Departure Directions, Migratory Timing and Non

This article was downloaded by: [Fränzi Korner-Nievergelt] On: 18 December 2012, At: 06:36 Publisher: Taylor & Francis Informa Ltd Registered in England and Wales Registered Number: 1072954 Registered office: Mortimer House, 37-41 Mortimer Street, London W1T 3JH, UK Ringing & Migration Publication details, including instructions for authors and subscription information: http://www.tandfonline.com/loi/tram20 Departure directions, migratory timing and non- breeding distribution of the Red-backed Shrike Lanius collurio: do ring re-encounters and light-based geolocator data tell the same story? Fränzi Korner-Nievergelt a b , Lukas Jenni a , Anders P. Tøttrup c & Gilberto Pasinelli a a Swiss Ornithological Institute, Sempach, Switzerland b oikostat GmbH, Ettiswil, Switzerland c Center for Macroecology, Evolution and Climate, Department of Biology, University of Copenhagen, Universitetsparken 15, DK-2100, Copenhagen, Denmark Version of record first published: 18 Dec 2012. To cite this article: Fränzi Korner-Nievergelt , Lukas Jenni , Anders P. Tøttrup & Gilberto Pasinelli (2012): Departure directions, migratory timing and non-breeding distribution of the Red-backed Shrike Lanius collurio: do ring re-encounters and light-based geolocator data tell the same story?, Ringing & Migration, 27:2, 83-93 To link to this article: http://dx.doi.org/10.1080/03078698.2012.748508 PLEASE SCROLL DOWN FOR ARTICLE Full terms and conditions of use: http://www.tandfonline.com/page/terms-and-conditions This article may be used for research, teaching, and private study purposes. Any substantial or systematic reproduction, redistribution, reselling, loan, sub-licensing, systematic supply, or distribution in any form to anyone is expressly forbidden. The publisher does not give any warranty express or implied or make any representation that the contents will be complete or accurate or up to date. The accuracy of any instructions, formulae, and drug doses should be independently verified with primary sources. The publisher shall not be liable for any loss, actions, claims, proceedings, demand, or costs or damages whatsoever or howsoever caused arising directly or indirectly in connection with or arising out of the use of this material. Ringing & Migration (2012) 27,83–93 Departure directions, migratory timing and non-breeding distribution of the Red-backed Shrike Lanius collurio: do ring re-encounters and light-based geolocator data tell the same story? FRÄNZI KORNER-NIEVERGELT1,2*, LUKAS JENNI1, ANDERS P.TØTTRUP3 and GILBERTO PASINELLI1 1Swiss Ornithological Institute, Sempach, Switzerland 2oikostat GmbH, Ettiswil, Switzerland 3Center for Macroecology, Evolution and Climate, Department of Biology, University of Copenhagen, Universitetsparken 15, DK-2100 Copenhagen, Denmark This study explores differences and consistencies between ring re-encounter and light-based geolocator data from Red-backed Shrike when used for studying three aspects of bird migration: departure direction and its relationship with longitude and latitude, non-breeding distribution, and timing of migration. Departure directions were consistent between the two methods. They indicate a funnel-shaped migration with individuals from southwest Europe taking a detour via the eastern Mediterranean rather than migrating via Gibraltar. This indicates that an original migration route has been retained after colonisation of the breeding range. Non-breeding distributions differed substantially between birds ringed and re-encountered and birds tracked by geolocators. This difference may be due to spatio- temporal heterogeneity in ring re-encounter probability and/or due to the two samples of birds belonging to different populations. The monthly average ring re-encounter location moved later southward during autumn and earlier northward during spring migration than the geolocator positions, because of an over-representation of re-encounters in the north. The results emphasise the importance of combining different sources of data when analysing migration patterns of animals that are difficult to track. Migration towards subtropical or tropical areas in winter has been observed in southern German and Austrian is a characteristic life-history trait of many bird species populations of Blackcap Sylvia atricapilla that started to breeding in temperate climate zones (Alerstam 1990). migrate towards the UK in the 1960s (Helbig 1994). Energy-demanding long-distance flights and the stages in Subsequently, temporal segregation of spring migration stopover or wintering areas, where the habitat may be led to reproductive isolation and genetic and phenotypic completely different from the breeding grounds, may divergence into two sympatric populations (Rolshausen have important implications for the ecology, behaviour et al 2009). Observing such changes in migratory Downloaded by [Fränzi Korner-Nievergelt] at 06:36 18 December 2012 and population dynamics of species (Webster et al 2002, behaviour may thus allow insight into the evolutionary Helm et al 2006, Norris & Marra 2007). To understand mechanisms of bird migration. However, the unbiased the ecology and population dynamics of a species or a measurement of migratory direction is a prerequisite for population, it is therefore important to know when and detecting changes in migratory behaviour. where individuals are migrating. Knowledge of the distribution of bird populations during Migration directions are heritable (Helbig 1991). They the non-breeding period is important for various reasons, are often adapted to the specific locations of breeding including the study of carry-over effects (Norris 2005, and wintering areas in relation to topography such as Norris & Marra 2007) or migratory connectivity (Webster mountains, seas, or deserts (Bruderer 1997a). When et al 2002), as well as for conservation purposes (eg Fox & environmental conditions change or a species expands Salmon 1988). Ecological conditions at stopover or to new breeding areas, migratory direction may evolve wintering sites can affect breeding success and population rapidly. Such a rapid evolution of migration direction dynamics (Norris & Marra 2007). As an example, in the Red-backed Shrike Lanius collurio, low breeding success is associated with dry weather at the autumn stopover sites * Correspondence author (Schaub et al 2011) and fluctuations in breeding Email: [email protected] population size are positively related to rainfall in the Q 2012 British Trust for Ornithology 84 F. Korner-Nievergelt et al autumn stopover sites and in the wintering areas (Pasinelli Ring re-encounters have improved our knowledge of bird et al 2011). To detect such carry-over effects of factors migration hugely (Zink 1973–85, Zink & Bairlein 1995, acting at large spatial scales, it is sufficient to know the Wernham et al 2002). However, almost every study based approximate locations of stopover and wintering sites. on ring re-encounter data has struggled against bias caused However, to study the effects of local factors such as by spatial and temporal heterogeneity in ring re-encounter management and human impacts, stopover sites and probability (Perdeck 1977, Siriwardena et al 2004, Korner- wintering areas need to be accurately identified. Nievergelt et al 2010). To draw unbiased inference on bird In addition to identifying the stopover and wintering migration behaviour from ring re-encounters, precise locations, it is important to know when and how long information on the spatial and temporal patterns of ring these areas are used. When the temporal and spatial re-encounter probability is needed. Comparing results occurrence of favourable ecological conditions change in from ring re-encounters with those from alternative the non-breeding area, we expect that birds should also technologies such as satellite telemetry or light-based adjust their movement behaviour. Such behavioural geolocation may allow detection of inconsistencies changes can be detected only when the timing of between the methods and may thus inform us about migration can be measured accurately. The study of the spatial and temporal patterns of ring re-encounter timing of migration by observing departure, passage or probability. Whereas results from ring re-encounters are arrival of birds has recently provided clear evidence of susceptible to spatial and temporal heterogeneity in ring climate change affecting bird migratory behaviour re-encounter probability, tracked birds might not (Hüppop & Hüppop 2003, Jenni & Kéry 2003). In the constitute a random sample of the populations of interest. Red-backed Shrike, arrival in the breeding area has Furthermore, when estimating locations using light-based shifted earlier during the last century in western Poland geolocators, topography, habitat, weather and behaviour of (Tryjanowski et al 2002) and in Scandinavia (Tøttrup the bird can produce substantial errors, especially in the et al 2006). Furthermore, knowledge of the timing of estimated latitude (Lisovski et al 2012), whereas locations migration and of the duration of active migration may of ring re-encounters can, in most cases, be assumed to be provide insights into the energetics of bird migration accurate. Conversely, the date of geolocated birds is (Moore & Kerlinger 1987, Bayly 2006). known exactly, while the date of ring re-encounters may be Unfortunately, the study of migration in small birds is inexact. A combination of these two approaches may yield hampered because of their body size. Several methods a more comprehensive understanding

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