Analysis of partial migration strategies of Central European raptors based on ring re-encounter data I n a u g u r a l d i s s e r t a t i o n zur Erlangung des akademischen Grades eines Doktors der Naturwissenschaften (Dr. rer. nat.) der Mathematisch-Naturwissenschaftlichen Fakultät der Ernst-Moritz-Arndt-Universität Greifswald vorgelegt von Daniel Holte geboren am 06.10.1981 in Neuss Greifswald, den 14.06.201828.03.2018 Dekan: Prof. Dr. Werner Weitschies 1. Gutachter : PD Dr. Martin Haase 2. Gutachter: Dr. Sven Renner Tag der Promotion: 14.06.2018 Table of Contents A. Synopsis 7 1. General introduction 7 1.1 Marking animals 7 1.1.1 Bird ringing 8 1.2 Bird migration 10 1.2.1 Partial migration 11 1.3 Target species 11 1.3.1 Common kestrel 12 1.3.2 Common buzzard 12 1.3.3 Eurasian sparrowhawk 13 1.4 Study aims and hypotheses 13 2. Methods 15 2.1 Partial migration 15 2.2 Predicting ring re-encounters considering spatial observer heterogeneity 16 3. Results and Discussion 18 3.1 Partial migration 18 3.2 Predicting ring re-encounters considering spatial observer heterogeneity 21 4. Cited literature 25 B. Manuscripts 29 Paper I 29 Paper II 47 Paper III 65 Contributions to manuscripts 95 C. Eigenständigkeitserklärung 97 D. Curriculum Vitae 99 E. Scientific contributions 101 F. Danksagung 103 A. Synopsis 1. General introduction The history of ornithology goes far back in human history and its beginning is probably not clearly definable. Already in the fourth century B.C., Aristotle described about 140 bird species and he declared the study of birds to be a worthy activity for philosophers, which made ornithology become a science (Stresemann 1951). Currently, birds – more precisely their characteristics and capabilities as well as their ecology – are in these times of rapid environmental changes highly relevant objects for scientific research. The technological progress we have experienced during the last decades has also reached the ornithological research. It revealed for instance phylogenomic relationships among and between families, species and populations using DNA analyses (e.g. Fregin et al. 2012; Prum et al. 2015; Barani- Beiranvand et al. 2017), physiological traits, such as ultraviolet colours in plumage and beak colouration (e.g. Armenta et al. 2008; Schull et al. 2016), or aspects of ecology and behaviour, such as migratory flyways and wintering grounds, using satellite telemetry or isotope analyses (e.g. Strandberg et al. 2009; Seifert et al. 2016). Among many others, these findings help us to understand “the world of birds”, from an individual’s life cycle to complex interrelations within and between populations, which is a fundamental requirement to consult birds as indicators for ecology and to develop protection strategies. 1.1 Marking animals Animals get marked all over the globe for different purposes. For instance, pets like cats and dogs are marked with collars, ear tattoos and microchips in order to identify them if they get lost and found again. Livestock get ear marks to differentiate individuals to e.g. control for their productivity. Female sheep get marked with different colours depending on the male with which they mated. However, the approach of marking animals is not only used for domestic, but also for wild animals. In scientific research, animals get marked for several reasons including tracking their movements (e.g. Strandberg et al. 2009), observing their mate choices (e.g. Shave & Waterman 2017), or defining home ranges (e.g. Šegvić-Bubić et al. 2018). Depending on the study aims, the technical progress and the monetary budget, animal marking is carried out using e.g. spray colours and dye, leg and wing tags, light-level geolocators or radio 7 transmitters including GPS tracking devices. Colour marking is applied mainly in studies in which behaviour of different individuals is observed (e.g. Shave & Waterman 2017). Leg and wing tags, geolocators as well as radio and GPS transmitters, however, can be used to study the spatio-temporal allocation and the movements of individuals, such as dispersal (e.g. Schmidt et al. 2017) and migration, including the determination of breeding and wintering sites (e.g. Omori & Fisher 2017), up to exact migration routes and fuelling sites (e.g. Strandberg et al. 2009; Lislevand & Hahn 2015; Hiemer et al. 2018). In order to avoid or at least to limit impairments that may influence the behaviour of a marked animal, the weight of the tag which is supposed to be applied must not exceed 5% of the animal’s body mass (at least in terrestrial vertebrates, see Murray & Fuller 2000). This requirement has led to a miniaturization of devices allowing even to mark insects in order to follow their flyways (e.g. Kissling et al. 2014). A less sophisticated but therefore cheap, hence widely used method of marking animals is the approach of bird ringing. 1.1.1 Bird ringing The scientific bird ringing method was implemented more than 100 years ago by the Danish teacher Hans Christian Mortensen (Baillie et al. 2007). Birds are caught or taken from the nests and get marked with a metal and/or a plastic ring which carries an individual inscription consisting of a mixture of figures and letters (= ring number). This inscription functions like an ID card, which in case of being re-encountered by re-sighting or re-catching the ringed bird or by finding its carcass can be assigned to the respective bird unambiguously. In Europe, about 5 million birds get ringed each year (Baillie et al. 2007), providing the potential to create big databases with a huge amount of information. The quantity and quality of information that goes into these databases strongly depend on the kind of data that has been collected during ringing as well as reported as a re-encounter. While ringing is performed by expert and trained scientists and volunteers, a re-encounter can also be made by laymen. In this occasion, ring re- encounters mainly result from findings of dead birds. This can be a problem regarding the accuracy of information about the details of re-encounter and the circumstances that led to a bird’s death. In some cases even the time of dying is unknown or the re-encounter site is given only vaguely. The latter occurs mainly in reports that have been made before GPS and cell phone positioning became broadly available. In addition, uncertainties about age and sex of 8 ringed individuals may reduce the explanatory power of ring re-encounters. These uncertainties can result from trapping adult birds in which the age is not clearly determinable or from the absence of sexual dimorphisms at least at the ringing time. Finally, the probability to re- encounter a ringed bird is not equally distributed in space and time (e.g. Korner-Nievergelt et al. 2010a). It depends on the species – in terms of body size, habitat, ecology etc. – as well as on the potential observers. Observers may differ in knowledge and education, interest and social status as well as in the political situation and population density of the region where they live. Moreover, a re-encounter only goes into the databases if the observer contacts the corresponding ringing scheme and reports the ring. The willingness to report a re-encountered ring differs between observers as well, again depending on knowledge and interest, but also on the facilities to make a report. For example, web-based reporting applications have advanced ring reporting rates in the last two decades (see e.g. Boomer et al. 2013), whereas restrictions in hunting may reduce the reporting willingness, because illegal hunting activities that would be revealed by a report could be punished. There have been some approaches implemented to correct for observer heterogeneity (e.g. Kania 2009; Korner-Nievergelt et al. 2010a, 2010b, 2012; Cohen et al. 2014; Thorup et al. 2014) but they all have one thing in common: additional information which supplements the ringing data is required. One of the most promising procedures combines ring re-encounters with data derived from tracking methods, such as satellite telemetry and geolocators (Korner-Nievergelt et al. 2010a; Thorup et al. 2014), which, however, cannot be applied retrospectively. Other approaches are based on socio-demographic factors, where observer distribution and re- encounter probabilities are estimated by human population densities or political borders (Korner-Nievergelt et al. 2010a). All this additional information is usually not available when starting an analysis of ring re-encounter data. It must be collected, if possible, as part of the study or obtained from other sources with much additional effort. Hence, these methods are only conditionally applicable. Due to the lack of adequate methods, the results of ‘classical’ ring re-encounter analyses which do not correct for observer heterogeneity should be interpreted carefully. Despite all those limitations and uncertainties, ring re-encounters have filled our databases with more than 2 million records until 2007 only in Europe (Baillie et al. 2007). In contrast, studies 9 that use new technologies (e.g. GPS tracking) are often limited in sample size because budgets for scientific research are usually small and, thus, confine the number of devices that can be applied. The huge numbers in ring data bases result from the facts that bird ringing is conducted mainly by many well trained volunteers (~ 10,000 ringers in Europe organized by the national ringing schemes; Baillie et al. 2007) and material costs are relatively low. Accordingly, about four million birds are ringed in Europe each year (Baillie et al. 2007). Many of the resulting datasets have been analysed and large voluminous ring recovery atlases have emerged (e.g.