Discerning the status of a rapidly declining naturalised bird: the Golden Pheasant in Britain

Whilst many introduced non-native plants and animals become naturalised or even invasive, others fail to persist. Golden Pheasants (Chrysolophus pictus) have occurred in multiple regions outside of their native China, with the largest populations establishing in the United Kingdom. Now very rare in the UK, ongoing releases make its continued ‘wild’ status dubious. The Golden Pheasant in Britain provides a case study of an introduced species that at first appeared to thrive before declining to the point where no viable wild populations remain. Here, we outline the history of Britain’s Golden Pheasants before describing their current status. To do so, we reviewed the relevant literature, engaged in personal communications with rural staff and birdwatchers, and carried out a survey of a putative remnant population. We conclude that there are 37–40 ‘wild’ Golden Pheasants left in the UK, within two regions (both populations are dependent on human management via supplementary releases, food provision, or predator control, and therefore can no longer be considered to be truly naturalised as of 2023). This represents a significant decline from a 1993 UK population of 1000–2000. There is no evidence to suggest that Golden Pheasants persist in the UK as a self-sustaining population in 2023. We use this case study to discuss the issues associated with determining whether non-native populations are viable in the long term, and situations where apparently successful colonists then decline to extinction

Limited domestic introgression in a final refuge of the wild pigeon

Domesticated animals have been culturally and economically important throughout history. Many of their ancestral lineages are extinct or genetically en dangered following hybridization with domesticated relatives. Consequently, they have been understudied compared to the ancestral lineages of domestic plants. The domestic pigeon Columba livia, which was pivotal in Darwin’s studies, has maintained outsized cultural significance. Its role as a model organism spans the fields of behavior, genetics, and evolution. Domestic pigeons have hybridized with their progenitor, the Rock Dove, rendering the latter of dubious genetic sta tus. Here, we use genomic and morphological data from the putative Rock Doves of the British Isles to identify relictual undomesticated populations. We reveal that Outer Hebridean Rock Doves have experienced minimal levels of introgres sion. Our results outline the contemporary status of these wild pigeons, high lighting the role of hybridization in the homogenization of genetic lineages.publishedVersio

Parasite exchange and hybridisation at a wild-feral-domestic interface

Interactions between wild, feral, and domestic animals are of economic and conservation significance. The pigeon Columba livia is a synanthropic species in a feral form, but it also includes the rare Rock Dove. C. livia is an important player at the wild-domestic interface; acting as a carrier of avian diseases, and the feral form threatens Rock Doves with extinction via hybridisation. Despite its abundance, little is known about drivers of disease prevalence in C. livia, or how disease and hybridisation represent synergistic threats to Rock Doves. We focused on infection by the parasite Trichomonas, first collating prevalence estimates in domestic and free-living populations from relevant studies of C. livia. Second, we characterised variation in the diversity and prevalence of Trichomonas among three C. livia populations in the United Kingdom: a feral; a Rock Dove; and a feral-wild hybrid population. Across multiple continents, free-living pigeons had lower Trichomonas infection than captive conspecifics, but the effect was weak. Environmental factors which could impact Trichomonas infection status did not explain variation in infection among populations. Among the British populations, strain diversity varied, and there was lower parasite prevalence in Rock Doves than feral pigeons. Individual infection status was not explained by the available covariates, including hybrid score and site. The drivers of Trichomonas prevalence are unclear, perhaps due to idiosyncratic local-scale drivers. However, given the population-level variation in both infection prevalence and introgressive hybridisation, the potential combined effects could accelerate the Rock Dove’s extinction. Further study of the synergistic effects of multiple types of biotic interactions at the wild-feral-domestic interface is warranted – especially where vagile, globally distributed and superabundant animals are involved