Tag Archives: study

How camouflaged birds decide where to blend in

How camouflaged birds decide where to blend in
(University of Exeter, Physorg 31 July 2017; Photo: Project Nightjar)

Animals that rely on camouflage can choose the best places to conceal themselves based on their individual appearance, new research shows.

The camouflage and concealment strategies of various animal species have been widely studied, but scientists from Exeter and Cambridge universities have discovered that individual wild birds adjust their choices of where to nest based on their specific patterns and colours.

The study looked at nine remarkably hard-to-see ground-nesting bird species (nightjars, plovers and coursers).

“Each individual bird looks a little bit different, and we have shown that they can act individually,” said project co-leader Professor Martin Stevens, of the Centre for Ecology and Conservation on Exeter’s Penryn Campus in Cornwall.

“This is not a species-level choice.

“Individual birds consistently sit in places that enhance their own unique markings, both within a habitat, and at a fine scale with regards to specific background sites.”

The study, carried out in Zambia, showed that individual birds chose backgrounds that enhanced their camouflage to the visual systems of their main predators – being better matched to their chosen backgrounds than to other places nearby.

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Bird echolocation inspires new engineering

(Birgitte Svennevig 2 August 2017)

All animals use a combination of senses to survive. But where the majority typically rely on one or two especially sensitive sensory systems, the oilbird excels by apparently having keen senses all-around.

In addition to its extremely sensitive vision, the oilbird has the neural foundation for a powerful olfactory sense, bristles by the beak for tactile sensation, and a powerful echolocation sense, normally found in bats and cetaceans.

“This complex sensory apparatus, where the animal has the ability to combine input from so many well-developed senses, is interesting to study,” says Signe Brinkløv of the Sound, Communication and Behaviour Group at the Department of Biology, University of Southern Denmark.

As a biologist, she is interested in understanding how the oilbird uses its senses to achieve the best possible conditions in its natural surroundings. From a more applied perspective, she wants to apply knowledge of animal sensory systems in new engineering.

“We have come a long way towards understanding individual senses. But senses complement each other, and the balance between different sensory inputs affects the behaviour of the animal when tackling various challenges—this becomes a very complex field of study, which is difficult to transfer from laboratory to natural conditions. If we can learn more about it, perhaps we can transfer the knowledge to technological developments,” she says.

An example is the interaction between vision and the sense of hearing, which the animal uses when it echolocates. With echolocation, the animal emits sounds that are returned as echoes from the surroundings and enables it to judge the distance to surroundings or distinguish between food items and other features.

“Today, drones are often controlled manually by a drone operator who is dependent on the video footage from the drone and thus the sense of sight in order to control it. But it quickly becomes difficult to navigate with such a system in darkness or when visibility is poor. If you could combine the sense of sight and echolocation on a drone to navigate based on input from both systems, then more opportunities open up. For instance, it could fly safely and perhaps autonomously in the dark or in between trees in a forest,” says Signe Brinkløv.

Signe Brinkløv and her colleagues have studied the echolocation of oilbirds in Trinidad. Oilbirds are nocturnal and live in caves in groups of up to several thousand individuals. At night, they leave the cave to find food. Their ability to echolocate enables them to navigate to and from their nests without bumping into the rocky walls of the cave, even in pitch black darkness.

The researchers hope that with further study of the interaction between oilbird vision and echolocation, they can develop a model that can be applied by sensory researchers and robotics engineers.

The study was published in Royal Society Open Science. It is based on sound recordings of echolocating cave-dwelling oilbirds at Asa Wright Nature Centre, Trinidad. The authors are Signe Brinkløv, Coen Elemans and John Ratcliffe.

Signe Brinkløv is a biologist at Department of Biology. Apart from birds, she also studies porpoise and bat communication. The oilbird (Steatornis caripensis) got its name because just before leaving the nest, the fledglings become so fat that their weight exceeds that of the adults. Just like whales, oilbirds have been used in the past for extraction of oil. Oilbirds also produce other sounds than their echolocation signals, which has led to several Spanish nicknames, including Guácharo and Diablotin (little devil), reflecting ghostly sounding calls which led the local Indians to compare the entrance to the birds’ caves with that to the land of the dead.

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.

The common cuckoo is an effective indicator of high bird species richness in Asia and Europe

Cuculus canorus2.jpg
(Federico Morelli, Anders Pape Møller, Emma Nelson, Yanina Benedetti, Wei Liang, Petra Šímová, Marco Moretti, Piotr Tryjanowski 29 June 2017)

Introduction

Why is the common cuckoo Cuculus canorus a fascinating bird species for humans? What are the main reasons for the species being known as “a messenger of spring and morality”1, and why is it so conspicuous in human culture? A review of folklore shows clearly that the enigmatic cuckoo has driven the collective imagination of people throughout the world for thousands of years. First and foremost the cuckoo-call is associated with seasonal change. The timing of arrival of the cuckoo and the vigour of its calls were also used as indicators of the weather2, 3. In ancient Egypt, Aristophanes wrote that its arrival was associated with harvest time2. Cuckoo lore is intimately linked with change and metamorphosis1,2,3 and its call reflects the real world passing of time when seeds are transformed into crops, maidens are married and maids become mothers.

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Results

A total of 65,234 observations of bird occurrence in 3,592 sample sites in different environments were collected from ten European and two Asian countries. The maximum bird species richness per point count in all countries ranged from 12 species (Finland), to 28 species (San Marino and Switzerland).

_________

Sample sites were treated as statistically independent observations because the spatial autocorrelation in all studied countries was not significant

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The temporal trend in common cuckoo populations was positively correlated with the overall trend in bird populations in European countries

__________

Discussion

Cuckoo as indicator: Extending species surrogacy from Europe to Asia

This study provides new evidence on the common cuckoo as a surrogate of bird species richness, previously tested in some European countries. This suggests that the common cuckoo is potentially a prime bioindicator in Eurasia. Even if related to different host species, and considering that the common cuckoo is not the only parasitic cuckoo in Asia24, we found the same pattern than in Europe: Occurrence of the common cuckoo is positively correlated with bird species richness in both continents. The implications related to finding the same pattern in Europe and in Asia are important from an ecological point of view. First, in Asia, C. canorus has different host species than in Europe. Second, the common cuckoo is not the only brood parasite in China and Japan. So, C. canorus is subject to a greater competitive pressure from other cuckoo species in Asia than in Europe. However, common cuckoo still shows the same capacity as surrogate of bird species richness, highlighting the process linking this particular (and charismatic species) to overall bird diversity.

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Our study shows that the population trend of common cuckoo, as well as climate suitability trend for the common cuckoo, follow the overall trend for populations of all other passerines species and the climate suitability trend in all Europena countries. This result supports the hypothesis that common cuckoo is a suitable bioindicator, making the species also sensible to climate change scenarios. When using proxies of population trends, many aspects need to be considered. For instance if within country variation in population abundance trends of different species is larger or smaller than variation among countries, and also how trends of other bird species can be related to the average community trend.

Read whole study

 

Molting feathers may help birds deal with environmental contaminants

Preview image
(Wiley 20 July 2017)

Mercury is a ubiquitous environmental contaminant that affects the health of birds and other wild animals. Two varieties of songbird—zebra finch and European starling—were found to shed mercury accumulation with their feathers in a recent study.

During a molt, both species quickly eliminated mercury from their blood and significantly reduced mercury concentrations in other tissues. This, coupled with a migration out of contaminated sites, may help birds deal with exposure to environmental toxins.

“It came as no surprise that feather molt accelerated the mercury elimination, but we did not expect the rates to differ so markedly from the non-songbird species that have been studied previously. Understanding species differences as well as how molt contributes to mercury elimination can improve risk assessments,” said Margaret Whitney, co-author of the Environmental Toxicology & Chemistry study.

Birds avoid crossing roads to prevent predation

(Science Daily 19 July 2017)

Roads can be dangerous to wildlife. Animals making the perilous journey against the traffic run the risk of meeting an untimely death. Until recently, it was widely believed, unlike other animals, birds were largely unaffected by the presence of roads and traffic, simply because they could fly.

A new study, published in the open-access journal, Frontiers in Ecology and Evolution, reveals this is not the case. Birds can find roads challenging too – they are less likely to be found next to roads and are hesitant to cross them.

“We observed fewer bird species and individuals of each species near to roads. In addition, they were less likely to cross wide roads,” says Christopher Johnson, who completed this research as part of his graduate studies at the Griffith University, Brisbane, Australia. “We found the smaller-bodied, forest-dependent species were the most affected, avoiding all but the narrowest of roads.

A keen bird-watcher, Mr. Johnson spent many hours carefully recording birds seen next to and crossing roads of different widths around the southern suburbs of Brisbane, Australia. He made sure that the vegetation on either side of the road of his recording sites were the same, as it was more likely that bird crossings occurred between similar habitats. These results were compared to the number of birds seen and heard in the vegetation 100m in from the roadside, to see if the species and numbers of individuals differed.

“For this study, we decided to try something new, by looking at the influence of different road widths (two, four and six-lanes) on bird crossings. In addition, we analyzed the road-crossing ability of birds of different body sizes and whether the type of bird, for example, small forest dependent, large forest dependent, honeyeater or urban tolerant species, had an effect,” explains Mr. Johnson.

The results were quite clear. The widest roads – six-lane carriageways – had fewer bird species and individuals of each species crossing them than the narrower two- and four-lane carriageways. When they looked at the different body sizes and bird types, it was the smaller forest-dependent species that showed the biggest difference.

The authors have suggested several reasons for these findings, such as birds choosing not to come out into the open for fear of predation and the creation of territorial boundaries, as breaks in vegetation can be used by birds to mark the edge of their territory. In addition, many highly aggressive, territorial bird species were seen to be taking advantage of the space near the roads, which would put off other birds crossing.

The findings of this study raises concerns, because bird species play an important role in the health of our natural environment.

Professor Darryl Jones, co-author of the study and Deputy Director of Environmental Futures Research Institute and the School of Environment at the Griffith University explains. “Birds perform a range of services that are of huge benefit to humans, from controlling pests such as mosquitoes and flies to the pollination and seed dispersal of many plants, including those of economic and medicinal value. By restricting bird movements through transportation networks, we are limiting their ability to perform these services and, ultimately, undermining the benefits we gain.”

The authors of the study strongly advise that measures are put in place to connect fragments of forest across roads, allowing wildlife to move freely.

“People use the road transport system to get from point a to b. Unfortunately, this has a negative impact on wildlife movement, particularly within urban environments,” says Daryl Evans, who also collaborated on this the research and is based at the Griffith University. “There are wildlife-friendly solutions to many of these issues, such as specially-designed overpasses, fauna underpasses and fencing so animals can avoid accessing the road, all of which need to be incorporated into the design of our road systems.”

“Further studies should look at the impacts of man-made breaks in vegetation, such as forest tracks and park walkways on bird movements,” adds Professor Jones. “We are currently using our data to identify the ‘at risk’ bird species within suburban areas, to assist with conservation management.”

Clever crows can plan for the future like humans do

Clever crows can plan for the future like humans do

(Markus Boeckle And Professor Nicky Clayton 14 July 2017)

This contrasts with all of the previous studies in future planning, which have focused on naturally occurring behaviour. For example, we know that California scrub jays cache their food according to their future needs. And that bonobos, chimpanzees and orangutans select, transport and save appropriate tools for future needs.

General intelligence

These studies have shown that animals can plan for the future – but they left an important question open for debate. Are animals only able to plan to use abilities that have evolved to give them a specific advantage, or can they flexibly and intelligently apply planning behaviour across various actions? Most critics would say the former, as the animals were tested in naturally occurring behaviours.

But the new research provides the first compelling evidence that animal species can plan for the future using behaviour that doesn’t typically occur in nature. This supports the view that at least some cognitive abilities in animals don’t evolve just in response to specific problems. Instead, it suggests that animals can apply these behaviours flexibly across problems in a similar way to humans.

It seems that, in corvids and apes, intelligence is not a system to solve a predefined set of problems (dedicated intelligence) but rather a computational system to improvise new solutions (improvisational intelligence). But it is still unclear what this cognitive system exactly is and how it evolved.

What’s needed now is neuro-biological evidence of general intelligence in animals. We also need to investigate how flexible and improvisational behaviour evolved. Then we might be able to see how crows’ ability to plan for the future fits in with their broader cognitive powers.

Humans aren’t as unique as we used to think. Not, at least when it comes to making plans for the future. Scientists originally thought humans were the only animals that made plans but, over the past decade, studies on non-human primates and the crow family have challenged this perspective.

For example, we’ve seen that these animals are able to store tools for later use, cache food in places where it will be needed the most, and hide pieces of the sort of food they know will be running low in the future.

In all these studies, the animals had to consider what to do, where to do it and when to prepare for certain specific future events. The latest research shows that ravens can indeed anticipate the “what, where and when” of a future event on the basis of previous experiences. But unlike the previous studies, this work tested the birds in behaviour they don’t normally show in the wild. This provides evidence that they have a much more general ability to plan for the future than previously thought.

Food hoarding is common in members of the crow family (corvids) because they often eat from perishable animal carcasses, which provide lots of food but are only available for a short amount of time. To create a suitable cache of food they need to work out what to store, where to put it and when to do so.

The new study, published in the journal Science, tested the birds outside this naturally occurring behaviour, which may have evolved specifically because it gives crows a survival advantage. Some crow species are known to naturally use tools to retrieve food. So the researchers tested whether the birds could store and retrieve a tool so they could get at their food after a gap of 17 hours – something we wouldn’t expect them to do naturally. The scientists didn’t give the birds a chance to learn this behaviour first but they were still able to instantly select the tool out of a number of unnecessary items.

In another experiment, the researchers taught ravens to select a token from a number of items that they could then exchange for food. Again, the birds then showed that they could plan for the future using this new behaviour. They were able to store this token and then retrieve and use it when they were offered the chance to exchange it for food 17 hours later.

This contrasts with all of the previous studies in future planning, which have focused on naturally occurring behaviour. For example, we know that California scrub jays cache their food according to their future needs. And that bonobos, chimpanzees and orangutans select, transport and save appropriate tools for future needs.

General intelligence

These studies have shown that animals can plan for the future – but they left an important question open for debate. Are animals only able to plan to use abilities that have evolved to give them a specific advantage, or can they flexibly and intelligently apply planning behaviour across various actions? Most critics would say the former, as the animals were tested in naturally occurring behaviours.

But the new research provides the first compelling evidence that animal species can plan for the future using behaviour that doesn’t typically occur in nature. This supports the view that at least some cognitive abilities in animals don’t evolve just in response to specific problems. Instead, it suggests that animals can apply these behaviours flexibly across problems in a similar way to humans.

It seems that, in corvids and apes, intelligence is not a system to solve a predefined set of problems (dedicated intelligence) but rather a computational system to improvise new solutions (improvisational intelligence). But it is still unclear what this cognitive system exactly is and how it evolved.

What’s needed now is neuro-biological evidence of general intelligence in animals. We also need to investigate how flexible and improvisational behaviour evolved. Then we might be able to see how crows’ ability to plan for the future fits in with their broader cognitive powers.