Causes and spatio-temporal variations of non-natural mortality in the Vulnerable Spanish imperial eagle Aquila adalberti during a recovery period

Abstract

AbstractThe analysis of 267 records of non-natural mortality of the Spanish imperial eagle Aquila adalberti over a 16-year period (1989-2004) shows an annual rate of 15.1 individuals found dead per year and that electrocution (47.7%) and poisoning (30.7%) were the most frequent causes of mortality. Most cases (91.7%) were of human origin, and of those 92.3% were accidental. Just over half (50.2%) were related to the transmission of electricity and human activity (collisions and electrocution), and 40.7% related to game practices and livestock protection (control of predators). No differences between sexes were found but subadults were electrocuted more frequently than expected whilst adults were poisoned more frequently. In breeding areas poison was the most frequent cause of mortality, whereas electrocution was the most common cause of death in dispersal areas. Poisoning occurred more frequently than expected in the Northern and Southern regions compared to the West-Central region. Electrocution was significantly more frequent in the West-Central region, and less common in the Southern region. The increase in electrocutions over the last few years is associated with previous non-permanent corrections on electricity power lines, whilst the increase in the cases of poisoning appears to be associated with the use of illegal poison in predator control by small game practices and for livestock protection. Permanent corrections in power lines and more research and awareness effort in the small game sector are recommended to reduce human-induced mortality in this Vulnerable species.