acase@tulane.edu / Animal movements shape individual fitness and population-level trends, and current work seeks to improve our understanding of movement in natural systems at a variety of observational scales. Individuals are assumed to move in ways that maximize fitness, but the environmental and ecological conditions that they experience often divert them from optimal outcomes. Describing the ways in which behaviors are adjusted in response to these dynamic conditions offers insights ranging from individual-level fitness outcomes to broader patterns of gene flow across species’ ranges. In this dissertation, I utilize genetic data, individual animal tracking, and species distribution modeling to examine the movement and foraging ecology of the brown pelican (Pelecanus occidentalis), a top predator in the northern Gulf of Mexico, a highly dynamic environment impacted by human activities, seasonal change, and other more punctuated disturbances. With these approaches, I characterize regional, individual, and population-level patterns of movement in relation to environmental change as well as individual energetic demands. My findings provide a more comprehensive understanding of pelican behavioral ecology, and demonstrate the degree to which novel methodologies can be leveraged to further a broader understanding of animal movement in dynamic natural systems. / 1 / Brock Geary

Island nesting seabirds are the most threatened group of avian fauna and are particularly vulnerable to habitat disturbance. The white-eyed gull nests exclusively on islands in the Red Sea and Gulf of Aden, many of which are facing anthropogenic pressure. The Al Wajh archipelago in the northern Red Sea hosts the largest population of the white-eyed gulls in Saudi Arabia and is currently undergoing tourism development for one of the country’s largest ongoing “Gigaprojects”. The habitat preferences and movement ecology of the white-eyed gull are understudied, and the species’ ability to respond to rapid habitat modification is unknown. In 2021, a ground census was conducted on all 92 islands of the Al Wajh lagoon to determine the distribution of white-eyed gull nests. In total, 55% of the white-eyed gull metapopulation were found on islands where development is either ongoing or upcoming, with the one of the largest and densest colonies occurring on an island already undergoing development. The baseline census presented here should be viewed as a first step in understanding the population dynamics of the white-eyed gull and predicting their response to enhanced anthropogenic change in the Al Wajh lagoon.

No description available.

Parasites are important drivers of ecological and evolutionary processes in their hosts. However, hosts often differ in how they are affected by parasitism, which can be important in how parasite effects on individuals scale up to the population level. Hosts may differ intrinsically in their susceptibility to parasitism, and extrinsic factors may impose constraints on how hosts allocate resources between immunity, maintenance and reproduction, thereby further affecting their ability to cope with infection. These extrinsic factors include the host’s ecological environment, for example food availability or weather, and its social environment, that is its interactions with conspecifics. This is particularly true during a reproductive attempt when individuals interact closely with other family members. Not only might immediate impacts of parasitism differ between and within parents and offspring, but the direct effects of parasitism on a host could have further indirect consequences for other family members through their behavioural interactions with parasitised individuals. The distribution of direct and indirect effects among all family members could affect the outcome of the breeding event and individuals’ future performance. However, teasing apart these various avenues of parasite impacts on families may be difficult if parasite burden or susceptibility is correlated between family members. In this thesis, I explore the consequences of parasitism for different family members of the European shag Phalacrocorax aristotelis infected with gastrointestinal nematodes, over a range of ecological conditions. In chapter 2, I demonstrate that chicks’ responses to anti-parasite treatment across four years vary between siblings and with environmental conditions, which may be mediated by resource allocation among siblings. In chapter 3, I explore how costs of parasitism are distributed among the whole family by simultaneously treating chicks and/or parents with an anti-parasite drug and measuring the outcomes for all family members. Treatment has a more marked effect for the non-treated generation than for the treated individuals, suggesting that parasitism may have important indirect costs. In chapter 4, I investigate whether within-brood variability in the effects of anti-parasite treatment and its cross-generational impacts are mediated by behavioural change, and show that chick treatment but not parent treatment influences several aspects of behaviour in the nest. In chapter 5, I demonstrate that the impact of chick anti-parasite treatment on parents persists beyond the breeding attempt, with parents of treated chicks foraging less overwinter and breeding earlier the following year, whereas there is no persistent effect of parents’ own anti-parasite treatment. Lastly, I provide an appendix examining the parasitology of the system in detail, including an assessment of in situ and proxy measures of worm burdens of chicks. This thesis demonstrates that parasitism can be a key component, previously overlooked, of reproductive performance in seabirds, a group that plays an important ecological role as apex predators and thus indicator species of the marine environment.

Methylmercury (MeHg) is a global pollutant that can bioaccumulate and biomagnify along the aquatic food chain, causing adverse outcomes in humans and wildlife. Effective biomonitoring programs are needed to identify high exposure populations and to develop proper mitigation strategies. However, biomonitoring results showed high inter-individual variability in the relationship between MeHg exposure and body burden. Moreover, the gut microbiota can potentially play a role in MeHg transformations, and it is widely believed that the gut microbiota may be the underlying reason for the variability between and within a population. However, the microbially-mediated mechanisms of Hg transformation in the gastrointestinal environment is poorly understood. The overarching goal of my thesis is to investigate the role of gut microbiota in MeHg transformation in human, and the relationship between environmental pollutants and the gut microbiota of sentinel species such as river otters (Lontra canadensis) and seabirds (Arctic Tern [Sterna paradisaea], Black Guillemot [Cepphus grille], Common Eider [Somateria mollissima], Double-crested Cormorant [Phalacrocorax auratus], and Leach’s Storm Petrel [Oceanodroma leucorhoa]). My thesis consists of four research papers. In the first paper, I discovered that the gut microbiota`s ability to demethylate MeHg is significantly enhanced by altering the diet. In my second paper, I discovered a novel MeHg degradation pathway. In the third and fourth papers, I explored the effect of Hg and other environmental contaminant exposure on river otters and seabirds gut microbial community structures and found a relationship between prey selection and diet to the gut microbial structure. In conclusion, my thesis explores the relationship between diet, prey selection, environment contaminants and the humans and wildlife gut microbiota and contributes to understanding the gut microbiota’s role in biomonitoring of ecosystem and human health.

Seabirds are vulnerable to a wide range of impacts at sea and function as important indicators of ocean health. A detailed understanding of their movements and distributions at sea, as well as the types of behaviour in which they engage and the extent to which those activities make them vulnerable to different impacts is critical in effective conservation planning. But their elusive lifestyles and mobility have hampered studies of their at-sea behaviour. Using miniature data loggers deployed on Manx shearwaters Puffinus puffinus this thesis explores the movements, distribution and behaviour of a small-medium pelagic, procellariiform seabird during foraging trips at sea. Foraging distributions were most variable during the pre-laying period when females departed the colony to build their egg. Females foraged close to the colony when local resources were adequate, but more typically foraged in distant shelf edge waters. Males returned frequently to the colony during this period and typically foraged close by, but also in shelf edge waters when local resources were poor. During incubation and chick-rearing the foraging movements of birds tracked from up to four colonies showed considerable inter-annual variability, but were largely constrained to the Irish and Celtic Seas and the inshore waters of west Scotland. Birds from each of the colonies foraged in waters local to their own colony, but also in more distant locations, including the productive Western Irish Sea and Western Irish Sea Front where birds from multiple colonies co-foraged, presumably at high densities. At-sea behaviour was organized into three principal activities representing: (1) sustained direct flight, (2) sitting on the sea surface, and (3) foraging, comprising tortuous flight interspersed with periods of immersion and diving in pursuit of prey. Foraging was highly constrained to daylight hours during which birds engaged in bouts of diving separated by periods of flight or rest on the surface. Most dives were up to 6 m deep, lasting up to 13 s, but some much deeper dives (maximum 55.5 m) were also made. During chick-rearing the use of short and long duration trips may allow parents to control provisioning effort and their own body condition. However, reducing parents’ requirement to provision their chick (by supplemental chick feeding) did not appear to alter the at-sea movements and behaviour of parents, suggesting that at-sea behaviour probably is controlled more by foraging conditions and prey distributions than by the nutritional demands of the chick.

Age-related variation in demographic rates has significant consequences for population and evolutionary dynamics, and understanding the processes driving such variation is therefore an important aspect of evolutionary ecology. Reproductive performance may vary over the lifetime of an individual, and this may be the result of both variations in reproductive effort and changes in individual competency. For example, increasing experience is likely to have beneficial effects on reproduction during early life, and senescence, or declines in physiological function, may have negative impacts on the performance of older individuals. The rate at which these changes occur can vary dramatically between species, and even between individuals of the same species. However, understanding the causes and consequences of this variation in the rate of ageing is not always straightforward. As well as the individual-level processes described, the phenotypic composition of successive age classes will contribute to age-related variation observed at the population level. Abrupt changes in performance, such as the poor performance of first time breeders, may be obscured if individuals vary in their age at first reproduction. Population-level patterns may also be influenced by selection; for example, the selective disappearance of low quality individuals from older age classes may mask senescent declines in the performance of longer-lived individuals. Moreover, the physiological mechanisms that underpin within-individual changes in performance are not well understood. Unravelling the drivers of such age-related variation requires longitudinal data, following individuals throughout their lives, which presents challenges for the study of natural populations. Albatrosses are among the longest lived vertebrates. In this thesis, I use data from three species of albatross breeding at Bird Island, South Georgia (54°00’S, 38°03’W) to explore age-related variation. Focusing primarily on the wandering albatross, Diomedea exulans, I characterise the relationship between age and various reproductive traits, and decompose the population-level patterns to reveal effects of experience, senescence and terminal effects across the reproductive lifespan of individuals. I then consider foraging behaviour as a proximate driver of changes in reproductive performance in this species. Using tracking data collected over a 20 year period, I find limited evidence for age-related variation in foraging trips taken throughout the breeding cycle. Going one step further, I explore telomere dynamics in the wandering albatross, examining the potential for telomere length to act as a physiological marker of individual state. Finally, I move on to a species comparison, incorporating data from the black-browed (Thalassarche melanophris) and grey-headed albatross (Thalassarche chrysostoma). I compare the population- and individual-level ageing patterns of these three closely related species, and consider these in light of their differing life history strategies.

Understanding the life history response of animal populations to environmental selection pressure is a central research theme in evolutionary ecology and conservation biology. Our current knowledge of life history traits in animal populations is, however, mostly based on studies conducted on temperate systems, contrasting with the fact that a large number of species live in the tropics. The roseate tern (Sterna dougallii) is a oceanic seabird showing mainly a tropical distribution with a relatively fragile conservation status, making it an interesting case study. In this thesis, ten years of data (1998-2007) were used to determine the main demographic traits of the tropical roseate tern population breeding on Aride Island, Seychelles (western Indian Ocean), and to explore their relation with environmental factors. We focused on the estimation of reproductive success, age at first reproduction (sexual maturation) and age-specific survival probabilities in relation to both oceanography of the study area (food availability) and quality of the breeding habitat. By using chlorophyll concentrations as a proxy measure of marine fish stocks, we showed that the overall low reproductive success in this population (range 0.0 0.57 chick/pair) is mainly dictated by the strong inter-annual fluctuations in local food supply conditions around Aride Island. Reproductive success was also found to be related to the spatial variation in vegetation characteristics of the nesting (woodland) habitat used by the terns. Birds nesting in densely-vegetated areas with a closed canopy cover had higher chick mortalities, presumably through a high level of parasitism by ticks, when compared to those breeding in more open areas such as forest clearings. By relying on capture-mark-recapture methods, age of first reproduction was estimated at 3-4 years and age-specific survival probabilities at 0.62, 0.77 and 0.81 in juveniles (1-year), immature individuals (2-years), and breeding adults (3-years and older), respectively. Most of these demographic parameters were also found to be influenced by oceanographic conditions (e.g. Indian ocean Dipole) and the levels of tick infestation during the chick-growing period. We further show how these vital rates can be incorporated into a simple population viability analysis in order to model population dynamics (i.e. population growth rate) and, ultimately, to provide local managers with conservation measures. Finally, the contribution of this work to the global knowledge of tropical seabird life histories is discussed through a comparison with demographic parameters of temperate roseate tern populations.

Successful preservation of Earth’s biodiversity requires an understanding of the processes that generate new species. The generation of species without gene exchange is considered predominant; however, a growing body of evidence indicates that populations can diverge while exchanging genes, and that this may be common. Previous research hypothesized that blue-footed (Sula nebouxii) and Peruvian (S. variegata) boobies diverged from their common ancestor while exchanging genes. Here, I combine ecological and genetic perspectives to thoroughly evaluate this hypothesis. Using a panel of eight molecular markers, I estimate population differentiation for each species. I find evidence of weak population differentiation for both species, an uncommon pattern in seabirds, and argue that specialization to an unpredictable food resource has shaped contemporary population differentiation. Next, I use molecular markers and morphology to evaluate the hybrid status of five morphologically aberrant individuals. I report that all are likely F1 (first generation) hybrids, and are the product of crosses between female Peruvian boobies and male blue-footed boobies. Sex biases in pairing may occur because of an underlying preference for elaborate courtship displays. I then expand the dataset to 19 loci and use cline theory and Bayesian assignment tests to characterize the hybrid zone, to examine introgression, and to evaluate the hybrid status of the aberrant individuals. The hybrid zone is most likely maintained by strong endogenous and exogenous selection against hybrids and dispersal of parentals into the hybrid zone (a tension zone), and introgression is low for nuclear loci and absent for mitochondrial loci. Finally, I test the hypothesis that this species pair diverged from their common ancestor with gene flow using recently developed analyses and multiple loci. Divergence without gene flow is rejected and unidirectional introgression of sex-linked loci during divergence is reported. The results of this study support the hypotheses that: 1) populations can diverge while exchanging genes; 2) the Z chromosome may play a role in avian speciation; and 3) organisms specialized to variable foraging environments should exhibit low population differentiation. This study adds to our understanding of both population differentiation and speciation in seabirds, and the generation of new species more generally. / Thesis (Ph.D, Biology) -- Queen's University, 2011-04-06 13:55:32.151

Many animals including marine mammals and several seabird species dive in large groups, but the impacts that social interactions can have on diving behaviour are poorly understood. There are several potential benefits to social diving, such as access to social information or reduced predation risk. In this body of research I explore the use of social information by groups of diving animals by studying the behaviour of European shags (Phalacrocorax aristotelis) diving in “foraging rafts” in the Isles of Scilly. Using GPS tracking I establish where shags regularly forage in relation to bathymetry and areas where foraging rafts frequently formed. Using these data I show that the foraging ranges of different colonies overlap and that foraging ranges of individual shags are often predictable. This suggests that social information will be of less value while searching for foraging patches. However, using observational studies to further explore the conditions and areas in which foraging rafts formed, I show that advantages such as anti-predation or hydrodynamic benefits are unlikely to be the main drivers of rafting behaviour in the Scillies. I therefore suggest that access to social information from conspecifics at a foraging patch may be one of the main benefits diving in groups. Using a dynamic programming model I show that individuals diving in a group benefit from using social information, even when unable to assess conspecific foraging success. Finally I use video analysis to extract the positions and diving behaviour of individuals within a foraging raft and compare this to simulated data of collective motion and diving behaviour. The results of these studies indicate that an individual being able to utilise dives of conspecifics to inform their own diving decisions may be one of the main advantages of social diving.