Populations and Energetics of Taiga Birds near Fairbanks, Alaska

IN their annual breeding cycle, birds remove quantities of nutrients and energy from the taiga ecosystem each summer. A major portion of these nutrients and energy are returned to the system directly in the form of excrement, molted feathers, eggshells, and in the dead bodies of individuals that fall to the ground or are eaten by predators. Some portion of the annual production leaves the taiga ecosystem, as most of the species nesting in the taiga migrate south in fall. As breeding populations are maintained at about the same level from year to year, the amount of energy and nutrients equivalent to the annual production of young is transported south and deposited through mortality and predation in other ecosystems each year. As a part of an initial assessment of the structure and function of the taiga ecosystem in interior Alaska, the populations and energetics of wild birds were investigated in summer 1971 on a biological research preserve adjacent to the developed portion of the University of Alaska campus near Fairbanks (65 ø 54' N, 147 ø 50' W). Some studies on the composition of vegetation, small mammal populations (Grodzinski 1971a, 1971b; Whitney 1973), and the decomposer organisms of this preserve have been made. Further studies to complete our understanding of this complex system are planned and in progress. The objective of the present study was to estimate the amount of energy removed by the avian element of the consumer group in taiga forest of interior Alaska in summer by (a) censusing the bird populations throughout the summer, and (b) measuring the resting metabolic rate of selected species at the prevailing daytime summer temperatures and converting these measurements o the requirments of free-living birds.