The team uses the human-led migrations and the comprehensive monitoring of wild birds by GPS transmitters, for successful research within the framework of international cooperation. The main research focus includes bird flight, bird migration, ecology, behaviour and history of Northern Bald Ibises. For the research on handicaps of animal biologging, the Waldrappteam was awarded the Animal Welfare Prize of the Forster-Steinberg Foundation in 2022. Meanwhile, the company even built its own wind tunnel to investigate related issues with trained animals under standardised experimental conditions.

Bird Flight and Migration

Characterization of bird formations using fuzzy modelling

Perinot E., Fritz J., Fusani L., Voelkl B., & Nobile M. S. (2023). Journal of the Royal Society Interface, 20(199), 20220798.
In this study, the line formation of Northern Bald Ibises was analysed using fuzzy logic. For this purpose, high-precision position data of 29 free-flying Northern Bald Ibises were collected using Global GNS loggers to investigate whether the spatial relationships within a formation can be explained by the birds adopting energetically advantageous positions, with fuzzy logic enabling the modelling of aerial vortex formation. The results provide insight into the complex dynamics of formation flight and give clear indications that the birds’ behaviour in the formation is characterised by energy efficiency.

Upwash exploitation and downwash avoidance by flap phasing in ibis formation flight.

Portugal SJ, Hubel TY, Fritz J, Heese S, Trobe D, Voelkl B, Hailes S, Wilson AM & Usherwood JR (2014). Nature, 505, 399 – 402.
This study investigated the mechanisms of formation flight with special attention to the aerodynamic implications of the V-shaped formation. It was shown that juveniles position themselves in optimum aerodynamic positions during human-led migration. The birds also capture the upwash of the wingtip of the bird in front by synchronizing their flap cycle.

Matching times of leading and following suggest cooperation through direct reciprocity during V - formation flight in ibis

Voelkl B, Portugal SJ, Unsöld M, UsherwoodJR, Wilson AM & Fritz J (2015).  Proceedings of theNational Academy of Sciences 112 (7) 2115–2120.

This study investigates formation flight in juvenile Northern Bald Ibises during a human-led migration. It could be shown that the birds cooperate by taking turns in front and trailing position on a dyadic level. Furthermore, evidence was found that propensity to reciprocate in leading has a direct effect on the size and cohesion of the formation.

Relation between travel strategy and social organization of migrating birds with special consideration of formation flight in the northern bald ibis.

Voekl B & Fritz J (2017). Phil. Trans. R. Soc. B 372:20160235.

In this study analysed formation flight in Northern Bald Ibises during a human-led migration. The data provide evidence for a correlation between leading and trailing on the dyadic level. This pattern is suggestive of direct reciprocation as a means for establishing cooperation during formation flight.

Empirical evidence for energy efficiency using intermittent gliding flight in Northern Bald Ibises. Frontiers in Biology.

Mizrahy-Rewald O, Perinot E, Fritz J, Vyssotski AL, Fusani L, Voelkl B & Ruf T (2022). Frontiers in Biology.

Bird change between flapping and gliding during flight (intermitted flight) to save energy, however the benefits of switching between these two flight stages have never been proven. We equipped juvenile birds during human-led migration flights with high precision data loggers, to measure heart rate as a proxy for energy requirement. When changing from flapping to gliding, the birds’ heartrates already decreased after one second. At a gliding proportion of about 20%, we measured a maximum of 11% energy saving.

Soaring and intermittent flap-gliding during migratory flights of Northern Bald Ibis

Wehner H, Fritz J, & Voelkl B. (2022) Journal of Ornithology, 671–681.

This study investigated the effects of different flight patterns on the energy expenditure during a human-led migration with Northern Bald Ibises. During the so-called intermitted flight, where flapping phases are regularly interrupted by short gliding phases, the bird lowered the wing beat frequency by 13–20%. Another energy saving strategy was thermal soaring, where the birds circle in thermal updrafts predominantly by gliding on the outstretched wing. Overall, the birds spent 19 and 22% of the time soaring.

Bird Migration Physiology

Energy Expenditure and Metabolic Changes of Free-Flying Migrating Northern bald ibis.

Bairlein F, Fritz J, Scope A, Schwendenwein I, Stanclova G, van Dijk G, Meijer HAJ, Verhulst S & Dittami J (2015). PLoS ONE 10 (9) e0134433.

We investigated the metabolism and energy expenditure in juvenile Northern Bald Ibises during human-led migration flights. Energy expenditure was estimated using doubly-labelled-water while physiological properties were assessed through blood chemistry. Instantaneous energy expenditure decreased with flight duration, and the birds appeared to balance aerobic and anaerobic metabolism, using fat, carbohydrate and protein as fuel. This made flight both economic and tolerable.

The effect of flights on hematologic parameters in Northern Bald Ibises (Geronticus eremita).

Stanclova G, Schwendenwein I, Merkel O, Kenner L, Dittami J, Fritz J & Scope A (2017). Journal of Zoo and Wildlife Medicine 48(4): 1154–1164.

This study investigates the effect of flight in juvenile Northern Bald Ibises on different hematologic variables. The hematologic changes postflight in NBIs were largely consistent with those known from other birds.

Wind Tunnel Technology

A low-cost wind tunnel for bird flight experiments.

Grogger H, Gossar M, Makovec M, Fritz J, Voelkl B, Neugebauer K, Amann F. (2022). Journal of Ornithology, 163, 599–610.

This study describes the design and technology of a low budget blower-type wind tunnel as well as numerical simulations of the flow and measurements of the velocity distribution in the test section. Four Northern Bald Ibises were hand-raised and trained to fly in the wind tunnel.

NBI Genetics

Optimizing the genetic management of reintroduction projects: genetic population structure of the captive Northern bald ibis population.

Wirtz, S., Böhm, C., Fritz, J., Kotrschal, K., Veith, M. & Hochkirch A (2018). Conservation Genetics 19/ 4: 853–864.

This study investigated the genetic diversity in the European Northern Bald Ibis populations and the historic eastern population. The results indicate that the populations are not genetically distinct and that the separation of the populations occurred rather recently. The European Zoo population could be separated into several genetic lines, most of which are represented in the two European release population.

Isolation of microsatellite loci by next-generation sequencing of the critically endangered Northern bald ibis, Geronticus eremita.

Wirtz S, Böhm C, Fritz J, Hankelnd T & Hochkirch A (2016). Journal of Heredity, 107 (4) 363–366.

Microsatellites are one of the best suitable genetic markers for tracking short-term genetic processes over just a few generations up to direct parentship analyses. In this study, 15 of these markers specific for Northern Bald Ibises were identified and tested. This set of newly developed genetic tools can be used to monitor genetic parameters to provide guidance for the reintroduction process.

NBI Conservation and Translocation

Back into the wild: establishing a migratory Northern bald ibis Geronticus eremita population in Europe.

Fritz, J., Kramer, R., Hoffmann, W., Trobe, D. & Unsöld, M. (2017). Int. Zoo Yb. 51: 107–123.

By supporting reintroduction programs, zoological institutions contribute to conservation efforts and scientific achievements. An example of the multi-layered and diverse contributions that zoological institutions in general and, specifically, Vienna Zoo, Austria, can make is the reintroduction of the Northern bald ibis in central Europe.

NBI Biology , Ecology and History

Tracing the fate of the Northern Bald Ibis over five millennia: An interdisciplinary approach to the extinction and recovery of an iconic bird species.

Fritz J & Janák J (2022). Animals

This study traces the history of the Northern Bald Ibis through time with a particular focus on the present and ancient Egypt, where the bird was of cultural and religious significance, which it probably achieved due to its natural affinity for cultivated areas. The study further investigates the possible reasons for three disappearance events throughout time and their link towards human impact and climatic changes.

On the road to self - sustainability: reintroduced migratory European northern bald ibises Geronticus eremita still need management interventions for population viability.

Drenske S, Radchuk V, Scherer C, Esterer C, Kowarik I, Fritz J & Kramer-Schadt S (2023). ORYX.

This demographic study analyses the data of our Northern Bald Ibis population over 12 years. We found, that in our population survival rates are comparatively good and the reproduction rates is outstanding. The population is on the way to become self-sustaining within the next years. However, this will require further release and active management with special attention towards ensuring the survival of adult birds by implementing measures against illegal hunting and electrocution.

Quantification of Foraging Areas for the Northern Bald Ibis (Geronticus eremita) in the Northern Alpine Foothills: A random forest model fitted with data fusion of optical and actively sensed earth observation data.

Wehner H, Huchler K, Fritz J, et al.(2022). Remote Sensing, 14, 1-13..

Using the GPS positions of foraging Northern Bald Ibises during the breeding season in 2021, the authors identified habitats with a high foraging suitability. They characterized them by seven satellite-based remote sensing parameters to define a suitability index. Subsequently, the suitability of feeding sites throughout the northern Alpine foothills were modelled. This study is of particular importance for the reintroduction project, since the suitability map allows the identification of sites for management and translocation measures in the future.

The cultivable autochthonous microbiota of the critically endangered Northern bald ibis (Geronticus eremita).

Spergser, J, Loncaric, I, Tichy, A, Fritz, J & Scope A (2018). PLoS ONE 13(4).

In this study, a first description of the culturable microbiota in our Northern Bald Ibis population was made. A total of 94 microbial species were cultured, including 14 potentially new bacterial taxa. While the prevalence of traditional pathogenic microbial species was extremely low, opportunists such as Clostridium perfringens toxotype A were frequently present in the samples.

Handicaps of Biologging

The impact of shape and attachment position of biologging devices in Northern Bald Ibises

Mizrahy-Rewald O, Winkler N, Voelkl B, Grogger H, Ruf T & Fritz J (2023). Animal Biotelemetry.

In this study, the influence of different housing shapes of GPS devices on the aerodynamics of Northern Bald Ibises during flight was investigated. The study was conducted in a specially constructed wind tunnel with hand-raised animals. It was shown that both the housing shape and the position on the animal significantly affects the energy expenditure of the animals.

Biologging is suspect to cause corneal opacity in two populations of wild living Northern Bald Ibises

Fritz J, Eberhard B, Esterer C, Goenner B, Trobe D, Unsöld M, Voelkl B, Wehner H & Scope A (2020). Avian Research 11:38, 1-9.

In this paper, we present evidence that equipping Northern Bald Ibises with solar powered devices on the upper back is correlated with one-sided eye irritation, up to blindness. After removal of the device or repositioning it on the lower back, we observed a complete disappearance of these symptoms in the population. The eye-irritation could be attributed to the sleeping position of the birds, with their head on the back and one eye close to a device fixed on the upper back. Further research is urgently needed to understand the causal relationships in the interest of animal welfare.