Tag Archives: behavioural ecology

Good grief! Losing a friend brings wild birds closer together

(Physorg, Oxford University 17 May 2017;Photo: Molly Harwood)

New Oxford University research has revealed that instead of grieving, wild birds appear to adjust to the loss of a flockmate by increasing both the number and intensity of their relationships with other birds.

Human impacts around the globe are causing increasing numbers of wild animal populations to decline. The effects of losing a mate, friend or group member on remaining animals’ social behaviour is currently little understood. The research newly published in the journal Proceedings of the Royal Society B, sought to improve our understanding of how wild animals cope with loss.

Scientists from Oxford University’s Department of Zoology tracked the social interactions between more than 500 wild great tits over winter, whilst temporarily removing birds from flocks at random. By doing so, the team were able to assess how wild birds respond to losing their flockmates, providing new insights into social behaviour which may also have valuable implications for conservation programs.

Lead author, Postdoctoral Research Fellow Dr Josh Firth said: ‘We found that individual birds adapt to losing a flockmate by increasing not only the number and tightness of their social relationships to others, but also their overall connectedness within the social network of remaining individuals.’

Previous computational research has suggested that losing individuals may cause animal social systems to break down but the new findings suggest a brighter picture. If animals have the ability to adapt to the disruption caused by losing members of their group, important processes like information transmission may be maintained better than expected. In the same sense, strategies that focus on culling individual animals to prevent disease spread may be futile if the remaining animals respond by making new social links.

This research represents the first experimental test of how wild animal social networks respond to loss, and the findings share clear parallels with a recent study that looked at how losing a friend impacts human social networks. The human-based research used data from Facebook to show that following the death of a user friends of the deceased appear to become closer and increase their interactions over Facebook with each other.Dr Firth said: ‘Great tits are very sociable birds, and their relationships shape almost every aspect of their lives. A real benefit of studying these birds is that we can run experiments to test the principles of social behaviour. Interestingly, in this case the results appear surprisingly similar to what has been suggested for humans.’

‘Now we understand how birds adjust their social behaviour upon losing randomly chosen flockmates, we want to experimentally test the consequences of removing the key players and the most sociable individuals for conservation-related processes such as information and disease spread.’

Even non-migratory birds use a magnetic compass

(Lund University 18 May 2017)

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.

Although the magnetic compass of birds has been studied by the research community for a long time, the understanding of how it works is still very incomplete, according to Atticus Pinzón-Rodríguez.

Study on blue tits: Smell first, and then beg

(Universitaet Bielefeld 12 May 2017)

Nestling blue tits can discriminate between the smell of other nestlings and adapt their begging behaviour accordingly. This is the outcome of the latest study by Dr. Barbara Caspers and Dr. Peter Korsten from Bielefeld University to be published today on the 12th of May in the journal Functional Ecology.

In this subproject, Dr. Barbara Caspers and Dr. Peter Korsten from Bielefeld University and Marta Rossi from the University of Sussex in Brighton (Great Britain) examined the begging behaviour of seven-day-old blue tit nestlings from a population near the Dutch city of Groningen. ‘Blue tit nestlings beg to obtain food from their parents and may have to compete with as many as ten peers in the nest that are not all necessarily full siblings,’ explains Dr. Peter Korsten. In earlier studies of other songbirds, it was already found that this competition intensifies when nestlings are competing with non-kin. Then nestlings beg even more intensively for food.

In the present study, the research team presented nestlings of blue tits with two different smells: an familiar smell of siblings from their own nest and an unfamiliar smell of unrelated nestlings from another nest. In both experimental situations, the biologists then measured how much the nestlings begged. Results showed that blue tit nestlings beg longer and more intensely after being exposed to the smell of the unfamiliar nestlings compared to the familiar smell of their own nest mates. ‘Up to now, we did not know how songbird nestlings were able to discriminate between the smell of close kin and less related individuals when competing for food from their parents. Our study shows that they may well smell this difference,’ says Caspers.

Science had long assumed that birds cannot smell at all. Behavioural researchers together with Dr. Barbara Caspers at Bielefeld University have already been able to disprove this in earlier studies on zebra finches.

Birds choose their neighbors based on personality

(University of Oxford 7 May 2017; Photo Soru Epotok)

Birds of a feather nest together, according to a new study which has found that male great tits (Parus major) choose neighbours with similar personalities to their own.

Oxford University researchers investigated whether the personality of birds influences their social lives — in particular who they choose to nest near. The study involved analysing social network structure in a population of wild great tits at Wytham Woods, Oxfordshire, over six consecutive breeding seasons.

Lead author and doctoral student Katerina Johnson explained: ‘We found that males, but not females, were picky about personalities, with males opting for like-minded neighbours. Our results emphasise that social interactions may play a key role in animal decisions.’

This tendency for males to associate with other males of similar personality may be particularly important during the breeding season when aggression peaks. Males fiercely defend their territories and compete for opportunities to mate with females and so shyer males may avoid setting up home near bolder, more aggressive individuals. Females, however, likely choose where to nest based on the attractive qualities of males.

The results also showed that this personality assortment amongst males was not affected by local environmental conditions. ‘Just like students choosing their flatmates,” Katerina commented, ‘birds may pay more attention to who they share their living space with than simply location.” She added: “Animal personalities can influence their social organisation and humans are likewise known to form social networks based on shared attributes including personality.’

Just like us, animals display individual behavioural differences that are consistent over time and stable across different situations, and so may be thought of as personality traits. The researchers tested the personality of great tits by introducing them to a new environment and measuring how they responded. Whilst bold birds are keen to actively explore their new surroundings, shy birds tend to be more hesitant and cautious.

Katerina said: ‘This novel research finding may also help explain the evolution of personality and why individuals in a population differ in their behaviour. Rather than one particular personality type being favoured by natural selection as ‘the best’, different behavioural strategies may be equally good depending on who you choose to be your friends and neighbours.’

Perhaps by nesting closer to others of similar character, this may improve a bird’s chances of survival and passing on their genes to the next generation. For example, although having bold neighbours may result in more skirmishes between males, they might also gain a shared benefit by more effectively repelling intruders.

Feeding strategies in competing hummingbird species observed in a small area in Brazil

(Pensoft Publishers; 2 May 2017; Photo: Lucas Lanna)

Being the vertebrates with the highest metabolic rate thanks to their rapid wing flaps, the hummingbirds have evolved various types of feeding behaviour. While the nectar-feeders tend to go for food high in energy, strong competition affects greatly their preferences and behaviour towards either dominance, subordination, a strategy known as trapline and a fourth one named hide-and-wait, conclude the Brazilian scientists Lucas L. Lanna, Cristiano S. de Azevedo, Ricardo M. Claudino, Reisla Oliveira and Yasmine Antonini of Universidade Federal de Ouro Preto. Their conclusions following six months of observations in an Atlantic Forest remnant in southeastern Brazil are published in the open access journal Zoologia.

To test previous assumptions as well as their own hypotheses, the researchers placed artificial bird feeders filled with variable in concentration sugar-water solutions across four separate patches at the core of the forest fragment.

The scientists sought to find out whether the birds would show clear preference for the most sugary food source; whether larger size and heavier weight would guarantee better access to the most nutritious feeders; what strategies would be adopted by each species; and which ones would prove the dominant and most aggressive.

As expected, the scientists concluded that the birds prefer the most sugar-dense solutions. However, when subordinate species, such as the white-throated hummingbird and the versicoloured emerald, confronted dominant species guarding the most nutritious food sources, they would be either frightened or expelled following a short chase. Subsequently, these hummingbirds would resort to the feeders with low-sugar solutions.

In their turn, the Brazilian ruby and the violet-capped woodnymph proved to be the dominant and most aggressive species in the studied area. Upon seeing an ‘intruder’ in their territory, which might be either another species, or belonging to their own, they would vocalise their threats, alert them by perching by the feeder, or expel them following a short pursuit. However, they would only try to limit the access for subordinate hummingbirds if the energy that could be gained from the feeder exceeded the energy loss of the chase.

Contrary to another initial hypothesis, it was not the largest and heaviest species that were the dominant ones. There were two species of hermit hummingbirds which were the largest and the heaviest, however, they expressed no territorial or aggressive behaviour. Instead, they were recorded intruding in the territory of the two dominant hummingbird species. In their turn, the Brazilian ruby and the violet-capped woodnymph would often frighten them. Nevertheless, rather than fleeing, the ‘castaways’ were seen hiding in the shrubs, remaining quiet, and returning to the feeder as soon as the dominant bird was gone. This behaviour strategy, named hide-and-wait, has not been reported in hermit hummingbirds prior to this study, according to the authors.

Having reported all feeding strategies in their study, the scientists conclude that the dominant territorial species and the trapliners feed most frequently and most sufficiently, as they use the most sugary sources.

However, the authors note that the high abundance of food, as well as the presence of aggressive territorial species might have affected the hummingbirds’ behaviour and preferences.

Seabird parents compensate for struggling partners

(AOS 26 April 2017; Photo: L. Takahashi)

For species where both parents work together to raise their offspring, cooperation is key — it’s as true for birds as it is for us! A new study from The Auk: Ornithological Advances shows how pairs of Common Murres update each other on their condition so that when one partner needs a break, the other can pick up the slack.

Common Murre parents trade duties throughout the day — one stays at the nest while the other leaves to forage, hopefully coming back with a fish for the chick. Because brooding the chick requires much less energy than foraging, staying at the nest is preferable for a bird that’s in poor condition. Linda Takahashi, Anne Storey, and Carolyn Walsh of Newfoundland’s Memorial University, along with Sabina Wilhelm of the Canadian Wildlife Service, studied the “turn-taking ceremony” that parents perform when they switch places. They found that the time they spend preening each other provides a way for the two birds to exchange information about how they’re doing, so that if one is in poor shape the other can compensate.

The researchers observed 16 pairs of murres with chicks on an island off the coast of Newfoundland in summer 2009, recording their behavior when parents switched duties at the nest and capturing the birds to check their body condition. Their results show that these “nest relief” interactions take longer when one partner is especially low in body mass, suggesting that when brooders withhold preening and stall their departure, they’re letting their mates know that they need more time to rest; the returning mate can then compensate by going off to forage again rather than trading places immediately. Similarly, the brooding mate might let a struggling returner take over take over at the nest even if they haven’t brought back a fish.

“We had been doing murre field work for years in Witless Bay studying reproductive and parental behavior, and we became intrigued with the variation that we saw among pairs in their nest relief behaviors,” says Walsh. “Some nest reliefs were short and businesslike, while other nest reliefs seemed to involve a lot of interaction between the mates, and it took a long time for the mates to exchange brooding duty. When Linda Takahashi came to Memorial University as a master’s degree student, we decided that her project should focus on getting the details about this very interesting variation in murre nest relief behaviors.”

“The roles of avian pair members have been much studied in terms of energy investment and food delivery, but we are accustomed to thinking of these problems in terms of evolutionary tradeoffs. The ways in which contributions are actually negotiated within individual pairs has, until recently, been largely overlooked,” according to longtime seabird researcher Tony Gaston of Environment Canada. “Linda Takahashi’s paper addresses this deficiency, and this is a field which promises to open up additional avenues of research on within-pair communication.”

‘Happy wife, happy life’ meaningful for birds, too

‘Happy wife, happy life’ meaningful for birds, too (Victoria University; 19 April 2017)

Research from Victoria University of Wellington has shown for the first time that wild male birds read their partner’s behaviour to appropriately cater to her food desires.

Dr Rachael Shaw, a postdoctoral research fellow in Victoria’s School of Biological Sciences, conducted a study on a group of North Island robins based at Zealandia.

The research investigated whether male robins could give their mate the type of food that she was most likely to want during reproduction.

“Robins are a monogamous, food-sharing species, so were ideal for this experiment. The experimental procedure has only previously been used in the laboratory on Eurasian jays,” she says.

“We found male robins appropriately catered to their mates’ desire, even when the female’s behaviour was the only cue available to guide their choices.

“This suggests that females can signal their current desires to their mates, enabling males to respond to that.”

Dr Shaw says the finding raises the possibility that other species might be capable of doing the same.

“In many species food sharing by the male is vital to help the female offset the energetic costs of reproduction, such as egg laying and incubation. The male’s ability to give his mate what she wants could in fact be an important factor in determining the success of a pair, as well as influencing whether they stay together. These are really exciting avenues for future research.”

The experiment first involved establishing female robins’ eating habits. “I fed the females either meal worms or wax worms, and then gave them the choice between these two types of insect larvae. I found that after the females had eaten one type of insect, they would prefer to eat the other type when given the choice. This means that the female’s desire for a particular food is affected by what she has previously eaten.”

Based on this, Dr Shaw then tested if the male would also be able to choose the type of insect his mate was most likely to want (the one she had not just eaten).

“Regardless of whether or not he had seen what his mate ate first, the male still made the appropriate choices. This suggests that the female is likely to be displaying her current desire in her behaviour, and that the male is using these cues to identify the food that she wants.”

The research, co-authored by Victoria’s Associate Professor Kevin Burns and Professor Nicola Clayton from the University of Cambridge in the United Kingdom, was recently published in the journal Scientific Reports.

The field work and data collection was carried out by Dr Shaw with help from Victoria student Regan MacKinlay. Dr Shaw’s research is supported by a Rutherford Foundation postdoctoral fellowship and a Marsden Fast Start grant from the Royal Society of New Zealand.