Integrative Biology

Feral pigeons and wild boars

Management of feral pigeon populations

A high reproduction rate and a large food base allow large feral pigeon populations in almost every city worldwide. In order to find the properly designed control strategy that aims at lowering the number of an avian pest, the thorough understanding of the population processes of the considered species is needed. Estimates of demographic parameters as natality, mortality, immigration and emigration and of their variability are crucial when selecting an appropriate control strategy. These evaluations provide sensible hints regarding the feasibility of the intended control method itself. In the city of Basel we run nine feral pigeon lofts for more than 20 years providing broad scientific data. Recent results prove that only a small part of the breeding pairs, less than 10 percent, is able to compensate for losses due to mortality. Control strategies that encompass less than 90% of the breeding pairs therefore are unable to reduce a population. The only way to solve the pigeon problem is the reduction of the food supply by collaborating with general public.

Ectoparasites of feral pigeons and their reactions towards host-related stimuli
The close coexistence of large feral pigeon populations and humans in our cities implicates serious health risks. Several ectoparasites known to infest humans can migrate into human living space. Especially after their natural hosts are excluded from roosting and nesting areas ectoparasites search for new alternative hosts. We study the host seeking behavior of significant human pathogenic feral pigeon ectoparasites. One of these important ecto- parasites is the pigeon tick Argas reflexus. Being able to starve for years, A. reflexus can hide unnoticeably in the cracks and crevices of buildings. When biting a human host, the severity of the reaction to the bite can vary from mild symptoms to life-threatening conditions. With our study we hope to provide information about the main stimuli, which lead the parasites to their hosts. Furthermore we wish to contribute to a risk assessment for humans living close to feral pigeon nests or adjacent to buildings infested with feral pigeons.

Preventing wild boar (Sus scrofa) damage in agriculture – investiga- tion of deterrent systems
To prevent economic problems by high wild boar populations, an effective wild boar management has to be established. Besides the regulation of the populations by means of hunting, vulnerable crop fields have to be protected adequately. Crop protection is usually achieved by the use of electric fences, which is costly and time-consuming since fences need regular maintenance. Alternatively, various methods are available that claim effective deterrence of wild boars, however most of them lack scientific proof. In our study conducted in the Canton Basel-Land we investigated the effectiveness of solar- powered blinkers, an odour repellent, and a gustatory repellent in field experiments with free-ranging wild boars.

Solar blinkers and the odour repellent, which were investigated at baited luring sites, reduced the probability of wild boar visits by 8.1% and by 0.4% respectively. The gustatory repellent, which was investigated in experimental fields, did not have a significant effect on the frequency of damage events. Our study revealed, that none of the deterrents investigated was able to prevent wild boars from entering the experimental sites. To date, the only rec- ommendable means for damage prevention is the electric fence. Our results contribute to an assessment of legal foundations and common practice of field protection, compensation payments, and hunting by cantonal veterinary- and game authorities.

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