The life-history traits of two sympatric seabird species, the Common Sterna hirundo and Arctic Tern S. paradisaea, and the flexibility of these traits in relation to short and longer term changes in environmental conditions were measured at Coquet Island, N.E. England. The study focused primarily on inter and intraspecific differences in annual productivity and chick growth, adult time budgets and provisioning rates, and the relationships between these different aspects of reproductive performance. Of the two species, Common Terns delivered larger food items, delivered food at a higher rate to the nest and attended the nest more frequently, indicating that they made trips of shorter average duration. Daily metabolizable energy intake of chicks was about 30% higher in Common Terns than in Arctic Terns, yet the size-specific growth rates of the two species were almost identical, indicating a major difference between species in nestling energy budgets. Brooding appeared to play a less important role in the energy budgets of Common Terns, and the number of chicks that Arctic Terns could raise was probably limited not only by the rate at which parents could supply food to the nest but also by the requirements of chicks for brooding. Increased brood size, low annual food abundance and extreme weather conditions had a negative effect on chick mass development in both tern species. Flexibility of mass growth rates in Arctic and Common Terns may act as a fine-tuning mechanism to regulate provisioning in these species. By maintaining structural growth rates, final fledging mass and final fledging size of nestlings at the expense of retarded mass development rates, these species seem to be able to maximize annual reproductive output and possibly, for parents and nestlings, future survival. Predation of eggs and chicks was generally infrequent and affected mostly very young nestlings. However, Black-headed Gulls took many tern eggs in a year when inshore food supplies were particularly low.

Northern fulmars and Manx shearwaters are pelagic seabirds of the Order Procellariiformes, a group that is characterised by extreme life-history traits. Many of these traits have been associated with the unpredictability of marine food sources. However, fulmars and Manx shearwaters feed their chicks at relatively frequent intervals compared with other procellariiforms, and the life-history implications of this strategy are poorly understood. In this thesis I examined food provisioning and chick growth strategies in fulmars and Manx shearwaters, and discussed these strategies in the context of life history - environment interactions. 1 tested the efficacy of a periodic weighing method for assessing food provisioning, and found that this gave a very similar estimate of the frequency and size of feeds compared to periodic weighing combined with data on parental attendance, determined by radio tracking. However, periodic weighing was much less effective at distinguishing meals from one or two parents. In Manx shearwaters, chick growth was highly correlated with food provisioning rate, and both variables showed significant annual variation. Both individual and environmental effects contributed to this variation, and in particular, peak mass showed highly significant repeatability coefficients. Fulmars showed significant variation in breeding success, diet and chick growth between two years, but chicks were apparently heavier in a very poor year. This was caused by differential mortality of chicks in poor condition. In Manx shearwaters, male parents visited the nest more frequently and made a greater contribution to food provisioning than females, a strategy that has seldom been reported in sexually monomorphic seabirds. I used a cross-fostering experiment to examine the parent-chick interactions responsible for the mass recession period prior to fledging in Manx shearwaters. Both parents and chicks had an active role in controlling food intake, and the results indicated that mass recession was not caused by parental desertion as previously thought.

Seabirds commonly nest colonially on cliffs or inaccessible islands, so that oceanic effects on the quality or quantity of prey fed to chicks more often determine nest success than does terrestrial predation. However, when predators can access nests, impacts can be dramatic. In Kittlitz’s murrelet (KIMU), a rare and recently declining seabird, nests are widely dispersed in poorly accessible areas, growth rates are exceptionally high, and nestling periods are very short. This unique strategy may offset the vulnerability of their ground nests to predators but demands adequate deliveries of high-energy prey. We investigated whether variations in energy content of prey fed to chicks could alter growth rates and resulting duration of exposure to predators, and whether extending predator exposure had important effects on nest success. From 2009‒2016, we measured fish length with cameras, modeled prey energy content from chick energy needs, and measured chick growth rate and nest survival. We monitored an average 17 nests/year (139 total), of which 49% were depredated (almost all by red fox) and 25% survived to fledging. Prey were mainly Pacific sand lance (80%) and capelin (19%), with capelin having 2.3× higher energy per unit length. In a year of slow growth, sand lance energy density needed to increase by 31% from 4.29 to 5.64 kJ/g (within published values), or the proportion of capelin in the diet needed to increase from 5.6% to 27.2%, to achieve maximum chick growth. Adults could supply the energy required for maximum growth by delivering only 1.9 capelin/day versus 5.5 sand lance. Slow growth increased time to fledging by 5 days. This extended exposure to predation could decrease overall nest survival from 14.2% to 13.1%, a relative decrease of 7.7%. With reported breeding propensity of KIMU averaging only 20% and sometimes much lower (range 5 to 45%), even small effects on nest success may be consequential. Although direct predation was the main limitation to nest success, effects of ocean conditions on prey quantity and quality can have overriding effects in some years, and apparently small but substantive indirect effects in other years by mediating exposure to predation. Continued climate warming that adversely affects availability of high-energy fish and allows range expansion of terrestrial predators may have disproportionate effects on species such as KIMU with accessible nests and demands for energy-rich prey.

In this study, the effects of individual and combinatorial electrolyte solution comprised of carbohydrate, salt, and a stimulant injected into broiler hatching eggs on subsequent late term embryogenesis and post hatch performance up to D 10 were evaluated in separate trials. The effects of solution concentration and volume on embryo body weight and yolk reserves were likewise considered, and limited posthatch growth, body weight, and yolk sac effects of a compound electrolyte solution were evaluated. The individual and combinatorial effects of injected solutions were examined in an effort to yield the maximum physiological growth effects on embryogenesis from the metabolic pathways in which these compounds are involved. Limited effects on embryo and post hatch mortality were found. However, both post hatch yolk reserves and liver weights were affected by in ovo injection. These effects could be key in increasing bird weight by processing day.

This study attempted to explain an apparent inverse relationship between pack ice proximity and breeding success of Black Guillemots (Cepphus grylle) on Cooper Island, a barrier island in the western Beaufort Sea near Barrow, AK. I elucidated the first linear relationship between energy density and body size for the elusive Arctic Cod (Boreogadus saida). I discovered and ground-truthed the existence of previously unknown guillemot foraging habitat on small 50 m2 ice floes distant from the pack ice. I developed new daily metrics for quantifying the provisioning to linear (8 d – 18 d) and Post-Linear (19 d – fledge) chicks. I found daily consensus between Linear and Post-Linear chicks about the level of provisioning at the colony. Finally, I explained those daily changes with significant correlations with wind speed and direction. / October 2007

This study attempted to explain an apparent inverse relationship between pack ice proximity and breeding success of Black Guillemots (Cepphus grylle) on Cooper Island, a barrier island in the western Beaufort Sea near Barrow, AK. I elucidated the first linear relationship between energy density and body size for the elusive Arctic Cod (Boreogadus saida). I discovered and ground-truthed the existence of previously unknown guillemot foraging habitat on small 50 m2 ice floes distant from the pack ice. I developed new daily metrics for quantifying the provisioning to linear (8 d – 18 d) and Post-Linear (19 d – fledge) chicks. I found daily consensus between Linear and Post-Linear chicks about the level of provisioning at the colony. Finally, I explained those daily changes with significant correlations with wind speed and direction.

This study attempted to explain an apparent inverse relationship between pack ice proximity and breeding success of Black Guillemots (Cepphus grylle) on Cooper Island, a barrier island in the western Beaufort Sea near Barrow, AK. I elucidated the first linear relationship between energy density and body size for the elusive Arctic Cod (Boreogadus saida). I discovered and ground-truthed the existence of previously unknown guillemot foraging habitat on small 50 m2 ice floes distant from the pack ice. I developed new daily metrics for quantifying the provisioning to linear (8 d – 18 d) and Post-Linear (19 d – fledge) chicks. I found daily consensus between Linear and Post-Linear chicks about the level of provisioning at the colony. Finally, I explained those daily changes with significant correlations with wind speed and direction.