(138) Migración y ecología espacial de las poblaciones españolas de pardela cenicienta. Monografía n.º 3 del programa Migra. SEO/BirdLife. Madrid. 152pp.
Reyes-González, J.M., Z.Zajková, V. Morera Pujol, F.De Felipe, T.Militão, G.Dell’Ariccia, R.Ramos, J.M.Igual, J.M.Arcos & J.González-Solís (2017)
This publication analyses the movement ecology and at-sea behaviour of the populations of Scopoli’s and Cory’s shearwaters that breed in Spain, being both seabird species of conservation concern. Thanks to several research projects carried out by the University of Barcelona and SEO/BirdLife, a large set of remote tracking data was compiled in order to get critical knowledge to enhance conservation status of seabird populations breeding in Spain. The results included here arise from analysing part of this data set. We present the main insights found regarding ecology at-sea and year-round movements, including the identification of the foraging grounds, resting areas and commuting corridors during the breeding period, the migratory phenology, the behaviour, and the location of the wintering areas and main migratory flyways. Moreover, we provide to non-specialized readers an introduction to technical details of remote tracking systems employed in order to ensure a proper understanding of pros and cons of each methodology and a correct interpretation of results and figures. In accordance with recent phylogenetic studies and the British Ornithologists’ Union Taxonomic Committee recommendations, here we have considered the Mediterranean and the Atlantic taxa as two different species: the Scopoli’s Calonectris diomedea and the Cory’s shearwater C. borealis. This decision is also based on behavioural differences between taxa, including the migratory behaviour described in this monography, that support their consideration as different conservation units. Because of the number of individuals tracked, the amount and representativeness of colonies studied, and the set of years considered, the work presented in this book is probably the most ambitious and comprehensive effort undertaken to date to address the study of any species breeding in Spain through remote tracking systems. This book constitutes the third monography from the Migra programme (www.migraciondeaves.org), a long-term research project carried out by SEO/BirdLife since 2011, with the aim to use cutting-edge tracking technologies to unravel the movements and migration of birds breeding in Spain. Data was gathered using different remote tracking systems according to aims and limitations. Fieldwork and deployments were carried out at 13 different breeding colonies distributed across different regions of Spain: Balearic Islands (Cala Morell, Aire Islet, Pantaleu, Cabrera), Castellón (Columbretes Islands), Murcia (Palomas Islet), Almería (Terreros Islet), Chafarinas Islands, and Canary Islands (Alegranza Islet, Montaña Clara Islet, Timanfaya and Veneguera). We used ~20-25 g GPS loggers (from different manufacturers) in order to track the movements of adult individuals during the breeding period. These loggers were properly waterproofed in heat shrink tubing and attached to the back feathers using Tesa tape. Remote tracking was conducted from 2007 to 2015 and across the 13 breeding colonies referred above. We gathered 813,612 GPS locations and 1,546 foraging trips from 299 individuals. GPS data considered for the analyses correspond mainly to the chick-rearing period, but trips from prelaying and incubation were also included for birds breeding at Veneguera and Cala Morell colonies, where the most intensive fieldwork has been done. Light-level geolocation data loggers (manufactured by British Antarctic Survey and Biotrack LTd.), attached to plastic rings and deployed on tarsus, were used to study year-round movements. Many loggers were equipped with a salt-water immersion sensor, which also allowed the study of activity budgets and daily behaviour at-sea. Geolocators were deployed and recovered from 2007 to 2013 at 3 breeding colonies: Veneguera and Montaña Clara (for Cory’s shearwaters) and Pantaleu (for Scopoli’s shearwaters). This work includes data from 214 devices recovered, each working one and a half year on average. After analysing the light curves and before applying any filter, the dataset contained 203,427 geographic locations, corresponding to 309 tracks from 161 different individuals (Pantaleu: 72 trips from 46 individuals; Veneguera: 207 trips from 95 individuals; Montaña Clara: 30 trips from 20 individuals). For spatial analyses purposes, we modelled locations from geolocators in order to reduce uncertainty and get the most plausible trajectories. Through the large number of tagged individuals and breeding colonies studied, and thanks to the use of two different tracking systems, we obtained a comprehensive overview of the annual movements and at-sea behaviour of Scopoli’s and Cory’s shearwaters breeding in Spain. This allowed us to present new insights about foraging strategies, feeding grounds, migratory patterns and phenology for these populations. State-of-the-art algorithms to classify behavioural modes from GPS data were used to quantify behaviour at varying temporal and spatial scales and to build up behavioural landscapes. Furthermore, salt-water immersion data provided information to characterize individuals’ behaviour year-round, allowing us to compare performance and daily activity budgets among wintering areas. Because of the large number of individuals tracked year-round, we were also able to calculate migratory connectivity between breeding and wintering grounds. In addition, since we tracked a good amount of individuals for several years (some of them up to seven years) we also obtained new insights about spatial consistency and fidelity to wintering grounds. During breeding, some differences were found between species regarding behaviour, movement range and areas visited. Both species, but particularly colonies in the Atlantic, showed a clear preference for neritic waters far away from the colony, over the continental shelf near the mainland. However, they also used waters surrounding the colonies, in what is known as the dual foraging strategy during the chick rearing. In the Mediterranean, birds foraged along the Iberian coast from the strait of Gibraltar up to the Gulf of Lyon during the long trips, with some degree of spatial segregation among individuals from different colonies. In the case of birds at Chafarinas, birds commuted to the northern coast of Morocco, an area also used by birds from Palomas Islet. Overall, the distribution of trip length and duration values was not bimodal, which suggests that the size of the western Mediterranean basin is not large enough to promote a clear dual foraging strategy. Regarding population from the Canary Islands, birds consistently foraged along the highly productive African shelf, sometimes performing foraging trips of up to 1,000 km. Commuting flights were generally diurnal, whereas resting took place overnight. Birds were more active at sunrise and sunset, although they also foraged during the day. However, intensive foraging behaviour seems to occur in similar proportion during darkness and daylight, both in the Mediterranean and in the Atlantic. Indeed, in the Atlantic this behaviour seems to be more important during darkness in some moments, which may relate to individuals’ intrinsic factors (such as the internal state of the individuals that affects their motivation and performance to behave, e.g. physiological, neurological, etc,), the environmental conditions or the moon phase. The population of Scopoli’s shearwaters breeding in Spain spends the non-breeding period in 4 main wintering areas, sorted by importance: the Canary Current (African shelf from 14° N to 23° N), offshore waters of Angola and Namibia (from the equator to the parallel 22° S), oceanic waters of Guinea (around parallel 8° N and meridian 20° W), and off coast of Ghana (from the coast to the equator). Birds were more active during daylight across most of the wintering areas, with peaks of activity at sunrise and sunset. In the area of Guinea, however, birds were more active at night. On the other hand, Cory’s shearwaters breeding in Spain use 6 different wintering areas during the non-breeding period, sorted by importance: the Benguela Current off the coast of Namibia (from 10° S to 40° S), the Agulhas Current, the confluence between the Benguela and the Agulhas currents (around the parallel 40° S), the Canary Current (from 10° N to 25° N), the Brazil Current (from 15° S to 40° S), and the centre of the South-Atlantic (around parallel 45° S and meridian 25° W). Birds were more active during daylight, especially at sunrise and sunset, with the exception of the Canary Current where activity during daylight and darkness were similar. Both species showed some trend towards being more active during darkness with an increasing depth and distance from the coast, suggesting population plasticity in the foraging strategies to adapt to the environment of each wintering area. This population plasticity is probably related to diversity of strategies across individuals, since results indicate 75% of them use a single area repeatedly over several years and show a high degree of intra-individual overlap. As the wintering areas used by the two species differ, so do the migratory flyways. Scopoli’s shearwaters reached the wintering areas following the coastline during the postnuptial migration, but entered into the pelagic areas of the North Atlantic during the prenuptial migration on their way back to the breeding colonies. This detour was more common in individuals wintering in the southern areas. Cory’s shearwaters showed more complex migratory patterns, but overall, their complete migratory flyways -looking at prenuptial and postnuptial migration together- drew an 8-shape loop across the Atlantic, taking advantage of the prevailing winds. In both species, the prenuptial migratory corridors were weaker and more spread than the postnuptial ones. Regarding the migratory phenology, the duration of wintering period was slightly longer for Scopoli’s shearwaters, while the breeding period was longer in the case of Cory’s shearwaters. The results provided by this monography, thanks to advances in remote tracking technologies, unveil key knowledge about year-round at-sea ecology of Cory’s and Scopoli’s shearwaters, including behavioural strategies adopted throughout the year and in different areas. The insights presented here are fundamental to better define its conservation status. Nowadays Cory’s and Scopoli’s shearwaters are probably among the best-known seabird species, primarily thanks to the intensive use of remote tracking. However, there are very few marine areas proposed for the conservation of these species so far, and the majority of them are related to areas used during breeding. At national scale, the results presented in this book support largely those areas identified by SEO/BirdLife as Marine IBAs in spain (Arcos et al., 2009), which were later on included in Natura2000 network by the Spanish Government (BOE, 2014). The results also reveal the great ubiquity of these species compared to other procellariforms for which marine IBAs have been identified, since Scopoli’s shearwaters use the entire Iberian and Balearic continental shelf, and Cory’s shearwaters use the African continental shelf, from southern Morocco to the north of Mauritania, to feed during the reproductive period. At the same time, however, some degree of spatial segregation tends to occur among birds from different colonies. Both aspects have strong implications for conservation. On one side, it is important to highlight that marine protected areas are useful to develop concrete site-specific conservation actions, but these local actions necessarily need to be complemented with more relaxed actions at regional or trans-boundary (both political and ecosystem) scales. On the other side, spatial segregation of foraging grounds among colonies may allow to link impacts at sea with population trends at each breeding colony. The information regarding wintering areas and migratory flyways is even more original, since it will allow proposing new marine IBAs on international waters, outside jurisdictional Spanish waters. In fact, BirdLife has already started this process worldwide as well as in several specific areas of the Atlantic (e.g. the Canary Current, the North Atlantic, Tristan da Cunha archipelago, etc.) for which the data used in this work are an important part of the main data set. Regarding interactions with human activities, the better knowledge of spatiotemporal patterns of these populations of Cory’s and Scopoli’s shearwaters will allow us to identify overlap with potentially negative disturbances and threats (such as fishing and longlining, oil spills, etc.), guiding the design and implementation of locally adapted management actions. Overall, this information can be extremely helpful to better identify and address main threats and implement conservation and management actions at-sea that guarantee the viability of the shearwater populations. The greatest upcoming challenge is that social and political stakeholders involved in seabird and marine conservation become willing to effectively incorporate these new generation tracking tools in the conservation programs and strategies.