Tag Archives: foraging

New paper explores why Peru’s parrots eat clay

New paper explores why Peru’s parrots eat clay
(Jenna Marshall 4 August 2017; Photo Donald Brightsmith)

For more than 16 years, researchers and volunteers have been observing wildlife along the clay cliffs of Southeastern Peru’s Tambopata River. They’ve gathered data every day, logging more than 20,000 hours and building one of the most extensive datasets on tropical parrots in the world.

In a new paper published in Ibis, Elizabeth Hobson, a postdoctoral fellow with the Arizona State University-Santa Fe Institute Center for Biosocial Complex Systems, and Donald J. Brightsmith, a professor in the Texas A&M University College of Veterinary Medicine & Biomedical Sciences (CVM) and director of the Tambopata Macaw Project, begin to analyze the data from this long-term study.

In particular, the team explores the potential drivers behind geophagy—or intentional soil consumption—they’ve regularly observed in 14 different parrot species there.

This region of the Tambopata River in Southeast Peru is an ideal spot to study the nearly two-dozen parrot species that live nearby in the Amazon rainforest. In the thick foliage of the jungle, the birds are difficult to see, but when they emerge to gather up beakfuls of the sodium-rich clay soil, “it’s a crazy, screaming kaleidoscope of color,” Hobson said.

“They’re all quiet when they take flight, but in a few seconds, they all begin to scream, and some drop bits of the clay from their mouths,” said Brightsmith, who has led the Tambopata Macaw Project since 1999. “It’s an incredible experience.”

But geophagy is a somewhat confounding behavior—clay soil is basically inert.

“It doesn’t have proteins, carbohydrates, or really anything that you’d need,” Brightsmith said. “If we can understand why it’s so important to these parrots, we can learn more about the ecosystem and how it affects the other insects, birds, and mammals who also eat this soil.”

Geophagy occurs around the world and in many types of animals, and scientists have proposed many explanations for the behavior. In their paper, Hobson and Brightsmith explore the two leading theories for these Amazonian parrots—that clay soils help protect the birds from food toxins when ideal food sources are scarce and that clay soils provide necessary minerals not available in the parrots’ regular diet.

Like previous studies, their analysis suggests that toxin-protection is not a driver. But parrot geophagy there is highly correlated with breeding season, suggesting the increased nutritional demands are likely behind the soil consumption. This study also joins a large body of research suggesting that hunger for sodium, specifically, is that driver.

“There’s lots of evidence that’s pointing in that direction,” Hobson said. “Sodium in the rainforest is really rare, and the place on these clay licks most preferred by the birds also has the highest sodium content.”

Understanding how nutritional needs are—and are not—being met during breeding season becomes even more important in light of climate change, according to Brightsmith. Some of the larger macaws are already breeding right before a seasonal crash in the food supply, requiring parents take their fledgling young on long flights to find food.

“If climate change starts messing with the macaw’s food supply, it could disrupt their ability to breed,” he said.

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Grown-up gannets find favorite fishing grounds

(University of Exeter, Science Daily  27 July 2017)

Like humans, some birds can spend years learning and exploring before developing more settled habits.

A study of northern gannets has shown adults return to the same patch of sea over and over again to find food.

But younger gannets search far and wide and tend not to return to the same places — even if they find good hunting grounds, University of Exeter researchers found.

The study also compared successful breeding adults with those which failed to breed, and found successful breeders stuck to their feeding grounds more reliably.

“It’s common for birds like gannets to return to the same foraging grounds year after year,” said Dr Stephen Votier, of the Environment and Sustainability Institute on Exeter’s Penryn Campus in Cornwall.

“They disperse widely at sea, and the fact that they return to specific areas is presumably linked to finding good foraging conditions.

“However, gannets don’t breed until they’re four or five years old, and our research shows that this tendency to return to favoured foraging grounds is lacking in birds younger than this.

“This finding suggests that such behaviours are probably learned, and that gannets use their long period of immaturity finding good sites and remembering where they are.

“However, foraging sites in adults are not absolute — when experienced birds had more time on their hands after a failed breeding attempt, some became more exploratory. This suggests that refinement occurs throughout an animal’s lifetime.”

The research team studied gannets on the Welsh island of Grassholm, supported by the RSPB, and used precision global positioning system (GPS) loggers to find out whether individual birds returned to the same foraging grounds time after time.

Successful breeders showed strong attachment to certain areas and took similar routes when travelling to and from them.

Immature birds (aged two or three years) were much more varied both in foraging sites and routes taken.

The results support the “exploration-refinement foraging hypothesis” — that birds explore and slowly improve their foraging with age and experience.

Mystery of birds’ movements at sea solved

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RSPB 7 July 2017; Photo Chris Gomersall)

  • New research reveals where British and Irish seabirds go when they’re not on land.
  • The five year project GPS-tracked over 1,300 breeding seabirds and used computer models to predict where they go to find food.
  • Results reveal the majority of ‘hotspots’, where seabirds gather to feed, are concentrated in the coastal waters of Scotland, highlighting the need for robust conservation measures in this area.
  • The new maps will be used to protect threatened species by assessing potential impacts from offshore wind farms, pollution and other human activities on seabirds.  

New research has identified the most important areas for Britain and Ireland’s seabirds at sea, with the majority of ‘hotspots’ revealed in the coastal waters of Scotland.

Experts used GPS-tracking (1) and computer models on an unprecedented scale to map where breeding seabirds go when they leave land to feed, providing a unique insight into the lives of these enigmatic birds.

The study (2), headed by the RSPB in partnership with over a dozen scientists from leading research institutes (3), used five years of tracking data to estimate the areas used by four species: kittiwakes, shags, razorbills and guillemots.

This comes as the Scottish Government considers the creation of Special Protection Areas at sea to safeguard key seabird feeding areas, as well as planning future management of marine activities in Scottish waters outside of the EU and the Common Fisheries Policy.

During the project, lightweight GPS tags were fitted to over 1,300 adult birds from 29 different colonies. The tracking data was then used to create a computer model for each species, so that all of the important areas at sea could be predicted.

The results (see study maps attached) show the extent to which birds travel to find food. The majority of seabird ‘hotspots’, where different species gather to feed, are concentrated in the coastal waters of Scotland, highlighting the need for robust conservation measures to protect these areas. Overall, the four species use at least 1.5 million square km of sea around Britain and Ireland – an area three times the size of Spain.

This is a major step forward in our understanding of seabirds and is a powerful tool to help protect birds from potentially harmful activities at sea, including helping to make better decisions about where those activities can be undertaken to limit their impacts on seabirds.

Understanding more about our seabirds is vital because they are one of the most endangered groups of birds in the world. Over the last 30 years, kittiwake and shag numbers have declined by 72% and 68% respectively in Scotland. This is partly due to the impacts of climate change and fishing, and a new OSPAR report (4) underlines this trend, highlighting widespread seabird breeding failures in the North and Celtic Seas. Scotland is also home to internationally important populations of breeding seabirds so we have a global responsibility to safeguard them.

Dr Mark Bolton, RSPB Principle Conservation Scientist, said: “Our rich and diverse marine environment makes Britain and Ireland one of the greatest areas in the world for seabirds and this new research is further evidence of just how important our seas are for seabirds and their chicks during the breeding season. In order to strengthen this research and our predictions, there is an urgent need for a complete seabird census which will provide an accurate and up-to-date estimate of the size of our seabirds breeding colonies.”

Dr Ellie Owen, who led on the tracking work, said: “The sight and sound of hundreds of thousands of seabirds flocking to our shores is an amazing natural spectacle and something that we must help protect for future generations to enjoy. The methods used in this study could be applied to other seabird species, to show where they go at sea. This will be an invaluable tool in helping to protect seabirds, as it will greatly improve our ability to assess the likely impacts on breeding seabirds of offshore wind farms, oil spills and other potentially harmful activities in our increasingly industrialised seas.”

Dr Ewan Wakefield, lead author of the research, said: “Many seabirds are at the top of the marine food web. They feed on sandeels and other small fish but that prey is declining because of human pressures, including climate change. The result is that thousands of seabird chicks are dying each year because their parents can’t feed them. For the first time, this study provides us with a full map for each breeding colony of the feeding areas for some of our most important seabird species. That means we can now protect the places these birds catch the fish they need to feed their hungry chicks, securing the fate of future generations of these amazing creatures.”

Study reveals albatross interactions with fishing vessels in the southern ocean

Study reveals albatross interactions with fishing vessels in the southern ocean

An international research team involving the University has tracked the foraging patterns of albatrosses in the southern ocean and found that nearly 80 percent of them follow fishing boats, giving scientists new insight into the risk fishing vessels present to seabirds.

The extent to which albatrosses and fishing vessels overlap was revealed by newly developed XGPS radar loggers which were fitted to fifty-three incubating wandering albatrosses. The loggers are able to detect vessel radar by an omnidirectional micro strip antenna integrated with the bird’s geo-positional GPS device.

The data showed that during breeding, tagged Crozet wandering albatrosses patrolled over an area of more than 10 million square kilometres and as much as 79.5 percent of the birds equipped with the loggers detected vessels, at distances up to 2500 kilometres from the colony.

About 300,000 seabirds are killed annually in longline fishing, including albatrosses which are an endangered species and one of the most threatened families of birds internationally, with 15 of the 22 species in the group threatened with extinction.

The study took place in Possession Island in the Crozet Islands, in the southern Indian Ocean, from January to March in 2015 and 2016 and the research team included the University, the Centre d’Etudes Biologiques de Chize, France, Sextant Technology Ltd and the Museum of New Zealand Te Papa Tongarewa.

Henri Weimerskirch, from the Centre d’Etudes Biologiques de Chize who was the lead author, said: “This study is incredibly important, as albatrosses are well-known ship followers and their populations have been severely impacted through accidental mortality due to their encounters with fishing vessels.”

Liverpool Ecologist, Dr Samantha Patrick, said: “We know very little about fisheries in international waters due to both logistical and political constraints. However, wide ranging seabirds spend a large proportion of their time in these areas and so understanding their behaviour throughout their range is paramount.”

Susan Waugh, from Museum of New Zealand Te Papa Tongarewa, added: “This high rate of encounter shows that a far higher proportion of the population are exposed to fisheries mortality risk than previously supposed. The tagged birds showed varying patterns of encounter and attendance at vessels that challenge our perception of foraging behaviour of seabirds.”

“Being able to detect the presence of vessels throughout a species’ range is essential to derive comprehensive encounter, attendance and mortality rates and detect changes in foraging behaviour triggered by the presence of vessels.”

The paper `Use of radar detectors to track attendance of albatrosses at fishing vessels’  is published in the Conservation Biology online journal.

Birds’ feathers reveal their winter diet

(AOS 21 June 2017; Photo RM Jensen)
Influences outside the breeding season can matter a lot for the population health of migratory birds, but it’s tough to track what happens once species scatter across South America for the winter months. A study from The Condor: Ornithological Applications tries a new approach for determining what declining migratory grassland birds called Bobolinks eat after they head south for the winter—analyzing the carbon compounds in their plumage, which are determined by the types of plants the birds consume while growing their feathers during their winter molt.

Thanks to a quirk of photosynthesis, rice contains a different ratio of carbon isotopes than most of the native grasses in South America where Bobolinks winter. Rosalind Renfrew of the Vermont Center for Ecostudies and her colleagues took advantage of this, collecting feather samples from wintering Bobolinks in a rice-producing region and a grassland region and from breeding Bobolinks in North America. When they analyzed the feathers’ isotopes ratios, the results from South America confirmed that isotopes in Bobolinks’ feathers reflected the differences in their diets between regions with and without rice production. The samples taken in North America showed that the winter diet of most individuals was weighted more toward non-rice material, but that rice consumption was highest late in the winter, when rice is nearing harvest and the birds are preparing for their northbound migration.

Rice could be beneficial by providing the birds with needed calories as they prepare for their journey north, but it could also increase Bobolinks’ exposure to pesticides and threats from farmers who see them as pests. According to Renfrew and her colleagues, maintaining native grasslands, encouraging integrated pest management programs to reduce toxic pesticide applications, and compensating farmers for crops lost to feeding birds all would be helpful.

“The time spent coordinating the field work for this study may well have been greater than the time spent collecting the data,” says Renfrew. “It was truly a team effort, and the assistance we received from our partners was absolutely essential, especially in South America. Aves Argentinas and the Museo de Historia Natural de Noel Kempff Mercado provided priceless logistical support, and this study could not have happened without them. Some of the same partners have provided input on a Bobolink Conservation Plan that lays out actions to address threats to grassland birds in North and South America, based on results from this and other studies.”

“As Bobolink populations continue to decline, Renfrew and her colleagues use state-of-the-art isotope analysis techniques to assess the Bobolink’s diet on its South American wintering grounds,” according to John McCracken of Bird Studies Canada, an expert on grassland bird conservation who was not involved with the study. “The authors conclude that rice may have negative effects on Bobolinks, owing to its relatively low nutritional quality and from exposure to insecticides.

Birds of all feathers work together to hunt when army ants march

ruddy_woodcreeper.jpg
(SD, Drexel University 19 June 2017)
Army ants scare up a lot of food when they’re on the move, which makes following them valuable for predator birds. But instead of competing and chasing each other off from the ant “raids,” as scientists had thought, birds actually give each other a heads up when the ants are marching, according to a new Drexel University study.

For more than a decade — from 2005 until 2016 — Sean O’Donnell, PhD, a professor in Drexel’s College of Arts and Sciences, observed army ant “raids” and the birds that follow them. He hoped to find out whether birds really were aggressive toward each other during the ant marches or whether they actually cooperated to access the food (other insects and bugs) that ants rustle out of hiding.

After observing 74 swarms in Costa Rica, it seems birds are much more likely to play nice with each other.

“Overall, the results strongly supported facilitation — species help each other to exploit shared resources,” O’Donnell said of his study that was recently published in Biotropica.

In watching for the raids and the flocks that “attend” them, a key to avian cooperation may be what are termed “bivouac-checking” birds. These are birds that perch near the sites where army ants make their nests (bivouacs) and watch to see where and when the ants move. Birds that fall into that category include the ocellated antbird and the blue-diademed motmot.

The prevailing thought has been that these specialized birds liked to keep the ant colonies they watched to themselves, not allowing other species to horn in on their finds.

But a frequent high diversity of species in flocks following the ant columns showed O’Donnell that birds that didn’t specialize in tracking army ants (like the migrant species Kentucky warbler) were allowed to join and hunt.

So when bivouac-checking birds see the movement of the columns and take off, other birds take the cue. They either know birds like the ocellated antbird follow ant columns or recognize vocalizations the specialized birds make when chasing the colonies.

“Birds may use each other as a way of finding army ant raids, which are very hard to locate in the forest because they are widely spaced and the ants are mobile,” O’Donnell said. “Observations suggest some birds are attracted to other birds at raids, and birds may even follow each other when moving among raids of different ant colonies.”

However, there did seem to be some bullies.

O’Donnell noticed some pairs of species were almost never found in flocks together despite, independently, being ant-chasers. That indicated that these bird species might chase each other off as competition, or just avoid each other entirely. Pairs that seemed to be unable to be around each other included the blue-throated toucanet and the brown jay, as well as the wood thrush and the white-eared ground sparrow.

“These antagonistic pairs were often species of very similar body size or feeding behavior,” O’Donnell explained. “Perhaps these species do compete very strongly at army ant raids.”

All in all, finding that birds largely work together to forage at army ant raids seems to demonstrate that cooperation is a better survival strategy than trying to keep food from the raids for their own species.

“Having other birds around may be an advantage because there are more eyes and ears to detect predators,” O’Donnell said. “If the raid is hard to monopolize, and food is very abundant there, then the costs of allowing other birds to attend may be low, further favoring positive species interactions.”

Sandeels and seabirds: Protecting our seas in post-Brexit waters

kittiwakers.jpg(RSPB 14 June 2017; Photo: Andy Hay)

New research led by the RSPB shows that UK seabird populations could be affected by the amount of a critical fish species caught in the North Sea by an industrial fishery, highlighting the importance of continuing to work with other countries on fisheries management after leaving the European Union.

The study suggests a link between the amount of sandeels caught by fishermen and the breeding success of kittiwakes (a small species of gull, currently red-listed in the UK), with higher intensity fishing leading to lower numbers of chicks being produced.

In the North Sea, sandeels provide a vital food source for breeding seabirds but are also the target of an industrial fishery conducted mainly by Denmark. Tracking data of individual breeding kittiwakes by RSPB scientists indicates that the most productive sandeel fishing grounds, an area known as the Dogger Bank, overlap with foraging areas of kittiwakes from eastern English colonies, raising the prospect that the fishery could adversely affect the birds’ populations.

The Dogger Bank is the largest sandbank in the North Sea, straddling the waters of the UK (about 100 miles off the Yorkshire coast), Netherlands and Germany, and supporting a high density of sandeels.

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