Gannets were studied on the Bass Rock (Scotland) between 1960 and 1963, and particularly in a colour ringed group (the observation colony). The account is in two parts (general breeding biology and behaviour) which are amalgamated in this brief summary. The entire Gannet population of the Bass was estimated in June 1962 and a considerable increase over the 1949 population (last count) shown (about 4,800 pairs in 1949 to about 7,000 pairs in 1962, excluding 'club' birds). The increase in the observation colony was mapped in detail, for the period of the study. The mid-cliff regions of the Rock are the first to be re-populated each year. In the observation colony (and presumably in all areas) old pairs return before newer ones, and males before females. The maximum seasonal stay at the breeding Colony is from late January to early November. During this period both sexes actively defend the nest site by fierce fighting, where necessary, and a special aggressively-motivated 'ownership' display, bowing (analysed in detail). Sites are guarded continuously and males gather nest material throughout (females only after egg laying and for a much shorter period). Nest sites and mates are usually permanent, though females show less attachment to the site than do males (an attempt to separate the two effects is made). New sites (which may be on cliff ledges of various sizes or on flatted ground) are established only by males usually four years old (beginning in April) and are held a year before breeding is attempted. Birds tend to return to the same small area of the Colony from which they originated. Site establishment normally involves fighting (discussed in detail). Pair formation takes place only at the site; the male performs an advertising display - a modified form of bowing and females 'prospect' for such males. Males are conspicuously aggressive to females - especially in new pairs but also throughout life - and females show a high tolerance of male attack and an appeasement posture (facing-away) restricted to this situation. Males bite their mates whenever they meet on the site, and the pair then perform a prolonged 'friendly' meeting ceremony (mutual fencing). This, like male advertising, is a modified form of bowing. Laying begins late March or early April and continues (by first-time breeders) until late June or exception- ally the first half of July. Older females lay earlier and produce heavier eggs. Greater density also probably causes earlier and more closely synchronised laying. Incubation behaviour in both sexes was, in some cases, released by donated eggs, but others were refused close to the laying date of the pairs concerned. Males take slightly longer incubation stints than females. No two-egg clutches (except the product of different females) were found, though Gannets usually replace a lost egg in 6 - 32 days (first-time breeders significantly less often than experienced females). However two eggs are incubated as successfully as one. The incubation period, 43.6 days, is the same for new and experienced birds. Eggs lose 10 - 13% in weight during incubation (under- foot). Eggshells are not systematically removed. Hatching success for birds breeding at least the third time was 86% and for first-time breeders 62.5%. The nidicolous young may be fed immediately on hatching. Feeding, by incomplete regurgitation, continues for the entire pre-fledging period (no starvation period). The length of attendance spells drops sharply after hatching. Even during the phase of maximum chick growth, the pair spend some 15% of daylight hours together at the nest. The young reach a maximum of 150% of the adult weight. Starvation among chicks was never found during the study period. Juveniles leave the nest at about 90 days (both from new and experienced breeders). However the former lost more small chicks and had much lower overall success (49% of eggs laid gave fledged young in new pairs, 82% in experienced pairs). The growth of young was followed in detail. Parents do not discriminate in favour of their own young and will accept substitutes, probably at any stage in the chick's growth, and even when natural and foster chicks differ markedly in age. However adults repel wandering chicks and even attack unguarded ones. Furthermore, chicks normally stay strictly on their nests. These factors prevent doubling up. Artificially twinned nests revealed that if the chicks were of about the same age both survived and were adequately fed, though fledging at about 94 days and growing slightly slower than singles. A significant age difference (three or more days) however led to the persecution of the younger by the older and hence its starvation. Excluding such cases, pairs with twins gained an 80% reproductive advantage in 1962, the year of the experiment. The implications of the twinning results are discussed together with other factors (deferred maturity, non-breeding population, etc.) affecting recruitment rate. Return of colour ringed adults over the three years of the study gave a 6% annual adult mortality and thus a life expectancy of 16.2 years. Mortality between fledging and returning to breed is calculated to be about 80%. The ontogeny of behaviour in chicks is described. Juveniles show characteristic pre-leaving behaviour and fly well at the first attempt, though cannot rise for some days having alighted. They are not accompanied by parents and do not return to the nest. Adults tend to attack them on the sea. They may return to the breeding Colony in their first year, but do not normally do so until two or three years old. Immature plumage stages are described and illustrated. Body maintenance activity (preening, sleeping, plumage shaking, etc.) is described. Rotary head shaking is a response to peripheral tactile stimulation and occurs as a probable displacement reaction in some fear situations. The ordinary sideways head shake is shown to be a simple movement which has been incorporated into several complex displays and also occurs alone, in ritualised form, in at least one signal situation. Social behaviour away from the nesting site is discussed and contrasted (in complexity) with breeding behaviour. A special posture (sky-pointing) which precedes and accompanies movement away from the site is discussed here. Its comparative occurrence within the Sulidae is also discussed. Finally adaptations to cliff nesting in the Gannet and Kittiwake are compared. The two show many similarities, evolved convergently, but also several important differences (apart from those inevitably resulting from dissimilar phylogeny). The general discussion centres round the importance of the site and associated aggression in the Gannet's breeding biology.

Les oiseaux marins sont des espèces emblématiques. Passeuses de frontières, de la mer à la terre, de l’air à l’eau, des pays du nord au pays du sud, elles créent un lien entre les différents sociaux- écosystèmes marins de notre planète. Du fait de leur ubiquité, elles sont exposées à de nombreuses menaces autour du monde. Parmi elles, les interactions avec les pêcheries représentent la part de risque la plus importante pour ces espèces lorsqu’elles sont en mer. Leur statut de conservation en est affecté, et des actions prioritaires visant à réduire ces impacts doivent être mis en place. Ces espèces bénéficient de l’intérêt, voir de la sympathie des populations et le grand public est sensible au sort de leurs populations. Mettre en place des stratégies et des outils permettant la conservation des populations d’oiseaux marins répond donc à une demande sociétale urgente.Le fou de Bassan (Morus bassanus) est une espèce emblématique de la conservation des oiseaux marins en France métropolitaine. Au sein de la Réserve Naturelle Nationale de l’archipel des Sept-Îles, la seule colonie de reproduction Française de cette espèce bénéficie d’un statut de protection fort. Malgré cela, au cours de la dernière décennie, notre étude a mis en évidence une inversion de la dynamique de la population et une baisse du succès reproducteur. La mise en place d’un suivi bio-télémétrique nous a alors permis de chercher à comprendre et expliquer ces changements. Nous avons notamment mis en évidence, que durant la saison de reproduction, les fous des Sept-Îles souffraient de la diminution de leurs proies naturelles et se rabattaient alors sur des rejets de pêche. La consommation de ces subsides anthropiques affecte les efforts de recherche alimentaire, la condition des individus et finalement leur reproduction. De plus, nous avons montré que durant la période internuptiale, ils étaient exposés à de forts risques de captures accidentelles et à une diminution globale de leurs proies préférentielles, affectant les taux de retours à la colonie et expliquant potentiellement la baisse observée de la taille de la population.Ces travaux nous amènent à conclure que la bonne conservation des fous des Sept-Îles, comme celle de toute la mégafaune marine, ne pourra se faire qu’en adoptant une approche écosystémique des pêches. Particulièrement, le partage de certaines ressources entre prédateurs supérieurs et pêcheries devra être pris en compte dans la gestion des stocks, la diminution des rejets de pêche devra être favorisée et des aires marines protégées pélagiques excluant les activités de pêche, dessinées à partir des zones d’intérêt pour les oiseaux marins, devront être mise en place. / Seabirds are flagship species, boundary objects linking air and water, oceans and continents, Northern and Southern countries, binding a great variety of socio-ecosystems across the planet. Due to their ubiquity, they are exposed to numerous global threats. Among them, interactions with fisheries might be the main risk for seabirds at sea. The conservation status of seabirds is thereby affected, and priority actions due to reduce these impacts have to be established. Indeed, seabirds catch the attention of all stakeholders and of the general public, who are sensitive to the fate of their populations. Implementing tools and strategies allowing seabird conservation is therefore an urgent societal request. The Northern gannet (Morus bassanus) is emblematic of seabird conservation in metropolitan France, with a single breeding colony under strict protection within the Réserve Naturelle Nationale de l’archipel des Sept-Îles. Despite all conservation efforts, colony size and breeding success have been declining in recent years. A decadal biotelemetry study allowed us to test hypotheses linked to this decline. Notably, we showed that, during the breeding season, gannets shifted from feeding on natural prey, to taking fisheries waste. The consumption of these anthropogenic subsides affects foraging effort, adult body condition and reproductive output. Further, we showed that, during the inter-breeding period, gannets were exposed to enhanced bycatch risk and competition with fisheries for small pelagic fish. This had a strong impact on adult inter-annual return rates to the colony, potentially explaining the recent decline of the Sept-Îles gannetry. Overall, we conclude that an integrated conservation plan for Northern gannets, as well as for the marine megafauna in general, is only possible through ecosystem-based fisheries management. Specifically, the joint use of fish stocks by marine predators and fisheries should be taken into account by management schemes, at-sea dumping of fishery wastes should be reduced, and marine protected areas including true no-take zones should be designed, also by taking into account the spatial ecology of the marine megafauna such as seabirds.

Seabirds are wide-ranging apex-predators and useful bio-indicators of marine systems. Nevertheless, changes are occurring in the marine environment, and seabirds require protection from the deleterious effects of climate change, fisheries, pollution, offshore development, introduced predators and invasive species. The UK supports internationally important populations of seabirds but also has vast wind and wave resources, therefore understanding how seabirds use the marine environment is vital in order to quantify the potential consequences of further exploiting these resources. In this thesis I first describe the range of wave energy converting devices operational or in development in the UK, and review the potential threats and benefits these developments may have for marine birds. I then synthesise data from colony-based surveys with detailed information on population dynamics, foraging ecology and near-colony behaviour, to develop a projection model that identifies important at-sea areas for breeding seabirds. These models show a positive spatial correlation with one of the most intensive at-sea seabird survey datasets, and provide qualitatively similar findings to existing tracking data. This approach has the potential to identify overlap with offshore energy developments, and could be developed to suit a range of species or whole communities and provide a theoretical framework for the study of factors such as colony size regulation. The non-breeding period is a key element of the annual cycle of seabirds and conditions experienced during one season may carry-over to influence the next. Understanding behaviour throughout the annual cycle has implications for both ecological theory and conservation. Bio-logging can provide detailed information on movements away from breeding colonies, and the analysis of stable isotope ratios in body tissues can provide information on foraging during the non-breeding period. I combine these two approaches to describe the migration strategies of northern gannets Morus bassanus breeding at two colonies in the north-west Atlantic, revealing a high degree of both winter site fidelity and dietary consistency between years. These migratory strategies also have carry-over effects with consequences for both body condition and timing of arrival on the breeding grounds. Finally, I investigate the threats posed to seabirds and other marine predators during the non-breeding period by collating information on the distributions of five different species of apex predator wintering in the Northwest African upwelling region. I describe the threat of over-fishing and fisheries bycatch to marine vertebrates in this region, and highlight the need for pelagic marine protected areas to adequately protect migratory animals throughout the annual cycle. In summary, the combination of colony-based studies, bio-logging, stable isotope analysis and modelling techniques can provide a comprehensive understanding of the interactions between individuals and the marine environment over multiple spatial and temporal scales.

Thesis (Ph.D.) - University of St Andrews, May 2007.

Management and conservation of populations of animals requires information on where they are, why they are there, and where else they could be. These objectives are typically approached by collecting data on the animals’ use of space, relating these to prevailing environmental conditions and employing these relations to predict usage at other geographical regions. Technical advances in wildlife telemetry have accomplished manifold increases in the amount and quality of available data, creating the need for a statistical framework that can use them to make population-level inferences for habitat preference and space-use. This has been slow-in-coming because wildlife telemetry data are, by definition, spatio-temporally autocorrelated, unbalanced, presence-only observations of behaviorally complex animals, responding to a multitude of cross-correlated environmental variables. I review the evolution of techniques for the analysis of space-use and habitat preference, from simple hypothesis tests to modern modeling techniques and outline the essential features of a framework that emerges naturally from these foundations. Within this framework, I discuss eight challenges, inherent in the spatial analysis of telemetry data and, for each, I propose solutions that can work in tandem. Specifically, I propose a logistic, mixed-effects approach that uses generalized additive transformations of the environmental covariates and is fitted to a response data-set comprising the telemetry and simulated observations, under a case-control design. I apply this framework to non-trivial case-studies using data from satellite-tagged grey seals (Halichoerus grypus) foraging off the east and west coast of Scotland, and northern gannets (Morus Bassanus) from Bass Rock. I find that sea bottom depth and sediment type explain little of the variation in gannet usage, but grey seals from different regions strongly prefer coarse sediment types, the ideal burrowing habitat of sandeels, their preferred prey. The results also suggest that prey aggregation within the water column might be as important as horizontal heterogeneity. More importantly, I conclude that, despite the complex behavior of the study species, flexible empirical models can capture the environmental relationships that shape population distributions.