Syftet med den här studien var att undersöka om revirstorleken påverkar den reproduktiva framgången hos lövsångarhanar. Datan samlades in i södra Sverige mellan 1984 och 1988 och består av etableringsdatum av revir, revirstorlek, antal partners (en eller ingen), datum för parning, antal ägg i kullen och antal flygga ungar. Det fanns inget samband mellan revirets storlek och de olika variablerna. Inte heller fanns det något samband mellan revirstorlek och hanens ålder när samma individ följdes över tid. Det fanns inget samband mellan revirstorlek och huruvida hanarna parades eller inte. Sammanfattningsvis påverkar inte revirstorleken hanens reproduktiva framgång. Istället finns det andra faktorer som troligtvis påverkar, som revirets kvalitet (t.ex. föda och predatorskydd), hanens ankomsttid, hanens sångrepertoar, hanens ålder samt föräldrarnas kondition. / The aim of this study was to examine if territory size of Willow Warbler males affects reproductive success. The data were collected in the south of Sweden between 1984 and 1988 and consist of date of establishing territory, territory size, number of partners (one or none), date of pairing, number of laid eggs and number of fledglings. There were no relationships between territory size and the different variables, nor was there a relationship between age of the male and territory size when following the same individual over time. There was also no relationship between territory size and whether or not the males reproduced or not. In summary, I could find no relationship between territory size and male reproductive success. Instead, other factors are likely to affect reproductive success, such as territory quality (i.e., abundance of food, safety from predation), male time of arrival, male song repertoire, male age and the body condition of the male and his partner.

For most taxa, maximizing fitness depends on maintaining access to adequate resources. Territories provide exclusive use of resources for an individual or a family group, thus facilitating successful reproduction. The economic defensibility of a territory depends on the quality, abundance, and distribution of its resources as well as the amount of competition that an individual must endure to maintain exclusive access. The benefits of defense must outweigh the costs for territoriality to be profitable. Territory owners may benefit from territories with high quality resources, but they also may incur greater costs defending these resources from competitors. In contrast, territories with poor quality resources provide fewer benefits to an owner but also may have fewer competitors vying for those resources. Resource quality may change over time, especially in habitats in which periodic ecological disturbances, such as fire, occur. As a result, the cost-benefit equation of defensibility also changes over time. The Florida Grasshopper Sparrow (Ammodramus savannarum floridanus), an Endangered subspecies, is a habitat specialist endemic to the Florida dry prairie, a pyrogenic ecosystem found only in south-central Florida. As a result A. s. floridanus has evolved with frequent fires and its demography is strongly influenced by the structural habitat characteristics, such as sparse woody vegetation and large amounts of bare ground that occur with frequent fire. The objective of my study was to determine what factors associated with fire (i.e. habitat structure and prey abundance) affected the "decisions" of male A. s. floridanus to defend a territory. I hypothesized that fire and the resources resulting from fire would have an impact on territory size and placement. I predicted that territories in more recently burned habitat would be of higher quality and that sparrows would avoid areas with a longer time since fire. I conducted my study at Kissimmee Prairie Preserve State Park in Okeechobee County, FL. One half of my 100-ha study plot had experienced two growing seasons since the last fire and the remaining half had experienced only a single growing season since fire at the start of my study. I mapped territories of all males within my study plot twice over the breeding season; once during the early season (nest building and incubation) and once during the late season (nestling and fledgling stages). In addition, during each survey I collected arthropods and surveyed vegetation composition within territories and at random, unoccupied points within the study plot. I compared the differences between the habitat characteristics of territories and unoccupied areas, the differences between the territories of the males that occupied the two-year rough and those in the one-year rough, males that abandoned their territories mid-season and those that remained in the study plot, and the seasonal changes in territory characteristics between the early and late season territories of males that persisted. My results indicate that A. s. floridanus selects certain habitat characteristics in which to place territories. Males preferred areas with fewer shrubs and more bare ground, which is consistent with previous studies. Prey biomass did not differ between territories and unoccupied areas. Nonetheless, although the mean mass of individual arthropods was larger in unoccupied areas, the numerical abundance of orthopterans, damselflies, and spiders was significantly higher in territories than in unoccupied areas. Sparrows were more likely to abandon their territories if they occurred in the two-year rough as opposed to the one-year rough. Territories in the two-year rough were significantly larger, had poorer quality habitat, and tended to have less prey than those in the one-year rough. The sparrows that persisted throughout the season significantly increased their territory size in the late season; however, very little spatial shift occurred, suggesting that they merely increased their territory size rather than moved to new sites. Early-season territories in the one-year rough were completely exclusive, but late season territories showed considerable overlap, suggesting lack of defense and a shift toward home ranges as opposed to exclusive territories. The habitat quality in late-season territories decreased (more shrubs, less bare ground) from the early season. Unexpectedly, however, the biomass of prey increased. This increase coincides with an increased demand for prey because sparrows are provisioning young. It seems likely that the costs of defense increase at this time because time and energy spent in defense come at the expense of time spent provisioning young. Because prey increases in the late season, the need to defend exclusive territories may decline.

Im Rahmen eines internationalen Projektes von Kranichschutz Deutschland (NABU, WWF, Lufthansa) wurden in den Jahren 1995 bis 2000 in Mecklenburg Vorpommern Untersuchungen zu Verhalten und Lebensraumansprüchen reproduzierender Graukraniche durchgeführt. Die zentrale Hypothese der Arbeit lautet: Eine gute Nahrungsverfügbarkeit, eine geringe Vegetationshöhe und ein geringer Vegetationswiderstand sollten zur Bevorzugung bestimmter Revierbereiche führen und somit die Reviergröße beeinflussen. Im Fokus standen außerdem die Wirkungen anthropogener Einflüsse. Da sich Kraniche während der Jungenaufzucht äußerst unauffällig verhalten, waren Grundlagen für effiziente Schutz- und Managementkonzepte kaum verfügbar. Erstmalig wurden die Habitatnutzung und die Reviergröße von Kranichfamilien mit Hilfe der Radiotelemetrie ermittelt (Null-Peak-Peilung). Zur Abschätzung des Vegetationswiderstandes wurde ein neues Verfahren entwickelt. Innerhalb der Reviere beeinflussten der Feldanbau mit Raps, landwirtschaftliche Störreize, die Nahrungsverfügbarkeit und die Jagdausübung die Habitatnutzungsintensität (HNI) am stärksten. Der Nahrungserwerb erfolgte in fast allen Habitattypen. Naturnahe bzw. extensiv genutzte Habitate wurden signifikant häufiger frequentiert als intensiv bewirtschaftete Nutzflächen. Die HNI der Kranichfamilien korrelierte signifikant mit der Verfügbarkeit der Nahrung. Straßen und Straßenverkehr beeinflussten die HNI ebenfalls. Der Mindestabstand zu Kreisstraßen war signifikant größer (mittlerer Abstand 308m) als zu Bundesstraßen (141m). Die Einflüsse der Vegetationshöhe und des Vegetationswiderstandes auf die HNI waren meist von geringer Bedeutung (keine Korrelation bzgl. der HNI). Habitate wurden erst gemieden, wenn bestimmte Schwellenwerte überschritten wurden (Veg.-höhe > 1m, Veg.-widerstand auf einen definierten Dummy >8N). Kranichreviere waren durchschnittlich 69,7ha (max.=131,8ha) groß.Ein Ausblick präsentiert künftige und bereits begonnene Projektvorhaben.