMODA

 | FEBRUARY 28, 2011, 4:45 PM

Photographs courtesy of the Slug and the Squirrel

When Sara Moonves, T’s fashion editor, received a terrarium as a holiday gift, the entire office was smitten. This bijou oasis provided a moment of tranquility in the midst of the daily style department chaos. Incredibly low-maintenance (they only need to be watered once), terrariums are just the thing for urbanites like us who are strapped for space and yearning for a patch of greenery. Further inspired by “Nocturne of the Limax maximus,”the artist and landscape designer Paula Hayes’s recent installation of cast acrylic and hand-blown glass containers filled with tropical plants at the Museum of Modern Art, we wanted to know where we could get a mini-garden all our own.

“I was shocked to learn that not everyone makes terrariums!” says the designer Jose Agatep, who grew up making terrariums with his father in their garden. Agatep surprised friends with these handmade flora snow globes, and they wanted more. “People started calling me an artist!” he excitedly recalls.

His terrariums, which he designs under the name the Slug and the Squirrel, come in all shapes and sizes and are a recent addition to Anthropologie’s home décor collection. The containers are welded together from vases, bottles and cups Agatep that finds at flea markets and then embellishes with silver. He fills them with plants from a local Philadelphia flower shop and soil and wood chips from along forest trails and train tracks. (He particularly likes taking components from the outdoors because they come with the bacteria and insects necessary to maintain the self-contained ecosystem, and sometimes they sprout mushrooms, much to his customers’ surprise.) “Everything is so … technology,” he says. “We need the nature. It’s a good reminder of how it used to be.”

The Slug and the Squirrel terrariums ($28 to $398) are available at select Anthropologie stores.

 

How I like to be wooed myself

OBSERVATORY

Design and Illusion, to Impress the Ladies

By SINDYA N. BHANOO

Published: January 23, 2012

Great bowerbirds, which live in Australia, get their name from the elaborate grass structures, or bowers, that the males build to woo prospective mates.

The bowers are impressive, featuring a long avenue of bones and stones — called a gesso — for females to inspect. But now scientists are reporting an even more impressive feature: The gesso includes a sort of optical illusion to make it appealing to females.

The males place smaller objects closer, and the larger ones farther away, creating the illusion that all the objects are similar in size, and that the gesso is smaller than it actually is. The better the illusion, the greater the male’s reproductive success.

“It’s the female’s view” that is most important, said John Endler, an evolutionary ecologist at Deakin and James Cook Universities in Australia, who was involved in the research. He and a Deakin colleague, Laura Kelley, report their findings in the current issue of the journal Science.

In a previous study, in which the scientists inverted the display, the birds restored it within three days, a sign of that the small-to-large configuration is critical. Females enter the grass structure and observe the gesso, while the male presents the female with various colored objects, usually fruits. She is able to see only the male’s head, and makes her decision based on presentation.

If she sticks around long enough, the male takes it as a positive sign and goes out to mate with her. A female might visit several males before deciding.

In a way, Dr. Endler said, the gesso display could be called artistry.

The illusion “is evidence that bowerbirds are actually creating art,” Dr. Endler said. “It can be regarded in an aesthetic sense because judgments are made.”

 

Birds on a lake

India Jane and I went early to pick up Oona from art class so she could feed the birds. It was a lovely sunset and the birds were happy to see us.

December 13, 2011, 4:04 pm For Sparrows, Terror Has Grim Consequences

By RACHEL NUWER

Michael ClinchyJust hearing the calls and sounds of predators frightened mother songbirds so much that they fed their nestlings less often, and more of them starved to death, according to a new study.   

Fear makes the wolf look bigger, or so goes a German proverb. And new research underlines the scientific basis for the adage: the mere hint of the presence of a predator can have life-or-death consequences for the terrorized prey, regardless of the true threat.

Biologists typically associate predator-prey relationships with direct killings, but a new paper in the journal Science explores the dynamic from a different angle. Researchers exposed song sparrow nesting areas in British Columbia to the sounds of other animals, including predators. The impact was far from trivial: mother birds that perceived predator presence had 40 percent fewer offspring than birds that were not exposed to predator noises.

“Animals in every taxa respond to predators,” said Liana Zanette, a population ecologist and conservation biologist at the University of Western Ontario and the lead author of the paper. “And being afraid of predators can affect the number of kids you produce.”

Dr. Zanette and her colleagues conducted their experiment in an area with minimal human disturbances. They surrounded bird nests with electric fences and netting to exclude actual predators and set up 24-hour surveillance cameras. The birds were divided into two groups; one was exposed to threatening predator sounds like crunching leaves, cawing crows and shrieking hawks, and the other listened to neutral sounds produced by geese, hummingbirds and seals.

The tapes were played every few minutes on a four-days-on, four-days-off cycle throughout the duration of the sparrows’ 130-day nesting cycle. The cycles of silence ensured that the birds did not become habituated to the noise. The researchers suggest that the level of constant noise, be it predator sounds or neutral sounds, was comparable to the noise level experienced by animals in urban parks.

Females exposed to predator noises suffered for it: they produced fewer eggs, and a greater proportion of them failed to hatch. More of their nestlings died, too, and those nestlings that did survive weighed less than their nontraumatized counterparts. Mother birds exposed to the hostile sounds built their nests in denser, thornier patches, were more skittish, spent less time at the nest and made fewer feeding visits compared with birds exposed to neutral sounds — all factors that contributed to their comparatively low success in rearing their young.

“Birds really seem to understand information in sounds,” Dr. Zanette said.

Although the results were gathered during a single breeding season, they could have population-level implications over a longer period of time. Not only did the frightened mothers produce fewer fledglings, but Dr. Zanette suspects that the surviving offspring probably have a decreased chance of thriving since most were underweight.

If young birds are under stress — for example, because they do not get enough to eat — they can also suffer from brain damage, which interferes with the ability to learn critical skills like where and how to forage. Dr. Zanette and colleagues are currently investigating whether or not the fledglings of scared mothers have a reduced survival rate after leaving the nest.

Bird behavior has a wider applicability in the animal kingdom. When wolves were reintroduced to Yellowstone National Park in 1995, Dr. Zanette said, their elk prey “behaved just like frightened sparrows.” Mother elk kept a wary eye out for predators rather than concentrating on feeding, elk gathered in more secure but less food-rich areas, and within a few years elk populations declined 50 percent.

That was not because wolves ate half the elk population — there are not enough wolves in Yellowstone to pull off such a feat — but because of a reduction in elk pregnancy rates. The shrinking elk population helped the entire ecosystem, which had been overgrazed by too many hungry elk.

Dr. Zanette thinks a finer understanding of these interactions can help inform conservation decisions like whether or not to reintroduce wolves to Scotland. Many areas of that country are overgrazed by deer, and wildlife managers are considering bringing the once-native wolf back to its old hunting grounds as a natural form of deer control.

The observation about sparrows and elk suggests that a large number of wolves probably won’t be necessary to get the job done; just enough to scare the deer into ecological balance may suffice.

Bluebirds rule vineyards

November 14, 2011, 7:35 am

In a California Vineyard, Bluebirds Earn Their Keep

By RACHEL NUWER

Julie JedlickaA male Western bluebird on a vineyard trellis.

In an innovative study, nest boxes installed at a California vineyard attracted hundreds of birds that picked the farmers’ crops clean of pests in exchange for the free housing. The experiment is heartening news for conservationists amid reports of shrinking habitats and population declines for so many species.

“Placing songbird nesting boxes in agricultural landscapes can provide suitable nesting sites for a lot of birds that used to be plentiful 100 or 200 years ago but lost their natural landscapes,” said Julie Jedlicka, an ornithologist at the University of California, Berkeley.

Dr. Jedlicka set out to study whether installing the nest boxes would help attract the birds and reduce pests. Her research, published last week in the journal PLoS One, confirmed her hunch. Compared with control areas in the same vineyard that did not have the nest boxes, areas with the boxes attracted twice as many birds early in the nesting season and had 2.6 times as many birds later in the breeding season.

Western bluebirds were responsible for much of the increase: 313 of them were counted at the nest box sites, versus 39 in control portions of the vineyard.

Over all, 1,122 birds representing 25 species made an appearance. Both the nest box sites and the sites without boxes had about the same number of species present, but the numbers of insect-eating species was 50 percent greater in areas with the nest boxes. Insectivorous birds removed about 2.4 times as many insect larvae at the nest box sites as they did in the control areas.

Laura BarrowJulie Jedlicka checks on a nest box in a vineyard in central California.

Dr. Jedlicka’s idea is not new. From 1885 to 1940, the federal Department of Agriculture devoted resources to studying “economic ornithology,” or using birds as biological controls for agricultural pests. After pesticides like DDT were developed during World War II, that approach largely faded in favor of a quick chemical fix. Now Dr. Jedlicka envisions a revival of economic ornithology through the lens of ecosystem services and bird conservation.

As cavity-nesting songbirds, bluebirds are particularly well suited to the task. Although they look for enclosures to build their nests, they tend to prefer those found within otherwise open spaces, and agricultural fields fit the bill. What is more, “they respond rapidly to new nesting opportunities,” Dr. Jedlicka said. Within one year of placing about 100 nest boxes in two vineyard study sites, bluebird families occupied over 75 percent of the boxes, she said.

Bluebirds are not picky about what they eat: caterpillars, beetles, and grasshoppers are all fair game. A bluebird family of five nestlings requires 125 grams of arthropods per day, and bluebird pairs can produce two broods per year.

The birds probably won’t replace farm pesticide use entirely. Some pests, like spider mites, are too small for bluebirds to consume.

Dr. Jedlicka hopes that wineries will gradually adopt the “Bird Friendly®” stamp, a certification already widely available for coffee growers. Vintners could then market their products to the growing eco-friendly consumer sector while helping the birds.

Wine growers aren’t the only farmers who can benefit: the combined range of North America’s three bluebird species extends across the United States. Farmers in Florida already use nest boxes to attract insect-eating birds, as do some apple orchard managers in New England.

Nest boxes can be used to attract bluebirds to urban gardens as well. “I imagine it would be difficult to find an agricultural system where this wouldn’t work,” Dr. Jedlicka said.

Bats talk superfast

 

Bats Find Their Way With Superfast Vocal Muscles

By ANAHAD O'CONNOR

Lasse Jakobsen and Coen Elemans

Daubenton’s bats (Myotis daubentonii) capturing prey.

By ANAHAD O'CONNOR

Published: September 30, 2011

The last thing an insect hears before it is eaten by a bat is what scientists call the terminal buzz, a sonar-based call that bats use to track their prey. Bats can produce these echolocation calls at a rapid rate, up to 190 calls per second; they also use the buzz to navigate.

It was never known precisely how they produced these calls so quickly. But now scientists are reporting that bats are able to make these calls thanks to superfast vocal muscles; they are the first mammals known to have this type of muscle. The muscles are very weak, but so quick that they can contract 100 times as fast as ordinary human muscles and 20 times the speed of humans’ fastest muscles, the ones in the eye.

Until now, superfast muscles had been found only in songbirds, rattlesnakes and certain fish, all of which use them to produce sound. Researchers at the University of Southern Denmark and the University of Pennsylvania wanted to see if they existed in mammals as well, which led them to look at Daubenton’s bat, a species found throughout Europe and Asia.

“I thought, ‘If we’re going to find them in mammals, it’s going to be bats,’ ” said an author of the study, Coen Elemans, an assistant professor at Southern Denmark. “If you hunt prey that is fast-moving and also evading you, it’s very important to produce these calls at a very, very high rate.”

In their study, which appears in Science, Dr. Elemans and his colleagues recorded the bats’ calls and determined when the echoes reached their ears. The scientists found that the bats’ brains could process the sounds even faster than their muscles could generate them: up to 800 calls per second, in some cases, before the calls would start to overlap with the echoes and cause confusion.

Spider Season

The Amish have a saying about spiders that I adhere to-except when they venture inside my house. "If you want to live and thrive, let the spider stay alive." They eat bugs, which is the reasoning behind it, I guess. Here's a handsome specimen by our driveway that captured our attention today. There was a bit of a breeze, which is why it was hard to get her in focus. Plus she was busy sucking the living daylights out of a common housefly.