What role do migration play for parasite burden?

Submitted by editor on 20 October 2015.

Influence of phylogeny, migration, and type of diet on the presence of intestinal parasites in the faeces of European passerine birds (Passeriformes)

Petra Bandelj, Rok Blagus, Tomi Trilar, Modest Vengust, Aleksandra Vergles Rataj

The first week of September of every year is a MUST for a small group of biologist, microbiologists and veterinarians. We meet at the bird observatory in Vrhnika, near the capital city of Slovenia. Our mission: simply enjoy. For that one week, dr. Tomi Trilar, is in charge of the observatory for ringing and monitoring passerine birds on migration. Because of his enthusiasm in explaining the what and the whys of bird anatomy and biology, quite some people spend every spare moment possible at the observatory, helping, learning and having fun. While handling wild birds and  learning about their behavior, several questions arise, and for veterinarians, the questions are usually infectious in nature. What kind of bugs do they carry? Is it possible to get a zoonotic disease while handling wild birds? What kind of parasites they have and is there a difference between different species in regards to their biology? All these questions of course need an answer and being around scientist, it's not long, until we organize a plan of action from the collection of the samples to their analyses. It looks simple and it truly is, because working with people that are passionate about their job, makes it fun and consequently simple. This is what research is about. Having fun in finding answers to questions that come your way.

Photo 2: dr. Tomi Trilar (Photo by: Petra Bandelj) returning from his hiding place

If we looked at the significance of our questions, we find that one quarter of all European breeding passerines and near-passerine birds migrate from the European continent to sub-Saharan Africa in autumn each year, which is estimated to be over 2 billion birds. This means that such migration can have an impact on local communities and can affect the health of birds or other animals, and also humans. So, it's important! But perhaps most importantly, in the long term, are warmer global temperatures that may favor parasite development and infectivity, which may consequently significantly impact the health of several animal populations.

At the end, we manage to collect droppings from 385 passerines (42 species), which showed a parasitic burden of 15.6%. Both phylogeny and the type of diet were associated with the presence of parasites in faecal samples of passerines. Our analysis suggests that the diversity of feeding sources of omnivore passerines exposes them to infection with intestinal parasites to a greater extent than granivore or insectivore passerines. Surprisingly, the presence of parasites in passerine faeces was not strongly influenced by migration. This was intriguing to us, since non-migratory passerines shouldn't be exposed to infective parasite stages during the winter, whereas migratory passerines should be constantly pressure by parasite infection in the warm environment. Therefore, studies like ours are important. We need to investigate and follow the prevalence of parasites and other etiological factors that can have a negative effect on passerine bird populations, so that we have the possibility to examine the influence of global warming on the prevalence of parasites (and other factors) in passerines in the future.

This paper answers our question, while raising few more, but we hope you can also appreciate it, as a baseline study for further, future investigations about the effect that climate change has on the parasitic burden in wild passerines.



P. Bandelj


Photo 1: Eurasian Nuthatch (Sitta europaea) (Photo by: Tomi Trilar)

Photo 3: Great Reed Warbler (Acrocephalus arundinaceus) (Photo by: Petra Bandelj)

Photo 4: Who is photo-shooting who? Tea Knapic, Eurasian Siskin (Carduelis spinus) and Petra Bandelj (Photo by: Tomi Trilar)

Photo 5: Common Redstart (Phoenicurus phoenicurus) (Photo by: Petra Bandelj)