1. Populationsökologie des Rauhfußkauzes Aegolius funereus
      mit Hilfe der wissenschaftlichen Vogelberingung

      siehe auch  http://www.ageulen.de
 
 
Untersuchungsgebiet:     200 qkm im Westharz                                              zurück

Das Untersuchungsgebiet besteht hauptsächlich aus Fichtenwäldern in Höhenlagen zwischen
450 bis 800 m ü.NN in einer geschlossenen Fläche von etwa 200 qkm.
51.52 N 10.14 E bis 51.37 N 10.32 E.
Es umfaßt die ehemaligen Forstamtsbezirke Seesen, Grund, Clausthal-Schulenberg, Altenau,
Walkenried, Kupferhütte, Sieber, Lonau, Riefensbeek, Stadtforst Osterode (Stand 1980).
Es liegt in den heutigen Forstamtsbezirken Seesen, Clausthal, Riefensbeek, Bad Lauterberg,
Stadtforst Osterode und Nationalpark Harz (Stand 2006).                          
Das Untersuchungsgebiet  wird begrenzt durch die Städte Seesen, Langelsheim, Hahnenklee, Clausthal-Zellerfeld, Altenau, St. Andreasberg, Zorge, Walkenried, Bad Lauterberg, Herzberg und Osterode.

Artenschutz- und Forschungsprojekt:

Im Untersuchungsgebiet gibt es in Höhenlagen oberhalb 500 m ü. NN. gute Lebensbedingungen
für den Rauhfußkauz. In den Fichtenforsten kam der Rauhfußkauz  bis 1973 allerdings selten vor, 
da geeignete Nisthöhlen fehlten.
Der Rauhfußkauz brütet hauptsächlich in Höhlen des Schwarzspechtes (Dryocopus martius)
und diese werden im Harz fast ausschließlich in Buchen gezimmert. Großflächige Buchenbestaende befinden sich
im Harz in tieferen Höhenlagen. Dort lebt der Waldkauz (Strix aluco), dem der Rauhfußkauz ausweicht.

Nach Anbieten von Nistkästen in den Fichtenwäldern wurden diese in wenigen Jahren vom Rauhfußkauz
besiedelt. Der Harz gehört inzwischen zu einem seiner bedeutendsten Brutgebieten in Norddeutschland.
Von 1975  bis  1977 wurden artgerechte Untersuchungsmethoden  entwickelt, die die Käuze bei ihren Aktivitäten
nicht beeinflüssen. Fast alle  Käuze  werden  mit Ringen der Vogelwarte Helgoland markiert.

In einem kombinierten Artenschutz- und Forschungsprojekt werden seit 1978 mit standardisierten Methoden 
Bestand und Struktur dieser Rauhfußkauz-Population erfasst. Dabei werden grundlegende Fragen der Ethologie,
Ökologie und Populationsdynamik dieser gefährdeten, hauptsächlich nachtaktiven Vogelart untersucht, insbesondere
im Zusammenhang mit dem zyklisch schwankenden Beuteangebot an Kleinsäugern und der langfristig sich durch
waldbauliche Maßnahmen verändernden Waldstruktur. Die Beute besteht hauptsächlich aus Erdmäusen
(Microtus agrestis) und Rötelmäusen (Clethrionomys glareolus) sowie Waldmäusen (Apodemus sylvaticus)
und Gelbhalsmäusen (Apodemus flavicollis).

       Publikationen  :

01.  SCHWERDTFEGER, O. 1979: 
        Neues Brutgebiet des Rauhfußkauzes (Aegolius funereus) im Westharz.
        Vogelkundliche Berichte Niedersachsens 11: 1 - 7.

02.  SCHWERDTFEGER, O. 1984: 
       Verhalten und Populationsdynamik des Rauhfußkauzes (Aegolius funereus). 
       Vogelwarte 32: 183 - 200.

03.  SCHWERDTFEGER, O. 1988 a: 
       Analyse der Depotbeute in den Bruthöhlen des Rauhfußkauzes (Aegolius funereus). 
       Vogelwelt 109: 176 - 181.
 

Analysis of the stored prey in the nest-holes of the Tengmalm´s Owl (Aegolius funereus).

During ecological studies of the population of Tengmalm´s Owl in the western part of the Harz mountains the prey stored in the nest-holes was registered. In 1150 controls from 1979 to 1987 alltogether 2100 prey items could be evaluated in 210 broods. From time of occupation of the nest-hole by the female to the age of two weeks of the youngest nestling stored prey was found, especially many during the periods of egg-laying and hatching. 74,5 % of the stored prey animals were voles Microtidae (Microtus agrestis and Clethrionomys glareolus). Of the rest 9,5 % were Apodemus mice, 8,7 % were shrews Soricidae, 2,3 % were dormice Gliridae and 5,0 % were birds. Related to the average figures in single years the clutch size of Tengmalm´s Owl correlated with the amoung of prey animals found in each control and also with the percentage of voles (Microtidae) in the stored prey.

04.  SCHWERDTFEGER, O. 1988 b:
       Modell zur Dispersionsdynamik des Rauhfußkauzes (Aegolius funereus). 
       VAN DEN ELZEN, R., SCHUCHMANN, K.-L. & K. SCHMIDT-KOENIG (Edit.).
       Proceedings International Centennial DO-G Meeting,
       Current Topics in Avian Biology. Bonn 1988: 241 - 247.
 

Model of the dispersion dynamics in Tengmalm´s Owl (Aegolius funereus).

In the Harz mountains a population of Tengmalm´s Owl has been intensively monitored for 12 years by capturing nearly all adults and controlling every brood. Population dynamics and behavioural results are summarized in a model of life strategy characterized by differential dispersion of juveniles, predominating site fidelity of males and high mobility of breeding females. Considering the insular distributional patterns of this owl in Middle Europe these features promote effective colonization, population stability in suitable habitats and optimal utilization of peaks in prey availability.

05.  SCHWERDTFEGER, O. 1990: 
       Die Bedeutung populationsökologischer Kenntnisse für den Artenschutz am Beispiel des Rauhfußkauzes
       (Aegolius funereus).. 
       Vogel und Umwelt 6: 10 - 21.

06.  SCHWERDTFEGER, O. 1991 a: 
        La signification du depot de proies dans le mode de reproduction de la Chouette de Tengmalm (Aegolius funereus). 
        JUILLARD, M. et al.(Edit.): Rapaces Nocturnes: 243 - 245.

07.  SCHWERDTFEGER, O. 1991 b: 
        Altersstruktur und Populationsdynamik beim Rauhfußkauz (Aegolius funereus). 
        Populationsökologie Greifvogel- und Eulenarten 2. 
        Wissenschaftliche Beiträge Universität Halle: 493 - 506.
 

Age composition and population dynamics in Tengmalm´s Owl (Aegolius funereus).

The age composition of a population of the Tengmalm´s Owl was investigated in the Harz mountains from 1979 to 1990 by capturing nearly all the adults, The ages were determined by the moult pattern of the primaries. The age composition was different between males and females. There were less 1-year-old males than females but there was a higher percentage of 4-years-old and older males than females. The best approximation of the observed age distributions through exponential-distributions were obtained by using yearly mortality rates of 30 % for males and 36 % for females. The mortality rate among fledged young owls is estimated to be 75 %. The immigration-rates and the emigration-rates were determined on the one hand under improving food conditions and on the other hand under decreasing food conditions. These rates were 20 % higher for females than those of the males, In part there were proved age dependences,

08.  SCHWERDTFEGER, O. 1993:
       Ein Invasionsjahr des Rauhfußkauzes (Aegolius funereus) im Harz - 
       Eine populationsökologische Analyse und ihre Konsequenzen für den Artenschutz. 
       Ökologie der Vögel 15: 121 - 136.
 

A year of invasion of Tengmalm´s Owl in the Harz mountains - 
A population ecological analysis and its consequences for conservation.

From 1977 until 1989 a population of Tengmalm´s Owl has been monitored intensively by controlling every brood and capturing nearly all adults in a study area of 170 qkm in the Harz mountains. Among those thirteen breeding seasons studied the year 1984 was extraordinary with respect to several population parameters:  Firstly, the number of 67 broods was four times higher than in the year before and still twice as high as in otherwise good years. Secondly, every tenth territorial male had two females, i.e. was bigynous. Thirdly, there were 241 fledglings, which is five times more than in the years 1983 and 1985 together. This increase of the breeding population was mainly due to immigration of subadults (from a distance of up 198 km) caused by both, a mass-increase of microtidae and the presence of elder territorial males, which had been present from 1983. When the microtus population declined many of the young Tengmalm´s Owls left the study area again (one female was found as far as 341 km away). This study confirms the importance of having large areas of suitable breeding habitat for this species of owl. Therefore, conservation is most effective by providing nestsites as well as habitat improvements. As a consequence, due to the high reproductive rates and high mobility of the subadults and females, this can be beneficial for populations in other areas.

09.  SCHWERDTFEGER, O. 1994:
       The Dispersion Dynamics of Tengmalm's Owl (Aegolius funereus) in Central Europe. 
       MEYBURG, B.-U. & R.C. CHANCELLOR (Edit.): Raptor Conservation Today.
       World Working Group on Birds of Prey and Owls: 543 - 550.
 

The Dispersion Dynamics of Tengmalm´s Owl Aegolius funereus in Central Europe.

In the course of population ecological studies on Tengmalm´s Owl in the Harz mountains the species´ distribution and its changes in space and time have been investigated. In an area of 200 qkm nearly all nests have been recorded and nearly all owls marked since 1978. In 1988 the results were summarized in a model of dispersion dynamics for the insular distributional pattern of Tengmalm´s Owl as is typical for Central Europe. Further results permit the procedure of emigration and immigration in connection with reproduction and mortality-rates to now be quantified and characterized by their dependence on fluctuating food conditions. Thus we get a survey of how a population of Tengmalm´s Owl consists of owls with fidelity to birth-place, fidelity to area and nomads. This is valid for both sexes and for different age groups. Considering the long period of study, the size of the investigated population, its age structure, its reproduction as well as recapturing rates, we can assume that the results are representative for Central Europe. The phenology of dispersion dynamics differs from that of Scandinavian investigations.

10.  SCHWERDTFEGER, O. 1996: 
       Wie optimiert der Rauhfußkauz (Aegolius funereus) seine Reproduktionsrate ? 
       Populationsökologie Greifvogel- und Eulenarten 3. 
       Wissenschaftliche Beiträge Universität Halle: 365 - 376.
 

How does the Tengmalm´s Owl (Aegolius funereus) optimize its reproduction ?

On a study area of 200 qkm in a pruce forest of the Harz mountains the breeding biology and population dynamics of Tengmalm´s Owl have been investigated by recording relevant data from 420 broods during the years 1979 through 1992. Results from these studies suggest that this species has adapted to the population fluctuations of his main prey species by three strategies: higher clutch sizes, a more intense courtship and care for the young, as well as a higher density of breeding adults, if food supply increase which is mainly due to first breeders of this population as well as immigrating owls. These trends are reversed, and more owls leave the study area, if food supply is declining. That clutch size is optimized for a maximum fledging rate was particularily evident in years of abundant prey. Averaged over all years only eggs of clutches above the mean of 2,4 eggs produced fledglings. The breeding success of individual years is affected by additional factors such as year-specific and local environmental conditions.

11.  SCHWERDTFEGER, O. 1997 a: 
        Der heimliche Rauhfußkauz - ein echter Harzer.
        Der Harz 62: 9 - 12.

12.  SCHWERDTFEGER, O. 1997 b: 
        Höhlennutzung und lokale Dispersionsdynamik beim Rauhfußkauz (Aegolius funereus). 
        Thüringer Landesanstalt für Umwelt, Naturschutzreport 13: 50 - 60. 
 

Use of holes und local dispersion dynamics on Tengmalm´s Owl (Aegolius funereus): 

In the course of population ecological studies on Tengmalm´s Owl in the Harz mountains the species´distribution and its change in space and time have been investigated. From 1979 to 1993 nearly 480 broods were recorded in the 180 nestboxes that were spread uniformly about the study area of 200 qkm. The yearly occupancy rate of the nestboxes fluctuated between 3 % and 52 %, averaging at 18 %. 40 % of the nestboxes were not used for breeding at all. 30 % were used only once and 30 % two or more times. The rarely occupated boxes were chosen mainly in years with abundant prey. 96 % of the recaptured females were breeding in a different hole the next time, most of them many kilometres away. 81 % of the males changed their hole within home ranges, which are only a few qkm large.

13.  SCHWERDTFEGER, O. 1999:
        Balzaktivität und Geschlechterverhältnis beim Rauhfußkauz (Aegolius funereus).
        Eulen-Rundblick 48/49: 32 - 36. 
 

Courtship activity and sex ratio on Tengmalm´s Owl (Aegolius funereus).

In the course of population ecological studies on Tengmalm´s Owl during 20 years in the Harz mountains the courtship activity of marked adults have been investigated. The males present their courtship songs from exponated positions and in front of one or more holes. After fertilization of a female the courtship activities regularly vanish during the egg-laying. The intensity of courtship in a population depends on the number of males that are still ready for a first-, replacement- or bigynie-brood. If there is a strong surplus of males courtship activities can last till the end of June. Such a disadvantageous sex ratio can be compensated by second broods of females, of whom the majority usually has immigrated. In the breeding period the intensity of a male´s courtship activity is mainly determined by the prey supply of voles and apodemus-mice. Locating the places of courtship activities can provide only a rough estimate of the number of males as well as of breeding intensity in a populaion.

14.  SCHWERDTFEGER, O. 2000:
        Entwicklung und Lebenserwartung junger Rauhfußkäuze (Aegolius funereus).
        Populationsökologie Greifvogel- und Eulenarten 4. 
        Wissenschaftliche Beitraege Universität Halle: 505 - 516.
 

Development and life-expectation of young Tengmalm´s Owls (Aegolius funereus).

In the course of population ecological studies on Tengmalm´s Owl in the Harz mountains the biometrie data of nestlings from 190 broods were analysed. The length of the longest vane of the primaries of wing was introduced as a measure of nestling development.The body mass of nestlings depended on this measure of development in a characteristic way: 1.) This relationship differed for male and female nestlings, which have been sexed at recapture. 2.) There was also a statistically significant difference between nestlings growing up with abundant and scares food supply. 3.) But there was no significant variation of this relationship among nest mates.When solely means of the body masses of these nestlings were compared, the differences between sexes and between years of different food supply were significant, too. In this case the body mass of nestlings also differed with the order of birth.

15.  SCHWERDTFEGER, O. 2001:
        Das Verhaltenssystem des Rauhfußkauzes (Aegolius funereus) und seine Bedeutung fuer den Artenschutz.
        Naturschutz und Verhalten, Goettingen 1999, UFZ-Bericht Nr. 2/2001: 73 - 80.
 

The behavioural system of Tengmalm´s Owl (Aegolius funereus) and its significance for species conservation. 

In the course of population ecological studies on Tengmalm´s Owl in the Harz mountains all broods have been recorded since 1979. In the study area of 200 qkm also the relevant influences of the environment have been registered. Furthermore, males and females have been identified almost completely by capture and ringing. An eco-ethological analysis of the results show, that social behaviour, reproduction behaviour and dismigration compose a system with which Tengmalm´s Owl is able to secure his existence and to achieve an optimal reproduction despite yearly changing food conditions. But for this, the breeding areas must have special qualities that go beyond the habitat requirements of the species. Only under these circumstances can the population of a species develop in a natural way and contribute to the metapopulation´s stability.

16.  SCHWERDTFEGER, O. 2002 a:
        Rauhfußkauz und Mensch.
        Eulen-Rundblick 50: 29 - 33. 

17.  SCHWERDTFEGER, O. 2002 b:
        Eulen (-) surfen im Internet.
        Eulen-Rundblick 50: 58 - 60. 

18.  SCHWERDTFEGER, O. 2003:
       Viel Bemerkenswertes zu einer Rauhfußkauzbrut Aegolius funereus.
       Ornithologische Mitteilungen 55, 5: 180 - 181.

19.  SCHWERDTFEGER, O. & H.-W. SENGE  2004 a:
        Beutetransport beim Rauhfußkauz (Aegolius funereus).
        Eulen-Rundblick 51/52: 48 - 50.

20.  SCHWERDTFEGER, O., Keil, H. & K.-H. Graef  2004 b:
        Bestandsentwicklung durch Nisthilfen - Arbeitsgruppen bei Rauhfußkauz (Aegolius funereus),
        Steinkauz (Athene noctua) und Schleiereule (Tyto alba).
        Eulen-Rundblick 51/52: 51 - 54.

21.  SCHWERDTFEGER, O. 2005:
        Monitoring beim Rauhfußkauz  Aegolius funereus -
        Welchen Einfluss haben Reproduktionsverhalten und Nestlingssterblichkeit auf die Erfassungsgenauigkeit ?
        Populationsökologie Greifvogel- und Eulenarten 5.
        Wissenschaftliche Beiträge Universität Halle: 585-601.


 Monitoring of the Tengmalm´s Owl Aegolius funereus - How do behaviour und mortality of nestlings influence the exactness of monitored data ?

In the course of population ecological studies of Tengmalm’s Owl in the Harz mountains all broods have been recorded for 24 years. In the study area of 200 sqkm the males and females have also been identified almost completely by capture and ringing. The results of these studies make it possible to analyse und to estimate mistakes in the important registered breeding parameters, that have been used in the monitoring programs.
All broods take place with different breeding partners. In years with a good prey supply, 10% of the males and also 10% of the females have replacement broods or second broods (bigyny and biandry) in the same area. As a rule, the later broods of the breeding season are replacement or second broods of females that have already brooded elsewhere that year. This is a further 10% of all females in the breeding season. Due to the changes of places and migration, it isn’t possible to recognize second broods and also to determine the total number of males without the possibility to capture and ring them.
Only in 22% of the broods do all eggs result in fledglings. Because of the high mortality rates of nestlings these should be counted as late as possible. If the nestlings are counted, when the female is still present and this number is regarded as number of fledglings, then this number can be overestimated with up to 28% in years with few prey and up to 7% in years with a large prey supply.

22.   SCHWERDTFEGER, O. 2006
        Migration and dispersion dynamics in the metapopulation of Tengmalm's Owl (Aegolius funereus)
        in Central Europe.
        Journal of Ornithology 147,  Suppl. 1:85


Migration and dispersal dynamics in the metapopulation of Tengmalm's Owl in Central Europe.

In a study of population ecology  in Tengmalm’s Owl (Aegolius funereus) in the Harz mountains, Germany, the dispersal of adult owls and concomitant spatial and temporal changes were examined.  Due to the lack of natural tree holes, nearly all breeding took place in 200 nest boxes spread uniformly about a study area of 200 km2. Over 28 years, 750 broods have been monitored within the area. 85% of male and 95% of female breeding adults have also been captured, and their age determined according to species-specific part-molt of the wings. Only 20% of broods were reared by local recruits; breeding production derives largely from owls immigrating from other breeding areas up to 600 km away. Here sex-related differences are involved, the proportion of immigrating and emigrating owls being almost twice as hight in females. Correspondingly, there were twice as many resident males.                                                                                                                                                                               Lifetime reproduction is now known. Mortality rates could be estimated from representative spot checks of the age structure of the metapopulation. Of the many immigrant owls over years, most disappeard again after breeding, which was itself aumented by bigyny and biandry. The annual size and make-up of the breeding populations fluctuated markedly with the abundance of small mammals: species of Micxrotus and Apodemus; in the 10 peak years of the study, almost twice as many juveniles fledged than in the other 18 years.                                                                                                                                      Fluctuation rates are compared with recaptures of ringed owls that shifted between other local populations, enabling calculation of a frequency distribution of migration distances; but such data are available for females. These data indicates, nevertheless, that Tengmalm's Owl shifts its local populations variably and patchily through central Europe from year to year. It is a strategy that enables the owl to take optimal advantage of locally asynchronous population cycles in small mammals.     

23.   SCHWERDTFEGER, O. 2007:
        Ungewöhnliche Feststellungen zur Verhaltensökologie des Rauhfußkauzes (Aegolius funereus).
        Vogelwarte 45: 310

24.   SCHWERDTFEGER, O. 2008:
        Ist der Rauhfußkauz  Aegolius funereus ein echter Harzer ? Uber die Bedeutung einer lokalen Population.
        Vogelkundliche Berichte Niedersachsens 40: 247-253


 Is the Tengmalm´s Owl Aegolius funereus.a typical bird species of the Harz mountains ?
Insights into the importance of a local population.

The local Population of Tengmalm’s Owl in the Western Harz Mountains has been the focus of ecological studies since 1979. Because of the lack of natural tree cavities, 200 nest-boxes were spread  regularly throughout a spruce-forest area of 200 qkm. situated at 450-800 meters above sea level. Over 28 years, 760 broods have been monitored. All the females and nearlyall the males have been captured. and ringed.  The stored  prey found in the nest boxes during the frequent controls has served as a basis for analysing the food of Tengmalm's Owl. The number  of broods, the average clutch size and the average number of stored prey correlate significantly for all years. Despite considerable fluctuations, the average number of broods remains constant in the long term. Consequently, the same applies to clutch size and prey supply.
Only 20 percent of the male and 11 percent of  the female breeding birds have grown up in the study area. Most of the broods have been reared by owls coming from breeding areas up to 550 km away. The proportion of breeding birds remaining in the study area is higher for males than for females. Inversely, the proportion of nomadic females is cleary higher. Therefore females can benefit from breeding areas with a currently rich supply of small mammals, also identifiable by active courtship of males.
In the Harz  mountains the Tengmalm's Owl has found ideal conditions in regions at middle altitude. Because of bare areas having got overgrow, the owl's main prey has changed from Microtus species to Apodemus species. The expected increase in tempests suggests the breaking up rhe forest as well as an improvement of forest structure. However, the future emergence of wide-spread beech grove may serve the predators of Tengmalm's O

25.   SCHWERDTFEGER, O. 2009:
        Life history and reproductive success in Tengmalm's Owl Aegolius funereus.  


Life history and reproductive success in Tengmalm´s Owl Aegolius funereus.

Within population ecological studies on Tengmalm’s Owl in the Harz Mountains, Germany, its breeding biology, food supply and population dynamics have been examined. Due to the lack of natural tree cavities, nearly all broods took place in 200 nest-boxes that are spread uniformly about a study area of 200 sqkm. 760 broods have been monitored during 1980-2005. The reproductive success is measured by the number of fledglings per year. Information about the individuals’ life history is obtained by capture and recapture. For this purpose, 95% of female and 85% of male breeding adults have been captured.
With regard to the broods examined during these 26 years, immigrant males have significantly higher reproductive success as those males already present before. This does not hold true for females. Inversely, for both sexes the reproductive success shows no connection with disappearance or presence in the following years. The adult owls that were captured only in one year are defined as nomadic, the others which were captured in at least two years as resident. No significant differences in reproductive success could be determined between nomadic and resident owls, neither for males nor for females. Only in years with high prey supply, the resident females have significantly higher success as the nomadic females. Thus the mating of nomadic males and resident females promises the highest reproductive success. However, this combination represents only 12% of all cases. 21 % of the broods of males and 13 % of those of females were reared by recruits. There are no significant differences in success compared to the broods of immigrants. The age structure of the breeding population allows the determination of survival probabilities. The males have a higher median survival rate as the females. This is also valid for resident owls compared to nomadic owls for both sexes.
.
26.    SCHWERDTFEGER. O. 2012: a
         Welche Informationen ergeben sich aus dem Balzgesang des Rauhfußkauzes ?
         Vogelwarte 50, 264-265

27.    SCHWERDTFEGER. O. 2012: b
         Von Rekruten, Migranten und fitten Räuzen ?
         Eulen-Rundblick 62, 22

28.    SCHWERDTFEGER, O. 2014:
         Monitoring beim Rauhfusskauz (Aegolius funereus) -
         Die Bedeutung von Balzverhalten und Geschlechterverhältnis.
         Populationsökologie Greifvogel- und Eulenarten 7.
        Wissenschaftliche Beiträge Universitaet Halle.


 Monitoring of the Tengmalm´s Owl (Aegolius funereus)  -
The importance of courting behaviour and sex ratio.

The research object is a nestbox-population of Tengmalm's Owl in the spruce forests of the  Harz mointains. The study area covers of about 200 km2 and has been observed completely since 1979. The nest boxes are checked frequently by constant methods. Nearly all adult owls are captured and ringed. By this means it is possible to measure the impact of the high variability and dynamics of the courting and breeding behaviour on the location and time of the breeding season.
The number of broods, the reproductive success and the temporal dispersion of the beginning of laying eggs change considerable from year to year. This is a consequence of cyclic fluctuations in the abundance of small mammals as well as of short term and long term changes in the composition of the breeding population. In each breeding season there appears to be more males than females. For the last 30 years 56 % were males and 44 % females. 29 % of the males had no brood.
The registration of phenological data using common monitoring-methods is very problematical with regard to the case of Tengmalm’s Owl due to its species’ characteristics. This owl lives nocturnally and nearly silently except during the mating phase. It breeds in holes of black woodpeckers that are difficult to reach, but also uses nest boxes as well. The peculiar courtship singing serves mainly the attraction of females and stops after mating. The imitation of singing can prompt the owl to change its location. The sole registration of calling and singing activities can only provide imprecise references of the occurrence of Tengmalm’s Owl.
Continuous checks of potential breeding holes from the end of February to the end of July provide precise quantitative data. At the same time vocalisations and the appearance of females and nestlings in the entrance of the holes and in the surrounding area can be recorded. Several courtship places of an individual owl, compensation broods, secondary broods and translocation of action spaces can only be determined by capturing und ringing.
                                   

29.    SCHWERDTFEGER, O., WINK, M.  2014:
         Lack of correlation between sex ratio and  food supply or other biotic variables
         in nestlings of Tengmalm's Owl (Aegolius funereus)
         Journal of Ornithology 155 (2): 497-505.


Lack of correlation between sex ratio and food supply or other biotic variables in nestlings of Tengmalm´s Owl Aegolius funereus.

Tengmalm's Owls (Aegolius funereus) (TO) exhibit a pronounced sexual size dimorphism, in which females are bigger than males, which have to provide  food for the breeding female and the brood clutch size and breeding success are strongly influenced by food supply, especially by the abundance of small rodents. Since 1979, the breeding ecology of TO has been studied in a nest box population  in the Harz Mountains.
In this study, the influences of food supply and other variables on sex allocation of young TO were analysed. Between 2001 and 2011 , all 758 nestlings from 176 broods were sampled.. There sex was determined by DNA analysis (PCR amplification of DNA markers on the sex chromosomes).  The main sex ratio was male-biased with 53,4 % male of offspring with yearly variations between 43,3 and 66,7 %. Nestling mortality was independent of sex. Food abundabce changes between good and bad years.. No correlations could be etablished between food supply by individual fathers and offspring sex ratio. Neither seasonal variation of hatching dates, the hatching order within a clutch nor individual fittness charakters of parents bad a significant influence on sex ratios. Yearly sex ratio did not diverge significantly from 50 %. The sex ratio fluctuated to the same degree in 5 good years and in 4 bad years.
These results are in contrast to a study in Sweden, where an influence was detected within a 3-year vole cycle of food supply on offspring sex ratio. There, the sex ratio was male-biased in the good year, unbiased in the subsequent year and female-biased in the bad year.

30.    SCHWERDTFEGER. O. 2014:
         Populationsökologische Zusammenhänge als Grundlage
         für den Artenschutz beim Raufußkauz Aegolius funereus
         Vogelwarte 52, 244-245


31.    SCHWERDTFEGER. O. 2014:
         Ein ungewöhnlicher Vergleich von Populationsstudien am Raufußkauz Aegolius funereus
         und am Waldbaumläufer Certhia familiaris
         Vogelwarte 52, 313

 
             Vorworte
           als Vorsitzender der AG zum Schutz bedrohter Eulen http://www.ageulen.de
   .
  WIESNER, J., SCHWERDTFEGER, O.1995.
  Rauhfußkauz und Sperlingskauz in Deutschland - Vorkommen, Reproduktionsbiologie und Schutz.
  Naturschutzreport 13, 1997.

  SCHWERDTFEGER, O. 1999.
  Editorial
  Aufbruch ins nächste Jahrtausend.
  Eulen-Rundblick 48/49, 1999.
  SCHWERDTFEGER, O. 2000.
  Welcome
  International Symposium Harz 2000.
  SCHWERDTFEGER, O. 2002.
  Editorial
  25 Jahre Arbeitsgemeinschaft zum Schutz bedrohter  Eulen - 20 Jahre als  bundesweite Vereinigung.
  Eulen-Rundblick 50, 2002.
  SCHWERDTFEGER, O. 2003.
  Welcome
  International Symposium Dornbirn 2003
.
  SCHWERDTFEGER, O. 2003.
  Themenheft Ökologie und Schutz  waldbewohnender europäischer Eulen.
  Die Vogelwelt, 5-6, 2003.
  SCHWERDTFEGER, O. 2004.
  Editorial
  Eulen-Rundblick 51/52, 2004.



Vorträge

auf Tagungen folgender Institutionen und Organisationen:
 (1) 
 Ornithologische Vereinigungen der Bundesländer
(2)
 Institut für Vogelforschung, Vogelwarte Helgoland, Mitarbeitertagungen
(3)
 Arbeitsgemeinschaft zum Schutz bedrohter Eulen
(4)
 Deutsche Ornithologen-Gesellschaft
(5)
 Populationsökologie von Greifvogel- und Eulenarten
(6)
 Internationales Kolloquium über Eulen, Schweiz
(7)
 Weltarbeitsgruppe für Greifvoegel und Eulen
(8)
 Ethologische Gesellschaft, Naturschutz und Verhalten  - Naturkundliche Gesellschaften
        (9)
 Internationale Ornithologen Kongresse I-O-C
      (10)
 Welt Eulen Konferenzen
      (11)
 Europäische Ornithologen Union


01.

Die Besiedlung des Westharzes durch den Rauhfußkauz.
Braunschweig 1981  (1).
02.

 Verhalten und Populationsdynamik des Rauhfußkauzes. 
Erlangen, Bayern  1983  (4).
03.

 Stand der Rauhfußkauzforschung in Norddeutschland. 
Grävenwiesbach, Taunus 1985  (3).
04.

 Methoden zur Untersuchung der Verbreitung und Ökologie des Rauhfußkauzes. 
Mitwitz, Bayern 1986  (3).
05.

 Verbreitung und Bestandsentwicklung des Rauhfußkauzes in Niedersachsen. 
Mitwitz, Bayern  1986  (3).
06.

 Analyse der Depotbeute in den Bruthöhlen des Rauhfußkauzes. 
Dieburg, Hessen  1987  (3).
07.


 Die Bedeutung populationsökologischer Kenntnisse für den Artenschutz am Beispiel 
des Rauhfußkauzes.
Breuberg, Odenwald  1989  (3).
08.

 Verdrängt der Waldkauz den Rauhfußkauz ? 
Homburg, Saarland  1990  (3).
09.

 Die Bedeutung der Deponierung von Beute im Reproduktionssystem des Rauhfußkauzes. 
Porrentruy, Schweiz  1990  (6).
10.

 Altersstruktur und Populationsdynamik beim Rauhfußkauz. 
Meisdorf, Harz 1990  (5). -  Porrentruy / Schweiz 1990  (6). -  Dortmund 1991  (2).
11.

 Modell der Populationsstrategie des Rauhfusskauzes. 
Bonn  1991  (4).
12.

 The Dispersion Dynamics of Tengmalm's Owl in Central Europe.
Berlin 1992  (7).
13.

 Wie stellt sich der Rauhfußkauz auf Schwankungen im Nahrungsangebot ein ? 
Weimar, Thüringen 1992  (3).
14.

 Wie reagiert der Rauhfußkauz auf Weibchenmangel ? 
Neuschönau, Bayerischer Wald 1993  (3).
15.

 Wie optimiert der Rauhfußkauz seine Reproduktionsrate ? 
Friedrichsbrunn, Harz 1994  (3), (5).
16.

 Rauhfußkauz und Mensch in Vergangenheit und Zukunft.
Bad Blankenburg, Thüringen 1995  (3).
17.

 Höhlennutzung und lokale Dispersionsdynamik beim Rauhfußkauz.
Bad Blankenburg, Thüringen 1995  (3). 
18.

 Die Bedeutung der Beringung beim Rauhfußkauz. 
Bad Blankenburg, Thüringen 1996  (2). 
19.

 Kann die Anwesenheit des Rauhfußkauzes durch Locken festgestellt werden ? 
Kalchreuth, Nürnberg  1996  (3).
20.


 Bleiben oder Wandern ? - Wie kommen die Fluktuationen in den Brutgebieten 
des Rauhfußkauzes zustande ?
Duisburg 1997 (3).
21.

 Rauhfußkauz - Mäuse - Beziehungen.
Jena  1998  (4).
22.

 Entwicklung und Lebenserwartung junger Rauhfußkäuze. 
Meisdorf , Harz 1998 (5).
23.

 Geschlechterverhältnis und Balzaktivität beim Rauhfußkauz. 
Tecklenburg, Osnabrück  1998  (3).
24.

 Über die Fitness junger Rauhfußkäuze. 
Wilhelmshaven 1999  (2). 
25.

 Welchen Einfluss haben Waldstruktur-Veränderungen auf eine Teilpopulation des Rauhfußkauzes ? 
Bayreuth 1999  (4).
26.

 Das  Verhaltenssystem des Rauhfußkauzes und seine Bedeutung fuer den Artenschutz.
Göttingen 1999  (8). 
27.

 Aufenthalts- und Lebenszeit-Reproduktion beim Rauhfußkauz.
St. Andreasberg, Harz 2000 (3).
28.

 Eulenforschung für den Artenschutz.
St. Andreasberg,  Harz 2000 (3).
29.

 Artenschutz für Eulen.
Ludwigsburg 2001 (3).
 30.


 Zeige mir Deine Schwingen und ich sage Dir, wie alt Du bist !
Staffelmauser und Lebensgeschichte beim Rauhfußkauz.
Schwyz, Schweiz  2001 (4).
31.


 Monitoring beim Rauhfusskauz - Wie beeinflussen Reproduktionsverhalten und Nestlingssterblichkeit
die Erfassungsgenauigkeit ?
Meisdorf , Harz 2002 (5).
32.
 
 Reproductive effort of Tengmalm´s Owl under periodical and long-term changes of living conditions.
Budapest, Ungarn 2003 (7).
33.

 Ansiedlung und Dismigration in der mitteleuropäischen Metapopulation des Rauhfußkauzes.
Halberstadt 2003 (4).
 34.
 Der Rauhfußkauz als echter Europäer - Individuelles Ortsverhalten und artspezifische Reproduktionsstrategie.
Dornbirn, Österreich 2003 (3).
35.

 Die Vorkommen des Rauhfußkauzes in Mitteleuropa.
Hamburg 2004 (1).
 36.
 Informationsgewinn durch Biometrie bei der Beringung des Rauhfußkauzes.
Hamburg 2005 (2).
 37.

 Investition und Gewinn bei der Reproduktion des Rauhfußkauzes.
Stuttgart 2005 (4).
 38.
    
Erfassung und Aussagekraft verhaltensökologischer Daten am Beispiel des Rauhfußkauzes.
Bad Blankenburg, Thüringen 2006 (2).
 39.


 Migration and dispersion dynamics in the metapopulation of Tengmalm's Owl (Aegolius funereus)
in Central Europe.
Hamburg 2006 (9).
 40.

 Faszination Rauhfußkauz - Einblicke in sein heimliches Leben.
Braunschweig 2006 (8).
 41.
 Ungewöhnliche Feststellungen zur Verhaltensökologie des Rauhfußkauzes.
Gießen 2007 (4).
 42.
 Life history and reproductive success in Tengmalm's Owl.
Groningen,  Niederlande  2007 (10).
 43.
Ansiedlungsverhalten von Waldbaumläufer und Rauhfußkauz.
Jena 2009 (2).
 44.
 The Population Dynamics of Tengmalm's Owl over 30 years.
Zuerich, Schweiz 2009 (11).
 45.
 Monitoring beim Rauhfußkauz - Die Bedeutung von Balzverhalten und  Geschlechterverhältnis.
Halberstadt 2010 (5).
 46.
 Natur neu entdecken und erleben.
Braunschweig  2011 (8).
 47.
 Von Rekruten,  Migranten und fitten Räuzen. - Die Bedeutung von Geburtsortstreue, Ein- und Abwanderung  sowie  Anwesenheitsreproduktion in einer Population des  Rauhfußkauzes.
Marsberg-Bredelar, Sauerland 2011 (3).
 48.
 Welche Informationen ergeben sich aus dem Gesang des Rauhfußkauzes ?
Saarbrücken 2012 (4).
 49.
 Populationsökologische Zusammenhänge als Gundlage für den Artenschutz beim Rauhfußkauz.
Bielefeld 2014 (4).                     
 50.
 Ein ungewöhnlicher Vergleich von Populationsstudien am Rauhfußkauz und am Waldbaumläufer.
Bielefeld 2014 (4).
 51.
 Entstehen und Vergehen einer Rauhfußkauzpopulation (Aegolius funereus)
Halberstadt 2014 (5).
 52.
 Vergangenheit und Zukunft des Raufußkauzes Aegolius funereus -
Erkenntnisse eines 40-jährigen Forschungsprojektes
Halle 2017 (4).
 53Zusammensetzung und Reproduktion einer Population des Rauhfußkauzes (Aegolius funereus)
Heidelberg 2018  (4)
 54Die Bedeutung des Gesangs beim Rauhfußkauz (Aegolius funereus)
Halberstadt 2018 (5)

Poster


 01.

 
 Wie passt sich das Reproduktionssystem des Rauhfußkauzes (Aegolius funereus) den Schwankungen im Nahrungsangebot an ? 
Wilhelmshaven 1994  (4) - Friedrichsbrunn, Harz 1994 (3),(5) - St. Andreasberg 2000 (3).
02.

 Der Rauhfußkauz im Harz: 25-jähriges Forschungs- und Artenschutzprojekt.
St. Andreasberg 2000 (3) - Meisdorf 2002 (5).
03.

 Wie frisst ein junger Rauhfußkauz eine Spitzmaus ?
St. Andreasberg 2000 (3) - Ludwigsburg 2001 (3).



Filme

O. SCHWERDTFEGER & H-W. SENGE :


 01.

 Rückblick Harz 2000.
Ludwigsburg 2001 (3). 
 02.

 Ein heimlicher Bewohner des Harzes - der Rauhfußkauz.
Meisdorf, Harz 2002 (3), (5) - Dornbirn, Österreich 2003 (3).
03.

 A secret occupant of the Harz mountains - the Tengmalm´s Owl.
Budapest, Ungarn 2003 (7).
 04.

 Verhalten des Rauhfußkauzweibchens beim Fütterungsanflug.
Dornbirn, Österreich 2003 (3).
 05.

 Faszination Rauhfußkauz - Einblicke in sein heimliches Leben.
Stuttgart 2005 (4).
 06.

 Fascination Tengmalm's Owl - Insights into his secret life.
Groningen, Niederlande 2007 (10).
 07.
 Einblicke in ein verborgenes Leben
Halberstadt 2010 (5).
 08.
 Lichtblicke der Rauhfußkauz-Balz
Saarbrücken 2012 (4).



Filme über das Projekt



Seltener Kauz findet neue Heimat.

NDR 2005.

Wildnis Harz -. Im Reich der kleinen Eule.

NDR 2008, 2009, 2012, 2013

Der erste Frühling - Tierkinder in Niedersachsen

NDR 2010



Diplomarbeiten


 01.
 KÄMPFER, ANDREAS 1988.
Zum Territorialverhalten und zur Mauser des Rauhfußkauzes (Aegolius funereus) im Harz.
Institut fuer Wildbiologie und Jagdkunde der Universität Göttingen,
Prof. Dr. A. Festetics.
 02.



 FRANKE, CAROLA 2004.
Habitatwahl und Habitatqualität beim Rauhfußkauz (Aegolius funereus).
Zentrum für Naturschutz der Universität Göttingen,
Prof. Dr. M. Mühlenberg.



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