Northern Bald Ibis Geronticus Eremita Research Articles

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

AbstractThe northern bald ibis Geronticus eremita disappeared from Europe in the Middle Ages. Since 2003 a migratory population has been reintroduced in Central Europe. We conducted demographic analyses of the survival and reproduction of 384 northern bald ibises over a period of 12 years (2008–2019). These data also formed the basis for a population viability analysis simulating the possible future development of the northern bald ibis population under different scenarios. We analysed life stage-specific survival rates, rearing protocols and colonies, and the influence of stochastic catastrophic events and reinforcement translocations on population growth. Life stage-specific survival probabilities were 0.64–0.78. Forty-five per cent of the mature females reproduced, with a mean fecundity of 2.15 fledglings per nest. The complementary population viability analysis indicated that the Waldrappteam population is close to self-sustainability, with an estimated population growth rate of 0.95 and a 24% extinction probability within 50 years. Of the 326 future scenarios tested, 94% reached the criteria of extinction probabilities < 5% and population growth rates > 1. Stochastic catastrophic events had only a limited effect. Despite comparatively high survival and fecundity rates the population viability analysis indicated that to achieve self-sustainability the Waldrappteam population needs further translocations to support population growth and the implementation of effective measures against major mortality threats: illegal hunting in Italy and electrocution on unsecured power poles. The findings of this study are to be implemented as part of a second European LIFE project.

Threats to the Reintroduction Program of the Northern Bald Ibis (Geronticus eremita) in Italy: A Forensic Investigation.

The Northern Bald Ibis Geronticus eremita is an endangered species, and recently it was reintroduced in Europe by the Waldrappteam. The reintroduction program has been strongly threatened by several sudden deaths, mainly in Italy. The present study used a forensic approach to analyze all of the 27 Northern Bald Ibises found dead in Italy between 2016 and 2022, which were suspected to have been victims of poaching, and it followed the veterinary forensic guidelines. Human-related causes accounted for 60% of the deaths, including illegal hunting (30%), blunt force trauma (26%), and electrocution (4%). Natural causes, starvation (15%), predation (11%) and disease (7%), accounted for 33% of the deaths. 7% of the causes of deaths remained undetermined. This study uses a forensic approach to analyze, for the first time, the main causes of death in Geronticus eremita and highlights the relevance of detecting illegal actions related to endangered species and stopping the phenomenon of poaching.

Space use and site fidelity in the endangered Northern Bald Ibis Geronticus eremita: Effects of age, season, and sex

Summary Understanding space use of endangered species is critical for conservation planning and management. The advances in technology and data analysis allow us to collect data with unprecedented quality and inform us about the movements and habitat use of individuals and groups. With only about 700 individuals left in the wild, the Northern Bald Ibis Geronticus eremita is currently categorised as ‘Endangered’. However, little is known about the movements of this avian species in relation to breeding and individual differences. Using GPS transmitters we studied the movements of 32 Northern Bald Ibis from a semi-wild free-flying colony at the Konrad Lorenz Research Center in Austria during 1–4 years per individual. We investigated how sex, age class, breeding and non-breeding season affect space use and site fidelity. We found that individuals consistently showed high site fidelity, adults more than juveniles, and space use was highly overlapping between individuals and over successive years. When moving between different areas birds used consistent flyways thereby avoiding direct routes over mountainous areas. Adults had more expansive space use during the breeding season as compared to the non-breeding season, while juveniles only showed a slight decrease during the non-breeding season. We found no sex differences regarding space use or site fidelity. Our results lead to a better understanding of how Northern Bald Ibis move through their environment and how they use foraging areas, roosting sites, and space in general that in turn can help to inform conservation management of extant colonies and reintroduction programmes for new colonies.

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

Migratory journeys represent an energetic challenge for many long-distance migrants. The choice of flight times, migration route, altitude, travelling speed, wingbeat patterns, soaring as well as formation flight can all affect the energy expenditure for the journey. We monitored the flight patterns of two Northern Bald Ibises (Geronticus eremita) equipped with data loggers while crossing the Alps during a human-led migration from southern Germany to Tuscany. We observed that the birds used an intermittent flapping pattern, where phases of active flapping flight were regularly interrupted by short gliding phases. As a result of intermittent flight, the effective wing beat frequency was 13–20% lower than the observed wing beat frequency of 4.0 s−1. When local conditions allowed, the birds gained altitude through circling in thermal updrafts. During those circling bouts, gliding on the outstretched wing was predominant, though active wing flapping was still observed. Overall, the two birds spent 19 and 22% of the time soaring on the outstretched wing, accruing during that time 26 and 28% of the altitude gain required for the crossing of a major mountain range. This shows that, apart from formation flight, northern bald ibis use at least two more strategies—thermal soaring and intermittent flap-gliding—for improving energy economy during migratory flights.

Corneal opacity in Northern Bald Ibises (Geronticus eremita) equipped with radio transmitters

ABSTRACT This note is intended to try to shed light on the discoveries made entitled “Biologging is suspect to cause corneal opacity in two populations of wild living Northern Bald Ibises (Geronticus eremita)”. In this article, researchers participating in a reintroduction program for this endangered species in Europe document the unilateral corneal opacity that took place after birds were equipped with solar radio transmitters fixed on their upper-back position. The authors propose several possible effects caused by the device to explain the problem, and they conclude that the most parsimonious explanation for the symptomatology is a repetitive slight temperature rise in the corneal tissue due to electromagnetic radiation by the Global System for Mobile Communications (GSM) module of the device. The proposal of this communication is that these effects do not necessarily have to be thermal, but they can be non-thermal and thus more subtle and insidious. These effects may be caused by electromagnetic radiation at low levels but in long-term exposure.

Quantification of Foraging Areas for the Northern Bald Ibis (Geronticus eremita) in the Northern Alpine Foothills: A Random Forest Model Fitted with Optical and Actively Sensed Earth Observation Data

The Northern Bald Ibis (Geronticus eremita, NBI) is an endangered migratory species, which went extinct in Europe in the 17th century. Currently, a translocation project in the frame of the European LIFE program is carried out, to reintroduce a migratory population with breeding colonies in the northern and southern Alpine foothills and a common wintering area in southern Tuscany. The population meanwhile consists of about 200 individuals, with about 90% of them carrying a GPS device on their back. We used biologging data from 2021 to model the habitat suitability for the species in the northern Alpine foothills. To set up a species distribution model, indices describing environmental conditions were calculated from satellite images of Landsat-8, and in addition to the well-proven use of optical remote sensing data, we also included Sentinel-1 actively sensed observation data, as well as climate and urbanization data. A random forest model was fitted on NBI GPS positions, which we used to identify regions with high predicted foraging suitability within the northern Alpine foothills. The model resulted in 84.5% overall accuracy. Elevation and slope had the highest predictive power, followed by grass cover and VV intensity of Sentinel-1 radar data. The map resulting from the model predicts the highest foraging suitability for valley floors, especially of Inn, Rhine, and Salzach-Valley as well as flatlands, like the Swiss Plateau and the agricultural areas surrounding Lake Constance. Areas with a high suitability index largely overlap with known historic breeding sites. This is particularly noteworthy because the model only refers to foraging habitats without considering the availability of suitable breeding cliffs. Detailed analyses identify the transition zone from extensive grassland management to intensive arable farming as the northern range limit. The modeling outcome allows for defining suitable areas for further translocation and management measures in the frame of the European NBI reintroduction program. Although required in the international IUCN translocation guidelines, the use of models in the context of translocation projects is still not common and in the case of the Northern Bald Ibis not considered in the present Single Species Action Plan of the African-Eurasian Migratory Water bird Agreement. Our species distribution model represents a contemporary snapshot, but sustainability is essential for conservation planning, especially in times of climate change. In this regard, a further model could be optimized by investigating sustainable land use, temporal dynamics, and climate change scenarios.

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

AbstractThe 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.

Comparison of reproductive success between parent-reared and hand-reared northern bald ibis Geronticus eremita in captivity during Proyecto Eremita

Modern zoos actively collaborate in the conservation of many endangered species by captive breeding for reintroduction. This paper presents the reproductive success of a captive colony of northern bald ibis Geronticus eremita (NBI) at ZooBotanico de Jerez between 1993 and 2013 (21 years). Between 2004 and 2011 was “Proyecto Eremita”, a study of the best releasing techniques for hand-reared NBI in Cadiz in order to establish a free-range, self-sustained population in the wild. During this period, first-clutch eggs were artificially incubated and chicks were hand reared until fledgling stage, allowing the pair to produce a second or replacement clutch that was parent reared. This paper compares the colony’s reproductive success between the years where one single clutch was reared by the pairs (n=13) and the years of Proyecto Eremita (n=8), with two clutches, the first hand reared and the second parent reared. The reproductive success rate was measured in 300 nests. A total of 268 fledglings reached 2 months old, the age considered here as the reproductive success. Two reproductive variables were significantly higher during the Proyecto Eremita years: mean number of fledglings per nest (1.8 versus 0.3) and overall number of fledglings recorded per year (26.5 versus 4.3). The reproductive success of hand-reared clutches was similar to parent-reared clutches. There was a significant and negative effect of colony size on the percentage of birds paired and on reproductive success. Parent-reared clutches during the Proyecto Eremita showed a higher reproductive success compared to parent-reared clutches outside this period. The data show that a remarkably high percentage of mating pairs outside of the Proyecto Eremita period failed at reproduction, probably due to density-dependent effects. The combination of hand-rearing and parent-rearing methods used in this study was a very effective tool to significantly increase the number of fledglings produced for the reintroduction programme.

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.

Effects of bio-loggers on behaviour and corticosterone metabolites of Northern Bald Ibises (Geronticus eremita) in the field and in captivity

BackgroundDuring the past decades, avian studies have profited from the development of miniature electronic devices that allow long-term and long-range monitoring. To ensure data quality and to inform understanding of possible impacts, it is necessary to test the effects of tagging. We investigated the influence of GPS-transmitters on the behaviour and physiology (levels of excreted corticosterone metabolites, CM) of an endangered bird species, the Northern Bald Ibis (Geronticus eremita). We considered effects of GPS-tags in two contexts: (1) aviary (i.e. in captivity), focussing on short-term effects of transmitters on locomotion, foraging and maintenance behaviour (20 individuals that differed in sex and age observed for 10 days) and (2) field, focussing on intermediate-term effects of transmitters on locomotion, foraging, maintenance behaviour, dorsal feather preening, social interactions and physiology (CM) (24 individuals observed for 79 days). In both contexts, focal animals were equipped with bio-logger backpacks mounted with a harness.ResultsIn the aviary, behavioural observations were limited to the first days after tagging: no differences were found between individuals with GPS-tags and their controls with respect to the behavioural parameters considered. In the field, no behavioural differences were found between the GPS-tagged individuals and their controls; however, 1 month after tagging, individuals with GPS-tags excreted significantly more CM than their controls before returning to baseline levels.ConclusionsOur results suggest that GPS-transmitters did not affect foraging, locomotion and maintenance behaviour in the Northern Bald Ibis in the short- or intermediate-term. However, they did affect the hypothalamic–pituitary–adrenal reactivity in the intermediate-term for 1 month before returning to baseline levels the next month. As the Northern Bald Ibis is listed as endangered, evaluating possible adverse effects of bio-logging is also relevant for potential conservation and reintroduction research.

First record of the northern bald ibis Geronticus eremita (Linnaeus, 1758) in Bulgaria

The paper reports on the first record of Geronticus eremita in Bulgaria (13-16 January 2019; town of Karlovo), a specimen released from the captive population in Rosegg Tierpark, Austria and caught alive in the town of Karlovo (CS Bulgaria). Regardless of the attempts to be rescued a few days later, it died.

The Northern Bald Ibis Geronticus eremita in Morocco since 1900: Analysis of ecological requirements

SummaryThe Northern Bald Ibis (NBI) Geronticus eremita, is an ‘Endangered’ bird species of which only very few wild breeding colonies have survived along the Atlantic coast of south-west Morocco. This paper analyses ecological conditions of the 72 breeding sites of the NBI that have been known since 1900 in Morocco. Characterisation of breeding sites is based on physical criteria (elevation above sea level, geomorphology, mean annual precipitation and types of landscape) as well as land use, vegetation cover, infrastructure and types of settlement within three perimeters (0–1 km, > 1–5 km and > 5–10(20) km) using Google Earth satellite images. Statistical analyses of the number of breeding pairs, fledglings and rainfall during different quarters of the year from 1994 to 2016 in the two remaining breeding sites in Souss-Massa National Park and Tamri showed expected patterns as well as unexpected differences between the two localities. Based on our findings and indications in the literature, we suggest general and specific recommendations for potential future translocation projects of the NBI. Based on the analysis of the 28 breeding colonies existing after 1977, two elements emerge as the most important prerequisites: a low level of disturbances at the breeding sites and adequate feeding areas at a reasonable distance of 5–15 km.

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

From the perspective of zoological institutions reintroduction projects offer many possibilities to link conservation and research programmes. 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 Geronticus eremita in central Europe. The involvement of zoological institutions ranges from the provision of eggs or birds for release trials, to financial and advocacy support, including with government agencies and non‐governmental organizations. Through involvement at a steering level at the coordinative association ‘Förderverein Waldrappteam’ and as a partner in the EU LIFE+ reintroduction project, Vienna Zoo directly contributes to the shape of the reintroduction project for this Critically Endangered species, and provides much more than technical and infrastructural support. The reintroduction of the Northern bald ibis is broadly in line with the reintroduction guidelines of the International Union for Conservation of Nature. This project provides added benefits not only through its work to prevent the illegal hunting of migratory birds but also the production and dissemination of scientific research.

Differences in foraging ecology determine variation in visual fields in ibises and spoonbills (Threskiornithidae)

Variations in visual field topography among birds have been interpreted as adaptations to the specific perceptual challenges posed by the species’ foraging ecology. To test this hypothesis we determined visual field topography in four bird species which have different foraging ecologies but are from the same family: Puna Ibis Plegadis ridgwayi (probes for prey in the soft substrates of marsh habitats), Northern Bald Ibis Geronticus eremita (surface pecks for prey in dry terrestrial habitats), African Spoonbill Platalea alba and Eurasian Spoonbill Platalea leucorodia (bill‐sweeps for prey in shallow turbid waters). All four species employ tactile cues provided by bill‐tip organs for prey detection. We predicted that the visual fields of these species would show general features similar to those found in other birds whose foraging is guided by tactile cues from the bill (i.e. bill falling outside the frontal binocular field and comprehensive visual coverage of the celestial hemisphere). However, the visual fields of all four species showed general features characteristic of birds that take food directly in the bill under visual guidance (i.e. a narrow and vertically long binocular field in which the projection of the bill tip is approximately central and with a blind area above and behind the head). Visual fields of the two spoonbills were very similar but differed from those of the ibises, which also differed between themselves. In the spoonbills, there was a blind area below the bill produced by the enlarged spatulate bill tip. We discuss how these differences in visual fields are related to the perceptual challenges of these birds’ different foraging ecologies, including the detection, identification and ingestion of prey. In particular we suggest that all species need to see binocularly around the bill and between the opened mandibles for the identification of caught prey items and its transport to the back of the mouth. Our findings support the hypothesis that sensory challenges associated with differences in foraging ecology, rather than shared ancestry or the control of locomotion, are the main determinants of variation in visual field topography in birds.

Satellite tracking reveals the migration route and wintering area of the Middle East population of Critically Endangered northern bald ibis Geronticus eremita

Since its discovery in 2002 the small colony of northern bald ibis Geronticus eremita in the central Syrian desert remains at perilously low numbers, despite good productivity and some protection at their breeding grounds. The Syrian birds are migratory and return rates of young birds appear to have been poor but because the migration route and wintering sites were unknown little could be done to address any problems away from Syria. Satellite tracking of three adult birds in 2006–2007 has shown they migrate through Jordan, Saudi Arabia and Yemen to the central highlands of Ethiopia. The three tagged birds and one other adult were found at the wintering site but none of the nine younger birds that also left Syria were with them. At least four birds wintered elsewhere because they returned to the colony the following spring. The return migration followed the western shore of the Red Sea through Eritrea to Sudan before crossing the Red Sea into Saudi Arabia, then northwards to Syria. The adults appeared to be at low risk on the wintering site although we recommend protection. Threats along the migration route now need to be assessed and mitigated, and further effort made to determine the movements of subadults and young birds.

The provision of supplementary fresh water improves the breeding success of the globally threatened Northern Bald Ibis Geronticus eremita

The Northern Bald Ibis Geronticus eremita is a globally threatened species with its main remaining world population breeding in an area of sea cliffs and coastal semi‐desert steppe near Agadir in southern Morocco. Between 1998 and 2002, we showed experimentally that the small‐scale provision of fresh water near the breeding colonies led to an increase in the productivity of the birds. The increase was greatest in years with low natural rainfall but was positive in all years tested. The supplementary fresh water appears to help buffer productivity against the impacts of low rainfall and its provision is now part of the ongoing conservation measures for this species.

Discovery of a relict breeding colony of northern bald ibis Geronticus eremita in Syria

The eastern population of the northern bald ibis Geronticus eremita had been presumed extinct following the loss of the colony in Birecik, Turkey, in 1989. However, occasional sightings of birds in Yemen, Eritrea, Saudi Arabia and Israel during the 1980s and 1990s suggested that there was still a colony somewhere in the Middle East. Intensive field surveys in spring 2002, based on the knowledge of Bedouin nomads and local hunters, revealed that the species has never become completely extinct on the Syrian desertic steppe. Following systematic searches 15 old nesting sites were found, one of them still hosting an active breeding colony of seven individuals. The species appears to have been relatively common in the area until 20 years ago, when a combination of overexploitation of rangelands and increasing hunting pressure initiated a dramatic decline.

The status and recent breeding performance of the critically endangered Northern Bald Ibis Geronticus eremita population on the Atlantic coast of Morocco

The main wild population of the Northern Bald Ibis Geronticus eremita breeds on the Atlantic coast of Morocco in the Agadir region. This paper describes the numbers of breeding pairs over the last two decades, the recent breeding performance, the causes of egg and chick losses and their conservation implications. Since 1980 there has been no overall decline in numbers with, over the last 5 years, 59–74 pairs breeding and a peak prebreeding population of around 220 birds. In contrast with the now extinct Northern Bald Ibis populations in Turkey and elsewhere in Morocco, the birds are present in the Agadir region throughout the year and do not appear to migrate from the area outside the breeding season. Breeding performance is highly variable from one year to the next but does not appear to be related to rainfall in the vicinity of the colonies as has been reported elsewhere. It is suggested that coastal fogs in this region may buffer the adverse impacts of low rainfall and may in part account for the year‐round residency of the birds. The main causes of breeding failures have been loss of eggs to predators and, most importantly, poor chick survival as a result of starvation and predation. Conservation action to date has focused on reducing the negative influences on breeding success but it is recognized that for such a long‐lived bird adult survival is also likely to be an important limiting factor on the population size.

First evidence of mtDNA sequence differences between Northern Bald Ibises (Geronticus eremita) of Moroccan and Turkish origin

We examined two segments of the mitochondrial genome of Moroccan and Turkish Bald Ibises. One point mutation was consistently discovered in a 307 bp portion of the cytochrome b gene which was population specific. This is the first indication of a genetic differentiation between the two populations. The consequences of this finding for the conservation of the highly endangered bird are discussed. In future captive breeding and releasing programmes, only birds of known origin should be used.

First evidence of mtDNA sequence differences between Northern Bald Ibises (Geronticus eremita) of Moroccan and Turkish origin

First evidence of mtDNA sequence differences between Northern Bald Ibises (Geronticus eremita) of Moroccan and Turkish origin