Native Landscaping in Urban Areas Can Help Native Birds

Iturria: Science Daily

ScienceDaily (Aug. 22, 2012) — A recent study of residential landscape types and native bird communities in Phoenix, Ariz., led by a University of Massachusetts Amherst urban ecologist suggests that yards mimicking native vegetation and wildlands offer birds "mini refuges," helping to offset the loss of biodiversity in cities and supporting birds better than traditional grass lawns and non-native plantings.

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Residential yards mimicking nearby native vegetation and wildlands offer birds “mini refuges.” (Credit: UMass Amherst)

The study, led by Susannah Lerman with her advisor Paige Warren at UMass Amherst, and Hilary Gan and Eyal Shochat at Arizona State University, is one of the first to use quantitative measures and a systematic approach, with 24-hour video monitoring, to assess and compare foraging behavior of common backyard birds in yards in Phoenix, at the northern edge of the Sonoran Desert. It appears in the current issue of PLOS ONE.
It is also one of the first to conduct experiments to compare different types of a single urban landscape form (residential yards), Lerman says. Overall, the study found that desert-like, "xeric" yards had a more even bird community and superior habitat compared to moist, or "mesic," grass lawns in the Phoenix area.
She explains, "We already know that bird communities differ and there are more desert birds found in the desert-type yard. With this study, we're starting to look at how different yards function, whether birds behave differently by yard type. We do that using behavioral indicators, specifically foraging, as a way to assess the bird's perception of habitat quality between the two yard designs."
Lerman and colleagues conducted the experiment in 20 residential yards at least 1.8 miles (3 km) apart, making it unlikely that the same birds would visit more than one study yard. Half of the yards were xeric, or desert-like, while the other 10 were mesic, with exotic green lawns. Homeowners removed bird feeders before and during the 24-hour experimental data collection period during February and April 2010.
The researchers set up feeding stations (seed trays) in each yard to simulate resource patches like those used by wild birds. Plastic trays had 0.70 ounce (20 g.) of millet seed mixed into six lbs. (3 kg) of sand, and were left out on a low stool for 24 hours. Later, Lerman and colleagues removed the trays, sifted out and weighed uneaten seed to the nearest 0.01 gram. This represents the giving-up densities (GUD) or amount of seed remaining, which quantifies the foraging decision and quitting point for the last species visiting a seed tray. Trays were videotaped for the entire 24-hour experiment.
This experiment assumes that an animal behaving optimally will quit foraging a seed tray when its energy gains equal the "costs" of foraging, Lerman explains. Costs include predation risk, cost of digestion and missed opportunities to find food elsewhere. As time spent foraging a seed tray increases, so do costs associated with foraging. When a bird first arrives at the tray, seeds are easy to find, but this gets harder as it is depleted. Each bird makes a decision about whether to spend time searching in the tray or to move on to a new patch in the yard. The "giving up" point will be different for different species and in different environmental conditions. Birds visiting seed trays in yards with more natural food available will quit a tray sooner compared to birds in resource-poor yards.
Since the method only measures the foraging decisions for the last species visiting the seed tray, the researchers devised a mathematical model for estimating the foraging decisions for all visiting species. Using the videotapes, they counted every peck by every bird for each tray to calculate the relationship between the number of pecks and grams of seed consumed (the GUD) for each seed tray. This was the GUD-peck ratio for the last species visiting the seed tray.
They then estimated the seed consumption (GUD) for all other species visiting the seed tray based on the number of pecks per tray when each species quit. "We know how many pecks each species had and can put that number into the model and calculate the number of grams at that point," Lerman explains. This greatly enhances the GUD method by expanding the ability to assess foraging decisions for all species visiting trays.
In all, 14 species visited the trays, 11 of which visited both yard types. Abert's towhee, curve-billed thrasher (species unique to the Sonoran desert), house finch and house sparrow were the most widespread tray visitors.
In this study, the researchers found that birds foraging in mesic yards depleted the seed trays to a lower level (had lower GUDs) compared to birds foraging in xeric yards. Further, species that visited trays in both yard designs consumed more seed from trays placed in mesic yards, indicating lower habitat quality compared to the xeric yards. Similarly, foragers in the desert-like yards quit the seed trays earlier due to greater abundance of alternative food resources in those yards, spending more time foraging in the natural yard and less at the seed tray.
Lerman says that by videotaping the trays, counting pecks and measuring giving-up points by species, this work also advanced the GUD method, allowing researchers to disentangle some of the effects of bird community composition and density of competitors, and how these factors affect foraging decisions between two different landscape designs. Results continue to build evidence that native landscaping can help to mitigate the impacts of urbanization on common songbirds, she says.

Rock Sparrows React to Infidelity by Singing Louder

Iturria: Science Daily

ScienceDaily (Aug. 23, 2012) — Rock sparrows indicate their age and their reproductive success with their songs and react to infidelity with a higher song volume.

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A male rock sparrow: His song reveals a lot about his qualities as a potential mate, so females will be listening carefully to his performance. A team of researchers from the Max Planck Institute for Ornithology in Seewiesen and the University of Copenhagen have discovered that the tempo, the pitch, and the amplitude of song reflect male reproductive success. (Credit: Henrik Brumm/MPI for Ornithology)

The song of male songbirds is multifaceted and has two main functions: to repel rivals and to attract mates. Females often pay attention to certain features within a song, such as the presence of special syllables, to assess the quality of the singing male. A team of researchers from the Max Planck Institute for Ornithology in Seewiesen and the University of Copenhagen has now found that the tempo, the pitch, and the amplitude of song reflect male reproductive success in rock sparrows. Surprisingly, the more successful and older males sang their songs with a higher pitch and a slower tempo than yearling males. However, older males lost paternity more often in their own nest but could more than compensate this by a larger number of extra-pair young, resulting in the highest reproductive success. Cuckolded males regardless of whether they were young or old, sang louder -- perhaps as a response to the absence of their unfaithful mate.
Female birds often have a hard job to do in order to assess the quality of a prospective mate. Many males literally dress up their feathers to impress females. For songbirds, it is apparently easier as they are able to modify their songs in a sensational manner. However, the question remains as to which song trait a female should pay particular attention -- should she perhaps monitor the number of all song syllables a male is able produce? For species with large song repertoires this would take quite long. Therefore females are better off to listen to special features within male song, such as the so-called "sexy syllables" in the songs of canaries. This means, the more a certain song trait a male is able to sing, the higher its quality, and the female can look forward to healthy and strong offspring. This also might hold true for the trait song amplitude, as in some species loud song is more attractive than silent song.
An international team of researchers headed by Henrik Brumm from the Max Planck Institute for Ornithology in Seewiesen apparently has now found the opposite scenario in a population of rock sparrows in the French Alps. The researchers recorded the songs of male rock sparrows in two subsequent breeding seasons with a special emphasis on the amplitude. The conditions in the field make measurements of amplitude relatively difficult, making it a rather neglected topic in behavioural research. The birds were nesting exclusively in wooden nestboxes that were attached to utility poles and which they also used as singing posts. In this way the researchers were able to attach the microphones to the pole in a defined distance to the singing bird, which is essential for a reliable determination of the sound pressure level. Additionally, the researchers conducted a paternity analysis by means of the microsatellite method.
Rock sparrows sing a very simple song that consists of only one element that is repeated several times to form a song bout. This is in clear contrast to other birds such as the nightingale, which has a huge repertoire of different song types. Surprisingly, the researchers found that those birds that were singing at a lower rate and a higher pitch sired a larger number of extra-pair young in other nests. Successful males, which were mostly older, could be distinguished from their younger, yearling rivals by their slower song tempo. Older males had a higher status and probably they did not need to advertise it by their song.
In contrast, one-year old males were not able to compensate for the lower attractiveness by a higher song rate and a lower pitch. Moreover, those males that sang louder were more likely to lose paternity in their own nest; but again there were age-dependent differences: Older males had a higher loss of paternity in their own nest and sang at higher amplitudes compared to their younger rivals. "The high amplitude song of males that lost paternity is not a quality characteristic but rather the desperate attempt to tighten the pair bond to the unfaithful partner," says Erwin Nemeth, first author of the study. The older males were able to compensate their paternity loss in their own nest by gaining more extra-pair young, whereas there is nothing else for the younger yearling males but to wait for better times in the next year.

Two New Owl Species Discovered in the Philippines

Iturria: Science daily

ScienceDaily (Aug. 17, 2012) — Two new species of owls have been discovered in the Philippines, and a Michigan State University researcher played a key role in confirming their existence.

Two new species of owls have been discovered in the Philippines, and an MSU researcher played a key role in confirming their existence. (Top left: Cebu Hawk owl. Bottom right: Camiguin Hawk owl.) (Credit: Courtesy of Oriental Bird Club: original painting by John Gale)

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The discovery, which is featured in the current issue of Forktail, the Journal of Asian Ornithology, took years to confirm, but it was well worth the effort, said the paper's lead author Pam Rasmussen, MSU assistant professor of zoology and assistant curator of mammalogy and ornithology at the MSU Museum.
"More than 15 years ago, we realized that new subspecies of Ninox hawk-owls existed in the Philippines," she said. "But it wasn't until last year that we obtained enough recordings that we could confirm that they were not just subspecies, but two new species of owls."
Announcing the finding of a single bird is rare enough. But the discovery of two new bird species in a single paper is so rare that Rasmussen and the other researchers couldn't recall the last time it happened.
The first owl, the Camiguin Hawk-owl, is found only on the small island of Camiguin Sur, close to northern Mindanao. Despite being so close geographically to related owls on Mindanao, it has quite different physical characteristics and voice. At night, it gives a long solo song that builds in intensity, with a distinctive low growling tone. Pairs of owls give short barking duets that start with a growl. They also are the only owls to have blue-gray eyes.
The second new discovery was the Cebu Hawk-owl. This bird was thought to be extinct, as the forests of Cebu have almost all been lost due to deforestation. But it had never been considered a distinct form. Study of its structure and vocalizations confirmed that it was a new species. In fact, it was the unique calling or vocalizations of both owls that confirmed that the new classifications were warranted.
"The owls don't learn their songs, which are genetically programmed in their DNA and are used to attract mates or defend their territory; so if they're very different, they must be new species," Rasmussen said. "When we first heard the songs of both owls, we were amazed because they were so distinctly different that we realized they were new species."
The owls have avoided recognition as distinct species for so long because the group shows complex variation in appearance that had been poorly studied, and their songs were unknown. Both islands are off the beaten path for ornithologists and birders, who usually visit the larger islands that host more bird species.
Sound recordings of both new owl species and those from other islands are available free on AVoCet.
Since the discovery process is both tedious and time consuming, it took a team of scientists and contributors to confirm the owls' existence. The team included individuals from BirdLife International, the Oriental Bird Club, Philippines Biodiversity Conservation Foundation Inc. and Birdtour Asia. Additional support was provided by National Geographic.

Iturria: BBC

 

9 August 2012 Last updated at 19:14 GMT

Sleep deprived birds have more chicks

By Nick Crumpton BBC News

 

For pectoral sandpipers, losing sleep means gaining offspring

Continue reading the main story

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Sleep deprived birds appear to have greater mating success, according to a study conducted in Alaska.

By analysing sleep patterns and testing the paternity of chicks, a team of researchers from Germany and Switzerland have found that male individuals that sleep less, sire the most offspring.
This is at odds with the assumption that sleep loss retards the ability to perform complex tasks.
The research is published in Science.
Out all night The birds studied were pectoral sandpipers (Calidris melanotos), which engage in long migrations between the Southern and Northern hemispheres.
In May and June, the shorebirds mate and nest on the barren tundra of Alaska, when the area experiences almost 24 hours of sunlight.
During fieldwork near Barrow, director of the Avian Sleep Group at the Max Planck Institute for Ornithology and leader of the study, Prof Bart Kempenaers noticed a peculiar behaviour.
"He discovered that these male pectoral sandpipers were being incredibly active throughout the 24-hour period," co-author Dr Niels Rattenborg told BBC News.
"We used a variety of methods to gain insight into what was actually going on up there. What were these sandpipers doing? We put transmitters on their back that could measure when they were moving. So we could record patterns throughout 24 hours, over a period of several weeks," Dr Rattenborg said.
By analysing these data, along with brain activity recordings, the team found that some male pectoral sandpipers were extremely active during the whole day, whereas others were engaging with fewer females, choosing instead to sleep.
You snooze, you lose Dr Rattenborg and his colleagues then tested the paternity of the young that were laid on the site.
"We collected every egg on the study site, incubated them, hatched them and then got DNA from each of the chicks, so we could tell how many chicks a given male sired. Then we returned the chicks to the mothers out in the field," Dr Rattenborg said.
This paternal data proved that the individuals that were the most active - up to 95% of 24 hours - sired the most young, despite having hardly slept over a period of weeks.

Male and female pectoral sandpipers were equipped with tags to monitor their activity

The behaviour may be linked to the mating strategy employed by the birds, as pectoral sandpipers are "polygynous", meaning males mate with many females during periods of intense competition, whereas other species of sandpipers concentrate their efforts on a single female.
"We also observed that the monogamous species of sandpipers nesting in exactly the same area had periods of inactivity during the dimmest part of the 24 hour period. So they seemed to be sleeping, where some of the male pectoral sandpipers are engaging in almost constant activity," said Dr Rattenborg.
The findings were a surprise to the team, especially as the sleep deprived males seemed to suffer no ill-effects, returning to the breeding site the following year.
"There's an extensive body of research looking at the effects that sleep loss has on performance in a variety of types of animals. Pretty much across the board these studies showed that even losing a relatively small amount of sleep, just a couple of hours a night, has adverse effects on our ability to perform waking functions," explained Dr Rattenborg.
Yet this appeared not to faze the "super-active" pectoral sandpipers with the individuals developing "adaptive" sleep loss being more successful, from an evolutionary point of view, even after migrating vast distances from the Southern hemisphere.

Iturria: Science Daily

Studies Shed Light On Why Species Stay or Go in Response to Climate Change

ScienceDaily (Aug. 17, 2012) — Two new studies by scientists at UC Berkeley provide a clearer picture of why some species move in response to climate change, and where they go.

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The Ash-throated Flycatcher, a low-elevation species, shifted its range downslope in response to climate change, researchers found. (Credit: Morgan Tingley photo)

One study, published online Aug. 6, in the journal Global Change Biology, finds that changes in precipitation have been underappreciated as a factor in driving bird species out of their normal range. In the other study, published August 15 in the journal Proceedings of the Royal Society B, researchers found a sharp decrease in range for the Belding's ground squirrel, but noted some surprising areas where the species found refuge.
The two studies exemplify the type of research being explored through the Berkeley Initiative in Global Change Biology, or BiGCB, an ambitious effort to better understand and predict how plants and animals will respond to changing environmental conditions by studying how they have responded to earlier periods of climate change.
The first study's findings challenge the conventional reliance on temperature as the only climate-related force impacting where species live. The authors noted that as many as 25 percent of species have shifted in directions that were not predicted in response to temperature changes, yet few attempts have been made to investigate this.
"Our results redefine the fundamental model of how species should respond to future climate change," said study lead author Morgan Tingley, who began the research as a graduate student in UC Berkeley's Department of Environmental Science, Policy and Management. "We find that precipitation changes can have a major, opposing influence to temperature in a species' range shift. Climate change may actually be tearing communities of organisms apart."
The findings are based upon data gathered from the Grinnell Resurvey Project, which retraces the steps of Joseph Grinnell, founder of the UC Berkeley Museum of Vertebrate Zoology, in his surveys of Sierra Nevada wildlife from the early 1900s. The resurvey project, which began in 2003, was led by Craig Moritz, former UC Berkeley professor of integrative biology, and his colleagues at the Museum of Vertebrate Zoology.
For the bird study, the researchers included 99 species in 77 historic survey sites in Lassen Volcanic, Yosemite and Sequoia national parks, as well as in several national forests. In the century that has passed since the original Grinnell survey, summer and winter temperatures have increased an average of 1-2 degrees Celsius in the Sierra Nevada. Yosemite experienced the most warming -- with average temperatures increasing by 3 degrees Celsius -- while parts of Lassen actually got cooler and much wetter.
Among the bird species that moved upslope are the Savannah Sparrow, which shifted upward by 2,503 meters, and other meadow species such as the Red-winged Blackbird and Western Meadowlark. The ones that shifted their range downslope include both low-elevation species like the Ash-throated Flycatcher and Western Scrub-Jay, and high-elevation species like the Cassin's Finch and Red-breasted Nuthatch.
"Temperature did not explain the majority of these shifts," said Tingley, who is now a postdoctoral researcher at Princeton University's Program in Science, Technology and Environmental Policy. "Only when we included precipitation as an explanatory variable did our models adequately explain the movement patterns we observed."
The researchers found that while rising temperatures tended to push birds to cooler regions upslope, increased precipitation, which is more common at higher elevations, pulled them downslope.
"We believe many species may feel this divergent pressure from temperature and precipitation, and in the end, only one wins," said Tingley.
Notably, more than half of the bird species in each of the three study regions did not shift their range despite pressures from climate change. "Moving is a sign of adaptation, which is good from a conservation standpoint," said Tingley. "More worrisome are the species that have not shifted. How are they adapting? Are they moving, but we just can't detect it? Or are they slowly declining as environmental conditions gradually become less ideal where they live?"
The answers are complex, as illustrated by the second UC Berkeley paper about range changes for a species of squirrel found in the mountains of the western United States.
In that paper, researchers again used information obtained from the Grinnell Resurvey Project. Through visual observations and trapping surveys conducted throughout the mountains of California, they discovered that the Belding's ground squirrel had disappeared from 42 percent of the sites where they were recorded in the early 1900s. Extinctions were particularly common at sites with high average winter temperatures and large increases in precipitation over the last century.
"We were surprised to see such a dramatic decline in this species, which is well-known to Sierran hikers and was thought to be fairly common," said study lead author Toni Lyn Morelli, a former National Science Foundation postdoctoral researcher who was based at UC Berkeley. "In fact, the rate of decline is much greater than that seen in the same region for the pika, a small mountain-dwelling cousin of the rabbit that has become the poster child for the effects of climate warming in the contiguous United States."
Morelli added that the squirrels are thriving in areas that have been modified by humans. For example, irrigated Mono Lake County Park serves as an artificial oasis that sustains squirrel populations despite otherwise hot and dry conditions in eastern California.
"As predictions indicate that the range of the Belding's ground squirrel could disappear out of California by the end of the century, these areas might be particularly important for this and other climate-impacted species," said Morelli, who is now a technical advisor for the U.S. Forest Service's International Programs in the Democratic Republic of Congo.
Although the Belding's ground squirrel is widespread, the rapid decline in its distribution is of concern because it is an important source of food for raptors and carnivores. However, the paper suggests that even when climate change causes large range declines, some species can persist in human-modified areas.
"Taken together, these two studies indicate that many species have been responding to recent climate change, yet the complexities of a species' ecological needs and their responses to habitat modification by humans can result in unanticipated responses," said Steven Beissinger, professor at UC Berkeley's Department of Environmental Science, Policy and Management and the senior author on both studies. "This makes it very challenging for scientists to project how species will respond to future climate change."
Funding from the National Science Foundation, National Park Service, and California Landscape Conservation Cooperative helped support this research.

Bird Louse Study Shows How Evolution Sometimes Repeats Itself

Iturria: Science Daily

ScienceDaily (Aug. 16, 2012) — Birds of a feather flock together and -- according to a new analysis -- so do their lice.

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Barred owl. (Credit: © Feng Yu / Fotolia)

A study of the genetic heritage of avian feather lice indicates that their louse ancestors first colonized a particular group of birds (ducks or songbirds, for example) and then "radiated" to different habitats on those birds -- to the wings or heads, for instance, where they evolved into different species. This finding surprised the researchers because wing lice from many types of birds look more similar to one another than they do to head or body lice living on the same birds.

The study appears in the journal BMC Biology. (Watch a video about the research.http://www.youtube.com/watch?v=FRTqiOL65og)
Wing lice are long and narrow and insert themselves between the feather barbs of a bird's wings. This allows them to avoid being crushed or removed by a bird when it preens, said Kevin Johnson, a University of Illinois ornithologist with the state Natural History Survey. Johnson conducted the new analysis with Vincent Smith, of the Natural History Museum in London, and Illinois graduate student Scott Shreve.
"If you were just guessing at their ancestry based on external traits, you would think the wing lice on different birds were more closely related to one another than they were to head or body lice on the same bird," Johnson said. "But that's just not the case."
Each type of louse is adapted to life on a particular part of the body. Head lice are rounder than wing lice, for example, and have triangular, grooved heads. The groove helps them cling to a single feather barb so their bird host can't scratch them off.
Body lice are plump and will burrow into the downy feathers or drop from feather to feather to avoid being preened. And the lice known as generalists, which range all over the bird, have their own method of escaping preening: They run.
"The similarities between the lice living in specific habitats on the bodies of birds are really striking," Johnson said. "But it appears that those similarities are the result of what we call 'convergent evolution': The lice independently arrived at the same, or similar, solutions to common ecological problems. This occurred only after they had colonized a particular type of bird."
In the new analysis, Johnson and his colleagues drew up two family trees of feather lice. The first tree grouped the lice according to physical traits; the second mapped their genetic relationships.
The two trees looked significantly different from one another, Johnson said. The genetic tree showed that different types of feather lice living on the same type of bird were often closely related, whereas lice that had evolved to survive on specific bird parts, such as the wing, were only distantly related across bird groups, he said.
The history of feather lice turns out to be a very robust example of convergent evolution, Johnson said.
"Here we see how evolution repeats itself on different bird types," he said. "The lice are converging on similar solutions to the problem of survival in different microhabitats on the bird."
The Illinois Natural History Survey is a division of the Prairie Research Institute.