Avian Malaria in the Scandinavian Mountains from 1999 to 2020

Abstract

This study investigates and describes the Haemosporidian parasite composition of the host bird community in the Ammarnäs area from 1999 to 2020, along with the effect of avian malaria infection on host body condition, based on a data set comprising body measurements and infection status for the Plasmodium, Haemoproteus, and Leucocytozoon genera in captured birds from five sample years, and also a data set comprising the body measurements of recaptured birds. Leucocytozoon was consistently the most prevalent Haemosporidian genus in Ammarnäs, although its prevalence appears to be on a decreasing trend. Remarkably, 2020 was the first year when a case of Plasmodium infection has been detected, which gives rise to a new opportunity to record the introduction of a new Haemosporidian genus in the area in future studies. Although juveniles were more prevalent in the community, Leucocytozoon was more prevalent in adult hosts. The most common host species were the brambling (Fringilla montifringilla), the Eurasian siskin (Spinus spinus), and the willow warbler (Phylloscopus trochilus). The results indicate no significant difference in physical condition - measured by weight index - between healthy and infected birds. However, a difference close to significance was found in redwings (Turdus iliacus), where as expected healthy birds had a higher weight index than infected ones, and also in willow warblers, where healthy birds seem to have a lower weight index, suggesting the possibility of a different strategy in dealing with infection. No significant effect of infection was detected in the recapture data. As for the Leucocytozoon parasite community, its composition is diverse and similar to other comparable northern habitats. The most prevalent lineages were BT1, BRAM2, and BRAM3, and they were also constantly present in the community through the years. There were several lineages, such as PARUS20, that were only found in one year and never again afterwards, suggesting unsuccessful introductions in the community, and also two lineages - ZONALB22 and ZONALB34 - which were found in 2020 for the first time, remaining to be seen whether they will establish themselves as a part of the local parasite community in the future. This study has given a detailed description of the trends in the parasite and host communities in Ammarnäs, and may lay a foundation for future studies and monitoring efforts in the area. To gain more statistical power to detect trends in the investigated communities, more sampling and a more standardized and consistent sampling procedure are needed in the coming years.

Popular Abstract

Birds are among the most beloved wildlife that us people encounter daily – we find their colourful plumage charming and their cheerful trills endearing. But birds, just as us humans, have their own daily trouble to tackle, one of these being dealing with infection. Among the many perils they may face is that of parasites, which may completely change their life once acquired since birds, unlike us, do not have a healthcare system to help treat them. Among the most studied types of parasites that affect birds are the avian malaria parasites, which can be part of several genera. In Sweden, the most common avian malaria parasites are of the Leucocytozoon, Haemoproteus, and Plasmodium genera, which are also the main focus of my study. The immediate symptoms given by infection with such parasites vary greatly in severity depending on the different parasite and host bird species, but in songbirds, which are the focus of this study, they are usually mild but may affect the long-term survivability of the bird.

In this project I investigate the status and the community trends between 1999 and 2020 of the avian malaria parasite and the host bird communities in an area close to Ammarnäs, a small town in the mountainous area of northern Sweden, near lake Tjulträsk. I looked into the prevalence of the parasites, the effects of infection on the birds’ bodily condition, the parasite lineage composition in the community, and the possible effects of climate change on all of these aspects. Firstly, Leucocytozoon was consistently the most prevalent genus of avian malaria parasites found in Ammarnäs, so it became the main focus of the study. However, it was also found that its prevalence is on a decreasing trend, for which a reliable cause could not be determined from the information available to date and thus remains to be discovered. Although the community is comprised mostly of young birds hatched in the same year, adults were more likely to be infected, which suggests that birds may encounter the parasites more in the places they migrate to than in Ammarnäs. Furthermore, there was no evidence for local effects of climate change, with average summer temperatures and precipitation levels varying widely through the years with no particular trend. As for the effects of infection on the physical condition of the birds, there was no general trend for all bird species, but for one – the redwing – there was a trend for healthy birds to be in better shape than ill ones, and for another – the willow warbler – the trend was the opposite, possibly due to differences in how they manage infection. The parasite community composition and its changes throughout the years were described. Some types of parasites were found to be the main components of the community and consistently present since 1999 to the present day, while others were only temporarily part of the community. There were two types of avian malaria parasites that were found for the first time in 2020, and their fate in the community remains to be seen through future studies.

This study has described the trends in the parasite and host bird communities over the past few decades and has laid a stepping stone for future research of the topic. Still, more investigation is needed to disentangle the mysteries of the parasite-host dynamics in Ammarnäs, including more consistent sampling and a focus on the same bird species of interest each year.

• author: Jecu, Diana
• supervisor: Olof Hellgren
• organization: Degree Projects in Biology
• course: BION03 20231
• year: 2024
• type: H2 - Master's Degree (Two Years)
• subject: Biology and Life Sciences
• language: English
• id: 9149198
• date added to LUP: 2024-02-28 13:53:30
• date last changed: 2024-02-28 13:53:30