Hansbauer, M., Munck, A. & I. Storch: Die Punkt-Stopp-Zählung zur Erfassung der Avifauna in Flussökosystemen: ein Methodentest. Testing the Point Count Method to record the avifauna in river ecosystems.

The Point Count is a relative method to record bird communities. It is a time and work saving alternative to more costly methods such as territory mapping, and is therefore often used for monitoring. The aim of this work was to examine the influences of external and methodological factors on results of the Point Count Method used in river ecosystems in Bavaria. The birds were counted twice for 3, 5, 10 and 15 minutes between April and June 2001 at 24 points in each of three study sites that varied strongly in habitat structure. At six chosen points per study area birds were counted five times for five minutes. Additionally at one point in Obermenzing and one point in Muehltal birds were counted during the course of a day, three days at each site. Distance to the river (at the banks or 200 m away), periods of observation, temperature and rainfall had significant influence on the counted number of species. During the first 90 min. after sunrise, however, the number of recorded species was not significantly influenced by the time since sunrise. In order to record at least 80 % of the species occurring in an area, two counts per season with 10 min. counting intervals per point were required. All-day-surveys showed that in the early morning, around and after sunrise, most bird species were counted; between 10:00 a.m. and 11:30 a.m. the cumulative curve of species numbers started to flatten. The five 5-min-counts during the season revealed that with only two counts 76 % of the species (on average) could be recorded instead of 100 % after five counts (not corresponding to the total number of species in the area). The wider the observation radius, the more species were recorded. The results of this work confirmed, that the Point Count is a method that can easily be used in different types of landscapes. External and methodological factors, however, may strongly affect the results. Hence, this method is not useful to obtain absolute quantitative numbers of individuals per area, but if the Point Count Method is applied under standardised conditions over years, trends in bird communities, especially for the more common species can be recorded.

Orn. Anz. 42: 111-146

Strewe, R.: Arealstrukturen von Tangaren (Thraupinae) im südwestlichen Kolumbien. Areal structures of Tanagers (Thraupinae) in southwestern Columbia (South America).

Biogeographic studies of the areal structure and areal dynamics of Thraupinae were conducted over two years within the Endemic Bird Area Chocó on the Pacific slope of the Westandes in the department Nariño, Colombia. Thraupinae were selected, as a characteristic group of the avifauna of the Chocó, distributed in all elevational zones on the Pacific slope of the Westandes and presenting a high portion of endemics. The studies were realised within an altidudinal gradient between 400 to 3200 m and included the vegetation zones of humid lowland, premontane and montane forest.
The macrochorological categorisation of the 75 Thraupinae species registered within the study area resulted in six different areal types. The Andean areal type shows the highest portion with 48 % and 20 % of the tanager species are endemic for the Chocó. The Andean species are dominant in the premontane and montane elevation zone, while on the lower slopes and in the lowlands species of the trans-cisandean (16%), the Chocó-Magdalena (3%) and the Chocó-Caribbean (12%) areal type are characteristic. A significant distribution limit for the lowland species was registered at 500-600 m. The most important distribution limit for the premontane tanager species was identified in the elevation zone between 2300-2400 m within the transition zone of pluvial premontane and montane forests. Highest concentrations of Thraupinae species were found between 400 m and 1700-1800 m, with the maximum of 30 species at La Planada, resulting from the overlapping of the areal limits of lowland and premontane species. The endemic tanager species occur below 2300 m, with concentrations of eight species between 400-800 m and 1300-1600 m.
The species specific elevation amplitudes for the study area reach from 400 to 1900 m. While species with small elevational amplitude (<1000 m) and distribution in the lowlands have relatively wide distribution areas, the Chocó endemics with comparable elevation amplitudes and distributions within the premontane range of the Westandean slope have small distribution areas resulting from steep topography, which make them sensible against anthropogenic habitat destruction.
Additionally to the project objectives information on the distribution structure of endemic and globally threatened bird species was collected. The analysis of the results on the areal structure of Thraupinae and on the endemic and threatened bird species allows the identification of conservation priorities in the region. The project shows clearly the necessity of conservation strategies and conservation activities in Nariño. The existing strategies and nature reserves are not sufficient for the sustainable protection especially of the endemic fauna. Future conservation activities within the Chocó must include the premontane elevation zone between 600 and 1800 m.

Orn. Anz. 42: 147-152

Social and non-social hunting of juveniles of Montagu's Harrier Circus pygargus during a post-fledging period was observed in south-east Poland. Social hunting sessions were of imitative character since no form of cooperation between juveniles was observed. Social hunting was found to be more effective (8.3.%) as compared to non-social (5.3 %) of lone individuals but the difference fell into the range of statistical insignificance. During both social and non-social hunting the juveniles caught Green Grasshoppers Tettigonia viridissima, a certain number of which was eaten mid-air. For social hunting the fledglings preferred fields covered with oat and laid down wheat, while lone birds prefered areas covered with laid- down wheat only .

Orn. Anz. 42: 153-154

KITOVSKI, I.: Do Marsh Harriers (Circus aeruginosus) tend to rob Honey Buzzards (Pernis apivorus)? Neigen Rohrweihen dazu, Wespenbussarde zu parasitieren?