Biology subjects

Oppel, S.

Publications and source records attributed to Oppel, S..

2 recordsLinked to original sources

bioRxiv2020

Major threats to a migratory raptor vary geographically along the eastern Mediterranean flyway

Millions of large soaring birds migrate from the Palaearctic to Africa every year, and follow distinct flyways around the Mediterranean Sea. While there is conservation concern for many long-distance migratory bird populations, the magnitude and geographic range of threats affecting birds along flyways are poorly known, which complicates efficient mitigation. We used an endangered soaring migrant, the Egyptian Vulture Neophron percnopterus, as an example species to assess important threats in 13 countries along the eastern Mediterranean flyway. We tracked 71 birds using satellite telemetry to quantify mortalities, surveyed 4198 km of powerlines to detect dead birds, conducted 910 interviews to quantify the prevalence of poison use, and assessed the magnitude of direct persecution by surveying markets and hunters. We lost 44 birds (50% in Europe and the Mediterranean Sea, 16% in the Middle East, and 34% in Africa), and mortality causes varied geographically. Inadvertent poisoning resulting from rural stakeholders targeting predators occurred along most of the flyway. On the breeding grounds in eastern Europe, poisoning and collision and electrocution continue to be major threats. Electrocution on small and poorly designed electricity pylons was most severe in Turkey, Ethiopia and Saudi Arabia, while direct persecution to meet market demands for belief-based use of vulture products appears to be the largest threat in Nigeria and Niger. Illegal direct persecution for leisure is a major threat in the Middle East and Egypt. Although our work cannot quantitatively estimate which of the identified threats has the greatest demographic impact on Egyptian Vultures, none of threats are species-specific and are therefore relevant for many other migratory birds. Our assessment highlights the key threats per country that range states need to address to meet their obligations under the Convention of Migratory Species to protect migratory birds.

zoology↗

bioRxiv2020

Mouse eradication is required to prevent local extinction of an endangered seabird on an oceanic island

Petrels (Procellariidae) are a highly diverse family of seabirds, many of which are globally threatened due to the impact of invasive species on breeding populations. While predation by invasive cats and rats has led to the extinction of petrel populations, the impact of invasive house mice Mus musculus is slower and less well documented. However, mice impact small burrow-nesting species such as MacGillivrays prion Pachyptila macgillivrayi, a species classified as endangered because it has been extirpated on islands in the Indian Ocean by introduced rodents. We use historic abundance data and demographic monitoring data from 2014 to 2020 to predict the population trajectory of MacGillivrays prion on Gough Island with and without a mouse eradication using a stochastic integrated population model. Given very low annual breeding success (0.01 fledglings per breeding pair in poor years (83%) or 0.38 in good years (17%), n = 320 nests over 6 years) mainly due to mouse predation, our model predicted that the population collapsed from ~3.5 million pairs in 1956 to an estimated 175,000 pairs in 2020 despite reasonably high adult survival probability ({phi} = 0.901). Based on these parameters, the population is predicted to decline at a rate of 9% per year over the next 36 years without a mouse eradication, with a 31% probability that by 2057 the MacGillivray prion population would become extremely vulnerable to extinction. Our models predict population stability ({lambda} = 1.01) and a lower extinction risk (<10%) if mouse eradication on Gough Island restores annual breeding success to 0.519, which is in line with that of closely-related species on predator-free islands. This study demonstrates the devastating impacts that introduced house mice can have on small burrowing petrels and highlights the urgency to eradicate invasive mammals from oceanic islands.

ecology↗