Assessing the Prevalence and Drivers of Trichomonas gallinae in UK Hawfinch (Coccothraustes coccothraustes) Populations

<p dir="ltr">Trichomonas gallinae is a pathogenic, protozoan parasite. It can cause lesions in the oral cavity of infected birds, known as trichomonosis, which can prevent the bird from feeding. This can lead to death of the bird by starvation. The parasite has previously been noted in chaffinches (Fringilla coelebs) and greenfinches (Chloris chloris), where it has been linked to their decline. Recently, signs of trichomonosis have been reported in UK hawfinch (Coccothraustes coccothraustes) populations. </p><p dir="ltr">The hawfinch is a red listed bird in the UK, isolated to a few strongholds. The reason for its decline is unclear, however it has been suggested to be due to declining habitat and predation. It is not yet known how much of an effect T. gallinae could have on these populations or what drives the cases. To our knowledge, no study has yet to looked at subclinical cases of T. gallinae in hawfinches, but it has been confirmed in some by post-mortem analysis. </p><p dir="ltr">The first chapter looked at the prevalence of T. gallinae in 3 populations of hawfinches in the UK, testing whether any biological covariates and study sites were linked to the presence of T. gallinae. This involved sampling hawfinches (both live and dissected) and using PCR to look for positive cases of T. gallinae along with any specific strains. </p><p dir="ltr">83 hawfinches were sampled, and 5 hawfinches were dissected. Of the live samples, 32 were positive for T. gallinae. No bird sampled showed signs of trichomonosis, suggesting that these infections were sub-clinical. Of these 17 samples were used to create a phylogenetic tree based on a primer called ITS and 12 were used to create a phylogenetic tree based on a primer called Fe-hyd. Longer term studies are needed to fully understand the effects of the parasite, but it is suggested that mitigation measures are used such as periodical moving of feed sites to minimise risk while ringing these birds. </p><p dir="ltr">The second chapter looked at what may be driving cases of T. gallinae in hawfinches, testing whether avian community composition and bird feeder usage could be potential drivers. This used camera trapping and co-occurrence analysis to look at species associations and evaluate if these associations could be driving cases of T. gallinae. An online questionnaire was used to look at bird feeder usage.</p><p dir="ltr">Hawfinches were associated with chaffinches at both sites that were looked at. As chaffinches are known to contract T. gallinae, this association may be driving cases. Further studies sampling both hawfinches and chaffinches at the same site are needed to fully explore if there is a link. No factor was significant in presence of hawfinches in garden. Very few respondents reported hawfinches which could suggest that these birds rarely visit gardens. Most reports of hawfinches in gardens were within 10 km of one of the sampling sites but the response rate was low. Further studies looking specifically at these areas would help confirm if hawfinches are using bird feeders and this should be combined with sampling of these feeders to see if T. gallinae is being spread at them.</p><p dir="ltr">This study sets a foundation for future work to fully understand T. gallinae in hawfinches.</p>