Illegal hunting, power lines and domestic cats are destroying the gray teal, a duck characteristic of the wetlands of the southeast of the peninsula that is at risk of disappearing. This is stated in a study carried out by a team of researchers from the University of Alicante, the Miguel Hernández University of Elx and IMEDEA, a joint center of the CSIC and the University of the Balearic Islands.
The report concludes that, if the unnatural mortality of this species is not reduced by at least 40%, the recovery programs for the gray teal in Spain will fail.
As the researchers explain, in Spain a lot of media attention is paid to species in danger of extinction such as the Iberian lynx, the brown bear or the imperial eagle, but the seven species that are in critical danger of extinction, that is, those that have an imminent risk of disappearance are much less known. These species include two birds, two mammals, one plant, and two mollusks.
Among them is a duck, the gray teal. This species, considered the most endangered duck in Europe, practically disappeared a decade ago, when only a few dozen breeding pairs were detected in the area around Doñana and the wetlands in the south of Alicante.
To reverse this situation, both the autonomous communities and the central government undertook various conservation actions, including a recovery program with the release of specimens bred in captivity. Thanks to this program, more than three thousand specimens have been released in recent years, but despite this, gray teal populations are not improving as expected.
With the aim of evaluating the effectiveness of the recovery program, researchers from the aforementioned institutions have carried out a study that has allowed us to know the survival of the individuals released in the Valencian Community, identify the main causes of mortality and, finally, evaluate the future viability of the species. For this, the data provided by sightings of ringed individuals has been key, as well as data collected through GPS devices with which more than 40 specimens have been equipped in recent years.
The results of the study indicate that mortality from non-natural causes, such as illegal hunting, collisions with power lines or predation by cats, triples natural mortality.
Illegal hunting, whether due to identification errors on legal hunting days or due to poaching, stands out as the most significant cause of mortality for the species, since it affected one in three marked specimens, both captive-bred and wild specimens. To determine the causes of mortality, the use of GPS devices was crucial, since it made it possible to accurately identify the place and day of death.
Unfortunately, 50% of GPS devices stopped transmitting data unexpectedly. Researchers suspect that it could largely be due to illegal hunting, since 70% of these devices suddenly stopped working when the bird was inside a preserve. Furthermore, the results warn that the presence of domestic cats in wetlands is an emerging threat that must be addressed carefully since cases of predation by these cats have been detected, which can cause significant losses.
Roberto Rodríguez Caro and Esther Sebastián González are the two researchers from the UA Department of Ecology who participated in the study. Pérez García points out that “many specimens are being released in recovery programs, but they are not able to establish themselves because mortality is very high.”
The analyzes indicate that the unnatural mortality of these birds should be reduced by 40% to recover the populations. To achieve this, the authors propose several urgent measures that include prohibiting the hunting of waterfowl during hours with poor visibility to avoid confusion and accidental deaths of non-game species, increasing the prosecution of poaching, controlling exotic predators in wetlands, and improving management. of water to reduce outbreaks of diseases such as botulism.
The researchers also indicate that some improvements could be made to recovery programs based on captive breeding and release. They suggest that the strategy of delaying the release of captive-bred birds until the end of the hunting season could have negative long-term effects, by increasing habituation to humans and dependence on predictable food sources. Finally, they make recommendations to reduce the stay in captivity and provide anti-predator training to birds released in breeding cages.
