We have been studying Barn Owls for more than 30 years. The first nestbox was installed in 1986, marking the beginning of our adventure. Alexandre Roulin published his first papers in local journals such as Nos Oiseaux before working at the university and becoming head of his research group. Discover a glimpse of our research through a chronological selection of about thirty of our scientific articles. These days, journal articles are exactly how scientific knowledge is created and shared. Discover all the articles here. A book published in English summarizes this knowledge, a book that will be published in French and German in 2021.
Barn Owl coloring varies from white to reddish-brown and from completely clear to fully spotted. What causes these color variations? How are these colors coded in the genes? Are there geographic variations? If so, why? Are these color differences linked to the physiology or the behavior of the individual owls? And so many other things!
A Barn Owl’s diet and how it varies over time or geography enables us to better understand this species, and in the long run, to better protect it.
Barn Owl nestlings are very noisy at night. We discovered that they are negotiating amongst one another to see who will receive the next prey brought into the nest. Looking at sound, volume, frequency, and the length of the cries, but also at theft or gifts of prey, we examine the family life of a Barn Owl.
A broad subject in ornithology, our group has studied the reproductive behavior of Barn Owls in precise detail. From egg laying to a juvenile’s first flight, from nesting site to parental divorce, we are trying to understand all aspects of reproduction.
Barn Owl survival is a subject we feel strongly about, in particular in our study zone, and we would like to have a greater impact. To do this, we are studying the elements that have a positive or negative influence on the population size of the owls.
Here are a few articles about parasitism and the phylogenetic tree, meaning the family ties of ancestors and cousins of the Barn Owl. We deal with these subjects a bit less often, but they remain important.
Plumage coloring
Our first study on the color polymorphism of Barn Owls. It shows that the reddish-brown or white coloring of an owl is genetically inherited from its parents. That same year saw a publication proving that the size of the black spots at the base of the ventral feathers and the chest was also hereditary. These aspects were then confirmed numerous times.
Plumage coloring
This study suggests that males “prefer” to breed with females having large black spots on their bellies.
Plumage coloring
An owl’s coloring is a sign of genetic quality. The larger the black spots on the ventral feathers of a female, the stronger the immune response of her owlets to a specific antigen.
negociation
Barn Owl nestlings “negotiate” vocally to know who will receive the next prey brought into the nest by the parents.
Plumage coloring
Barn Owls with more spots on their plumage are more resistant to attacks by the parasite fly Carnus hempaterus.
reproduction
Barn Owls are one of the rare species who produce two egg clutches per year. Roughly half of the females who initiate a second clutch change partners to do so.
Good years are characterized by a high survival rate, a mass arrival of immigrants and, in parallel, the departure (emigration) of many young birds of our population toward other populations.
reproduction
Barn Owls are monogamous. Males and females customarily raise their young together. 98% of young are born of males who feed them. Paternity is thus very strong and there are few extra-marital young.
Plumage coloring
Survey of the knowledge base on the factors favoring the evolution, maintenance, and adaptive functions of color polymorphism in Barn Owls.
In the 20th century, the population of Swiss Barn Owls experienced three large headcount reductions following several severe winters.
Headcount fluctuations within a population are primarily influenced by variations in the survival rate of adults while breeding success, in fact, has a weaker impact. This means that even if many juveniles fledge in a given year, this does not necessarily translate into many nesting pairs the following year.
divers
Female Barn Owls lay their eggs in substances that improve chick resistance to the parasitic fly Carnus hempaterus.
Plumage coloring
Study of the multiple roles of hormones regulating, among other things, the synthesis of melanin, the pigment responsible for coloring in many animal species. Darker colored animals are generally more aggressive, more sexually active and more resistant to stress and infections.
Plumage coloring
In the northern hemisphere (but not in the south), Barn Owls have larger spots in the equatorial zone compared to temperate zones.
negociation
Barn Owl nestlings have longer cries if they are hungrier than their brothers and sisters. They adapt the length of their cries with respect to the other owlets in order to come to an agreement as to who is hungrier and “deserves” the next prey.
Plumage coloring
In Europe, the geographical variation of coloring is maintained through natural selection. It’s better to be tan in the north and white in the south! This idea was then confirmed through a theoretical study conducted in 2014.
Plumage coloring
Females with more spots manage the stress hormone, corticosterone, better than the females with less spots.
Plumage coloring
Females with large black spots survive better during their first year of life compared to those with small spots.
Plumage coloring
Study summarizing different discoveries on the links between colors and quality of the individuals.
negociation
Description and study of the behavior of giving prey amongst young Barn Owls.
negociation
Study on the frequency of cries, as well as their duration, in negotiations amongst young Barn Owls. The level of hunger has more influence on the number of cries than their duration. This explains why, in a negotiation process, the number of cries is more important for influencing the behavior of a brother or sister compared to the length of the cries.
negociation
The owls are polite; they don’t cut across each other! In this way, a young owlet almost never interrupts a brother or a sister when he or she cries. This characteristic was studied again in 2018.
Plumage coloring
Given that the melanin-based coloring confers certain advantages and non-melanin coloring has other benefits, we should expect that these colorations won’t be identically affected by climate change.
reproduction
Description of certain reproductive parameters in our population of Barn Owls, notably the influence of weather conditions during the breeding season.
Plumage coloring
Study of the effect of the MC1R gene, partly responsible for the color polymorphism of Barn Owls.
negociation
Not only does hunger dictate how a chick adjusts its negotiating cries but also its social interactions. The young continually adjust their cries according to the “mood” of their brothers and sisters.
alimentation
General study on the presence of insect-eating small mammals in the diet of European Barn Owls. Done following the same studies on the presence of reptiles, amphibians, bats, birds, and invertebrates in the diet of European Barn Owls.
Plumage coloring
Following the last ice age, the Barn Owl reclaimed European territories via two pathways along Mediterranean coastlines. One group went from the Middle East and another from Northern Africa and Spain. This is when the russet plumage color appeared. This means that the European ancestor owls were white.
divers
We determined the phylogenetic tree, a kind of family tree of the species, of the Barn Owl and its many cousins. This tree was refined in 2018.
Plumage coloring
This study shows that the selective factors for an animal’s coloring also affect other physiological properties. This means there is a strong genetic link between the genes involved in color and those involved in other functions.
Plumage coloring
At the international level, the reddish-brown color is more common in humid regions, and the white color is more broadly distributed in dry regions.