Ecology of Red Admiral Migration
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ECOLOGY OF RED ADMIRAL MIGRATION Ecology of red admiral migration Oskar Brattström Dissertation Lund 2007 Before I sink, into the big sleep, I want to hear, I want to hear, the scream of the butterfly “When the Music’s Over” – Jim Morrison 1967 A doctoral thesis at a university in Sweden is produced either as a monograph or as a collection of papers. In the latter case, the introductory part constitutes the formal thesis, which summarizes the accompanying papers. These have either already been published or are manuscripts at various stages (in press, submitted or in ms). Cover: photo by Oskar Brattström Layout: Gunilla Andersson/ZooBoTech Proofreading: Oskar Brattström Printed by Xanto Grafiska AB, S Sandby ISBN 978-91-7105-259-9 SE-LUNBDS/NBZE-07/1113+136 pp Contents Page Ecology of red admiral migration 9 Introduction 9 The study species 9 Research objectives 12 Methods 12 Estimates of genetic differentiation 12 Wing length measurements, sex determination and estimates of lipid content 13 Analysis of stable isotope ratios 13 Orientation experiments 14 Migration counts at a coastal site 15 Results 16 Genetic structure of European red admirals 16 Studies of red admiral winter ecology 16 Annual patterns in the timing and origin of the migrants 18 Flight directions and orientation mechanisms 20 Coastal migration in relation to local weather 21 Conclusions and directions for future studies 21 References 23 Amiralens flyttningsekologi 27 Tack! 31 This thesis is based on the following paper: IBrattström, O., Åkesson, S. & Bensch, S. AFLP reveals cryptic population 37 structure in migratory European red admirals. – Manuscript. II Brattström, O. 2006. Is there seasonal variation in size and mass of 49 Red Admirals Vanessa atlanta on Capri, Italy. – Ornis Svecica, 16, 69–73. III Brattström, O., Wassenaar, L. I., Hobson, K. A. & Åkesson, S. 2007. 57 Placing butterflies on the map – testing the regional geographical resolution of three stable isotopes in Sweden using a monofagus Nymphalid, the peacock (Inachis io). – Submitted. IV Brattström, O., Bensch, S., Wassenaar, L. I., Hobson, K. A. & Åkesson, S. 71 Understanding migration patterns of European red admirals (Vanessa atalanta) using stable hydrogen isotopes. – Manuscript. VBrattström, O., Shapoval, A., Wassenaar, L. I., Hobson, K. A. & 87 Åkesson, S. Annual patterns in migration of red admirals (Vanessa atalanta) at Rybachy, a coastal site in northern Europe (Kaliningrad). – Manuscript. VI Brattström, O. & Åkesson, S. Flight direction of red admirals (Vanessa 103 atalanta) during autumn migration in southern Sweden – results from orientation cages and release experiments. – Manuscript. VII Brattström, O., Kjellén, N., Alerstam, T. & Åkesson, S. 2007. Effects 117 of wind and weather on red admiral (Vanessa atalanta) migration at a coastal site in southern Sweden. – Submitted. Paper II is reprinted with permission from the publisher. Ecology of red admiral migration When discussing the topic of insect migration (1958), the butterflies were so many that they people will often mention the same behaviour hid the light of the sun. We also find that these in birds, since most people are unaware that butterflies moved from Saxony towards Bavaria many insect species migrate across continents (in modern Germany); a migration route that is each year. As pointed out by Williams in his still today used by the same species each au- classic book about insect migration (1958), tumn (e.g. Spieth & Kaschuba-Holtgrave these phenomena were reported in literature, 1996, Spieth et al. 1998). Modern studies of and even discussed in relation to prevailing butterfly migration have mainly focused on the winds as early as 3000 years ago. Book of Exo- monarchs (Danaus plexippus) in North Ameri- dus, Chapter 10, Verses 13 to 15: “and the ca. Studies of this species’ remarkable migration Lord sent an east wind that blew across Egypt have been going on since 1857, and an excellent the rest of the day and all that night. By morn- review of all monarch studies from that point ing, locusts were swarming everywhere (…) up until the mid 1990s has been compiled by The ground was black with locusts, and they Brower (1995). The monarch is an exception ate everything left on the trees and in the fields. from most other migratory butterflies as its mi- Nothing green remained in Egypt—not a tree gration is rather well known to the general pub- or a plant.” and then in verse 19: “the Lord sent lic in the area where it can be observed. a strong west wind that swept the locusts into From Europe, there are numerous published the Red Sea”. Even though the source of both observations of the migration habits of both locusts and wind is a matter open to debate, butterflies and moths, but only a few experi- there is no doubt that this kind of insect migra- mental (e.g. Spieth & Kaschuba-Holtgrave tion could have substantial impact on human 1996, Spieth et al. 1998) or long-term studies lives in our early history. Since butterflies do (e.g. Stefanescu 1997, 2001). Our knowledge not have this great an impact on human socie- about butterfly migration is mostly reconstruct- ty, we will have to move ahead more than two ed from snap-shots along presumed migratory thousand years before we have sources men- routes. This has been compiled by adding to- tioning their migration. And when we finally gether different observations of large scale mi- have such a reference, this is because the butter- gratory events, or by comparing first and last flies in question happened to interrupt some- reported sightings of different species across thing that has always been very important in their range throughout different years. our history. From the twelfth century, we know of a re- port from a battlefield mentioning not just ar- The study species mies of men but also a huge army of butterflies, probably large whites (Pieris brassicae). Accord- Among the butterflies that can be found in Eu- ing to this report, mentioned by Williams rope, the red admiral (Vanessa atalanta) stands 9 Ecology of red admiral migration No pain, no gain! The red admiral to the left looks like it has been through a lot of troubles getting there, while the one to the right looks in pristine condition. They were both photographed on 11 July 2006 at Ottenby, Öland. Since red admirals found in this area can come from various natal regions at this time of year (Paper IV) it is possible that the one to the left has flown all the way from the Mediterranean Sea while the other one might come from an area much closer to Öland. Photo: Oskar Brattström. out among all long distance migrants showing about the migration ecology of red admirals. the perhaps most regular pattern of migration. Before presenting the work we have done, I will In the British Butterfly Monitoring Scheme, briefly present what was previously know about the average yearly change in number of red ad- the red admirals’ migration ecology followed by mirals seen is two-fold, while the closely related a presentation of the studies we have per- painted lady (Vanessa cardui), being a more ir- formed, including more detailed comparisons regular migrant, varies as much as six-fold on to previous studies focusing on the same type of average (Pollard & Yates 1993). There are of questions. course larger fluctuations in numbers than for The red admiral is a Nymphalid butterfly most resident species but red admirals can be that can be found in North America, North Af- observed in good numbers every summer in rica, most parts of Europe, and in the western- most parts of northern Europe while many oth- most parts of Asia (Eliasson et al. 2005). Each er migrants can be completely missing some spring, the European red admirals initiate large years. The occurrence in the most northern scale migrations towards the north. There are parts of the distribution range is much more observations of these northward migratory variable than further towards the south (Elias- flights from Italy (Benvenuti et al. 1994, 1996), son et al. 2005), but large numbers of red admi- Spain (Stefanescu 2001), Britain (Williams rals can reach as far as northern Norway some 1951) and Scandinavia (Hansen 2001) in years (Strann et al. 1995). March through June, but some studies have Because of the many reported sightings of questioned whether the individuals leaving the large migrations of red admirals and a few or- Mediterranean area will reach northern Europe ganised studies focussing on this species in par- to any considerable extent (Roer 1961, Baker ticular, we have a reasonably good knowledge 1972). As it is known that red admirals can also about the yearly pattern of migration. But as we hibernate, even though the significance of that shall see there are still gaps in our present behaviour is questionable, the previously men- knowledge. The aim of this thesis is to close tioned studies have suggested that the species some of these gaps by experimental studies only migrate short distances as if the whole pop- aimed at solving several separate open questions ulation made a short movement towards the 10 Ecology of red admiral migration north each spring (Fig. 1a). Lately, the com- eration hatches and additional reproduction mon view (e.g. Mikkola 2003b, Eliasson et al. events might even occur. Red admirals are regu- 2005) suggests that the migration is rather ex- larly observed as late as October in northern tensive and covers long distances (Fig. 1b–c), Europe (Henriksen & Kreutzer 1982, Eliasson but none of the published studies have man- et al. 2005). Each year migration in large num- aged to prove that the Mediterranean spring bers towards the south is reported in autumn migrants really reach as far north as, for exam- throughout Europe (Willimas 1951, Roer ple, Scandinavia each spring.