1 1 INFERRING THE WINTERING DISTRIBUTION OF THE MEDITERRANEAN 2 POPULATIONS OF EUROPEAN STORM PETRELS (Hydrobates pelagicus ssp 3 melitensis) FROM STABLE ISOTOPE ANALYSIS AND OBSERVATIONAL FIELD 4 DATA 5 INFIRIENDO LA DISTRIBUCIÓN INVERNAL DE LAS POBLACIONES 6 MEDITERRÁNEAS DE PAÍÑO EUROPEO (Hydrobates pelagicus ssp melitensis) A 7 PARTIR DE ANÁLISIS DE ISÓTOPOS ESTABLES Y DATOS OBSERVACIONALES 8 DE CAMPO. 9 Carlos Martínez1-5-6, Jose L. Roscales2, Ana Sanz-Aguilar3-4 and Jacob González-Solís5 10 11 1. Departamento de Biologia, Universidade Federal do Maranhão, A. dos Portugueses S/N, 12 Campus do Bacanga, 65085-580, São Luís, Brazil, E-mail: [email protected] 13 2. Instituto de Química Orgánica General, Consejo Superior de Investigaciones Científicas, 14 Juan de la Cierva 3, 28006, Madrid, Spain, E-mail: [email protected] 15 3. Animal Demography and Ecology Group, Instituto Mediterráneo de Estudios 16 Avanzados, IMEDEA (CSIC-UIB), Miquel Marquès 21, E-07190 Esporles, Islas 17 Baleares, Spain, E-mail: [email protected] 18 4. Área de Ecología, Universidad Miguel Hernández, Avenida de la Universidad s/n, 19 Edificio Torreblanca, 03202 Elche, Alicante, Spain 20 5. Institut de Recerca de la Biodiversitat (IRBio) and Departament de Biologia Evolutiva, 21 Ecologia i Ciències Ambientals, Facultat de Biologia, Universitat de Barcelona, Av. 22 Diagonal 643, 08028, Barcelona, Spain, E-mail: [email protected] 23 6. Corresponding author. 24 25 Author contributions: All authors formulated the questions; J. L. R., A. S.-A. and J. G.- 26 S. collected data; all authors supervised research; J. L. R. and J. G.-S. designed methods; 27 C. M. and J. L. R. analyzed the data; C. M. led the writing of the article. All authors 28 contributed to the drafts and gave final approval for publication. 29 30 Abbreviated title: WINTERING DISTRIBUTION OF MEDITERRANEAN STORM 31 PETRELS 32 Key words: Atlantic Ocean, Isotopic Seascapes, Mediterranean Sea, Pelagic Birds. 33 Number of words: 4,392 34 Research Paper 35 ORCID: Carlos Martínez, 0000-0002-3169-4581; José L. Roscales, 0000-0002-0446-6911; Ana 36 Sanz-Aguilar, 0000-0002-4177-9749; Jacob González Solís, 0000-0002-8691-9397. 37 2 38 SUMMARY- Bird migration studies have been increasing recently thanks to the 39 miniaturization of tracking devices. However, for the smallest pelagic species, tracking 40 methodologies have remained impractical and thus, important gaps in knowledge still exist. In 41 the case of the European Storm Petrel (Hydrobates pelagicus), while Atlantic populations are 42 thought to overwinter along the south-western African coast, the wintering grounds of 43 Mediterranean birds remain more enigmatic. We performed stable isotope analysis (SIA) on P1, 44 S8 and P10 feathers from 33 adult birds captured in three Atlantic colonies and 156 adult birds 45 in seven western Mediterranean colonies to infer their wintering areas. In addition, we collated 46 all observational field data, both from peer-reviewed publications and the grey literature, to 47 complement our inferences from SIA. Isotopic profiles of feathers moulted at the breeding 48 grounds (P1) differed between birds captured at northern Atlantic and Canary Islands colonies, 49 but were similar for feathers moulted at wintering grounds (S8 and P10), indicating a low 50 migratory connectivity. Isotopic values of feathers from western Mediterranean birds differed 51 from those of Atlantic birds and showed Mediterranean values for all feathers, indicating that 52 birds remain in Mediterranean waters during the winter. Variance in the isotopic values was 53 greater in wintering than in breeding feathers, suggesting that birds disperse over larger areas. 54 Isotopic values of feathers moulted during the non-breeding period could match a post-breeding 55 movement towards the southern and eastern Mediterranean. This inference matches the 56 distribution of the few winter reports, which are mainly concentrated in south-central 57 Mediterranean, mostly in the Tunisian Platform. Our results suggest this region as the main 58 wintering grounds for Mediterranean Storm Petrel. 59 SUMARIO- Los estudios sobre la migración de las aves se han incrementado recientemente 60 gracias a la miniaturización de los dispositivos de seguimiento. Sin embargo, para las especies 61 pelágicas más pequeñas, los métodos de seguimiento han permanecido poco prácticos y por 62 tanto continúan existiendo importantes lagunas de información. En el caso del Paíño Europeo 63 (Hydrobates pelagicus), mientras se considera que las poblaciones atlánticas invernan a lo largo 64 de la costa Sudoeste africana, continúa sabiéndose muy poco sobre los cuarteles de invierno de 65 las aves mediterráneas. Realizamos un análisis de isótopos estables (AIE) en plumas P1, S8 and 66 P10 de 33 aves adultas capturadas en tres colonias atlánticas y 156 aves adultas en siete colonias 67 en el Mediterráneo occidental, para inferir sus áreas de invernada. Además, recogimos los datos 68 de observaciones de campo, tanto de publicaciones con revisión como de literatura gris, para 69 complementar nuestras inferencias a partir del AIE. Los perfiles isotópicos de las plumas 70 mudadas en las áreas reproductivas difirieron entre las aves capturadas en las colonias del 71 Atlántico Norte y en las Islas Canarias, pero fueron similares para plumas mudadas en áreas de 72 invernada, indicando una baja conectividad migratoria. Los valores isotópicos de las plumas de 73 las aves del Mediterráneo Occidental difirieron de las del Atlántico y mostraron valores 74 mediterráneos para todas las plumas, indicando que las aves permanecen en aguas 75 mediterráneas durante el invierno. La variancia de los valores isotópicos fue mayor en las 76 plumas mudadas durante el invierno que durante la reproducción, indicando que las aves se 77 dispersan por áreas más extensas. Los valores isotópicos de las plumas mudadas durante el 78 invierno son compatibles con un movimiento post-reproductivo hacia el sur y tal vez hacia el 79 este dentro del Mediterráneo. Esta inferencia es coherente con la distribución de los pocos 80 registros invernales existentes, que se concentran sobre todo en el centro-sur del Mediterráneo, 81 principalmente en la Plataforma Tunecina. Nuestros resultados apuntan a esta región como la 82 principal área de invierno del Paíño Europeo Mediterráneo. 83 3 84 INTRODUCTION 85 Studying bird migration is very important to the design and development of conservation 86 policies, both at migration routes and in non-breeding areas, as well to understanding the 87 mechanisms driving migration processes. Migration patterns are extremely variable, not only 88 among species, but also among populations and individuals within populations (Newton 2008; 89 Rappole 2013). The complex movement patterns of pelagic seabirds are influenced by food 90 abundance and distribution, but also by winds and marine habitat features (e.g., Sanz-Aguilar et 91 al. 2012). Traditional methods to study bird migration, such as ringing, have revealed that 92 European Storm Petrels are highly phylopatric to their breeding areas (e.g. Sanz-Aguilar et al. 93 2009), but has provided little insight into migration routes and wintering areas, as rings are 94 rarely recovered at sea. 95 During the last few decades, tracking technologies have been developed as the most reliable 96 alternative to study bird migration. Studies involving extrinsic markers, such as PTTs (Platform 97 Terminal Transmitters) and geolocators, are increasingly common (e. g. Kays et al. 2015). 98 These devices have followed a continuous process of miniaturization, allowing the tracking of 99 smaller-sized animals. However, even today studies using geolocators have not been published 100 for the smallest pelagic species, such as small Storm Petrels (<30g). 101 Alternatively, intrinsic markers, such as stable isotope analysis (SIA) of H, C and N (δD, δ13C 102 and δ15N), can be used to study large scale movements in a wide range of animals (Rubenstein 103 & Hobson 2004). More specifically, values of δ13C and δ15N have been primarily used to study 104 the trophic structure of animal communities, since these values are integrated from prey values 105 into the tissues of the predators in a predictable manner (Hobson & Welch 1992; Roscales et al. 106 2011). Nevertheless, assuming diet among individuals and populations is fairly homogeneous 107 and given that differences in isotopic baseline levels among distant geographic areas are often 108 very large, SIA of C and N has been recently applied to the study of the spatiotemporal 109 movements of birds using information on geographical and temporal isotopic variation, i.e. 110 isoscapes both in terrestrial (Hobson & Wassenaar 2008) and marine environments (Cherel et 111 al. 2016, Polito et al. 2017). Consumer’s tissues integrate, via the diet, the isotopic baseline 112 indicating the food source’s time and place of origin (Cherel & Hobson 2007). Particularly, 113 feathers are a valuable tissue to study migration using SIA because they remain chemically inert 114 after their formation. In the ocean, isotope baselines among marine food webs are known to 115 vary geographically as a consequence of differences in nutrient cycles at the base of the food 116 web (Graham et al. 2010; McMahon et al. 2013). For example, δ15N values in feathers of 117 Scopoli’s shearwaters (Calonectris diomedea) increased from an average value of 10.37‰ in 118 the first primary feather moulted in the Mediterranean to 13.44‰ in the 10th primary feather 119 moulted in the Atlantic (Ramos et al. 2009b). This change cannot be easily attributed to changes 120 in diet, since it would mean a change in one trophic level, but to differences in baseline levels 4 121 between some areas of the two basins (e.g. McMahon et al. 2013). The first isotopic geographic 122 gradients have been recently described (Graham et al. 2010; Ramos & González-Solís 2012; 123 McMahon et al. 2013) and the first studies using this variability to reveal seabird movements 124 are just starting to emerge (Jaeger et al.