What to measure to predict brain size in birds?

At least in part, the brain’s capacity to process cognitive processes depends on the mass of neural tissue involved – the more tissue, the more information can be processed. In fact, studies often find a positive relationship between brain size and cognitive performance. However, majority of these studies are based on comparisons between different species. Growing number of scientists is now trying to understand how more subtle differences between individuals of the same species are related to their cognitive skills, which is often a big challenge when studying animals in nature.  

A first study in the barn swallow proposed to use external head measurements, which require handling but not the sacrifice of the study subject, as an accurate approximation for brain mass. In this collaborative research with Joanna Bialas and Marcin Tobółka (Poznań University, Poland), we employed this method for the first time in a small Galliform, the Common Quail. We measured both the external head dimensions of the birds as well as the weight of their brains, and tested how well these two measurements were related to each other. Despite we did find that these measurements were correlated, the correlation values we found were not strong enough to allow using external head measurements to predict an individual’s brain mass with high confidence. Moreover, the best predictor of brain mass was not head volume, as previously demonstrated in barn swallows, but the height of the head alone. We therefore recommend validating the original method of external head measurements in each avian species before making assumptions on how these measurements might be related to brain size and cognitive performance.  

You can access a full version of the article here

The work was funded by the FWF Der Wissenschaftsfonds Lise Meitner Fellowship (M2520-B29)

The importance of synchronization in courtship

Male ring dove perching on a window box

Multimodal signals may carry additional information which is missing when component signals are presented separately. We used audiovisual playback of male ring doves’ courtship to investigate female response to display stimuli differing in their audiovisual timing. We created a shifted stimulus where audio was shifted relative to video by a fixed value and a jittered stimulus, where each call was moved randomly along the visual channel. We presented females with a same stimulus type, that is, control, shifted, or jittered, for 7 days. We recorded their behavior and assessed pre- and post-test blood estradiol concentration. We found that playback exposure increased estradiol levels, confirming that this technique can be efficiently used to study doves’ sexual communication. Additionally, chasing behavior (indicating sexual stimulation) increased over experimental days only in the control condition, suggesting a role of multimodal timing on female response. This stresses the importance of signal configuration in multimodal communication, as additional information is likely to be contained in the temporal association between modalities.

You can access a full version of the article here

Funded by the Vienna Science and technology Fund (WWTF) grant N. CS18-021

Sweet sap, savory ants

Birds, the descendants of carnivorous dinosaurs, lack part of the sweet receptor found in mammals. This should leave them insensitive to sugars. However, recent studies have shown that both hummingbirds and songbirds have regained the ability to sense sugar by repurposing their savory receptor to now detect carbohydrates in fruits and nectar. How other birds sense sugars, and the extent to which taste receptor responses track the immense dietary diversity of birds, is unclear. To investigate this question, Julia Cramer and Maude Baldwin from the Research Group Evolution of Sensory Systems at the Max Planck for Ornithology/Max Planck for Biological Intelligence, together with colleagues from the Cornell Lab of Ornithology, Meiji University, the Swedish University of Agricultural Science and our lab focused on woodpeckers. Although primarily insectivorous, this group of birds also contains multiple species that include sugar-rich sap, nectar, and fruits in their diets.

Using behavioral tests of wild birds, the team showed that woodpeckers clearly prefer sugar and amino-acids over water. Surprisingly, wrynecks – a member of the woodpecker group whose diet is almost exclusively composed of ants – displayed preferences for amino acids but not sugars. Functional analyses of taste receptors confirmed that woodpecker receptors were sensitive to sugars, whereas those of wrynecks were not. Interestingly, ancestral reconstructions indicated that the common ancestor of wrynecks and woodpeckers already possessed a modified savory receptor capable of responding to sugars. A meticulous dissection of differences between wryneck and woodpecker receptors revealed unexpectedly that changes in only a single amino acid in the wryneck receptor selectively turned off sugar-sensing: the birds kept their ability to taste savory, which is likely important for insect-specialist birds that consume a protein-rich diet.

These results trace an evolutionary history in which an early gain of sugar sensing in woodpeckers —possibly arising in an earlier ancestor and therefore older than woodpeckers themselves — was followed by its reversion when the wryneck receptor was later altered. Further investigation will be required to describe how specific changes in taste receptors, and in other physiological and sensory systems, are related to the rich dietary diversity across birds.

You can access the full version of the paper here.

Flight efficiency in Northern Bald Ibises

Birds face high energy demands during their flight. Some species alternate between flapping and gliding, which should allow them to save energy. We equipped hand-raised Northern Bald Ibises (Geronticus eremita) with data loggers during human-guided migration. We monitored the position of the birds, wingbeats, overall dynamic body acceleration (ODBA), and heart rates as a proxy for energy expenditure. The energy expenditure was significantly affected by the length of flapping and gliding bouts. At a gliding proportion of about 20%, we measured a maximum of 11% saving based on heart rate measurement. This study provides empirical evidence that intermittent flight is energetically beneficial and can reduce the high costs of flights.

You can access the full paper by clicking the button below

Energy consumption as determined by heart rate and overall dynamic body acceleration (ODBA) decreases as the duration of the gliding phases increases

Two PhD positions available at the Doctoral School Cognition, Behaviour and Neurobiology

The University of Vienna offers 2 PhD positions within the uni:docs Fellowship Programme. The two 3-year PhD positions are fully paid and are based at the Department of Behavioral and Cognitive Biology at the Faculty of Life Sciences. The working language of the department is English.  We welcome early career researchers from all over the world. The PhD candidates will be embedded in the newly founded Vienna Doctoral School for Cognition, Behavior and Neuroscience (VDS CoBeNe) at the University of Vienna. The main goal of VDS CoBeNe is quality assurance in PhD training and education. The doctoral school stands for promotion of inter- and transdisciplinary knowledge exchange. More information at https://vds-cobene.univie.ac.at/phd-call/cobene-unidocs-calls/

Deadline for applications: July 31st, 2022

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Androgen response to simulated intruder in a territorial poison frog

Thirty years ago, an explanation for the facultative increase of males’ androgen levels in response to social challenges was proposed as the “Challenge Hypothesis” (Wingfield et al., 1990). Since then, numerous studies have tested this hypothesis across different animal taxa with diverse life history. We tested the Challenge Hypothesis in the highly territorial poison frog, Allobates femoralis. We compared males’ androgen concentrations between a non-stimulated condition (baseline) and following a simulated territorial intrusion (post-STI) conducted by playing back the territorial call through a loudspeaker. We took advantage of water-borne hormones sampling, a non-invasive technique, to characterize androgen levels, and showed that it closely reflects circulating plasma testosterone levels. Our results demonstrate that water-borne androgen increases after a STI in A. femoralis males only when males approached the playback loudspeaker. Therefore, our results provide novel support to the Challenge Hypothesis in a territorial frog.

This work is a result of a collaborative effort lead by Camilo Rodriguez. You can access the full paper by following this link.

Learned components of courtship

A focus on postural displays, choreographies and construction abilities

Song learning research has provided a plethora of information on the proximate and ultimate explanations for learning of vocal displays. However, sexual displays involve a variety of components including body postures, sequences of movements, and modification of the environment for attracting prospective mates. Although visual displays are widespread and prominent, only few studies have investigated the role experience and learning may play on motor performance of non-vocal courtship signals.

In this review paper, we use the framework provided by vocal learning research as a guide to investigate whether, and how, motor displays may be learned. We review the available evidence which suggests that learning of visual courtship components is more widespread than had been previously assumed, and identify the areas where more research is needed. The full text of the article can be found at this link.

This paper was funded by the Austrian Science Fund (FWF) (W1262-B29), and by the Vienna Science and Technology Fund (WWTF) (CS018-021).

Giovanni Spezie

Cliodhna Quigley

Leonida Fusani

Unshaded coffee plantations impose a heavy load on thermoregulation

The effects of land-use conversion and agricultural intensification on tropical birds have been widely studied, but focused largely on ecological and functional patterns. Replacement of forest with monocultures alters microclimatic conditions throughout the landscape. In this work, we investigated the differences in microclimatic temperatures across forest, shaded and unshaded coffee plantations and studied the physiological impacts on four Neotropical bird species that thrive in agricultural landscapes. Unshaded coffee plantations presented birds with the most challenging thermal environment but all species were able to withstand current maximum temperatures. However, replenishing water lost to dissipate heat in unshaded farms might become a problem if temperatures will keep raising. The full article can be found in this link

Otto Monge

Leonida Fusani

Ivan Maggini

The article is the result of a collaboration with Stefan Dullinger and Christian Schulze of the Department of Botanic, University of Vienna

Ghrelin modifies migratory behaviour in nature

On migration, most passerine birds stop over along the way to rest and refuel. A network of hormones signals metabolic fuel availability to the brain in vertebrates, including the recently discovered gut-hormone ghrelin. Here, we show that ghrelin participates in the control of migratory behaviour during spring migration in a wild migratory passerine. We administered ghrelin to yellow-rumped warblers (Setophaga coronata coronata) caught during stopover and automatically radio-tracked their movements following release. Ghrelin rapidly induced birds to move away from the release site, indicating that the ghrelin system acts centrally to mediate stopover departure. The effects of the hormone treatment declined within hours following release and did not affect the overall rate of migration. These results provide experimental evidence for a pivotal role of ghrelin in the modulation of stopover decisions during migration, and offers insights into the regulatory functions of metabolic hormones in the dialogue between gut and brain in birds.

The study was a collaboration with Christopher G. Guglielmo, Scott A. MacDougall-Shackleton, and Yolanda E. Morbey of the Advanced Facility for Avian Research, University of Western Ontario, Canada, and Hiroyuki Kaiya of the National Cerebral and Cardiovascular Center Research Institute, Japan.

Funding was provided by the Marie Skłodowska-Curie Individual Global Fellowship 798739 GHRELMIGRA to Sara Lupi

Access the full publication here.

Oxytocin and singing

Does singing have different effects on physiology compared to other vocal activities? In a study conducted together with colleagues of the Department of Behavioural and Cognitive Biology, we examined the association of salivary levels of oxytocin, corticosterone and testosterone with different types of activities conduced solo or in group.

Singing and speaking were associated with decreases in salivary oxytocin concentrations, when performed together or alone, however, oxytocin concentrations decreased by less after singing together than after speaking together. Singing together improved self-perceived emotional status and social connectedness more than speaking together.

You can read the full paper here