(Dana Kobilinsky 15 May 2017; Photo:)
Fewer storms that bring wind and rain may be causing North American tree swallows (Tachycineta bicolor) to lay their eggs earlier in the spring, according to new research.
The impacts of this early egg laying isn’t known, but the trend points to what researchers say is an overlooked effect of climate change. Many studies look at the effects of warming temperatures on wildlife, but these researchers took into account the effects that less wind and rain in central Alaska have on the birds.
“In spring when the birds are doing their business, their habitat is not warmer at all,” said Daniel Doak, a professor at the University of Colorado Boulder and the senior author on the recent study that his undergraduate student led. “It’s a weak trend. But the storminess trend is very strong.”
As part of their study published in Proceedings of the Royal Society B, the researchers looked at data collected on swallows in two study sites in central Alaska over the past 15 years. The swallows are an extremely resilient species, Doak said, which makes them easy to study. “They’re a model species for effects on many different species,” he said. “They’re easy to study because they are less perturbed by human disturbances.”
The researchers recorded phenology information such as when the individual birds were laying eggs, hatching and fledging. Then, they reviewed weather station data from NOAA and the National Park Service and took note of climate data including temperatures, windiness and precipitation.
They found that frequent, small spring windstorms, which tend to slow down the breeding process, have become rarer over the past three decades. As the springs have gotten less windy, the birds are laying eggs earlier.
“Birds fine tune what they’re doing when there’s climate variation year to year,” Doak said. He and the other authors hope to study nest success, fledging and rearing of the species at these sites to determine what effects an earlier breeding time has, but he also hopes the study shows the importance of studying climate change impacts other than temperature.
“Climate change really has multiple dimensions,” he said. “We’ve been simplifying it down to the fact that things are getting warmer.”
Not only migratory birds use a built-in magnetic compass to navigate correctly. A new study from Lund University in Sweden shows that non-migratory birds also are able to use a built-in compass to orient themselves using the Earth’s magnetic field.
The researchers behind the current study have received help from a group of zebra finches to study the magnetic compass of what are known as resident birds, that is, species that do not migrate according to the season. Zebra finches are popular pet birds in many homes. Originally, they come from Indonesia and Australia where they search for food in a nomadic way.
“We wanted to know how a magnetic compass works in non-migratory birds like these”, says Atticus Pinzón-Rodríguez, doctoral student in biology at the Faculty of Science at Lund University.
In the current study, researchers have looked closer at the zebra finches’ ability to utilise the Earth’s magnetic field and the different properties of this built-in compass. The results show that the zebra finches use a magnetic compass with very similar functions to that of migratory birds, i.e. one with a very specific light dependency and thus sensitivity to different colours and light intensities.
“Our results show that the magnetic compass is more of a general mechanism found in both migratory birds and resident birds. It seems that although zebra finches do not undertake extensive migration, they still might be able to use the magnetic compass for local navigation”, says Atticus Pinzón-Rodríguez.
(Duke University 11 may 2017; Photo Ryan Huang)
Stronger and more frequent hurricanes may pose a new threat to the sooty tern, an iconic species of migratory seabird found throughout the Caribbean and Mid-Atlantic, a new Duke University-led study reveals.
The study, published this week in the peer-reviewed open-access journal PeerJ, is the first to map the birds’ annual migratory path and demonstrate how its timing and trajectory place them in the direct path of hurricanes moving into the Caribbean after forming over the Atlantic.
“The route the birds take and that most Atlantic-forming hurricanes take is basically the same, only in reverse,” said Ryan Huang, a doctoral student at Duke’s Nicholas School of the Environment, who led the study. “That means these birds, who are usually very tired from traveling long distances over water without rest, are flying head-on into some of the strongest winds on the planet.”
“This is worrying because we know that as Earth’s climate changes, we expect to see more frequent and powerful hurricanes in the future — meaning that the chances of sooty terns being hit by storms will likely go up,” Huang said.
Hurricane season typically lasts from June to November, with peak activity occurring in August and September.
A new map produced by the research shows that sooty terns leave their breeding colony at Dry Tortugas National Park in the Florida Keys each June as hurricane season starts. They migrate southward and eastward across the Caribbean through summer and early fall, before skirting the northern coast of South America and arriving at their winter habitat off the Atlantic coast of Brazil in November.
Huang and his colleagues charted the migratory path by recording and mapping the dates and locations of all sooty terns banded for study at the Dry Tortugas since the 1950s but found dead elsewhere. They also mapped locational data retrieved from birds that were fitted with satellite-telemetry tracking tags. When they overlaid all this data with maps of hurricane paths from the same period, they discovered a striking correlation.
“While it’s impossible to say just how many of the birds died as a direct result of the hurricanes, we saw a strong relationship between the numbers and locations of bird deaths and the numbers and locations of hurricanes,” said Stuart L. Pimm, the Doris Duke Professor of Conservation Ecology at Duke’s Nicholas School.
“What’s really interesting is that it’s not just the big category 4 and 5 storms that can kill large numbers of birds. A series of smaller, weaker storms may have the same impact as that of a single large, strong storm,” Pimm noted. “In September 1973, Tropical Storm Delia, a small storm in the Gulf of Mexico, killed a lot of birds because they were in the wrong place at the wrong time.”
Although sooty terns are neither rare nor endangered — 80,000 or more of them are estimated to breed in the Dry Tortugas each year — they have long been used by scientists as an indicator species to determine the health of the region’s marine environment.
“If there are changes taking place in the ocean, you’ll see corresponding changes taking place in the health of these tern populations, among other indicator species,” Huang said. “That’s what makes our findings somewhat concerning. If these birds are experiencing negative effects from changing ocean conditions, they are unlikely to be the only species affected.”
(Victoria Tereshono 8 may 2017)
Birdwatchers were delighted by the thousands of Ruffs that gathered at the end of April in Turau Meadow, Belarus. While the area is usually an important stopover for the species, this time the impressive numbers broke records in the country.
Despite the cold weather, bird migration is in full swing. Millions of birds have started moving from their wintering grounds in Africa, stopping over in the cold tundra of Eurasia.
At this time of the year, Turau Meadow in Belarus becomes a paradise for nature lovers – as many as 150,000 Eurasian Wigeon Mareca Penelope and 20,000 Black-tailed Godwit Limosa limosa can gather in these plains, sometimes in a single day.
But this year, it’s the Ruff Calidris pugnax that gave birdwatchers the most joy, when thousands of these long-necked birds blanketed the skies.
While this site is currently the largest stopover site for the species during their spring migration across Europe, this year the numbers were a surprise to everyone.
A group of ornithologists, including researchers from APB (BirdLife Belarus), registered a record number of 120,000 Ruffs in a single day, which hadn’t been reported since the observations began in Turau Meadow back in 1997.
Turau Meadow is an open floodplain in the middle of Pripyat River and one of Europe’s most essential nesting and stopover areas for more than 50 migratory wading bird species such as Black-tailed Godwit, Great Snipe Gallinago media and Eurasian Oystercatcher Haematopus ostralegus – the three of them classified as Near Threatened by BirdLife for the IUCN Red List. And these species don’t only stop there – this is where they nest.
For this reason, the floodplains were categorized as an Important Bird and Biodiversity Area by BirdLife and, since 2008, it has been recognized as a locally significant wildlife sanctuary by the Belarussian authorities.
(AOS 3 May 2017)
The Gulf of Mexico is hugely important to birds that migrate between North America and the Neotropics — almost all migrants have to go around it or across it. However, coastal habitats around the Gulf of Mexico face more and more threats from human activity. A new study brings together what we know — and don’t know — about the state of the region’s ecosystems and the birds that pass through them.
Understanding the population impacts of events during migration requires knowing which species are using what coastal habitats, how good those habitats are, where the birds are coming from, and where they’re going. Birds use a variety of coastal habitats, from vast tracts of hardwood forests to patches of vegetation embedded in agricultural or urban areas. The amount of food present in these areas, the intensity of competition for that food, and the danger from predators all shape how well a certain spot can meet a migrating bird’s needs. Threats to birds passing through the Gulf of Mexico include coastal habitat loss from forest clearing, wetland filling and dredging, and shoreline hardening; tall structures like cell phone towers and wind turbines; and, of course, climate change.
More data is needed in all of these subjects. Today the Gulf of Mexico Avian Monitoring Network is taking on the enormous task of coordinating monitoring across the region by integrating the efforts of multiple organizations and agencies. Doing this well will require close cooperation between the United States, Mexico, and Caribbean countries.
“Many migratory bird species are declining, including the species that breed in our backyards every summer, and we’re trying to understand if events that occur during migration might impact birds here on the breeding grounds. Our focus is the Gulf of Mexico region because it’s a bottleneck for migratory land birds — a place they have to move through every spring and fall,” says the Smithsonian Conservation Biology Institute’s Emily Cohen, the lead author of the Review. “Birds use these coastal habitats twice a year to eat and rest before and after their spectacular non-stop flight across the Gulf, which can take up to twenty hours! What’s going on during these migratory journeys is the final frontier for bird biology, and many new tools are making it possible to solve the mysteries of migration that previously limited our ability to develop conservation priorities.”
“This Review highlights the tremendous importance of the Gulf of Mexico to migratory birds, not only from an ecological and conservation perspective, but also as an opportunity to understand mechanisms that drive the evolution of migration across dozens of families,” according to Erik Johnson of Audubon Louisiana, an expert on bird conservation in the region. “As this paper makes clear, preserving this landscape is a tremendous responsibility shared across multiple countries, and our collective success has implications for how our descendants across North America will experience the amazing phenomenon of bird migration.”
(AOS 3 May 2017; Photo T. Boves)
The tools ornithologists use to track the journeys of migrating birds provide invaluable insights that can help halt the declines of vulnerable species. However, a new study from The Condor: Ornithological Applications shows that these data come at a cost—in some cases, these tracking devices reduce the chances that the birds carrying them will ever make it back to their breeding grounds.
Geolocators are small devices attached to birds that record light levels over time, which can be used to determine location. They’re widely used to study migration patterns, but studies have suggested that some species may be negatively affected by carrying them. Douglas Raybuck of Arkansas State University and his colleagues monitored male Cerulean Warblers with and without geolocators to see how they fared, and they found that while geolocators had no effect on the birds’ nesting success in the same season following their capture, birds with geolocators were less likely to reappear on their territories after migration the next year—16% of geolocator-tagged birds returned from migration, versus 35% of the birds in the control group.
The data gained from geolocator studies are enormously useful for bird conservation, and on a global scale those benefits are likely to outweigh potential the costs. The results from this study suggest that the potential impacts of individual research projects need to be carefully evaluated, but we should remember that only a small number of birds are ever tagged relative to the total size of the population under study.
The researchers captured Cerulean Warblers in Pennsylvania, Missouri, and Arkansas by luring them into nets using call recordings and wooden decoys. Outfitting some with geolocators but others with only identifying color bands, they monitored the birds’ nests and then searched for them the following year to determine whether they’d returned. “Re-sighting males and identifying their unique color-band combinations as they moved about in the canopy was not always easy, but our dedicated and skilled field crew did a fantastic job of overcoming these obstacles, which were compounded by inclement weather and the rugged topography of the sites,” says Raybuck.
“New technologies such as geolocators and automated radiotracking arrays have led to a surge in new tagging studies of migratory songbirds,” according to York University’s Bridget Stutchbury, an expert on geolocators and the conservation biology of North America’s migratory songbirds. “Finding that tagged birds were far less likely to return the next year compared with un-tagged birds puts researchers in a serious dilemma, because despite the potential costs of tagging small birds, long-distance tracking is essential to find out which wintering and migratory stopover sites should be highest priority for conservation.”