In birds and other species alike, pairs can face considerable difficulties with reproduction. Scientists of the Department of Behavioural Ecology and Evolutionary Genetics have now shown in an extensive analysis of 23,000 zebra finch eggs that infertility is mainly due to males, while high embryo mortality is more a problem of the females. Inbreeding, age of the parents and conditions experienced when growing up had surprisingly little influence on reproductive failures.
Copyright drawing: Yifan Pei
Researchers led by Manfred Gahr in Seewiesen have investigated the relationship of bird families. For the first time, they have been able to clarify the relationship of all families of non-passerine birds and almost all families of passerine birds. The new family tree is based on gene sections that do not code for proteins, but contain sequences that are specific to the families and their genera.
Copyright image: André Labetaa
Across virtually all human cultures, couples prefer to conceal sexual intercourse from the sensory perception of conspecifics. Yitzchak Ben Mocha from the former Humboldt Research Group in Seewiesen has analysed ethnographies from 249 cultures and found this striking uniformity of human preference despite the considerable cultural differences. Relying on his previous finding of a parallel phenomenon in the Arabian babbler, Ben Mocha developed the "cooperation maintenance hypothesis" to explain why individuals conceal matings from the sensory perception of conspecifics. Using this hypothesis, Ben Mocha predicts in which social species habitual concealment of mating by dominant group members may be found.
Scientists of the department Behavioural Neurobiology have investigated the neural basis of the vocal interaction of zebra finch pairs that form lifelong partnerships. The researchers found that in males, the neurons of a specific brain area (the so-called HVC) were activated as soon as they heard the calls of their female partner, even if the later was not present. What is particularly exciting, however, is the finding that in the presence of females, i.e. in a normal social context, the HVC neurons are only activated by the calls of the females, if the males were able to anticipate them in advance. In this case, in a way that has not yet been clarified, a neuronal excitation and then a reaction of the mentioned male HVC neurons occurs before the call of the female. The male was thus able to respond more quickly to the female calls, which probably plays an important role for pair bonding and thus breeding success.
Hummingbirds are the smallest birds with the fastest heart rate and the largest flight muscles, just to name a few record-breaking characteristics. Some species communicate through complex sounds that are learned early in life, comparable to the process of language acquisition of humans. How exactly these complex sounds are produced has now been discovered by scientists from Seewiesen in collaboration with the Zoologische Staatsammlung München using three-dimensional computer tomography scans, with which they were able to create a high-resolution digital map of the morphology of the vocal organ (syrinx) of the black hummingbird. Due to its location on the outside of the thoracic cavity and the course of the muscles, the syrinx is not affected during the extensive flight movements. The small organ also contains ossicles that are potentially related to the production of high-pitched sounds. Altogether, the hummingbird syrinx enables precise control and production of the sounds.
Migratory starlings are avian athletes that fly long distances in conditions that can push them very close to their physiological limits. Glucocorticoids are hormones that increase during endurance exercise to provide ready-to-use fuel to satisfy the high energy demands; however, prolonged exposure to high glucocorticoids is detrimental. A new study of researchers from Seewiesen, the US and Poland with European starlings in the wind tunnel show that dietary anthocyanins – antioxidants present in colored berries selected by birds especially during migration –control excessive secretion of glucocorticoids when birds are flying for long durations. This supports the novel idea that dietary anthocyanins have important metabolic functions that also attenuate the endocrine stress response triggered by endurance flight.
Urbanization is increasing worldwide; most humans nowadays live in cities. Despite of the associated general decline in diversity due to habitat fragmentation, availability of resources or pollution, there are examples of species that successfully colonize urban habitats. Now, a group of researchers around Jakob Mueller and Bart Kempenaers performed a genome-wide comparision of urban against rural burrowing owls, a bird species that colonized South American cities just a few decades ago. Among other things, the researchers found in city birds selection signals in genes that act in synapses and neuron projections in the brain with potential control functions for cognitive and emotional behaviour and could thus play an important role in the adaptation to the urban environment.
(Image copyright: José L. Tella)
Starlings sleep five hours less per night during the summer. Compared to winter, the birds take more mid-day naps and live under higher sleep pressure. During full-moon nights, starlings sleep around two hours less than usual. In their study, researchers of the Universities of Groningen and Zurich together with research group leader Niels Rattenborg from Seewiesen show that sleep regulation in starling birds is highly flexible and sensitive to environmental factors.
Sjoerd J. van Hasselt, Maria Rusche, Alexei L. Vyssotski, Simon Verhulst, Niels C. Rattenborg, and Peter Meerlo: Sleep Time in the European Starling Is Strongly Affected by Night Length and Moon Phase. Current Biology, 19 March 2020
Winter associations predict social and extra-pair mating patterns in blue tits. Researchers of the Max Planck Institute for Ornithology and the MPI for Animal Behaviour show in their new study that blue tits that often foraged together during winter were more likely to end up as breeding pairs or as extra-pair partners, whereby bonds between future breeding partners seem to establish earlier in winter than those between future extra-pair partners.
Male pectoral sandpipers typically visit several potential breeding sites during the short arctic summer. The decision about where to go next seems to be made opportunistically: they often leave in the direction the wind takes them. Researchers of the Max Planck Institute for Ornithology in Seewiesen tracked the flight path of 80 males with the help of small satellite transmitters and found that breeding areas in the Russian Arctic are more likely to be visited under tailwind conditions. In an environment where the summer is short and mating opportunities are unpredictable, individuals may save time and energy by using wind support.
In birds, timing of arrival in a breeding area influences who ends up breeding and who does not. This aspect of behaviour, well-known in migratory birds, has now been studied for the first time in a non-migratory species, the blue tit. Carol Gilsenan, Mihai Valcu and Bart Kempenaers found that arrival time in the breeding area was an individual-specific and fitness-relevant trait for this resident bird species, as early-arriving individuals were more likely to breed in that year. The study suggests that it might be worthwhile to consider migration on different scales, not only as movements over thousands of kilometres to wintering grounds, but also more generally as movements between breeding and non-breeding sites.
Parrots are considered extraordinarily clever animals. Alex, the famous Harvard-based African grey parrot, communicated with a vocabulary of more than 500 human words, could answer questions and classify objects spontaneously. Scientists from the Max-Planck-Institute for Ornithology based at the research station outpost for parrot comparative cognition in the Loro Parque in Tenerife, Spain, have shown that parrots exhibit a high level of social intelligence and cooperativeness. They readily help others, even when there is no immediate opportunity for reciprocation. Moreover, they reciprocate received favours and do not appear jealous, if conspecifics obtain a better reward than themselves. This further supports that they have evolved a level of intelligence comparable to that of great apes, crows and dolphins.
Everybody knows about the difficulty of focusing on a conversation during a loud party. How can active sensing animals like bats move in large groups and still be able to detect each other despite jamming? Thejasvi Beleyur and Holger Goerlitz show in their new modelling study in PNAS that a focal bat in the center of a group can still detect its closest neighbours in groups with 100 bats. Neighbor detection is improved for longer call intervals, shorter call durations, denser groups and more variable flight and sonar beam directions. Although the bats only detect their closest and frontal neighbours, this gives them sufficient information to prevent collisions, and to follow each other when emerging in dense swarms.
The timing of spring migration is vital for birds. Returning too late comes at a cost. In 1981, Ebo Gwinner, former director of the MPI for Ornithology demonstrated how an internal clock is responsible for the correct timing of flycatchers’ migration. Replicating this experiment more than twenty years later, Barbara Helm, student of Ebo and now Professor at the University of Groningen and guest researcher in Seewiesen has shown there is an evolutionary response of this clock to climate change, as migratory restlessness in spring is advanced by more than nine days.
Open link to the study with click on the image
Image with kind permission from Ralph Martin, Germany; www.visual-nature.de
Noise pollution is one of the leading environmental health risks in humans. In zebra finches, noise affects their health and the growth of their offspring: Researchers at the Max Planck Institute for Ornithology in Seewiesen found that traffic noise suppresses normal glucocorticoid profiles in the blood, probably to prevent negative effects of chronically elevated levels on the organism. In addition, the young chicks of noise-exposed parents were smaller than chicks from quiet nests.
When a male or female white-browed sparrow-weaver begins its song, its partner joins in at a certain time. They duet with each other by singing in turn and precisely in tune. A team led by researchers from the Max Planck Institute for Ornithology in Seewiesen found that the nerve cell activity in the brain of the singing bird changes and synchronizes with its partner when the partner begins to sing. The brains of both animals then essentially function as one, which leads to the perfect duet.
The focus of the new Max Planck Institute of Animal Behaviour in Radolfzell and Konstanz will be the investigation of Collective Behaviour. Besides of the existing departments of Martin Wikelski and Iain Couzin, another research department will be established. Margaret Crofoot from the University of California in Davis will investigate the formation of complex societies using the group behaviour of monkeys as an example. She is particularly interested in how the collective behaviour of a group emerges from the contacts and relationships between individuals.
(Image: Axel Griesch)