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All dressed up and a god on the dance floor – in Saturday Night Fever, John Travolta made an impression both on the big screen and with the audience. Birds do it in a similar way, combining an attractive plumage with an acrobatic performance. The evolution of avian courtship displays was the focus of an international study conducted with the participation of researchers from the University of Veterinary Medicine Vienna using manakins, a group of birds found throughout the American tropics.

For their study, the researchers compared the elaborate courtship behaviour of two closely related species, golden-collared manakins (Manacus vitellinus) and white-collared manakins (Manacus candei), and their hybrids, focusing on a small island population of hybrids off the coast of Panama.

Courtship dance beats genetic similarity

The study confirmed that the island birds were genetically similar to the mainland hybrids, which in turn were more similar genetically to the white-collared manakin parental species. The research team then analysed the courtship dance, which is performed within an area demarcated by small saplings, which the courtship male cleans before his courtship dance (jump-snap routine).

The researchers were surprised to find that hybrid males, despite their genetic similarity to white-collared manakins, performed key dance manoeuvres like golden-collared manakins. Other elements of the hybrids’ dance performance either did not differ from that of the white-collared parents or was a mix of the courtship dance of both parental species.

Modular evolution in response to sexual selection

But why does the courtship dance of hybrid males resemble that of golden-collared manakins when the genetic background of the hybrids is more consistent with white-collared manakins? The researchers suspect that selected components of the dance routines of golden-collared manakins have been adopted by white-collared manakins through sexual selection.

Leonida Fusani, the study’s last author and head of the Konrad Lorenz Institute of Ethology at Vetmeduni Vienna, explains this process in evolutionary terms: “We hypothesise that such modular evolution occurs in response to sexual selection, whereby specific components of the bird’s dance routine shift to yield a broader change in its functional appearance.”

The article "Beyond plumage: acrobati c courtship displays show intermediate patt erns in manakin hybrids" by  Julia Barske, Matthew J. Fuxjager, Claudio Ciofi, Chiara Natali, Barney A. Schlinger, Tim Billo and Leonida Fusani was published in „Animal Behaviour“.

Video vom Balzritual

Wissenschaftlicher Artikel

2023-05-11

Biologging devices are often attached to birds for research purposes and to collect important data. Now a team of researchers led by the University of Veterinary Medicine Vienna has investigated the aerodynamic effect of biologgers with northern bald ibis, an endangered species of bird, in a wind tunnel. The results showed that biologging devices significantly influence energy expenditure and flight distances, and that aerodynamic optimizations and proper positioning on the birds’ bodies can significantly reduce the detrimental effects.

There has been little scientific research to date regarding the impact of biologgers on animal aerodynamics and hydrodynamics. This stands in marked contrast to the increasingly extensive use of such technologies in wild-living animals. Recently, there have been growing concerns about the detrimental effects that these devices may have on the animals involved.

While the focus in biologging has long been solely on reducing weight, the researchers in this study investigated the aerodynamic effects of the devices. For this purpose, the northern bald ibises (Geronticus eremita) were trained to fly in a wind tunnel where heart rate and dynamic body acceleration (VeDBA) were measured as parameters for energy expenditure in relation to different logger shapes and wind flow directions.

The perfect biologger: attached to the back of the body and aerodynamically shaped

“Our data demonstrates that the position of biologging devices significantly influences the flight distances, and that shape has a considerable effect on energy expenditure. Unfavourable shape and positioning not merely affect the amount of energy expended during flapping flight; the energetically probably more important effect is that the devices impair the bird’s ability to glide or soar, which forces them to perform the energetically much more demanding flapping flight more frequently,” says the study’s first author, Ortal Mizrahy-Rewald from the Research Institute of Wildlife Ecology at Vetmeduni, summarizing the key findings of the study.

A complementary study with wild-living northern bald ibis during spring migration demonstrates that the position of the devices on the birds’ backs affects the length of the flight stages. “Birds that carried the devices on the upper back had significantly shorter flight stages compared to birds with a device positioned further towards the tail,” as Mizrahy-Rewald explains.

Little effort required to reduce detrimental effects

According to the researchers, the detrimental effects can be reduced with relatively little effort through a strictly aerodynamic design of the housing and increased consideration of aerodynamics when attaching the device to the animal’s body. In birds, the attachment of biologging devices via leg loops to the lower back is clearly preferable to the common attachment method via wing loops on the upper back. Nevertheless, the importance of drag reduction may vary between systems, as the benefits of having a biologging device close to the centre of gravity may outweigh the increase in drag that this involves.

The article “The impact of shape and attachment position of biologging devices in Northern bald ibises” by Ortal Mizrahy‑Rewald, Natalie Winkler, Frederik Amann, Katharina Neugebauer, Bernhard Voelkl, Herwig A. Grogger, Thomas Ruf, and Johannes Fritz was published in Animal Biotelemetry.

Scientific article

2023-05-08

An international team of scientists, including Leonida Fusani and Ivan Maggini from the Konrad Lorenz Institute of Ethology of the Vetmeduni, conducted a review of literature on the response of tropical birds to thermal variation, with a focus on their vulnerability to warm conditions. The team used an integrative or synthetic review approach, which involved searching online databases for relevant studies. They analyzed the empirical data from the retrieved studies and tied it together with the physiological processes that can confer vulnerability or resilience to answer questions about the thermal tolerances of tropical birds and their vulnerability to global warming.

The scientists explored the influence of microclimatic alterations, such as those caused by land-use change and humidity, on physiological vulnerability. They identified knowledge gaps and suggested future research directions to guide comprehensive analyses of tropical bird vulnerability to the effects of global warming. The team emphasized the importance of addressing the void of knowledge on the physiological response of tropical birds to global warming before attempting to relate distributional rearrangements to thermal sensitivity, as previously recommended.

They were able to confirm that the assumption that tropical species are more sensitive to climate change due to low physiological capacity to withstand temperature fluctuations and being near their limits of heat tolerance under current climatic conditions is not a fundamental characteristic of tropical birds, as indicated by evidence from the literature. While community-level rearrangements such as biotic attrition and elevational shifts have been observed in birds, there is no consistent evidence of direct physiological sensitivity to warming. Before examining the relationship between distributional changes and thermal sensitivity in tropical birds, it is crucial to address the lack of understanding regarding their physiological response to global warming.

More research is needed to understand how different ecological contexts affect the response of populations and species to warming, which would provide a better understanding of current and future community rearrangements in tropical birds. It is predicted that tropical communities will be affected more by climate change than those in higher latitudes, leading to frequent redistributions of tropical communities and turnovers benefiting warm-adapted species, leading to the thermophilization of communities. While it is commonly assumed that thermal sensitivity is the main driver of these rearrangements, empirical evidence from physiological studies is limited, especially for tropical endotherms like birds.

In conclusion, the researchers suggest that many tropical bird species possess sufficient physiological resilience to withstand thermal variation within the range of predicted future warming levels. Tropical birds are not necessarily more physiologically threatened by warming in the short term than birds residing at other latitudes. Nevertheless, some avian species in arid regions outside the tropics, such as southern Africa, Australia, the North American southwest, and the Iberian Peninsula, may face more imminent threats due to rising temperatures.

This does not mean, however, that tropical birds are entirely insensitive to warming, especially if the local average temperature increases by 5°C as predicted in worst-case scenarios. For instance, birds living in open areas and relying on gradients for passive heat dissipation would need higher levels of hyperthermia, which can prove challenging. (Hyperthermia is a condition where the body temperature rises above the normal range. In animals, including birds, this can occur due to exposure to high temperatures, which can lead to overheating and other physiological stresses) Also, birds inhabiting hot and arid or semi-arid environments that experience reduced or absent water sources during heat waves are equally vulnerable. Furthermore, climate-driven variations in rainfall regimes can cause more intense wet and dry seasons, altering the frequency of stronger humid-heat events and extending the dry season. Although climate change is a significant concern, it must be emphasised that anthropogenic habitat loss and degradation remain the major imminent threats to biodiversity. Land-use changes not only directly affect tropical bird diversity but also reinforce climate-driven threats by altering the microclimate.

To protect tropical bird diversity, the most promising approaches are to preserve vast forested areas along ecological gradients and to improve land management strategies.

The article "Physiologically vulnerable or resilient? Tropical birds, global warming, and redistributions" by Otto Monge, Ivan Maggini, Christian H. Schulze, Stefan Dullinger, and Leonida Fusani was published in Ecology and Evolution.

Scientific article

2023-04-24

The Pannonian Bird Experience (BEX) 2023 will take place in Seewinkel from April 23-30, 2023. Our team from the ringing center of the Austrian Ornithological Centre (AOC) will be part of the program there with the demonstration ringing of birds from April 28-30.

Bird ringing also has a long tradition at Lake Neusiedl. In addition to the actual ringing, the caught birds are also measured and weighed. This provides insightful data on the various aspects of bird migration over longer periods of time. You have the opportunity to see the birds up close, watching our experienced bird ringers .

The entire programme can be found on the BEX website.

2023-04-19

Scientists have long been working on modelling bird formations, in particular line formations. In the scientific literature, there are several attempts to model flock of birds flying in a cluster (as for example those wonderful flocks of starling that look like dancing in the sky). However, about birds flying in line formation there is little as it is rather challenging to collect data.

Within a project funded by the Austrian Science Fund FWF (grant no. FWF P 30620-BBL) and intramural funds of the University of Veterinary Medicine, Vienna, researchers from the Konrad Lorenz Institute of Ethology of the University of Veterinary Medicine and the University of Vienna, together with Team Waldrapp (Northern bald ibis) have collected and analysed data that  track a flock of Northern Bald Ibis (Geronticus eremita) during the human-guided migration south and collected data on line formation. Data were collected in the frame of a European LIFE + project, with 50% contribution of the LIFE financial instrument of the European Union (LIFE + 12-BIO_AT_000143, LIFE Northern Bald Ibis) in a collaborative project led by the Waldrappteam.

Once the data was collected, they needed to classify when a bird was flying in the wake of another individual and when not. When a bird flies and flaps its wings, it produces vortexes of air behind itself: a downwash behind the body and two upwashes, in correspondence to the wingtips. If another bird position itself in order to catch the upwash, then it is flying in the wake of the other bird. It does so because it can gain lift and save some energy while flying. However, it is not so easy to determine where exactly these upwashes lie, how they develop, and their extent or limits because they do not have crisp boundaries, but fuzzy ones. Therefore, it is difficult to determine when a bird is exploiting the upwash and when it is not.

The researchers modelled these vortexes using fuzzy logic, which helps to model vague and uncertain concepts. In addition, the model allows to classify whether a bird is flying in the wake of another bird or not.

This is the first attempt in the scientific literature that tries to model line formations. Further steps will be to apply the model to investigate if birds that are flying in the wake are saving energy, to unveil patterns of movement while flying in formation, and to study social interactions and their influence during flight formation.

The article “Characterization of bird formations using fuzzy modelling" by Elisa Perinot, Johannes Fritz, Leonida Fusani, Bernhard Voelkl and Marco S. Nobile was published in Journal of the Royal Society Interface.

Scientific article

2023-04-13

A current international study led by the Konrad Lorenz Institute of Ethology at the Vetmeduni examined the effects of drone flights for research purposes on vultures. The researchers come to the conclusion that unmanned aerial systems offer significant advantages over other investigation methods. On the other hand, there are risks from potential disruptive effects at the breeding site of the birds of prey. The scientists therefore recommend using drones with a sense of proportion.

Vultures are among the world's most threatened bird species and play a unique role at the bottom of the food chain in ecosystems. They are therefore of great interest to science. The use of drones for research on them is developing rapidly. Reasons are technological advances, affordability and easy accessibility. However, there are a number of factors that must be taken into account when using unmanned aerial systems in order not to disturb the sensitive phase of the birds' reproduction.

An urgen need to close dangerous knowledge gaps

“The reduced disturbance of wildlife is the main argument for using modern observation and photo techniques with drones. The big unknown, however, is how animals will react and the potential for long-term negative consequences. To fill this dangerous gap, we strongly recommend documenting the use of drones with animals in captivity and in the wild. In addition, we need uniform guidelines for the use of drones in order to be able to scientifically interpret disturbances and bird reactions," says study lead author Richard Zink from the Konrad Lorenz Institute of Ethology at Vetmeduni, summarizing the most important results.

Better safe than sorry: use drones with care

Richard Zink also advocates a controlled use of drones: "Due to the lack of data on long-term disruptive effects, we advocate the precautionary principle. By following a set of species-specific recommendations, the potential negative impacts of drones can be limited and their value for conservation management maximized. In particular, the physiological and long-term effects on vulture health and reproductive success should be considered.”

Concrete recommendations to the international scientific community

According to the scientists, the high sensitivity and territorial behavior of most vulture species in particular pose considerable challenges to the use of drones. In general, the experts advise against the regular use of drones for nest inspections during the most sensitive breeding phases and in bad weather or when potential predators of the chicks are nearby. "We are not calling for a ban on the use of unmanned aerial vehicles for vulture researchers, but we expressly advocate careful examination of the circumstances and careful documentation of the effects," emphasizes Richard Zink, who is responsible for the study and together with his co-authors analyzed scientific research on the responses of European vultures and other similar species to drones.

The article "Assessing the potential disturbance effects on the use of Unmanned Aircraft Systems (UASs) for European vultures research: a review and conservation recommendations“ by Richard Zink, Elena Kmetova-Biro, Stefan Agnezy, Ivaylo Klisurov and Antoni Margalida was published in „Bird Conservation International“.

Wissenschaftlicher Artikel

2023-04-12