GATTER, W. & R. SCHÜTT: Langzeitentwicklung der Höhlenkonkurrenz zwischen Vögeln (Aves) und Säugetieren (Bilche Gliridae, Mäuse Muridae) in den Wäldern Baden-Württembergs
Competition for breeding holes between birds and mammals (Dormice Gliridae, Mice Muridae) in the forests of Baden-Wuerttemberg

For a number of decades the state forest administration authority of Baden-Wuerttemberg has put up nestboxes and checked them in autumn. In 1950 the number of boxes was 40,000; today it is 160,000-180,000.
Dormice have regularly been found in the nestboxes. In earlier years, most of those found were killed, which probably had a decisive effect on the nestbox population of these species. When the killings decreased in the 1980s, the rate of nestbox occupancy rose.
The nestbox population of Edible Dormouse rose to an average of 22 %, locally to more than 90 % in peak years. The Garden Dormouse, which is largely restricted to the Black Forest, today occupies 3 % of the nestboxes in a large section of that region. Around 1980, the nestbox population of Dormouse also rose considerably, although not so strongly as that of the other species. Competition with the Edible Dormouse is probably the main determining factor. Population densities are influenced by the nestbox density. It is obvious that the provision of nestboxes positively influences the populations. As nestbox usage increased, the rate of ”first occupancies” dropped. While in 1982 70 % of the boxes in the total area were empty before being taken over by the Dormouse, the proportion had fallen to 50 % by 1996. The Edible Dormouse followed a similar trend. A parallel decrease was found in the number of empty nestboxes at the end of the season. Apart from the early occupancy of nestboxes by the Dormouse, the preferred usage of empty boxes is interpreted, in agreement with HENZE (1991), as being a reaction to nest defence by birds in the other boxes.
An increase in the usage of nestboxes by bats, true mice and social insects has also been noted.
During the 1990s, up to 32 % of the nestboxes in the total area, and locally up to nearly 100 %, were used by mammals and insects during the course of the year. This has an increasing effect on the songbird population in the boxes.
The dormice and true mice are both predators and nest competitors. Except for the omnivorous Garden Dormouse, displacement through occupancy by dormice of the nestboxes is presumably of primary importance, while direct predation is only secondary. The degree of danger to bird species depends on their breeding period. Dormouse populations can disrupt the species structure of avian nestbox populations. The general increase in dormice in southern Germany during the past decades has altered the significance to songbirds of these previously insignificant predators. Even the most ineffective predator can become the most dangerous if it is common. The different predation and displacement strategies of the various nestbox competitors are described.
Many of the obtained results must certainly also be applicable to conditions in natural holes.

BOKRANZ, W.: Jagdstrategien und Beutespektrum des Kormorans Phalacrocorax carbo am Unteren Niederrhein. - Feeding behaviour and prey species of the Great Cormorant at the Lower Rhine

A lot of studies concerning the diet of the Great Cormorant Phalacrocorax carbo sinensis L. have been carried out during the recent ten years. Although very few investigations take in consideration that there might be a seasonal change in the choice of prey items and length as well as in the daily consumed fish mass. The investigation which underlies this text accompanied the cormorants and their feeding behaviour through nearly the whole year 1997. Birds have been counted at a single roost located near the Rhine from January until December. Feeding observations of the cormorants of that special region have been made from January until November. The kind and frequency of prey taken by the birds at the respective season has been determined by collecting and analysing the pellets regurgitated by birds that regularly spent the night at the roost. Pellets have been collected there from January until Oktober 1997 and both the prey items and the daily food intake of a single bird have been determined for each month of this period. 
Key words: cormorant, season dependent fishing behaviour, pellet analysis, seasonal difference in prey choice and fish consumption 

KRAUS, M. & W. KRAUSS: Die Schellente Bucephala clangula in der Oberpfalz: Bestandsentwicklung und Bemerkungen zur Brutbiologie. - Development of the breeding population of Goldeneye in Eastern Bavaria (Oberpfalz) with notes about breeding biology

In 1976 the first breeding of Goldeneye in Eastern Bavaria (Oberpfalz) was proved. Since then further settlements in Bavaria, Austria and Switzerland followed. The development at the Bodenwöhr depression was followed for 22 years until 1998. Already in 1979 there was a saturation with approximately 24 breeding pairs. As such all pairs, not only females with offspring, were counted on small fish-ponds in the middle of April. Holes of Black Woodpeckers serve almost exclusively as natural nest sites in the smooth conopy bark of old pines. Missing of breeding holes is not the limiting factor but the availability of food at the foraging areas. The migration of males starts in the beginning of May and is completed at the end of this month. The present breeding population of Eastern Bavaria is calculated to be 40 pairs. 50 pairs are estimated for Bavaria. It is assumed that even 100 pairs would not reach the capacity limit in Northern Bavaria.

RANDLER, C. & J. BLESSING: Invasion des Kernbeißers Coccothraustes coccothraustes im Herbst 1998 am Lotterberg bei Stuttgart. - Invasion of Hawfinch in autumn 1998 near Stuttgart

Counts of visible bird migration in autumn are carried out regularly in an area NW of Stuttgart (SW-Germany). Since 1992 we watched through more than 700 observation hours. In 1998 the highest ever autumn migration of Hawfinch was noted. 5679 birds have been counted  during 96 h of observation. In 1998 an average number of 60 birds/hour moved in southern and south-westerly directions compared with 4 birds/hour the years before (1992-1997). The highest day’s total was 1234 Hawfinches passing through in 4 h 50 min. Migration in 1998 started at the beginning of October, and peaked between the end of October and beginning of  November, more than two weeks later than usual. The day when half of the birds had been counted was 31st of October; in 1992-1997 it was 22 days earlier. Migration started at the beginning of sunrise and was most remarkable in the two subsequent hours. The average flock size in 1998 (11,9 birds/flock) was much higher than in 1992-1997 (2,6 birds/flock). Some factors responsible for this striking influx are discussed. Weather conditions could be ruled out. Such a phenomenon was visible around Oct. 17th, especially concerning Wood Pigeon Columba palumbus and Chaffinch Fringilla coelebs. 
The migration of Hawfinch occurred later, in much higher numbers than average and with larger flock sizes than in usual years. Higher hatching success in 1998 as well as increasing numbers of the breeding population in Northern European countries (e.g. more than tenfold in the Netherlands) of this species might produce higher numbers of migrating individuals.

KRAUSS, W.: Ergebnisse einer 10jährigen Bestandsaufnahme an einer Population des Gelbspötters Hippolais icterina im östlichen Nürnberger Pegnitzgrund.
Results of a ten year population survey on the Icterine Warbler at the eastern Pegnitz valley of Nuernberg

Icterine Warbler territories were located in the eastern Pegnitz valley of Nuernberg, where 1131 contacts by hearing were recorded on 321 days from 1989 to 1998. The median of the first arrival was 7th to 8th of May. The first bird was heard on the 29th of April and the last was heard on the 26th of July. In the morning about four times more Icterine Warblers were singing than in the afternoon. The number of territories varied from two to ten. These were randomly situated along the banks of the river. The maximum territory density was 2.2 per kilometer. Climatic conditions were not the only factor accounting for fluctuations in population density. Preferred territories were situated near water or close to human habitation and were occupied for more than five years.

Short communications

ANDRÄ, E.: Mischgesang eines Buchfinken Fringilla coelebs in Bad Aibling, Oberbayern.- Mixed song of a Chaffinch in Bad Aibling,Upper Bavaria

In the breeding season of 1997 a male Chaffinch (Fringilla coelebs) in Bad Aibling/Bavaria was singing two different phrases. Beside the normal Chaffinch song it performed an imitation of the Redstart (Phoenicurus phoenicurus) song phrase, but less frequently. The complete song is fixed on a tape.

FÖRSTEL, A.: Neue Beobachtungen und Brutnachweise des Sperlingskauzes Glaucidium passerinum im nördlichen Frankenjura. - New records of Pygmy Owl in the Frankenjura

An estimation of the population of Pygmy Owl in the Frankenjura (north Bavaria) of today is given with numerous observation data and some proofs for breeding. Traditional breeding sites according to older literature are still or newly occupied. Due to the considerable number of recent observations at new sites, a range extension in the study area is deduced.

HEISER, F., GAJEK, H. & R. SCHUBERT: Die Rüppellseescwalbe Sterna bengalensis, eine neue Art für Deutschland - Lesser Crested Tern Sterna bengalensis, first record for Germany 

On June 19th, 1995, an adult summer Lesser Crested Tern Sterna bengalensis was seen on the river Danube near Bertoldsheim, Bavaria, Germany. This is the first record for Germany, accepted by the German rarities commission. A detailed description is given.The occurrence of Lesser Crested Tern in Europe is shown and briefly discussed.