Summary
The energy demands and general food consumption rates of bird populations breeding in North American grasslands are estimated using a simulation model which employs information on population natural history and individual metabolism gathered from several study locations. The total breeding season energy demand of the grassland/shrub-steppe avifaunas ranged from 0.89 kcal m-2 season-1 in arid shrub-steppe to 2.92 kcal m-2 season-1 in a mesic tallgrass prairie. There was substantial variation between years and between census plots, however, and in general the average avian community energy demands did not differ significantly over the range of locations. Production accounted for 0.9 to 1.5% of the total seasonal energy demand. Roughly 11 to 18% of the seasonal energy flow was required in the production of eggs and maintenance and growth of nestlings and fledglings.
On the average, between 209 and 386 kg dry wt km-2 of prey were consumed by the bird communities breeding in the grassland locations. Seeds contributed more to the total biomass consumed at the drier plots, but in general, animal prey types comprised roughly 80% of the total biomass eaten. Phytophagous insects were the major component of the animal prey.
These low magnitudes of energy flow and biomass consumption attest to the relatively minor role of birds in the processing of energy and biomass in grassland ecosystems. If these populations do play an ‘importnat’ role in the functioning of grassland ecosystems, it must be quite subtle and indirect.
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References
Cody, M.L.: On the methods of resource division in grassland bird communities. Am. Naturalist 102, 107–147 (1968)
Cummins, K.W., Wuycheck, J.C.: Caloric equivalents for investigations in ecological energetics. Mitt. Int. Ver. Theor. Angew. Limnol. No. 18, 158 pp. (1971)
Fretwell, S.D.: Populations in a seasonal environment. Mongr. Popul. Biol. No. 5, 217 pp. Princeton: Princeton Univ. Press 1972
Gessaman, J.A. (ed.): Ecological energetics of homeotherms. A view compatible with ecological modeling, 155 pp. Logan, Utah: Utah State Univ. Press 1973
Giezentanner, J.B.: Avian distribution and population fluctuations on the shortgrass prairie of north central Colorado. US/IBP Grassland Biome Tech. Rep. No. 62, 113 pp. Fort Collins, Colorado: Colorado State Univ. 1970
Holmes, R.T., Sturges, F.W.: Annual energy expenditure by the avifauna of a northern hardwoods ecosystem. Oikos 24, 24–29 (1973)
Homes, R.T., Sturges, F.W.: Avian community dynamics and energetics in a northern hardwoods ecosystem. J. Anim. Ecol. 44, 175–200 (1973)
Kendeigh, S.C.: Energy requirements for existence in relation to size of bird. Condor 72, 60–65 (1970)
Kendeigh, S.C.: Monthly variations in the energy budget of the House Sparrow throughout the year. In: Productivity, population dynamics, and systematics of grainivorous birds (S.C. Kendeigh, J. Pinowski, eds.), pp. 17–43. Warsaw: Institute of Ecology, Polish Academy of Science 1972
Küchler, A.W.: Potential natural vegetation of the conterminous United States. Am. Geogr. Soc. Spec. Publ. No. 36 (Map) (1964)
Porter, D.K.: Accuracy in censusing breeding passerines on the short-grass prairie. M.S. Thesis, Colorado State University, Fort Collins, Colorado, 107 pp. (1973)
Rogers, L.E., Lavigne, R., Miller, J.L.: Bioenergetics of the Western Harvester Ant in the shortgrass plains ecosystem. Environ. Entomol. 1, 763–768 (1972)
Ryder, R.A.: Avian population studies on the Pawnee Site, 1968–1971. US/IBP Grassland Biome Tech. Rep. No. 171, 62 pp. Fort Collins, Colorado: Colorado State Univ. 1972
Strong, M.A.: Avian productivity on the shortgrass prairie of north-central Colorado. M.S. Thesis, Colorado State University, Fort Collins, Colorado, 70 pp. (1971)
Weiner, J., Głowacínski, Z.: Energy flow through a bird community in a deciduous forest in southern Poland. Condor 77, 233–242 (1975)
West, G.C., DeWolfe, B.B.: Populations and energetics of Taiga birds near Fairbanks, Alaska. Auk 91, 757–775 (1974)
Wiens, J.A.: An approach to the study of ecological interrelationships among grassland birds. Ornithol. Monogr. No. 8, 1–93 (1969)
Wiens, J.A.: Pattern and process in grassland bird communities. Ecol. Monogr. 43, 237–270 (1973)
Wiens, J.A.: Climatic instability and the “ecological saturation” of bird communities in North American grasslands. Condor 76, 385–400 (1974a)
Wiens, J.A.: Habitat heterogeneity and avian community structure in North American grasslands. Am. Midl. Naturalist 91, 195–213 (1974b)
Wiens, J.A.: Avian communities, energetics, and functions in coniferous forest habitats. Proc. Symp. Management Forest and Range Habitats for Nongame Birds. USDA Forest Serv. Gen. Tech. Rep. WO-1, pp. 226–265 (1975)
Wiens, J.A.: Population responses to patchy environments. Ann. Rev. Ecol. Syst. 7, 81–120 (1976)
Wiens, J.A., Dyer, M.I.: Rangeland avifaunas: Their composition, energetics, and role in the ecosystem. Proc. Symp. Management Forest and Range Habitats for Nongame Birds. USDA Forest Serv. Gen. Tech. Rep. WO-1, pp. 146–182 (1975)
Wiens, J.A., Dyer, M.I.: Assessing the potential impact of granivorous birds in ecosystems. In: Granivorous birds in ecosystems (S.C. Kendeigh, J. Pinowski, eds.), Chapter VI. Cambridge: Cambridge Univ. Press 1977
Wiens, J.A., Innis, G.S.: Estimation of energy flow in bird communities. II. A simulation model of activity budgets and population bioenergetics. In: Proc. 1973 Summer Computer Simulation Conference, Montreal, pp. 739–752. La Jolla, California: Simulation Councils 1973
Wiens, J.A., Innis, G.S.: Estimation of energy flow in bird communities: A population bioenergetics model. Ecology 55, 730–746 (1974)
Wiens, J.A., Nussbaum, R.A.: Model estimation of energy flow in northwestern coniferous forest bird communities. Ecology 56, 547–561 (1975)
Wiens, J.A., Scott, J.M.: Model estimation of energy flow in Oregon coastal seabird populations. Condor 77, 439–452 (1975)
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Wiens, J.A. Model estimation of energy flow in North American grassland bird communities. Oecologia 31, 135–151 (1977). https://doi.org/10.1007/BF00346916
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DOI: https://doi.org/10.1007/BF00346916