Research

• Territorial system in a crow population. A major part of my dissertation was based on mapping the the relations and territories of crows in an area of about 15 sq. km. In this area most adult crows and all fledglings were given wing tags that could be identified from a distance. The findings are reported in publication 15. Basically, young crows do not breed until they have established themselves in a territory. This may not happen until they are several years old. Until then, they spend the spring in smaller flocks. In winter time flocks are larger and may include territorial birds. However, in my study area, some territorial birds spent part of the winter in their territories as well. A territory is acquired in either of two ways. Some crows mate with widowed territorials, males or females. Sometimes pairs of young crows may find a "weakness" in the established territorial system and establish themselves there. When so happens, they have usually made exploratory visits to the area already in the previous year. Once established, territories (or mates) are almost never changed.
• Factors affecting clutch size in a crow population. I have studied factors affecting clutch size in this crow populations publication 2 and 7. In one experiment (reported in publication 10) I manipulated number of nestlings to asses the optimality of the clutch size. In another experiment (reported in publication 12 I manipulated number of eggs. This showed that time constrains may be another important factor for the clutch size.
  
• Roost as information centres. In a field experiment (publication 8), I and Staffan Tamm investigated the possibility that the roosting behaviour of crows (and ravens) could fascilitate the discovery of rich but ephemeral food sources. Indeed, after the first discovery (by single or few birds) of such a food source, many more birds arrived on the next day. This, we think, supported the "information center hypothesis".
• Other studies. Other crow studies have focused on nest sites (reports 1 and 5), use of road kills (report 17), and pheasant egg predation (reports 3, 11, 14 and 16).