Hellenic Ornithological Society, photo: I.Foufopoulos
Control of populations of seabird terrestrial predators

Islet of the Aegean SeaThe islands and islets of the Aegean and Ionian Sea give shelter to the majority of Greek seabird populations, providing them with ideal nesting, resting and wintering sites.Due to human activities, the areas available to seabirds on larger and inhabited islands have been reduced to a minimum. Therefore, the only terrestrial habitats suitable for seabirds left are uninhabited islands and islets. However, even these are not free from direct or indirect human impacts having, in many occasions, negative effects on seabird populations.

Among the main objectives of the LIFE project is the mitigation of rat (Rattus sp.) predation, one of the most important threats to Mediterranean Shag and Audouin’s Gull. Rat predation on seabird eggs, nestlings or even adult birds is a phenomenon common throughout the world, which leads to reduced breeding success or even worse, to abandonment of colonies. Rats are an alien invasive species in Greece, and can have negative effects not only on seabirds, but also on the rest of native fauna and flora including small mammals, birds, reptiles, invertebrates and endemic plants. Therefore, removal of rats from uninhabited islets is one of the necessary prerequisites for the restoration of ecological equilibrium in island ecosystems, bringing also long-term benefits to native animal and plant species.


Sketch: Vasilis Hatzirvasanis

For the reasons described above, the present LIFE project aims to the removal of rats from at least five island or islet complexes within the project areas hosting important Mediterranean Shag or the Audouin’s Gull colonies, covering a total land surface area of at least 400-500 ha. These rat removals are expected to significantly improve the breeding performance of the Mediterranean Shag and the Audouin’s Gull on the national level.

Removal of rats is time-consuming and costly, both in financial resources and human effort. Therefore potential rat removal sites must be prioritized prior to rat removal operations in order to ensure optimal ecological benefits for a given cost. The prioritization is based on information such as presence or absence of rats, the level of rat predation on seabird colonies, presence of other mammals and in general other fauna, type of vegetation and vegetation coverage of the islands, human presence and activities, accessibility of the islands both to people and rats, geographical and topographical characteristics of the islands, etc. Taking into account all these parameters and the estimated cost of rat removal operations, every islet and complex of islets is evaluated using cost-benefit analysis to determine those where the ecological benefits are the greatest, given the cost.

Islets in SkyrosSubsequently, for each high priority islet or islet complex, the removal method is designed and implemented to ensure an effective removal of rats and safety of other species, including seabirds. The removal of rats is followed by a systematic monitoring of the target islets to study the progress of the rat removal, its effect on the entire ecosystem and particularly on the seabirds breeding success. This monitoring must last at least one year before an islet can be declared rat-free.

On the other hand, prevention of rat invasion or rat reinvasion on rat-free islands is as important as their removal. For this reason, contingency measures are taken for all islands where rats have been removed, accompanied by an information campaign for the general public as well as specific social groups (e.g. fishermen, shepherds, tourists and others).

It should be noted that the removal of rats within the framework of the present project comes as the continuation of successful pilot rat removal operations of the LIFE-Nature project“Conservation of Falco eleonorae in Greece”, which proved the multiple benefits that rat removal provides to birds, other native fauna and the vegetation of the islets.


The first step in the prioritization of the islands for potential rat removal operations was the design of the prioritization method. The method is based on the Brooke-Hilton cost-benefit analysis and was further adapted to the Greek conditions and the needs of the LIFE project. Based on this method, required information was collected for the islands and islets in the project sites. Finally, prioritization analysis was carried out for 83 islet and island complexes hosting colonies of the Mediterranean Shag and/or Audouin’s Gull. The first 20 islet complexes with the highest priority of rat removal belong to the following regions:

Region No. of complexes
1. Thasos 2
2. Skyros 3
3. Kythera 2
4. Limnos 1
5. Amorgos 2
6. Leipsi 2
7. N. Sporades 2
8. Fourni 3
9. Agathonisi 2
10. Lesvos 1

The implementation of rat removal operations started on islets in Skyros in September 2010. Until autumn 2012, rat removal has been carried out on 19 uninhabited islets within 8 islet complexes where post-eradication monitoring is still in progress.

Region No. of complexes Total area (ha) % of P. aristotelis National population % of L . audouini National population
Skyros 2 11 2.6-3.2% 2.6-4.3%
Thasos 1 21 5.4-7.4% -
Kythera 1 3 - 2.4-12.0%
Fournoi 2 98 3.0-4.1% 3.2-24.6%
Amorgos 2 89 - 3.0-11.1%
Paros 1 29 1.3-2.0% -
Total 5 133 12.5-16.7% 11.2-52%

Throughout the entire duration of rat removal and during post-removal monitoring, the presence of rats is monitored with the use of bait stations, where bait consumption is checked on a daily basis. The example below demonstrates the progress of rat removal:

Progress of rat removal on selected islet of Skyros
Skyros islet animation

Θαλασσοκόρακας & Αιγαιόγλαρος

take part in the Greek seabird population census

 Identify six seabirds at a glance!

Dark coloured, long necked and short tail

Mediterranean Shag: rounded crown, steep forehead, slender bill, thin straight neck.

Dark coloured, long wings, just above the water

Cory’s Shearwater: brown above, white below, long glides.
Mediterranean Shearwater: dark above, light below, quick wingbeats. Usually in flocks.

White coloured gull, with long wings 

Yellow-legged Gull: light-coloured bill, eyes and legs. Dark grey mantle with white edge, and black wing tips, with large white spots. Yellow bill. Most common gull.
Audouin’s Gull: dark-coloured bill, eye and legs. Light grey mantle without obvious white edge and black wing tips, with small white spots. Red bill. Typically observed close to islands and small islets.

Tiny, black, just above the water

Storm-petrel: very small, white rump like a swallow. Very rare

LIFE Natura 2000

LIFE07 NAT/GR/000285
Concrete conservation actions for the Mediterranean Shag and Audouin's Gull in Greece, including the inventory of relevant marine IBAs

The project is implemented by the Hellenic Ornithological Society, in collaboration with the Hellenic Society for the Study and Protection of the Monk Seal (ΜΟm), the Hellenic Centre for Marine Research (HCMR), the Technological Institution (TEI) of Ionian Islands and the Portuguese Society for the Study of Birds (SPEA), with the financial support of the European Commission and the co-financing of the A.G. Leventis Foundation.
Number of downloads:
Last update: October 10, 2012

Coordinating beneficiary

Associated beneficiaries



Hellenic Ornithological Society Hellenic Society for the Study and Protection of the Monk Seal (ΜΟm) Hellenic Centre for Marine Research (HCMR) Technological Institution (TEI) of Ionian Islands Portuguese Society for the Study of Birds (SPEA) A.G. Leventis Foundation
attica group superfast ferries blue star ferries Anek Superfast ANEK
Copyright © 2019 Hellenic Ornithological Society
Themistokleous 80, GR-10681, Athens, Greece, Tel/Fax: +30 210 8227937, +30 210 8228704, e-mail:
Komninon 23, GR-54624, Thessaloniki, Greece, Tel/ Fax: +30 2310 244245, e-mail: