I examined habitat selection of middens within insect-damaged forest and compared home range and survival for Mt. Graham red squirrels (Tamiasciurus hudsonicus grahamensis) in insect-damaged and healthy forest. Squirrels used habitat in areas with < 69% tree mortality. Basal area, canopy cover, and log volume were greater at middens than random locations. Within midden sites, only greater basal area of live trees distinguished occupied sites from unoccupied sites. Surface temperature at occupied middens tended to be cooler than unoccupied middens. Squirrels living in insect-damaged forest had larger home ranges than in healthy forest. Squirrel body mass and reproductive condition did not differ between forest types, suggesting that insectdamaged forest provided adequate resources. However, squirrels inhabiting insectdamaged forest experienced lower survivorship and 50% fewer potential reproductive events than squirrels in healthy forest, implicating presence of an ecological trap. Preservation of remaining healthy forest is a priority for management of this endangered species.

The extensive alteration of global ecosystems, especially the changes caused by globalized and industrialized economic development activities over the last fifty years, have urged for a better understanding of the human-in-nature management system. Bangladesh, a densely populated developing country, is witnessing rapid environmental degradation while passing through different phases of industrial growth. Leather, one of the oldest industries in this country, provides a very positive picture in the country’s national economy and at the same time produces severe ecological and social crisis in a mutually reinforcing way. At first sight, it seems to fit the SES concept of social ecological trap. The previous scientific studies on ‘Hazaribagh’ leather processing unit in Bangladesh have investigated social, economic, ecological and stakeholder’s perspectives but did not address the pathway that has shaped the present situation. The objective of this case study was therefore to explore the reasons why change of this ‘Hazaribagh system’ has been impeded for so long and if the social-ecological trap concept could help to clarify the reasons for the chronic delay of the relocation of ‘Hazaribagh’ leather processing unit. This study has observed, through a historical investigation that a path dependent social ecological trap situation is persisting in the ‘Hazaribagh system’ where the economic opportunity is playing the role as a juncture between the phases of the process; and power mechanism and the disconnected SES has influenced and strengthened the claim. This study has also addressed some other underlying substantial social issues, which are influencing the process and might contribute to outline further research, and consequently provide insight to escape from the trap situation.

L’urbanisation des milieux est un phénomène croissant induisant des changements importants des habitats naturels auxquels doit faire face la biodiversité. Ces modifications rapides et profondes de l’environnement vont créer de nouvelles conditions potentiellement contraignantes pour les individus. En effet, le cocktail de paramètres artificiels (par exemple : lumière, bruit, pollution chimique) couplé à une présence humaine ainsi qu’une ressource alimentaire souvent modifiée et/ou peu disponible peuvent contraindre la survie et la reproduction des espèces ayant colonisées les milieux urbains. Par ailleurs, les modifications profondes des habitats urbains sont susceptibles d’amener les individus à mal décrypter les indices communément utilisés dans les milieux non perturbés conduisant ces derniers à des réponses maladaptatives, et les populations associées jusqu’à des situations de trappe écologique. C’est dans ce contexte que s’inscrivent ces travaux de thèse chez la Mésange charbonnière, Parus major. Ces oiseaux ont été suivis en reproduction dans des nichoirs placés sur des sites présentant des niveaux d’artificialisation variables, que nous avons quantifiés, au sein de la ville de Montpellier. La taille de la cavité de reproduction a été également manipulée expérimentalement (manipulation de l’indice). Nous avons pu observer une préférence pour les cavités les plus grandes ainsi qu’un investissement dans la ponte plus important mais un nombre de jeunes envolés plus faible relativement aux cavités de taille plus petite. Cette réponse maladaptative associée à la taille de la cavité nous a amené à nous questionner plus précisément sur le rôle des ressources alimentaires associées au milieu urbain et sur le potentiel adaptatif de nos oiseaux urbains. Les expériences menées, en lien avec les ressources alimentaires, ont mis en évidence qu’effectivement la ressource est un facteur clé contraignant la reproduction des mésanges urbaines. Par ailleurs, grâce à un dispositif forestier historique situé à une vingtaine de kilomètres de notre site d’étude urbain, nous avons testé la présence de deux écotypes urbains et ruraux. Nous avons pu mettre en évidence des différences de morphologies entre habitats, sans détecter pour autant de différence de condition physique. Pourtant, à l’échelle plus fine du gradient d’urbanisation, ces différences apparaissent. De plus, l’étude des personnalités des oiseaux a mis également en évidence un différentiel de personnalités inter-habitat mais aussi intra-habitat, qui soulève encore à l’heure actuelle des questions d’adaptation autour de ces phénotypes particuliers. Ces travaux soulignent la complexité des questions écologiques et évolutives dans les environnements fortement perturbés que sont les milieux urbains et nécessitent de continuer à approfondir nos connaissances afin d’apporter au mieux des solutions pour la gestion de la biodiversité urbaine. / Urbanization is an increasing phenomenon inducing dramatic modifications of natural habitats facing biodiversity. These rapid and drastic environmental changes create new conditions, potentially constraining individuals. Indeed, artificial parameters, such as light, noise and chemical pollution, coupled with human presence and food resources which are often modified and less available, should constrain survival and reproduction of urban species. Moreover, urban habitat changes could lead individuals to misinterpret natural environmental cues, inducing maladaptive responses and populations into an ecological trap. In this context, we developed this research project on great tits, Parus major to improve our understanding of avian adaptation in cities. We monitored great tit reproduction breeding in nest-boxes within an urbanization gradient, which has been quantified, in the city of Montpellier. We experimentally manipulated nesting-cavity size using different types of nest-boxes. We found that the birds preferred the largest artificial cavities for breeding when they could choose between small, medium-sized and large cavities. Individuals from the largest cavities also invested more in egg production, yet had a lower fledging success than those from medium-sized cavities. These results are an experimental demonstration of a trap mechanism in free-living animals. To test our hypothesis that food resources are an environmental key factor limiting reproductive performance in our urban great tit population, we conducted experiments modulating constraints on food resources. The conclusion of these experiments is that food is a limiting factor for reproduction. In addition, in a local adaptation framework, we examined if urban great tits possess particular phenotypic traits that differ from great tits that live in more natural conditions. We found that urban and rural great tits expressed differences in morphology and personality profiles both at the inter-habitat and intra-habitat level. Additional studies will be required to better understand the underlying mechanisms that link phenotypic and reproductive performance in individuals that face rapid environmental change and increased urbanization, also to improve biodiversity conservation programs in these environments.

Habitat fragmentation, and the resulting increase in edge habitat, has important effects on birds, including the increased probability of nest predation, changes in habitat structure, and the increased presence of non-native plant species. It is critical to understand the effects of fragmentation at all stages of the avian life cycle, including the often overlooked postfledging period. Because much of juvenile mortality occurs during the immediate postfledging period, and juvenile mortality contributes substantially to population dynamics, it is necessary to understand if fledgling survival is reduced in edge habitats and if fledglings' survival is influenced by their habitat use. During 2008 and 2009 I radio-tracked 52 fledgling Spotted Towhees (Pipilo maculatus) during the 30-day postfledging period in a 24-ha urban park near Portland, Oregon. Thirty-six fledglings (69%) survived the 27-day tracking period (an estimated 62.1% survived the entire 30-day postfledging period). At least 9 of 16 predation events were attributable to domestic cats (Felis domesticus) or Western Screech-owls (Megascops kennicottii). Although fledglings were more likely to be found near edges than the park interior, fledglings located closer to park edges had a higher probability of dying. However, I found that towhee nests were more likely to be found near edges, nests near edges produced more fledglings, and nestlings near edges were heavier. I used a STELLA-based stochastic model of nest success and fledgling survival to show that the benefits initially gained by nesting near edges were reversed during the postfledging period. The number of fledglings per nest that survived to the end of the 30-day postfledging period was significantly lower near edges than in the park interior. This apparent preference for nesting near edges, paired with higher fledgling mortality near edges, is consistent with the idea that edges are ecological traps. Fledgling habitat was significantly more structurally dense and had a greater abundance of non-native plant species, particularly Himalayan Blackberry (Rubus armeniacus), than nest habitat. Towhees avoided English Ivy (Hedera helix) for both nesting and care of fledglings. However, fledgling survival was not related to vegetation characteristics, which suggests that increased fledgling mortality near edges was a direct result of increased predator abundance or predation near edges, and was not an artifact of changes in habitat near edges. My results help to establish that fledgling survival and the unique habitat requirements of fledglings should be considered along with nest success and nest habitat when examining the effects of habitat fragmentation on bird populations. More broadly, this study has important implications for conservation, as it exemplifies how phenomena such as ecological traps created by anthropogenic changes in the environment can be overlooked if only one life history stage is studied.

Le comportement des thons tropicaux autour des objets flottants : De l'étude des comportements individuels et collectifs à l'étude du piège écologiqueLes recherches en halieutique ont pour objectif d'améliorer les connaissances sur le fonctionnement des populations de poissons afin de transférer celle-ci vers des outils de gestion. Ce travail de thèse repose sur un ensemble d'expériences et de modélisations destinées à approfondir notre compréhension générale du comportement associatif de poissons grands pélagiques avec des objets flottantes à la surface de l'océan. Notre objectif est de tester si les milliers d'objets flottants artificiels déployés par les pêcheurs (DCP - Dispositifs de Concentration de Poissons) constituent des pièges écologiques pour les thons tropicaux. Pour mener à bien ce travail, nous avons dans le premier chapitre caractérisé le comportement individuel de thons dans un réseau de DCP ancrés. L'analyse de données de marquage acoustique de 96 thons albacores (Thunnus albacares) (30-96 cm) à Hawaii montre que les thons présentent une plasticité comportementale forte face aux DCP qu'ils rencontrent mais également que le temps de résidence sous les DCP diminue avec la taille des individus. Afin de quantifier l'impact de l'augmentation de la densité de DCP il est essentiel de comprendre les mécanismes et les facteurs qui influencent les temps de résidences sous les DCP. Dans le second chapitre, des expériences de choix binaires suggèrent un rôle de la biomasse agrégée dans la formation, la maintenance et la dispersion des agrégations que forment les thons sous les objets flottants. La quantification de la dynamique des arrivées et des départs des poissons aux DCP permettra de valider les hypothèses que nous proposons concernant les mécanismes sociaux sous-jacents d'une part et d'autre part de tester l'influence de la qualité de l'environnement et de la densité de DCP sur les temps de résidences individuels et la distribution spatiale des populations. Dans le troisième chapitre, la comparaison de facteurs de condition de listaos (Katsuwonus pelamis) matures capturés en bancs libres et sous objets flottants dans une zone naturellement riche en objets flottants, et relativement peu impactée par le déploiement de DCP (Le Canal du Mozambique), nous a permis d'établir un point de référence essentiel pour estimer les effets des perturbations actuelles. Plus généralement, les résultats obtenus dans les différents chapitres tendent à conforter l'hypothèse d'un rôle social et non trophique des objets flottants dans l'écologie de thonidés. Les résultats obtenus durant cette thèse amènent à poser un regard nouveau sur l'hypothèse du piège écologique. Notre travail s'est principalement intéressé à un modèle biologique de choix, les thons tropicaux. Cependant le cadre théorique des questions abordées, les outils d'observations et les méthodes d'analyses développées sont assez génériques pour être appliqués aux autres espèces rencontrées sous les objets flottants. Cette recherche s'intègre plus généralement dans les problématiques visant à mieux comprendre les stratégies comportementales et la distribution des populations dans des environnements multi-sites. / Research in fisheries science aims at investigating the functioning of fish population with the objective of using this knowledge to propose sustainable management measures. This PhD thesis relies on a collection of experiments and modelling designed to further our knowledge on the aggregative behaviour of large pelagic fish with floating structures at the surface of the ocean. The overall objective is to test whether the thousands of man-made floating structures deployed by fishermen (also referred as Fish Aggregating Device –FAD) act as ecological traps for tropical tunas. To archive this main objective, it was first necessary to characterize the individual behaviour of tuna in a network of FAD. In the first chapter, the analysis of 96 acoustically tagged yellowfin tuna (Thunnus albacares) between 30-96 cm FL in the array of anchored FADs around Oahu (Hawaii, US) shows that individuals tuna exhibited behavioural plasticity while in the array and that behaviour around FAD is size dependent. In order to assess the impact of the increasing density of FAD, the major habitat modification, it is essential to understand the factors that influence the residence time at FADs. In the second chapter, binary choice experiments suggest that the aggregated biomass under the FAD play a role in the aggregative process. Nonetheless, quantification of arrival and departure dynamics of fish to FAD are required to validate the assumptions we proposed on the underlying social mechanism. Such model would, then, allow testing the effect of FAD density and environmental conditions on individual residence time and spatial distribution of population. In the third chapter, the comparison of skipjack tuna (Katsuwonus pelamis) condition between individual associated with logs and in free swimming schools in the Mozambique Channel, an area known to be naturally enriched with logs with few FADs, highlights the need for estimating reference points prior to assessing the impacts of anthropogenic modifications to habitats on animals.Combining the different chapters, our results tend to favour a social rather than a trophic role of floating objects in the ecology of tunas. More generally, we discuss what novel insight our results bring up on the ecological trap hypothesis. Tropical tunas represent an interesting model species on which we focused. However, the theoretical framework of the questions we addressed, the observation and analytical tools we developed are generic enough to be applied to the others species that are encountered around floating structures. In a broader extent, this work meets the general topic of studying behavioural strategies and distribution of population in multi-patch environment.

The Cerulean Warbler (Setophaga cerulea) is a mature forest obligate and one of the fastest declining songbird species in the United States. This decline may be related to a lack of disturbance within contemporary forests; however, the consequences of disturbance on the species have not been rigorously evaluated. Thus, we assessed multiple responses by Cerulean Warblers to a range of experimental forest disturbances across the core of their breeding range in the Appalachian Mountains. We quantified individual and population responses to these manipulations, and assessed the potential consequences of disturbance on the sexual signaling system. Male ceruleans were strongly attracted to intermediate and heavy disturbances at the stand scale. Despite attraction to disturbed habitats, nest success declined in these conditions, particularly in the highly productive Cumberland Mountains of northern Tennessee. Taken together, these opposing responses suggest that anthropogenically-disturbed forests may act as local ecological traps, but the impact of these local traps on the global population is dependent on several unestimated parameters. At a finer scale, selection for habitat features varied spatially. Males consistently selected for territories near canopy gaps and on productive slopes, but they displayed inconsistent territory selection in regards to tree diameter, basal area, overstory canopy cover, and canopy height. Females were more consistent in their selection of features within territories, selecting nest patches with large, well-spaced trees near disturbances. Floristically, female ceruleans consistently selected for sugar maples (Acer saccharum), white oaks (Quercus alba), and cucumber magnolias (Magnolia acuminata) as nest trees and they selected against red maples (A. rubrum) and red oaks (Q. rubra). Disturbances had little effect on male age structure, but males that occupied disturbed forest habitat were in better condition than those in undisturbed habitat. Parental behavior differed among disturbances, with birds in more highly disturbed habitats provisioning their young at greater rates, but bringing smaller food loads, potentially helping to explain the decrease in nest survival in disturbances. Finally, we found that male ceruleans displayed various plumage ornaments that signaled individual quality. However, the relationship between breast band width and body mass was contingent on habitat, and only existed in intermediate disturbances.

Lorsque des animaux montrent un choix préférentiel pour un habitat à effet puits, on dit alors qu’ils sont capturés par un piège écologique. La sélection de l’habitat est bénéfique dans les systèmes classiques de type source-puits, puisque les animaux vivant dans des habitats de haute qualité (natalité>mortalité), choisissent de migrer vers des habitats de faible qualité (natalité<mortalité), uniquement lorsqu’il n’y a pas suffisamment d’habitat de haute qualité disponible. A l’intérieur d’un habitat de type piège écologique le choix est dangereux, et peut conduire à l’extirpation rapide d’une espèce, puisque les animaux vivant dans des habitats de haute qualité choisissent de migrer vers des habitats de faible qualité, même lorsqu’il y a suffisamment d’habitat de haute qualité disponible. Les pièges écologiques ont lieu lorsque des changements naturels ou induits par l’homme se produisent rapidement et que des déterminants de la sélection de l’habitat qui étaient alors sélectionnés deviennent trompeurs, entraînant des choix d’habitats inadaptés de la part des animaux. Pour distinguer un habitat de type puits d’un piège écologique, des connaissances complémentaires sont nécessaires, sur la relation entre les préférences d’habitat et la qualité de l’habitat. Dans l’écosystème de Hwange, les lycaons semblent baser le choix d’habitat sur les déterminants écologiques améliorant la fitness. Ils ont une meilleure efficacité de chasse dans la zone tampon à l’extérieur du parc national de Hwange, une compétition moindre avec les lions et avec les hyènes, ainsi qu’un meilleur accès à des sites de terrier. En conséquence, à l’extérieur du parc national, les lycaons donnent naissance à des portées de chiots plus grandes. Cependant, la mortalité induite par l’homme, en raison de l’effet lisière, est si grande qu’elle excède la natalité. Néanmoins, du fait qu’ils sont incapables de juger avec justesse de la qualité de l’habitat, en intégrant la mortalité induite par l’homme, les lycaons font un choix d’habitat inadapté, et ils se déplacent vers le puits de mortalité, à l’extérieur de la sécurité de l’aire protégée. En d’autres mots, les lycaons de l’écosystème de Hwange sont capturés par le piège écologique, que constitue la zone tampon située à l’extérieur du parc national de Hwange. / When animals show a preferential choice for sink habitat they are said to have been caught in an ecological trap. Habitat choice behaviour is beneficial in classic source-sink systems, as animals living in high quality habitat (natality>mortality) only choose to migrate into low quality habitat (natality<mortality) when there is not enough high quality habitat available. Within an ecological trap habitat choice is detrimental and can lead to rapid extirpation of a species, as animals living in high quality habitat choose to migrate into low quality habitat even when there is enough high quality habitat available. Ecological traps occur when sudden natural or human induced changes cause formerly reliable settlement cues to be no longer associated with an adaptive outcome, causing animals to make a maladaptive habitat choice. To be able to distinguish a sink from an ecological trap additional knowledge of the relationship between habitat preference and habitat quality is required. Within the Hwange system African wild dogs seem to base their habitat choice on the right fitness enhancing ecological cues. They experience a higher hunting efficiency in the buffer zone outside Hwange National Park, less competition with lions and spotted hyenas and a better access to suitable den sites. As a result African wild dogs outside the National Park give birth to larger litters of pups. However, due to an ‘edge effect’, human induced mortality in the buffer zone is so high it exceeds natality. African wild dogs nevertheless make a maladaptive habitat choice and move into the mortality sink outside the safety of the protected area as they are unable to judge habitat quality accurately by taking this human induced mortality risk into account. In other words, African wild dogs in the Hwange system are caught in an ecological trap in the buffer zone outside Hwange National Park.

Presence of coastal aquaculture activities in marine landscapes is growing. However, there is insufficient knowledge on the subsequent ecological interactions between these activities and marine fish communities. The overall aim of this thesis was to evaluate the direct and indirect ecological effects of aquaculture activities on marine fish communities in Scotland. A combination of empirical and modelling approaches was employed to collect evidence of how aquaculture activities affect marine fish communities at the individual, population and ecosystem levels around coastal sea cages. The two fish farms evaluated in this research provided the wild fish sampled near the sea cages with a habitat rich in food resources which is reflected in an overall better biological condition. Results of the stomach content analysis indicated that mackerel (Scomber scombrus), whiting (Merlangius merlangus) and saithe (Pollachius virens) sampled near sea cages consumed wasted feed which was also reflected in their modified FA profiles. The overall effects of the two fish farms were more pronounced in young whiting and saithe than in mixed aged mackerel sampled near the sea cages. The phase space modelling approach indicated that the overall potential for fish farms to act at the extremes as either population sources (a habitat that is rich in resources and leads to an overall improved fitness) or ecological traps (a habitat that appears to be rich in resources but is not and leads to an overall poor fitness) are higher for juvenile whiting than for mackerel. Based on the empirical evidence and literature the two fish farms are more likely to be a population source for wild fishes. Using an ecosystem modelling approach indicated that fish farming impacts the food web in a sea loch via nutrient loading. Mussel farming relies on the natural food resources and has the potential to affect the food web in a sea loch via competing with zooplankton for resources which can affect higher trophic levels. The presence of both activities can balance the overall impact in a sea loch as compared to the impact induced if each of these activities were present on their own. Both activities have the potential do induce direct and indirect effects on the wild fish and the entire sea loch system. The results of this PhD identified several gaps in data and thus could be used to improve future sampling designs. It is important to evaluate the cumulative effect of the presence of aquaculture activities in terms of nutrient loading and physical structure in the environment. Using a combination of empirical and modelling approaches is recommended to gain further insight into the ecological impacts of aquaculture activities on wild fish communities. Results of this PhD study could lead to more informed decisions in managing the coastal aquaculture activities. Establishing coastal fish farms as aquatic sanctuaries can be of an advantage to increase fish production and conserve species that are endangered provided that no commercial and recreational fishing is allowed nearby. It would be useful to have long term monitoring of the fish stocks around the cages and if there is any production at the regional level. Additionally, information on behaviour, migration patterns should be collected to understand the impacts of aquaculture activities on fish stocks. From an aquaculture perspective, ecologically engineered fish farms in addition to careful site selection in new aquaculture developments may improve nutrient loading into the ecosystem.

Abstract In conservation biology, informed and sound management decisions depend on target specific information about the life history and demography of the endangered populations. I used long-term, individual-based life history data (breeding and capture-recapture data) to examine life-history and demography in order to assess population viability and management. My study systems consist of metapopulations of two endangered, long-distance migratory wader species breeding on Baltic coastal meadows, the Temminck’s stint (Calidris temminckii) and the Southern Dunlin (Calidris alpina schinzii), whose breeding habitats are mainly managed by livestock grazing. Demographic models indicated that both study populations were sinks, which persist through immigration due to low local recruitment insufficient to compensate for adult mortality or emigration. Philopatric Temminck’s stints had higher nest and apparent adult survival compared to immigrants. Consideration of dispersal status in population models resulted in the most realistic estimates of population growth and revealed a low demographic impact of immigrants. Immigrants had low return rates after reproductive failure, suggesting that the difference in apparent survival was partly caused by different breeding dispersal strategies. Thus, management actions improving reproduction, and thus site fidelity, should also influence viability. An artificial nest experiment indicated high trampling rates under recommended stocking rates on managed meadows. This was attributed to similar space use of nesting Dunlin and cattle. Cattle presence did not affect nest predation. Young Dunlin preferred intensively grazed low sward habitat over high sward habitat. Reproductive success was also higher in low sward habitat. However, nests in the preferred habitat had the highest risk of being trampled if not artificially protected. Thus, low sward habitat was found to work as an ecological trap if grazing was started too early in the breeding season. Due to the sink nature of the Dunlin population even small reductions in reproductive success caused by trampling were detrimental to long term viability. The results encourage continuation of the use of cattle grazing as a management tool, but also highlight the need for more detailed consideration of local grazing practices, especially when sketching management plans for endangered species. / Tiivistelmä Uhanalaisten lajien suojelussa tehokkaiden suojelutoimien suunnittelu edellyttää tietoa hoitokohteen elinkierron eri vaiheista ja niiden demografisesta merkityksestä. Käytän tutkimuksessani pitkäaikaisaineistoja (pesintä ja merkintä-takaisinpyynti) kuvatakseni tutkimuslajien demografiaa ja arvioidessani populaatioiden elinkykyä sekä hoitotoimia. Tutkimuskohteinani ovat lapinsirrin ja etelänsuosirrin, kahden uhanalaisen kahlaajan, Perämeren rantaniityillä pesivät metapopulaatiot. Näiden lajien elinympäristöjä hoidetaan pääosin laiduntamalla. Demografinen mallinnus osoitti molempien populaatioiden olevan nielupopulaatioita, joiden säilyminen on tulomuuton varassa sillä poikastuotto ei kompensoi aikuisten kuolleisuutta ja poismuuttoa. Tutkimusalueella syntyneiden ja sinne rekrytoituneiden lapinsirrien pesä- ja aikuissäilyvyydet olivat paremmat kuin tulomuuttajilla. Tämän huomioiminen populaatiomalleissa tuotti realistisimman kasvukertoimen arvion ja osoitti paikallisten rekryyttien olevan tulomuuttajia merkittävämpiä populaation kasvun kannalta. Pesinnässään onnistuneet tulomuuttajat palasivat seuraavina pesimäkausina epäonnistuneita todennäköisemmin. Paikallisilla rekryyteillä vastaavaa eroa ei havaittu. Ilmiö heijastellee tulomuuttajien muuttoalttiutta myöhemminkin ja voi kertoa erilaisista pesimädispersaalistrategioista. Lisääntymismenestyksen parantaminen voisi parantaa elinkykyä myös pienentämällä poismuuttoa. Tekopesäkokeen perusteella pesien tallausriski oli laidunnetuissa ympäristöissä korkea vaikka laidunnuspaine noudatteli hoitosuosituksia. Tämä johtunee ainakin osin laskennallista korkeammasta todellisesta laidunpaineesta, mikä puolestaan johtui lintujen ja karjan yhtäläisestä tilankäytöstä. Rekrytoituvat suosirrit suosivat voimakkaasti laidunnettuja matalakasvuisia niittyjä, joissa poikastuotto oli parempi kuin, laiduntamattomilla niityillä. Toisaalta, tallausriski on voimakkaasti laidunnetuilla niityillä suuri ja jo pienetkin pesätappiot uhkaavat suosirripopulaation elinkykyä. Täten laitumet voivat toimia ns. ekologisina loukkuina, jos laidunnus aloitetaan liian aikaisin suhteessa pesintään. Laidunnus on kuitenkin suositeltava hoitomuoto, sillä se näyttää tuottavan parhaita pesimäympäristöjä etelänsuosirrille. Tulosten mukaan laidunnuksen ajoitusta, laajuutta ja laidunnuspainetta on muokattava kohdekohtaisesti, jotta saavutetaan paras tulos uhanalaisten lajien suojelun kannalta.

Urbanization involves the conversion of natural areas to impervious surfaces, which can lead to an increase in the frequency and severity of flood events in cities. To mitigate flood risk, stormwater ponds are constructed to manage urban runoff. Stormwater ponds can also be colonized by wildlife, but their suitability as habitat is disputed due to potential toxicological risks. This study assessed the suitability of stormwater ponds as habitat for the bioindicators Odonata (dragonflies and damselflies) and determined environmental factors that impact their community structure. Odonata (adults, nymphs and exuviae) were sampled at 41 stormwater ponds and 10 natural reference ponds across the National Capital Region of Canada, with a subset of ponds sampled over four years (2015-2018). Plant communities, water quality and surrounding land cover were analyzed at each pond to determine their impacts on Odonata community structure. Overall, stormwater ponds had lower Odonata abundance and a greater variation in species richness and community structure compared to natural ponds but had comparable dragonfly reproduction rates. Plants were the most significant driver of Odonata communities, as stormwater ponds with a high richness of native wetland plants had higher Odonata abundance and community structures similar to natural ponds. Water quality was the second most important driver of Odonata communities with dragonflies showing greater sensitivity to urban contaminants than damselflies. While stormwater ponds had higher concentrations of trace elements than natural ponds (e.g. Ni, V, As), concentrations were generally below toxic levels for all elements except copper and chloride, the latter likely an input from winter road salting. Surrounding land cover was the least important factor affecting Odonata communities. In conclusion, this research demonstrated the importance of local-scale factors related to plants and water quality in sustaining Odonata communities and specifies recommendations for stormwater pond design and maintenance that enhance urban biodiversity.