The Gulf of Maine is a dynamic ecosystem with rapidly warming sea surface temperatures (SSTs), therefore it is vital to understand how species interactions vary over time and space. In chapter two, I quantify and compare dietary differences among four tern species, across seven islands in the region, over a 32-year period. Multivariate statistical analyses were employed to discern spatial and temporal differences in foraging ecology. Findings suggest there are significant differences between species and islands; however, only three prey species comprise the majority of chick diet for all terns and islands. The reliance on only a few prey items led to narrow foraging niches, potentially increasing their vulnerability to climate change, fisheries practices, or other localized disturbances. The third chapter characterizes long-term trends across nesting islands, describes within-season dietary phenology, and quantifies how warming SSTs may influence diet. Over time there was a declining trend in the occurrence of hake and increasing amounts of sand lance. In addition, hake and sand lance occur with higher frequency earlier in the season, while butterfish and “other fish” showed the opposite trend. Furthermore, results indicated that the within-season decline of hake occurs more rapidly in years with earlier spring thermal transition dates potentially indicating a phenological shift. Finally, warming SSTs were found to be negatively correlated with hake and positively correlated with the “other fish” prey group. Given projections of further warming in the region, understanding how the diet of these seabirds may be impacted in crucial to their conservation.

Successful management of coastal ecosystems requires an understanding of the distribution of key food web species through space and time relative to environmental predictors. Here, I examined the habitat use of an important forage species, the Pacific sand lance (Ammodytes hexapterus), using an inductive habitat modeling approach. I examined the presence/absence of Young-of-the-Year Pacific sand lance in the intertidal/shallow subtidal habitat of Barkley Sound, British Columbia. I determined sand lance occurrence using a beach seine at low tide, which was preferred to visual and intertidal digging detection methods due to its high detection frequency, ease of use, and ability to physically capture sand lance. I constructed models using environmental data measured at two different scales: 1) empirically measured environmental data (site-specific level) and 2) GIS derived environmental data extracted with a 200m buffer (landscape level). For each scale, I employed both logistic regression and classification tree modeling procedures to construct habitat models of sand lance occurrence at 55 study sites sampled during the summer of 2003. At the site-specific level, both logistic regression and classification tree models performed similar, however, classification trees were easier to construct and interpret as well as revealing interactions among variables undetected by logistic regression. Based on a deviance pruned classification tree, Grain Size Mean, Intertidal Eelgrass Presence, Absence, Major Substrate Low Intertidal, and Grain Size Sorting influenced sand lance occurrence at this scale, with importance values of 100, 79, 75, and 61 respectively. Standardized importance was based on the overall change in node impurity in the classification tree for each variable. At the landscape level, only Coastline Density was significantly related to sand lance occurrence, however, it was difficult to suggest this variables direct relation to sand lance habitat use. Overall, the habitat modeling approach identified important environmental variables influencing sand lance habitat selection at two different scales and stressed the utility of field data to construct and confirm these models.

The Kittlitz's murrelet (Brachyramphus brevirostris) is a rare member of the seabird family Alcidae that breeds in coastal areas of Alaska and Beringian Russia. The species belongs to the genus Brachyramphus, an unusual seabird taxon in which all three extant species nest non-colonially, situating their nests up to 75 km inland from coastal marine waters. This nesting strategy is different from that of most seabird species, which tend to nest colonially on remote islands or sea cliffs, where terrestrial predators are generally absent or cannot easily access nests. Within the genus Brachyramphus, Kittlitz's murrelet is notable because a majority of the global population appears to nest on the surface of the ground in rocky alpine habitat near inland or tidewater glaciers, foraging in adjacent marine waters influenced by glacial outflows. The unusual nesting habits of Kittlitz's murrelet have made the study of its nesting ecology difficult, and gaps therefore exist in our understanding of the species' breeding biology. Kittlitz's murrelet populations have declined substantially in core areas of its range, causing the U. S. Fish and Wildlife Service to designate the species as a candidate for protection under the Endangered Species Act. A better understanding of Kittlitz's murrelet nesting ecology is crucial for determining potential causes of these declines and for future management of the species. To this end, I studied Kittlitz's murrelet breeding ecology and nest site selection during 2008-2011 on Kodiak Island, Alaska, in an unglaciated area that was recently found to have large numbers of accessible nests. I and my colleagues found 53 active Kittlitz's murrelet nests in inland scree-dominated habitats and placed remote, motion-sensing cameras at 33 nests. Adults exchanged incubation duties at the nest every 24 or 48 h, almost exclusively during early morning twilight. Following hatching of eggs, parents provisioned their single nestling with an average of 3.9 to 4.8 fish per day, depending on the year. Parental visits to the nest during chick-rearing occurred primarily after sunrise in the early to mid-morning hours, and during evening twilight. Fish were delivered singly to the chick, and Pacific sand lance (Ammodytes hexapterus), a high-lipid forage fish, accounted for about 92% of all identifiable chick meal deliveries. Chick growth rates were high relative to confamilial species, consistent with the high quality of chick diets; the logistic growth rate constant (K) was 0.291, greater than that for any other semi-precocial alcid. Chicks fledged an average of 24.8 d after hatching and asymptotic chick body mass averaged about 135.5 g, approximately 58% of adult body mass. Age at fledging, asymptotic chick body mass (% adult mass), and the number of meal deliveries required to fledge a chick were all lower than or as low as any other species of semi-precocial alcid. The average estimated nest survival rate during 2008-2011 was 0.093 (95% CI = 0.01–0.30), which is extremely low compared to other species in the family Alcidae, and is almost certainly insufficient to sustain a stable population. The primary causes of nest failure were depredation (47% of total nest fates), mostly by red foxes (Vulpes vulpes), and unexplained nestling mortality on the nest (21% of nest fates). Saxitoxin and/or pathogenic endoparasite burdens were observed in five of six necropsied chick carcasses, suggesting possible causes for chick mortality not directly attributable to predation. Habitat characteristics of Kittlitz's murrelet nest sites differed significantly from unused sites at several scales. At a small scale (within 5 m of the nest), nest sites had a lower percent coverage of vegetation and higher percent coverage of intermediate-sized rocks (5–30 cm diameter), compared to randomly selected unused sites. Nest sites were also located on steeper, more north-facing slopes compared to randomly selected sites. Nest sites also had a lower percent coverage of vegetation than randomly-selected sites at larger scales (within 25 m and 50 m of the nest site). Nest sites were located significantly farther from the edge of densely-vegetated habitats than random sites. There was no evidence that nest sites were different from randomly-selected sites in terms of elevation, proximity to ridgelines, or proximity to the open ocean, although a low degree of variation within the study area for these habitat characteristics may have precluded detection of potential differences. Nest survival rates did not co-vary with slope, percent vegetation coverage, distance from vegetated edges, or percent cover of intermediate-sized rocks; however, this result may be an artifact of a limited sample size. The results of this thesis will provide managers with a better understanding of the factors that may limit Kittlitz's murrelet nesting success, such as nest predation and forage fish availability, as well as factors that may influence the quality and distribution of Kittlitz’s murrelet nesting habitat in the future, given on-going and progressive climate change. / Graduation date: 2013