Review of historical breeding sites of the Northern Bald Ibis Geronticus eremita in Syria and south-eastern Turkey

Summary An updated and comprehensive compilation and review of the historical breeding sites of the Northern Bald Ibis in Syria and south-eastern Turkey is presented accompanied by all available details. The original sources, dating from the first half of the 19th century to 2010, were thoroughly assessed and reviewed. A detailed distribution map of confirmed and unconfirmed historical Northern Bald Ibis colonies was developed, showing a cluster of colonies located in the central steppe of Syria, between the villages of Qaryatayn and Sukhna, while several other colonies were scattered along the Euphrates river from southern Turkey to Iraq, passing through Syria.

The northern bald ibis Geronticus eremita: history, current status and future perspectives

The northern bald ibis Geronticus eremita was once widespread throughout the Middle East, northern Africa, and southern and central Europe. Habitat destruction, persecution and the impacts of pesticides have led to its disappearance from most of its former range. It disappeared from central Europe > 400 years ago, but has persisted as a relict and slowly growing breeding population in Morocco, where c. 700 wild birds of all ages remain. In Algeria, the last confirmed breeding was in 1984; in Turkey the fully wild population disappeared in 1989, but a population remains in semi-wild conditions. In Syria a small population was rediscovered in 2002, only to subsequently decline to functional extinction. Restoration programmes have been initiated independently in several locations, with over 300 free-flying birds resulting from reintroduction projects in Austria, Germany, Spain and Turkey, to restore both sedentary and fully migratory populations. Maintaining current efforts in Morocco remains a high conservation priority.

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

Background In this paper, we present evidence that biologging is strongly correlated with eye irritation, with sometimes severely impairing effects. A migratory population of the Northern Bald Ibis (Geronticus eremita, NBI) is reintroduced in Europe, in course of a LIFE + project. Since 2014, all individuals have been equipped with GPS-devices. Remote monitoring allows the implementation of focussed measures against major mortality causes. Methods Initially all birds carried battery-powered devices, fixed on the lower back of the birds. Since 2016 an increasing amount of birds has been equipped with solar-powered devices, fixed on the upper back, the more sun-exposed position. In 2016, we observed opacity in the cornea of one eye (unilateral corneal opacity; UCO) during a regular health monitoring for the first time. Results By 2018, a total of 25 birds were affected by UCO, with varying intensity up to blindness. Clinical examination of the birds revealed no clear cause for the symptoms. However, only birds carrying a device on the upper back were affected (2017 up to 70% of this group). In contrast, none of the birds carrying devices on the lower back ever showed UCO symptoms. This unexpected relationship between tagging and UCO was discovered in 2017. After we took countermeasures by removing the device or repositioning it on the lower back, we observed an immediate reduction of the incidence rate without any new cases reported since January 2019. NBI roost with their head on the back, one eye closely placed to the device if it was positioned on the upper back. Thus, we conclude that the most parsimonious explanation for the symptomatology is either a repetitive slight temperature rise in the corneal tissue due to electromagnetic radiation by the GSM module of the device or a repetitive slight mechanical irritation of the corneal surface. Concrete evidence is missing so far. Meanwhile, cases of UCO were found in another NBI population. Conclusion Our observations indicate that further research in the fast-growing field of biologging is urgently needed. The findings question the positioning of devices on the upper back in birds roosting with the head on the back.

Social interactions change with season and age in Northern Bald Ibis

Understanding the association between an individual’s position within a social network and its sex and age across seasons can be useful information for conservation management. For example, identifying the social position of females within a group can provide insights into reproductive potential, while the position of juveniles may be related to survival and hence recruitment potential. In the present study, we used social network analysis to investigate the effects of season, sex, age and reproductive partner on social interactions in the endangered Northern Bald Ibis (Geronticus eremita). Via focal sampling we recorded the social behaviour of 39 individually marked, free-flying birds for 4 months over two seasons (autumn, winter). We observed the occurrence of affiliative and agonistic interactions and estimated proximity between colony members. We found that (1) individuals were in proximity with more colony members in winter than in autumn, and affiliative interactions occurred more often in winter, (2) older individuals occupied more central positions in the proximity network irrespective of sex, (3) males engaged more than females in agonistic interactions, whereas females received more affiliative interactions than males irrespective of age, and (4) most affiliative interactions occurred between former or potentially prospective reproductive partners. Our findings suggest that social relationships could modulate inter-individual distance and there may be sex-related differences in the investment into pair bond maintenance. Overall the findings of sex- and age-related differences in behaviour and social position contribute to understanding factors associated with breeding success and mortality risk in an endangered bird species.

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

Background In this paper, we present evidence that biologging is strongly correlated with eye irritation, suggesting a causal relationship with obvious impairing effects for the affected individuals. A migratory population of Northern Bald Ibises ( Geronticus eremita ) is reintroduced in Europe, in the course of a LIFE+ project (LIFE Northern Bald Ibis). Since 2014, all individuals are equipped with GPS-devices. Remote monitoring of the whole population allows the implementation of focussed measures against major mortality causes. Initially all birds carried battery-powered devices, fixed on the lower back of the birds. Since 2016, an increasing amount of birds were equipped with solar-powered devices, fixed on the upper back, as this is the more sun-exposed position. In 2016, we observed for the first time an opacity in the cornea of one eye (unilateral corneal opacity; UCO). From 2016 to 2018, a total of 25 birds were affected by UCO, with varying intensity up to blindness. However, only birds carrying a device on the upper back were affected (2017 up to 70% of this group). In contrasts, none of the birds which carried devices on the lower back ever showed UCO symptoms. This unexpected relationship between tagging and UCO was discovered in 2017. Since then, we started countermeasures by removing the device or repositioning it on the lower back. Results Northern Bald Ibises roost with their head on the back, one eye closely placed to the device. Thus, we conclude that the most parsimonious explanation for the symptomatology is either a repetitive slight temperature rise in the corneal tissue due to electromagnetic radiation by the GSM module of the device or a repetitive slight mechanical irritation of the corneal surface. Concrete evidence is missing so far. On our advice, UCO was also found in Northern Bald Ibises of a Spanish reintroduction project, in a completely consistent context. Conclusion Our results indicate that further research in the fast-growing field of biologging is urgently needed. The findings question the positioning of devices on the upper back in birds roosting with the head on the back.