Contrasting diet, growth, and energy provisioning in loons breeding sympatrically in the Arctic

Thesis (Ph.D.) University of Alaska Fairbanks, 2017Red- throated (Gavia stellata) and Pacific (G. pacifica) loons breed throughout Arctic Alaska, often on adjacent lakes. Despite having similar life histories and distributions, these species have contrasting population trends in Alaska. Red-throated Loon populations have fluctuated dramatically over the past 3 decades, while the population trend of Pacific Loons has remained stable. These species-specific, population-level differences may be related to the foraging behaviors of breeding adults: Red-throated Loons feed on marine fishes using central place foraging behavior, while Pacific Loons feed primarily on freshwater prey captured from their breeding lakes. In this dissertation, I examined how differences in diet composition during the breeding season were associated with individual fitness parameters, namely adult body condition, chick growth performance, and breeding success. I used results from this research to address the hypothesis that interspecific differences in foraging behaviors contribute to the contrasting population dynamics of Pacific and Red-throated Loons breeding in Alaska. Using stable isotopes and fatty acid biotracers of diet, I found that the diet of breeding Pacific Loons was composed of a mix of freshwater and marine prey, and that variation in diet composition was related to the size of the breeding lake. Pacific Loons nesting on small lakes consumed more marine prey, suggesting that small lakes were not profitable foraging habitat, but their use for nesting was enabled by the close proximity of marine foraging habitat. In contrast, Red-throated Loons nested on very small lakes and ate a diversity of marine fishes. Despite differences in diet, both species had similar body condition during late-incubation, indicating that their diets met adult energy requirements, and adults maintained similar lipid reserves despite differences in foraging behavior. I found that Red-throated Loon chicks grew rapidly, yet were only 66% of adult body mass when they departed their natal lakes for the sea at fledging. This pattern of chick growth reduced the length of the postnatal period, and, consequently, the amount of time adults had to fly to marine habitat to capture fish for their chicks. Red-throated Loons provisioned their chicks with sufficient energy to support high growth rates. Other loon species which do not fly to the sea to capture fish for their chicks, like the Pacific Loon, likely do not face similar selection pressure for reduced parental energy investment through rapid chick growth. In Red-throated Loons, the total energy demands of chicks over the postnatal period were reduced at the expense of increased daily energy demands during the period of rapid growth. Given this pattern of chick growth, variation in the availability of high-energy content prey exerts a strong influence on breeding success. Pacific Loons provisioned their chicks mostly freshwater invertebrates with low-lipid content. Consequently, Pacific Loon brood provisioning rates were much higher than those of Red-throated Loons, which provisioned their chicks large-bodied marine fishes. Brood-rearing Pacific Loons commonly departed their breeding lakes for marine habitat, presumably to forage for themselves; however, parents rarely fed their chicks marine fishes, suggesting that central place foraging was not an energetically profitable provisioning behavior for larger-bodied Pacific Loons. Reproductive success over 3 years was higher in Red-throated Loons than Pacific Loons due to higher chick survival rates. Estimates of maximum energy provisioning rates for broods demonstrated that the provisioning rates and diet composition of Red-throated Loons could more easily meet peak brood energy requirements than the provisioning rates and diet composition of Pacific Loons. Thus, lower survival of Pacific Loon chicks was associated with lower maximum energy provisioning rates. The use of both freshwater and marine prey may insulate Pacific Loons from changes in either foraging habitat. Further, Arctic lakes provide a reliable source of invertebrate prey for chicks, but a diet of invertebrates may limit chick production rates because of their small size and low lipid content. Although meeting maximum brood energy requirement by provisioning freshwater invertebrates was difficult for Pacific Loons, particularly for adults rearing the maximum brood size of 2 chicks, chick production rates were sufficient to maintain a stable population trend. Red-throated Loons' specialization on marine prey strongly links their energy intake to the availability of marine fishes, which can vary suddenly and dramatically with ocean climate. Foraging conditions for Red-throated Loons in this study supported high chick growth rate and high chick production rates. Low chick growth rate and low chick production documented at other sites in Alaska indicate that Red-throated Loon breeding success is highly variable. Low chick production rates may contribute to Red-throated Loon population dynamics in Alaska if the availability of important forage fish species is low over multiple breeding seasons. Pacific Loons may be better suited than Red-throated Loons to adapt to the changing Arctic environment given the flexibility of their foraging behavior and diet. Because Pacific and Red-throated loon chicks in coastal tundra habitat rely on different types of prey, chick survival can function as a sensitive indicator of changes in lentic and marine habitats in the Arctic

Male breast cancer in BRCA1 and BRCA2 mutation carriers : pathology data from the Consortium of Investigators of Modifiers of BRCA1/2

Background: BRCA1 and, more commonly, BRCA2 mutations are associated with increased risk of male breast cancer (MBC). However, only a paucity of data exists on the pathology of breast cancers (BCs) in men with BRCA1/2 mutations. Using the largest available dataset, we determined whether MBCs arising in BRCA1/2 mutation carriers display specific pathologic features and whether these features differ from those of BRCA1/2 female BCs (FBCs). Methods: We characterised the pathologic features of 419 BRCA1/2 MBCs and, using logistic regression analysis, contrasted those with data from 9675 BRCA1/2 FBCs and with population-based data from 6351 MBCs in the Surveillance, Epidemiology, and End Results (SEER) database. Results: Among BRCA2 MBCs, grade significantly decreased with increasing age at diagnosis (P = 0.005). Compared with BRCA2 FBCs, BRCA2 MBCs were of significantly higher stage (P for trend = 2 x 10(-5)) and higher grade (P for trend = 0.005) and were more likely to be oestrogen receptor-positive [odds ratio (OR) 10.59; 95 % confidence interval (CI) 5.15-21.80] and progesterone receptor-positive (OR 5.04; 95 % CI 3.17-8.04). With the exception of grade, similar patterns of associations emerged when we compared BRCA1 MBCs and FBCs. BRCA2 MBCs also presented with higher grade than MBCs from the SEER database (P for trend = 4 x 10(-12)). Conclusions: On the basis of the largest series analysed to date, our results show that BRCA1/2 MBCs display distinct pathologic characteristics compared with BRCA1/2 FBCs, and we identified a specific BRCA2-associated MBC phenotype characterised by a variable suggesting greater biological aggressiveness (i.e., high histologic grade). These findings could lead to the development of gender-specific risk prediction models and guide clinical strategies appropriate for MBC management.Peer reviewe

Behavioral constraints on harlequin duck population recovery from the Exxon Valdez oil spill in Prince William Sound, Alaska

I investigated the relationship between harlequin duck (Histrionicus histrionicus) behavior and lack of recovery from the Exxon Valdez oil spill in Prince William Sound, Alaska. First, I evaluated the hypothesis that harlequin ducks in winter have little flexibility to increase foraging time in response to disturbance because they are constrained to forage during daylight. Eight radio-tagged harlequin ducks wintering in Resurrection Bay, Alaska were monitored for evidence of dive-feeding at night. Each radio-tagged individual was detected during an average of 19.5 of 22 nocturnal monitoring sessions and signal loss indicative of diving behavior was not detected during a total of 780 minutes of signal monitoring. In contrast, the same 8 radio-tagged birds were detected during an average of 9.1 of 12 daytime signal monitoring sessions and signal loss indicated diving behavior during an average of 62 ± 7% of 5-minute daytime monitoring periods (total of 364 minutes of signal monitoring). Thus the harlequin ducks monitored in this study rarely, if ever, fed by diving at night, possibly due to reduced foraging efficiency and (or) increased predation risk at night. This result suggests that harlequin ducks in mid-winter may be severely time-limited in their foraging, especially in northern parts of their winter range. Therefore, subtle changes in energy requirements and (or) time-activity budgets as a result of continued exposure to residual oil from the Exxon Valdez oil spill may affect the ability of harlequin ducks to meet their daily energy requirements. Second, I tested the hypothesis that exposure to crude oil affects time-activity budgets of harlequin ducks. Controlled oil-dosing and plumage-oiling experiments were conducted using adult female harlequin ducks in captivity. I found no evidence that ingestion of weathered Prudhoe Bay crude oil affected the occurrence of feeding activity during 30-minute observation periods, nor was there evidence of effects on time spent feeding. Effects of crude oil ingestion on maintenance activity were detected, but were neither consistent between the 2 years of the study, nor dose-dependent for the 2 doses administered (2 and 20 mL kg⁻¹ wk⁻¹), and therefore did not strongly support an oil-dosing effect on maintenance activity. Consequently, these results provided little support for the hypothesis that oil ingestion affects time-activity budgets of captive harlequin ducks, at least for the doses and conditions of captivity used in this study. Plumage-oiling reduced feeding activity in captive harlequin ducks. The estimated probability of feeding during 30-minute observation periods for birds in the high-exposure oiling group (5 mL of crude oil) was 53% less than that of non-oiled controls. Oiled birds exhibited a trend of reduced time feeding with increasing level of external-oiling; this effect was greatest among birds in the high-exposure oiling group, which spent 43% less time feeding than non-oiled birds. Reduced feeding was associated with less time in the water dive-feeding and presumably lower heat loss. Trends in the occurrence of maintenance activity and time spent in maintenance activity for birds in the high-exposure treatment suggested plumage-oiling increased maintenance activity, but results were not conclusive. The behavioral changes associated with plumage-oiling in captivity would likely reduce fitness in the wild, where a high proportion of time must be spent in the water feeding. If residual Exxon Valdez oil sequestered in beach sediments enters the water column where it may be encountered by harlequin ducks, external exposure may lead to reduced feeding activity. This, in turn, may compromise survival, particularly during mid-winter when the time available for diurnal foraging is low and maintenance energy requirements are high