An IMEDEA (UIB-CSIC) study reveals that illegal use of poison is leading cause of mortality of red kites in Mallorca

milanesScientists at the Mediterranean Institute for Advanced Studies (IMEDEA, CSIC-UIB), in collaboration with researchers from the French Centre National de la Recherche Scientifique, have developed a new method of study that allows separating the contribution of each cause of mortality and the probability of correct detection in different species. The method, which has been illustrated in the study of the impact of the poison in the population of Red Kite (Milvus Milvus) in Mallorca, is published this month in the British scientific magazin Journal of Applied Ecology, and has been developed based on recoveries of red kites found dead on the field that had previously been marked for follow-up by ornithologists from the GOB (Balearic Ornithology Group) between 2000 and 2010.The scientific study, based on monitoring data of 146 kites, has identified the poison as the leading cause of mortality in Mallorca, responsible for more than 50% of deaths of this bird, while the electric power lines is responsible of 12%. Those most affected by the poison are two year old kites, the age at which they start to look for a territory to reproduce. The study estimates that the elimination of the poison would provide an increased survival of about 17% as well as a population growthtwo times faster than today.

Giacomo Tavecchia, main researcher of the study, states that “a first step towards the conservation of any stock is to identify the causes of death of individuals, quantify its impact and evaluate the importance of each. However, some causes are easier to detect than others and do not reflect their relative importance. For example, it is more likely to find a run over dead animal on a road than one that has been hunted, although the latter cause is more important.” Thus, analyzing the probability of detection of each case is of great interest to adopt effective conservation measures.

The collaboration between scientists from IMEDEA, the CNRS and the GOB has made it possible to further study the problem of the kite population in Mallorca and it can also be very useful for conservation, nationally and internationally. Furthermore, the most novel aspect of this new methodology is that it can be applied to the study of all multiplicative processes and in to particular epidemiological studies, as it bases on rebuilduing latent processes that have caused the observed events.

A new endangered bird

Many natural populations are threatened directly or indirectly from causes related to human activities. This is the case of the Red Kite (Milvus Milvus), a bird of prey declared endangered in Spain in February 2011. The kite is distributed throughout the European continent and some Mediterranean islands and its decline is due in large part to the illegal use of poison in hunting, electrocution and poaching. Being a bird specialized on tracking small carcasses scattered over the country is very vulnerable to poison, used illegally to “control” predators of game species.

Since early last century, the kite is in decline across Europe. In Spain, the decline has been dramatic. In Mallorca, as stated by Jaume Adrover, GOB ornithologist, “it was a relatively common bird until some decades ago but its population declined to only 8 pairs in 2000. Currently the population is 19 pairs. In Menorca the decline was even worse, going from 145 to only 15 couples in the last 25 years. “


Cite as: Modelling longitudinal data in Mortality Causes in the Presence of tag loss: application to raptor poisoning and electrocution. Giacomo Tavecchia, Jaume Adrover, Antonio Muñoz Navarro and Roger Pradel. Journal of Applied Ecology doi: 10.1111/j.1365-2664.2011.02074.x

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