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Is the Sacred ibis a real threat to biodiversity? Long-term study of its diet in non-native areas compared to native areas

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This paper presents the results of a 14-year study about the diet of the Sacred ibis in its main introduction area in France and its impact on native bird species, and compares the data to literature from its native area. During an initial period (1993-2004), the diet was essentially composed of invertebrates such as common aquatic insects (correlated with flooding) or Eristalis larvae picked from the mud (a vacant food niche in France), while scraps of meat taken from rubbish dumps were minor. These traditional preys taken from the same ecosystems as in its native area did not result in an exponential increase of the number of breeding Sacred ibises. Invasive Red swamp crayfish recently replaced other foods in its diet with a resulting sharp increase in breeding pair numbers (R(2)=0.48). As in other parts of the world, vertebrates constituted very accidental preys, and no bird species were really threatened by such predation. Conversely, the Sacred ibis can have a positive effect as a predator of invasive crayfish. Adding the species to the DAISIE list of the 100 most invasive alien species in Europe therefore appears debatable.
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... Sacred Ibises nesting in trees often, though not always, share colonies with herons and similarly large, colonial species and also breed in close proximity to large gulls on small islands. It has been claimed that Eurasian Spoonbills Platalea leucorodia were attracted by breeding Sacred Ibises and that the (then) locally rare Spoonbill population in France would benefit from the presence of ibises (Marion 2006). To test this, the locations of all nests of both species were plotted and their period of laying recorded over five breeding seasons at Gr and-Lieu ). ...
... Dry animal food was found in the stomach contents of ibises that continued to feed within the wildlife park they originated from. Marion (2013) suggested that the spread of the Red Swamp Crayfish was responsible for a sharp increase in the Sacred Ibis population in western France. Yet this is not supported by the available evidence, with a steady rate of ibis population growth maintained beyond the initial crayfish boom in the late 1990s ( fig. 2). ...
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The Sacred Ibis Threskiornis aethiopicus is common and widespread in its native range. The species’ adaptability means that it thrives in landscapes modified by human activity. In recent decades, non-native populations have become established in several areas of Europe as a result of escapes or deliberate releases from collections. Such populations have the potential to become established and increase quickly, and thus to have a significant impact on native species. This paper summarises the current situation in Europe, with particular reference to France. The largest non-native populations in Europe became established in France between about 1990 and 2005, prompting a costly eradication programme, the progress and results of which are described.
... African Sacred Ibis were introduced to Europe from Egypt (from where it later disappeared) in the 1700s, and small populations were maintained until the 1970s when they became popular exhibits in zoological gardens (Clergeau et al. 2010). A zoo in Brittany was the origin of the northern French invasive population, which had reached~3000 individuals by 2004 (Marion 2013). Similarly, another zoo on the Mediterranean coast was the source of a population there, which was said to have potential predatory impacts on threatened native birds. ...
... This prompted a nationwide call for their extermination, and caused conflict with people who argued for their aesthetic quality. Marion (2013) argued that as their principle diet is of invertebrates, they are not the predatory threat that others had claimed (see also Strubbe et al. 2011), although they are opportunistic predators of birds, reptiles, fish and amphibians. ...
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... the west coast of Taiwan. In 2020, the population reached over 10 000 individuals, and over the past few decades these ibises have disrupted local ecosystems in Taiwan as well as ecosystems elsewhere where they have invaded (Herring & Gawlik 2008, Marion 2013. ...
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The African Sacred Ibis Threskiornis aethiopicus is an invasive bird species in Taiwan and has expanded its distribution range rapidly over the past three decades. There is limited information available on the invasion process of African Sacred Ibises in Taiwan and its genetic consequences. We investigated whether genetic factors reflected the expansion of African Sacred Ibises and determined the extent to which two behaviour associated genes may have facilitated invasion. The dopamine receptor gene (DRD4) and the serotonin transporter gene (SERT), have both been found to be associated with novel‐seeking and bold behaviour in birds. We hypothesized that: (1) selection on temperament traits may determine the polymorphisms in these two genes and, (2) the likelihood of dispersal of African Sacred Ibis populations can be explained by the intraspecific variation at these two genes. To detect the signals of population expansion and natural selection, we compared intra‐population variation and inter‐population differentiation of DRD4 and SERT with those of a mitochondrial gene (COX1) and an additional intron. We recovered contrasting patterns of nucleotide variation between the mitochondrial and nuclear genes with no SNPs detected in COX1 compared to allelic polymorphism in DRD4 and SERT. Populations showed decreasing genetic diversity at DRD4 as their distance to the initial invasive locality increased, consistent with a rapid expansion from one founder population. However, we found little evidence of selection on DRD4 or SERT, suggesting that these behaviour‐related genes are unlikely to have played a significant role in the successful invasion of the African sacred ibises in Taiwan. We detected high levels of genetic variation at these two behaviour‐related genes despite the effects of inbreeding in these invasive birds.
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The spreading of invasive species in new continents can vary from slow and limited diffusion to fast colonisations over vast new areas. We studied the sacred ibis Threskiornis aethiopicus along a 31-year period, from 1989 to 2019, with particular attention to the first area of release in NW Italy. We collected data on species distribution through observations by citizen science projects, population density by transects with distance method, breeding censuses at colonies, and post breeding censuses at roosts. The birds counted at winter roosts in NW Italy increased from a few tens up to 10,880 individuals in 2019. Sacred ibises started breeding in 1989, with a single nest in north-western Italy. The number of breeders remained very low until 2006, when both overwintering and breeding sacred ibises started to increase exponentially and expand their range throughout northern Italy with isolated breeding cases in central Italy. In 2019, the number of nests had increased to 1249 nests in 31 colonies. In NW Italy, the density of foraging birds averaged 3.9 ind./km ² in winter and 1.5 ind./km ² in the breeding period, with a mean size of the foraging groups of 8.9 and 2.1 birds respectively. Direct field observations and species distribution models (SDM) showed that foraging habitats were mainly rice fields and wetlands. A SDM applied to the whole Italian peninsula plus Sardinia and Sicily showed that the variables best related to the SDM were land class (rice fields and wetlands), altitude, and the temperature seasonality. The areas favourable for species expansion encompass all the plains of Northern Italy, and several areas of Tuscany, Latium, Sardinia, and Apulia.
... Evidence of impacts on BD species due to egg predation (e.g. Bubulcus ibis, Chlidonias hybridus, Chlidonias niger, Sterna sandvicensis, Vanellus vanellus) (Clergeau & Yésou 2006 cited by Wright 2011, Marion, 2013 ...
Technical Report
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... Alors que chaque pays peut adopter une liste propre d'espèces envahissantes, et qu'en principe ne doivent être retenues à l'échelle européenne que celles présentant un caractère envahissant grave et généralisé, et qu'on peut détruire si c'est encore possible et à un coût financier ou environnemental acceptable, sans effets environnementaux collatéraux négatifs, on a assisté à l'inclusion d'espèces très localisées (par ex. le Gunnera qui n'est envahissant qu'aux Açores), ou impossibles à éradiquer (Ragondin, écrevisses d'origine américaines), ou ayant des impacts mineurs ou non avérés ou contestés (Ibis sacré, Perruche à collier, Strubbe et al. 2010, Marion 2013 mais voir aussi Dubois 2017). La France est ainsi forcée de contraindre les établissements commerciaux à liquider les stocks de ces espèces, mais tout en pénalisant ensuite les particuliers qui les détiendraient. ...
... Annual numbers of breeding pairs of Eurasian Spoonbills in each colony in France from 1973 to 2018 Discussion While overall decreases in the total number of breeding pairs of Spoonbills occurred in 2001, 2003 and 2005, mainly affecting the Grand-Lieu and Brière colonies (Marion 2013a), there was by contrast a very regular overall increase since 2006. However fluctuations still occurred in important site such as Brière since 2011 (from 133 breeding pairs in 2014 to only 33 in 2017,Figure 2) probably due to shooting or other deterrent actions against Sacred ibises in the main mixed colony leading to its abandonment(Marion 2013b). These actions probably contributed to the multiplication of new small colonies in Loire-Atlantique and the strong increase of existing colonies such as Guérande and Le Fresny, and maybe an emigration of some pairs to Charente-Maritime. ...
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The mania for native plants appears to be a recent phenomenon in Germany. It has accompanied demands for new ethics and a life close to nature. Some examples of this mania are presented here. A historical review of the scientific and professional development of landscape architecture in Germany sheds some light on these more recent developments. The work of landscape architect Willy Lange in Berlin in the early 20th century, and his reference to the laws of nature are crucial to understanding the current mania. So too is the special understanding of plant geography, which in Germany was called plant sociology. In the so-called Incorporated East Areas, the territory taken by Germany from Poland in World War II, to create an ideal German landscape, German landscape architects formulated “landscape rules” which reflected Lange's ideas about nature and design, as well as national Socialist criminal energy. The mania for native plants during National Socialism and the fact that this particular aesthetic point of view became governmental policy is particularly disquieting when one relates the phenomenon to more contemporary events.
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Five pairs of T. aethiopicus bred in 1993 in a flooded tree-nesting mixed colony of Platalea leucorodia, Ardea cinerea, Egretta garzetta and Nycticorax nycticorax in lake Grand-Lieu, France. This first successful breeding produced 11 flying young. In 1994, 40 pairs bred, breeding about 50 flying young. The feeding areas were situated in the lake, mainly on marsh grasslands, but also in the Loire Estuary (25km). The main prey (78%) was Eristalia sp., a dipteran larva, but birds also caught eels Anguilla vulgaris (16%) and shrimps Palaemonetes varians (6%). -from English summary