Seasonal variation of territory size with the Little Owl (Athene noctua)

Abstract

In a population of Little Owls (Athene noctua) at the Lower Rhine (FRG), the factors were studied that influence the size and shape of territories of this non-migrating, all-year territorial owl species. These studies were carried out between September 1984 and June 1987. The birds were individually marked with transmitter packages so that their locomotional movements could be monitored. Using a standard protable stimulus (a dummy with an attached loudspeaker) the territorial boundaries of 19 male Little Owls were surveilled during the different seasons of the year. Male Little Owls defended their territories in all seasons, but distinct seasonal changes of intraspecific aggressiveness and territory size were observed. The seasonal variations of territory size followed a common pattern in all studied Little Owls, in spite of individual differences in the size of the defended areas. The largest territories were defended in March/April during the courtship season [Formula: see text]. In May/June all male Little Owls reduced the size of their territories [Formula: see text]. This corresponds to the breeding and nestling period. The yearly minimum of territory size [Formula: see text] was reached in the summer months July and August when the fledglings were still fed in the parental territory. When the first-year birds started to disperse in autumn (September/October), the size of the defended areas of the adult tenants again increased [Formula: see text]. In winter (November to February), a further increase in territory size was observed for periods of warm weather [Formula: see text]. Male Little Owls, however, were less aggressive during winter than in the following courtship season. On cold winter days with a ground cover of snow territorial aggressiveness ceased. Pastures and meadows offered a continuous food supply almost throughout the year. In some seasons they were overproportionally represented in the territories of Little Owls compared to the general surroundings. In reaction to changing accessibility of food, the hunting ranges within the home ranges were shifted much faster than the boundaries of the defended territories. The significance of various factors contributing to the variability of territory size in Little Owls are discussed (e.g. availability of food, seasonal and individual differences in aggressiveness, experience in the occupied area, population density).

The status and population changes of the Little Owl(Athene noctua)in the south of Békés county (Hungary)

“…There are some studies dealing with population surveys (Finck 1990, Tomé et al 2008, Thorup et al 2010, Šálek & Lövy 2012, Šálek et al 2013, breeding habits and feeding analyses of Little Owls (Angelici et al 1997, Obuch & Kristín 2004, Lanszki 2006, Hámori 2014, Šálek et al 2016, however, only Hernandez (1988) dealt specifically with collecting and analysing species-related road-kill data. During his studies in Spain, he got similar results in the distribution of the collisions within a year, that is, the largest number of road-killed individuals occur in August and July after the fledging of juveniles, while the figures are lower in the rest of the year.…”

“…The size of the territories varies seasonally according to Finck (1990), with the largest area (28.1 ha) in March-April and the smallest (1.6 ha) in July-August, in the fledging periods of the juveniles. Grzywaczewski (2009) had similar results in Poland (9 ha is the smallest, and 27.5 ha is the largest territory).…”

Comparison of distance sampling and territory mapping methods for birds in four different habitats

“…Despite the inability to assess this rule or its validity in a 93 scientific way, using a constant number in that range will result in uncertainties if used for 94 estimating abundances for a whole study area. Furthermore, territories of birds can be highly 95 dynamic within the season (Knapton and Krebs 1974, Finck 1990, Pasinelli 2000, making the 96 territory a questionable metric for abundance estimation. One assumed strength of TM is that 97 it provides finer spatial detail and, therefore, can be better used to depict the spatial 98 distribution pattern of birds in an area and, additionally, can be correlated with habitat 99 distribution.…”

Demographic data on the Little Owl(Athene noctua)in Upper-Kiskunság (Hungary)

“…Pulli and adults were individually ringed, after being captured usually inside the nest box, or within a circle with 168-meter radius around it (covering 8.9 ha, which equals with 35% of the average home range of the Little Owl), based on the findings and recommendations of literature (Exo 1987, Finck 1990, Génot & Wilhelm 1993, Martínez & Zuberogoitia 2004, Sunde et al 2009, Šálek et al 2016. During ringing, pulli were not sexed, sex of older individuals (juveniles and adults) was identified.…”