Introduced predators are one of the main threats to island avifaunas. However, the magnitude of their impact in the Mediterranean has not often been studied. This is the case for the introduced alien black rats Rattus rattus, the most destructive predator of seabirds in the Mediterranean. Here, we analyse the impact of black rats on the breeding performance of Cory's shearwater Calonectris diomedea breeding at the Chafarinas Islands, an archipelago with a very high density of rats. An intensive rat control campaign (through anticoagulant poison) was carried out during 1999–2004 at two shearwater sub‐colonies with contrasting habitat features (vegetated vs. rocky). Breeding success of Cory's shearwaters increased in proportion to the effort of rat control. Such increase was mainly due to a decline in black rat predation on chicks, while eggs losses remained constant throughout the period. We found a differential effectiveness of rat control in each sub‐colony. The increase in breeding success after rat control was higher in the sub‐colony with lower breeding success (the vegetated habitat), but this parameter never reached the values shown by the other sub‐colony (the rocky habitat). Our results suggest that habitat characteristics of each case of study must be taken into account when designing and evaluating specific rat control programs.

Animals use environmental cues, social information and behavioural decision-making rules moulded by natural selection to decide where to breed. We assessed whether the presence of an alien nest predator, the Black Rat (Rattus rattus) is used by a colonial seabird, the Cory's shearwater (Calonectris diomedea), as an environmental cue in the selection of breeding sites. We compared potential habitat preference using quality of breeders and nest fidelity as response to nest predation between two sub-colonies with different habitat characteristics, breeding success and predation pressure. Quality of individuals was better in the predated habitat and birds did not perceive the presence of predators signalling differences in predation risk and in turn of breeding success. This failure of perception could be at two levels: in the selection of habitat for first breeding and in the breeding dispersal following a reproductive failure. Preference for the sub-colony with higher predation risk suggests the presence of an evolutionary trap. In fact, the introduction of alien predators probably transformed the behaviour of shearwaters in a maladaptive response due to a mismatch between the new environmental factors and their behavioural and evolutionary algorithms. This can be a common pattern in other species with little behavioural plasticity, evolved in stable environments free of predators.

We show the results of an eradication campaign against Rattus rattus developed in Rey Francisco Island (12 ha), Chafarinas islands, southwestern Mediterranean. Rat population size was estimated by snap trapping in up to 93.47 ind./ha and a trapping index of 9.58 captures/100 traps-night. We think that population was underestimated because of the number of traps found strung but without capture. Several products were tested in order to define the method of eradication. In 1992, we selected a second generation anticoagulant, pelleted brodifacoum 50 ppm into 5 l plastic containers as baiting stations. Bait consumption reached zero after three pulses, and intensive searching of tracks and signals were unsuccessful. After more than two years of absence of signals and sightings, in 1995, rat scats were observed in Rey Francisco, and the population rose dizzily. After several snap-trapping sessions in 1996, 1997 and 1999, when trapping success reached 37 captures/100 trap-nights, a new campaign started in autumnÀwinter 1999À2000 using flocoumafen 50 ppm inside 180 baiting stations. Eradication occurred with a very low risk for non-target fauna, setting less than 1 kg/ha of bait each time. Monitoring, both with snap traps and baiting at a lower intensity assures the absence of reinvasion.

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ABSTRACT- In spite of a late independence, obtained after a cruel war, Spain and Cuba have always mantained very close relations even during the worst periods of their history. The present contribution is a brief attempt to explain that the populations' movements and the family ties, among the popular classes of society as well as in the elites, have turned Cuba into the most Spanish land of America, occupying ever since the first place among Spain's foreign concerns.