Integrative Biology
The feral pigeon is an interesting model for studying evolutionary processes in urban ecosystems. In the Vienna population we proved 23 hereditary factors that influence plumage colour and pattern (Fig. 1). In our study, we suggest the existence of colour based selection processes on juvenile feral pigeons by comparing the differences in colour morph frequencies between juvenile and adult feral pigeons. We could demonstrate that melanic (dark-coloured) forms have a significantly better survival rate in the urban habitat than the comparison group of wild type birds. One colouration called Checkers, clearly seems to be handicapped. There is evidence that melanic feral pigeons are more resistant against diseases like for example ornithosis. Additionally, melanic pigeons seem to have a better resistance against physical influences.
Many features of how feral pigeons use the urban habitat remain unknown or controversial. In our GPS-project we studied the spatio-temporal use of the urban habitat by feral pigeons in Basel. We equipped feral pigeons with GPS-receivers that calculated and stored the position of the individual birds. The results showed that pigeons in Basel cover distances up to 5.3 km and individual home ranges cover up to 150 ha (Fig. 2). We additionally could prove that our feral pigeons show very individual feeding strategies and the composition of feeding flocks varies at different times and days. Home ranges of the lofts overlap partially and the use of the city varies according to season, breeding status, sex, and affiliation to a loft. The total ranges of the lofts showed an existing overlap between the various pigeon populations. This overlap explains the occurrence of epidemics in feral pigeon populations. Diseases can be transmitted at important feeding sites that are meeting points for pigeons from different parts of the city. Detailed information on the transmission routes are of human concern, since feral pigeons are a reservoir of human pathogenic diseases and parasites.
Feral pigeons can harbour at least 110 microorganisms pathogenic for humans. Seven of these have evidentially been transmitted to humans (Salmonella, Chlamydophila psittaci, Aspergillus, Candida, Cryptococcus neoformans, Histoplasma capsulatum and Toxiplasma gondii). Whirled up dust particles can cause allergic reactions to pigeon antigens in humans (Pigeon Breeder’s Lung). The most important ectoparasites of feral pigeons are the Red Blood Mite, Dermanyssus gallinae, the Pigeon Tick, Argas reflexus and the Pigeon Flea Ceratophyllus gallinae that can migrate into human living space when they lose their natural hosts. We described a case where a single pigeon nest was the source of a flea infestation in a couple that resulted in severe psychological distress.
In our project “Transmission of Chlamydophila psittaci from feral pigeons to humans in the urban environment” we study the possible transmission routes of Cp. psittaci from feral pigeons and their excreta to humans in the city of Basel. Cp. psittaci is the most significant zoonotic agent that can be acquired from feral pigeons. Until now 101 cases of transmission from feral pigeons to humans have been published. 43 of these infections (42.5%) have been attributed to loose or transient contacts to feral pigeons. We analyze faecal samples, water surface film samples from public fountains and air samples from public areas collected by bioaerosol-sampling. For analysis we use well-established PCR methods (ompA Nested-PCR and 16S-PCR). Additionally, we want to investigate the seasonal chlamydial shedding in individual birds. In our feral pigeon lofts of the “Pigeon Action of Basel” we have the unique possibility to investigate up to nine feral pigeon flocks in different areas of the city of Basel to perform a monitoring of Cp. psittaci under wildlife conditions. Thus we want to learn more about the epidemiology of this widespread zoonotic disease.
