Unregulated North Swedish rivers show large seasonal variations in their physical characteristics. During winter the whole littoral zone freezes solid, and in spring the water flow increases rapidly and the same areas become flooded. The two mayflies Parameletus chelifer and P. minor are common in the North Swedish river Vindelälven. They probably pass through a dormant egg stage in its mid-stream section. The first tiny nymphs appeared in January to March, but they did not become abundant until the ice broke up in May. At this time they migrated rapidly to the flooded upper littoral, some continuing into the tributaries. During  the migration phase, both species used chemoreception to orient themselves towards the flooded areas. The shoreward migration allowed the nymphs to avoid high current velocity, and to utilize unexploited food resources. The two species differed with respect to utilization of the upper littoral. Most Parameletus chelifer nymphs colo­nized a seasonal stream, while the P. minor nymphs were equally abundant at the river margin as in a seasonal stream. Both temperature and food quality differed between the river margin and the seasonal stream. Compared to P. minor specimens, those of Parameletus chelifer showed a somewhat higher optimum tempe­rature, and they gained advantage of the higher food quality observed in the seasonal stream. Parameletus chelifer specimens colonizing a seasonal stream had higher growth rate, higher fecundity, and probably also advanced emergence as well as larger adult size compared with those remaining at the river margin. In addition mortality from fish predation may be lowered by utilizing shallow seasonal streams. Specimens of P. minor had higher growth rate, larger adult size and advanced emergence in the seasonal stream compared with those at the river margin. Nevertheless, fecundity was equal in both habitats and the mortality caused by predation seemed almost similar in both habitats. In most years Parameletus chelifer specimens utilizing the seasonal stream thus obtain a higher fitness than those utilizing the river margin. In P. minor this diffe­rence was not so pronounced. However, due to mortality risks caused by an early desiccation of the seasonal stream, the long-term reproductive output of the two species probably varies irregularly in the two habitats. / digitalisering@umu

Abstract Parasites are an inseparable part of the life of wild birds. They may cause morbidity, mortality or reduction in fecundity. Parasite distribution in hosts is typically not uniform and many host factors (e.g. age) may affect the pattern of distribution. Under certain conditions, parasites even have the potential to regulate the host population. The grouse species of Finnish forests — the capercaillie Tetrao urogallus , the black grouse Lyrurus tetrix and the hazel grouse Tetrastes bonasia — harbour several species of intestinal helminth parasites. The populations have fluctuated in cyclic manner but the mechanisms behind the cycles are largely unknown. I studied the interactions of forest grouse and their intestinal helminth parasites by using intestinal samples collected by hunters in five game management districts during eight years (1995–2002). The most common parasite species in the samples was the nematode Ascaridia compar. Also, three species of cestodes (Skrjabinia cesticillus, Paroniella urogalli and Hymenolepis sp.) were found. Large size, male gender and age over 1 year were connected with an increased probability and intensity of A. compar infection. Juvenile grouse were commonly infected with cestodes while in adults infections were quite rare. The influence of inbreeding on the susceptibility to parasite infections was studied in the capercaillie by analysing microsatellite heterozygosity. The less heterozygous birds were more likely to be infected with A. compar and were more intensely infected suggesting negative influence of inbreeding on parasite resistance. An indirect negative effect of parasites was found by comparing bags hunted with a trained dog or without a dog. Grouse infected by cestodes were significantly more common in the dog-assisted bag. Thus, cestode infection seemed to make grouse more vulnerable to canine predation. The interaction between grouse population dynamics and parasites was studied by analyzing the grouse densities obtained from annual wildlife counts and parasite indices. A. compar was most common and most abundant in the years of grouse population decline. The grouse population growth rate was negatively correlated with the annual mean abundance of A. compar. Relative survival but not breeding success decreased as the abundance of A. compar increased. The findings suggest that A. compar influences the dynamics of Finnish grouse even though regular cyclic dynamics are no longer evident. / Tiivistelmä Loiset kuuluvat erottamattomana osana luonnonvaraisten lintujen elämään. Ne voivat aiheuttaa sairautta, kuolleisuutta tai hedelmällisyyden alentumista. Tyypillisesti loiset ovat levinneet isäntäpopulaatioon epätasaisesti ja monet isännän ominaisuudet (esim. ikä) vaikuttavat levinneisyyteen. Tietyissä oloissa loiset voivat jopa säädellä isäntäpopulaatiotaan. Suomalaiset metsäkanalinnut — metso Tetrao urogallus, teeri Lyrurus tetrix ja pyy Tetrastes bonasia — ovat useiden suolistoloismatolajien isäntiä. Metsäkanapopulaatiot ovat vaihdelleet syklisesti, mutta syklejä aiheuttavat mekanismit ovat yhä tuntemattomia. Tutkin metsäkanalintujen ja niiden suolistoloisten välisiä vuorovaikutuksia käyttäen metsästäjien vuosina 1995–2002 viidestä eri riistanhoitopiiristä keräämiä suolistonäytteitä. Yleisin loislaji näytteissä oli kanalintusuolinkainen, Ascaridia compar. Myös kolme heisimatolajia (Skrjabinia cesticillus, Paroniella urogalli ja Hymenolepis sp.) todettiin. Suuri koko, koirassukupuoli ja yli yhden vuoden ikä olivat yhteydessä suurempaan kanalintusuolinkaistartunnan todennäköisyyteen ja voimakkuuteen. Nuorilla (alle 1 v.) linnuilla heisimadot olivat yleisiä, kun taas aikuisilla tartunnat olivat varsin harvinaisia. Sisäsiittoisuuden vaikutusta loistartuntaherkkyyteen tutkittiin metsolla mikrosatelliittiheterotsygotian perusteella. Vähemmän heterotsygoottiset metsot olivat todennäköisemmin ja voimakkaammin suolinkaisten infektoimia, mikä viittaa sisäsiittoisuuden negatiiviseen vaikutukseen loisten vastustuskykyyn. Loisten epäsuora haitallinen vaikutus havaittiin, kun verrattiin koiran kanssa ja ilman koiraa metsästettyä lintusaalista. Heisimadot olivat selvästi yleisempiä linnuilla, jotka oli metsästetty koiran kanssa kuin ilman koiraa metsästetyillä. Heisimatotartunta näytti siis altistavan metsäkanoja koiraeläinten saalistukselle. Metsäkanalintu- ja loispopulaatioiden välistä vuorovaikutusta tutkittiin analysoimalla vuosittaisia metsäkanatiheyksiä ja loisten runsautta. Kanalintusuolinkainen oli yleisimmillään ja runsaimmillaan metsäkanatiheyden laskuvuosina. Metsäkanapopulaation vuosittainen kasvuvauhti korreloi negatiivisesti kanalintusuolinkaisen vuosittaisen runsauden kanssa. Suhteellinen elossasäilyvyys laski kanalintusuolinkaisen runsauden lisääntyessä, mutta lisääntymistuloksen suhteen ei ollut samaa ilmiötä. Löydökset viittaavat siihen, että kanalintusuolinkaisella on vaikutusta suomalaisten metsäkanalintukantojen vaihteluihin, vaikka syklisiä kannanvaihteluja ei enää havaitakaan.

Please read the abstract in the section 08summary of this document / Thesis (PhD (Zoology))--University of Pretoria, 2007. / Zoology and Entomology / unrestricted

La compréhension et la gestion des écosystèmes requièrent un maximum de connaissances sur les dynamiques de populations. Depuis 2007, la taille de la sardine (Sardina pilchardus) et de l’anchois (Engraulis encrasicolus) dans le Golfe du Lion a chuté tandis qu’au même moment, la population de sprat, qui a une faible valeur commerciale, a fortement augmenté. Les très forts enjeux économiques autour de ces espèces ont conduit au projet de recherche « EcoPelGol » dans lequel se situe cette étude portant sur les changements observés. La condition corporelle, la croissance ainsi que la structure en âge et en taille des sardines, des anchois et en partie des sprats ont été analysées sur les vingt dernières années. Alors qu’en 2005-2007, la situation semblait optimale pour les anchois et les sardines (taille et condition élevées), celle-ci s’est considérablement dégradée depuis 2008, l’anchois et la sardine étant significativement plus petits et plus maigres. De plus, une diminution de l’âge et de la croissance a été observée chez la sardine. Nous avons ensuite caractérisé les fluctuations des débarquements historiques (1865-2013) de l’anchois, de la sardine et du maquereau. La chute récente des débarquements a été mise en exergue, avec une situation inédite où la sardine est actuellement moins débarquée qu’avant les années 60, date à laquelle les débarquements ont fortement augmenté suite à un accroissement conséquent de l’effort de pêche. Bien que la majorité de la variance dans les séries de débarquements semble être engendré par les changements de l’effort de pêche, nous avons également observé une relation entre les débarquements et l’indice « Atlantic Multidecadal Oscillation » pour l’anchois et la sardine et avec le « Western Mediterranean Oscillation » pour l'anchois. Dans une troisième analyse, la pression de prédation du thon rouge sur l’anchois, la sardine et le sprat a été estimée pour voir si l’accroissement de la population du thon depuis 2007 lié à de nouvelle mesures de gestion a pu impacté les poissons petits pélagiques. Mais bien que la sardine et l’anchois soient les proies principales du thon, moins de 2% de leurs populations ont été consommés chaque année entre 2011-2013, et ce, sans sélectivité sur la taille de ces proies de la part du thon. Ainsi, le thon rouge n’a pas pu avoir un impact significatif sur la structure en taille ou les abondances des petits pélagiques. Dans le chapitre final, nous avons considéré la possible influence de pathogènes. Des analyses globales dirigées vers la détection des parasites, des bactéries et des virus ont été effectuées tout au long de l’année et ont révélées la présence ponctuelle et relativement faible de bactéries des genres Tenacibaculum et Vibrio et celle systématique de microparasites. Malgré l’impossibilité d’exclure leur pathogénicité, aucune lésion tissulaire n’a été attribuée à ces organismes, réduisant fortement la probabilité d’une épizootie. Nos travaux indiquent que les mécanismes « top-down », des pathogènes ou encore la pêche ne sont probablement pas les facteurs clés pour expliquer les changements observés chez les poissons petites pélagiques. À l'opposé, certains paramètres environnementaux ont expliqué une partie de la variabilité dans la condition corporelle des poissons et leurs débarquements. Nous concluons donc qu’un contrôle « bottom-up », et particulièrement un changement dans la quantité et/ou qualité du zooplancton, peut être la cause des phénomènes dans les populations des poissons petits pélagiques. Si cette thèse permet une avancée dans la compréhension de leur dynamique, des analyses complémentaires seront nécessaires pour confirmer notre hypothèse principale et pour estimer l’influence des autres facteurs agissant potentiellement en synergie. / Knowledge on population dynamics is key to the improvement of management and the understanding of ecosystem functioning. Since 2007, the size of sardine (Sardina pilchardus) and anchovy (Engraulis encrasicolus) in the Gulf of Lions (NW Mediterranean) has severely decreased, which has strongly affected the fisheries. Simultaneously, the commercially uninteresting sprat population increased remarkably. As the economic and ecological stakes are high, the EcoPelGol project of which this PhD is part was established. We first analysed the sardine, anchovy and (partially) sprat population for changes in body condition, growth and size and age structure over the last 20 years. We concluded that sardine and anchovy have had from 2008 onwards a distinctively poor body condition and size, and that sardine have also showed a concurrent decrease in age and growth. In contrast, both species were in optimal and average “health” during 2005-2007 and 1992-2004, respectively. Subsequently, historical landings of sardine, anchovy and mackerel were considered (1865-2013), of which the fluctuations were characterised and statistically related to environmental variables. The recent dramatic landings decrease was put into perspective, as for example sardine is now for the first time landed less than before the 1960s, when a big probably effort-related upsurge occurred. Despite most of the variability being explained by what looks like changes in fishing effort, a link was found between the sardine and anchovy landings and the Atlantic Multidecadal Oscillation and the anchovy landings and the Western Mediterranean Oscillation. Next, as a management associated bluefin tuna increase also happened since 2007, its predation pressure on all three small pelagic species was estimated. We concluded that although sardine and anchovy are bluefin tuna’s main prey items, less than 2% of each population (including sprat) was consumed annually during 2011-2013 and that there was no clear size selectivity. Thus, tuna could not have had a noticeable impact on the population abundance or size structure of the small pelagics. In the last chapter, an epizootic disease was considered. An all-embracing approach directed towards the all-year round detection of both general and specific parasites, bacteria and viruses revealed the mostly temporal and not necessarily high occurrence of only three groups: microparasites, Vibrio spp. (sometimes determined as Vibrio alginolyticus) and bacteria of the genus Tenacibaculum. Although we could not exclude their pathogenicity, significant tissue damage at a cellular or macroscopic level was never observed, making the disease hypothesis less likely. Thus, we considered several hypotheses and indicated that top-down control (through Bluefin tuna predation), pathogens and fisheries are unlikely to be main drivers. In contrast, some environmental parameters explained a part of the variability in fish condition and landings. After a final discussion on all probable theories we concluded that a bottom-up control, such as especially a planktonic change in quantity and/or quality, might be on the basis of the observed changes. Although this work is a great step towards the understanding of the small pelagic dynamics in the Gulf of Lions, further investigations will still be needed to confirm our main hypothesis and to estimate the potential synergetic effect of other drivers.

Les invasions biologiques produisent des assemblages d'espèces souvent inédits et sources de nouvelles interactions spécifiques. L'impact écologique d'une invasion peut être : (i) indirect si l'espèce envahissante entre en compétition avec une ou des espèces résidentes, et (ii) direct si l'espèce envahissante consomme ou parasite une ou des espèces résidentes. Ces deux types d'impacts sont susceptibles de s'appliquer aux insectes envahissants du genre Megastigmus (Hymenoptera: Torymidae), qui exploitent généralement une niche étroite partagée avec d'autres espèces résidentes, et contribuent à d'importantes mortalités dans les populations d'hôtes du fait de leur spécialisation sur les graines. L'objectif de cette thèse est de tester ces prédictions à travers l'étude de l'impact de l'invasion en France de Megastigmus schimitscheki sur : (i) M. pinsapinis, un compétiteur résident, et (ii) les populations en expansion de son hôte obligatoire, le cèdre de l'Atlas (Cedrus atlantica).Un suivi spatio-temporel des populations françaises de Megastigmus spp. révèle que l'expansion rapide de M. schimitscheki est associée à un déclin important de M. pinsapinis. Un modèle mécaniste et statistique a été développé afin de déterminer la contribution relative de la variabilité temporelle de la disponibilité en graines et des divergences de traits d'histoire de vie dans la dynamique de coexistence-exclusion de M. schimitscheki et M. pinsapinis. Nos résultats montrent que la phénologie plus précoce de M. schimitscheki est le principal facteur déterminant le succès de l'invasion de M. schimitscheki et l'exclusion compétitive de M. pinsapinis dans les zones de sympatrie des deux espèces.Nous avons développé une approche théorique de l'impact indirect de M. schimitscheki sur C. atlantica basée sur les modèles de réaction-diffusion. Nos résultats montrent qu'un effet Allee résultant de la prédation des graines sur un front d'expansion peut accroître la contribution des hôtes situés à l'arrière de ce front au pool génétique de la population. Ce phénomène a pour conséquence de freiner l'érosion de la diversité génétique au cours du processus de colonisation.Les approches expérimentales et théoriques développées au cours de cette thèse montrent que l'invasion de M. schimitscheki a un impact indirect négatif sur la démographie d'une espèce résidente occupant la même niche écologique, alors qu'elle pourrait favoriser directement le maintien de la diversité génétique des populations d'hôtes en pleine dynamique de régénération naturelle. / Biological invasions produce novel species assemblages in communities that likely result in novel interspecific interactions. Ecological impacts of invasions may be: (i) indirect, if the invader enters competition with resident species, and (ii) indirect if the invader is a predator or a parasite of resident species. Both indirect and direct ecological invasion impacts are likely to apply to invasive wasps of the Megastigmus genus (Hymenoptera: Torymidae), which exploit narrow ecological niches that overlap with those of resident insect species, and contribute to high mortality levels in host plant populations due to their high specialization on seeds. This thesis aimed at testing such predictions by studying the impacts of the invasion of M. schimitscheki on: (i) its resident competitor for the seed resource M. pinsapinis, and (ii) the expanding populations of its obligatory host the Atlas cedar (Cedrus atlantica) in southeastern France.An extensive spatio-temporal survey of Megastigmus spp. populations indicated that the rapid expansion of M. schimitscheki was associated with a strong decline of M. pinsapinis. A mechanistic-statistical modelling approach allowed us to show that an earlier phenology of M. schimitscheki had a stronger explanatory power of both invasion success and the competitive exclusion of the resident than temporal variation in resource supply.A theoretical approach of the indirect impact of M. schimitscheki on C. atlantica expansion dynamics was based on reaction-diffusion models. We showed that an Allee effect resulting from seed predation at the expansion front of a host population may increase the genetic contribution of host individuals situated in the bulk of the expansion front. Interestingly, this phenomenon results in a limited erosion of genetic diversity during the expansion phase of the host population.The empirical and theoretical approaches developed showed that the invasion of M. schimitscheki in French cedar forests had a strong and negative indirect impact on the demography of a resident species, but, parallely, such invasion may directly favour the maintenance of genetic diversity in expanding host plant populations.

A travers l'exemple du lièvre d'Europe (Lepus europaeus), l'objectif de cette thèse est de contribuer à une meilleure compréhension des mécanismes régissant les variations d'abondance observées dans les populations animales. Dans ce cadre la dispersion est pressentie comme l'une des principales sources de variation. Après avoir rappelé les principales notions théoriques nécessaires à l'appréhension de ce travail et décrit brièvement l'intérêt du modèle d'étude, nous abordons la problématique sous deux angles différents mais néanmoins complémentaires. Le 1èr est dédié à l'identification des facteurs promouvant les départs et favorisant l'installation des dispersants. L'âge, le sexe et la densité de congénères apparaissent comme les principales variables influentes. Le 2nd angle a pour objectif d'identifier les variables pouvant moduler le succès de la dispersion. Bien qu'induisant des départs supplémentaires, la chasse apparait comme facteur déterminant dans l'échec de la dispersion en augmentant les risques de mortalité pendant le transit. Aussi, la densité dans le site de départ est proposée comme variable diminuant la qualité phénotypique des dispersants. L'ensemble de ces résultats souligne l'importance des conditions environnementales rencontrées au moment du départ, pendant le transit et à l'installation dans la réussite de la dispersion. L'action combinée de la chasse et de la densité sur la dispersion est proposée comme mécanisme probable à l'origine des fluctuations d'abondance observées sur le court terme chez le lièvre d'Europe / Through the example of the European hare (Lepus europaeus), the aim of this work is to contribute to a better understanding of the mechanisms underlying the fluctuation of abundances in animal populations. In this context, dispersal may be seen as the main source of variation. After reminding the theoretical concepts needed to understand this work and briefly describing the interest of the model, we address the topic in two different but complementary approaches. The 1st one is dedicated to the identification of the factors that promote departures and favor settlement of dispersers. Age, sex and density appear to be the main explanatory variables. The 2nd approach is designed to identify the factors that modulate the success of dispersal. Although inducing supplementary emigrants, hunting appears as an important factor decreasing the success of dispersal by increasing the mortality risk during transience. In addition, density in the original site is proposed as one potential factor decreasing the phenotypic quality of dispersers. Overall, these results emphasize the importance of the environmental conditions encountered at the time of departure, during transience and settlement in the dispersal success. The combined action of hunting and density on dispersal is proposed as one potential cause for the short term fluctuations of abundances in the European hare

An appreciation of the role of mutualism is essential when studying ecology and evolution in most ecosystems. Information covering aspects of mutualistic interactions can serve as a complement to the somewhat one-sided perspective from the 1950’s and 60’s that is used when teaching biology. In this thesis I applied an in-depth approach in which variation in the interspecific interaction between Aphis fabae aphids and Lasius niger ants was studied both in the field and in the laboratory. An emphasis was put on studies spanning several consecutive aphid generations. This approach revealed important differences between ant tended aphids and those without ants. In the lab, I found an initial decrease in aphid adult size and reproductive investment in the first generations after the start of ant tending, which was followed by a recovery to the pre-tending situation after about four generations. Another laboratory experiment showed an increase in alate (winged aphid) production from exposure to aphid alarm pheromones, and an even stronger decrease in alate production from ant attendance, suggesting that ants have gained the upper hand in an evolutionary conflict over aphid dispersal. Results from a field experiment further emphasized the possibility of negative effects of ants on aphids, showing that ant-tended aphid colonies experienced a higher rate of parasitoid attacks, produced fewer alates and embryos in adult aphids. The thesis highlights the scope for variation in the net effect of the interaction for aphids, and argues that, depending on the environmental circumstances, the interaction may sometimes and perhaps even often not really be a case of mutualism. / <p>At the time of the doctoral defense, the following paper was unpublished and had a status as follows: Paper 4: Manuscript.</p>

This article examines a pattern of inter-community parties in a contemporary indigenous group, the Wari’ of Rondônia, Brazil. In rituals structured around acts and symbols of transgression, punishment, predation and death, Wari’ negotiate their relations with allies and potential allies. In a "fractal" pattern of sociality, this ritual encounter is replicated at other levels, in human relations with the spirit world, the world of ancestors and animals. These rituals are a key mediator of social reproduction (in relations among Wari’ communities) and biological reproduction (in relations with the spiritual forces that control aspects of subsistence and human death). Holding in tension simultaneous possibilities for cooperation and opposition, this framework for inter-group relations conceived as symbolic rivalry and voluntary reciprocal predation allows communities to cultivate and terminate political affiliations and commitments in response to changing circumstances. These ritual encounters play an important role in exchanges of information, and in defining and maintaining networks of flexible alliances and the possibility of mobility, which in the past helped Wari’ cope with historical pressures of inter-ethnic violence and epidemics. / El presente artículo analiza un patrón de fiestas intercomunidades en el caso de un grupo nativo contemporáneo: los wari’ de Rondônia, Brasil. Los wari’ manejan sus relaciones con aliados y potenciales aliados en rituales estructurados alrededor de actos y símbolos de trasgresión, castigo, depredación y muerte. En un patrón social "fractal" —es decir, un patrón con una estructura básica que se repite en diferentes escalas— estos encuentros rituales intercomunidades son llevados a otras dimensiones en las relaciones humanas con el mundo espiritual, el mundo de los antepasados y los animales. Estos rituales constituyen un mediador clave de la reproducción social para el caso de las relaciones tradicionales entre las comunidades wari’ y de la reproducción biológica en las relaciones con las fuerzas espirituales que controlan la subsistencia y la mortalidad. Si las posibilidades simultáneas de cooperación y oposición se mantienen en tensión dinámica, este marco de relaciones intergrupales, concebidas como de rivalidad simbólica y "depredación" recíproca voluntaria, permite a las comunidades cultivar o poner fin, según sea el caso, las filiaciones políticas y de compromiso en respuesta a circunstancias cambiantes. Estos encuentros rituales tienen un papel importante en los intercambios de información y la definición y mantenimiento de las redes de afiliaciones o alianzas caracterizadas por su flexibilidad y la posibilidad de movilidad que, en el pasado, permitieron que los wari’ sobrellevaran las presiones históricas de violencia interétnica y las epidemias.

Piscivorous birds are an integrated part of lake and coastline ecosystems. Despite decades of research it is yet unclear what influence fish eating birds have on the fish community. The aim of this literature study was to focus on how two fish eating birds, Great Cormorant and Great Crested Grebe, influence the fish community in shallow and eutrophic lakes. Different types of analysis methods have been used when doing research on the subject, including pellet analysis, stomach content analysis, tagging of fishes by “PIT”-techniques and analysis by observation. Results show that conclusions by studies tend to vary, but generally higher bird density, lower water temperature and a relatively high turbidity contribute to a higher influence on the fish community. Both bird species are opportunistic in their choice of food and catch prey of the species that occur locally. Both species also limit themselves in the prey size, but the choice vary over seasons because of water temperature and the birds requirements in association with breeding and migration. The significant level of influence seems to be when predation is conducted on younger and smaller fishes. The influence on the fish size can also be indirect, where predation on smaller individuals prevent fishes from becoming older and bigger. As studies tend to deviate in conclusion, no general answer to this issue can be given at present. Comprehensive research with several years of full control over both fish-and bird population is needed to find the proper conclusion.

Short breeding period and harsh climatic conditions are major limiting factors to which birds have to adapt in northern tundra regions. Despite this fact, dozen species of birds annually migrate into these regions to increase their chances to breed successfully. My diploma thesis focuses on incubation behaviour of the Arctic tern (Sterna paradisaea). The research for my thesis took place on the Norwegian archipelago Svalbard, in two particular locations: Adolfbukta and Longyearbyen. By using the method of continuous video recording, I described incubation behaviour of this specie in detail. Human activity is very different on each of Adolfbukta and Longyearbyen. On site Adolfbukta study was conducted during seasons 2012 and 2014, both with different predation pressure. Having known that, I could evaluate the impact of human activity as well as the impact of different predation pressure on incubation behaviour and breeding ecology of Arctic tern. The presence of human close to the colony had significant effect on incubation behaviour. Due to higher disturbances, incubating birds tended to leave their nests more often, attention paid to the nest was smaller and calm incubation (sleeping on the nest) was shorter by a half. Human activity had no effect on other displays such as average clutch size or...