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Oecologia

, Volume 42, Issue 3, pp 253–292 | Cite as

Diet niche relationships among North American grassland and shrubsteppe birds

  • John A. Wiens
  • John T. Rotenberry
Article

Summary

We consider the dietary relationships of the numerically dominant breeding bird species in four North American grassland/shrubsteppe habitats, sampled over 2–3 consecutive years. Overall, the diets of these species contained primarily insects: orthopterans comprised 29% of the diet biomass, coleopterans 24%, and lepidopteran larvae 23%, while seeds contributed 15% of the average diet. These diets varied substantially, however, and we evaluated several aspects of this variation. Intersexual differences in diets within a species were few, despite the occurrence of significant sexual size dimorphism in several species. For many species, however, there were substantial shifts in dietary composition between years at a given location; overall, the average between-year similarity of species' dietary composition was 70%. Different species exhibited rather different diet patterns. Horned Larks were relatively omnivorous, had broad diet composition niches, and varied considerably in diets between different locations. Meadowlarks were also broad-niched and geographically variable in their diets, but were the most highly carnivorous of the species we considered. Dietary niche breadths of Grasshopper Sparrows were intermediate, but diet composition was rather stable, both between years and between locations. Chestnut-collared Longspurs exhibited narrow diet niches, but substantial annual variation: each year this species apparently exploited a different but limited set of prey types rather heavily. Larger avian predators generally consumed a broader array of functional groups of prey, but did not differ in the taxonomic variety of their diets from small birds. Variation in diet composition between individuals within local populations was considerable; in most species, an individual contained on the average 30–40% of the prey taxa represented in entire population smaples.

Patterns of dietary overlap among species were quite inconsistent from year to year at most locations, although at the shrubsteppe site overlap among all species present was consistently quite high. Relatively few cooccurring species pairs exhibited low diet overlap. The degree of diet niche overlap was unrelated to body size differences of the birds, despite as much as six-fold differences in weight among some coexisting species. Relationships of the bird species on another dimension of the trophic niche, prey size, also differed substantially between sites and years. The ranking of co-occurring species by the mean sizes of the prey they consumed generally did not parallel their rankings by body sizes, and in some cases the smallest and the largest species present ate prey of similar sizes. At the shrubsteppe site, all the breeding species exhibited quite similar frequency distributions of prey sizes in their diets.

As species number and diversity increased in the breeding avifaunas, diet niche breadths generally decreased, species packing by prey size decreased, and diet composition niche overlap remained relatively unchanged. These trends are in at least partial agreement with predictions of diffuse competition theory, but the patterns were derived from broad inter-site comparisons of overall site averages, and the relationships generally did not hold within local assemblages of species. In general, our attempts to match values of dietary niche features with site characteristics failed to demonstrate close agreement with the predictions of prevailing ecological theory based upon assumptions of resource limitation and competition. Instead, our findings seem generally most consistent with the suggestion that food is not normally limiting to bird populations in these systems, and individuals and populations are exploiting the food resources in an opportunistic fashion, which leads to considerable individual, between-year, and between-location variation in diet compositions and interspecific overlaps.

Our attempts to discern clear relationships that accord with theoretical expectations in these avian assemblages are thwarted by our lack of detailed information on the resource base and by the lack of clear tests that will separate alternative hypotheses of community organization and structuring. We suggest that these complications may compromise the findings of many community studies.

Keywords

Niche Breadth Prey Size Sexual Size Dimorphism Diet Niche Intersexual Difference 
These keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.

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References

  1. Baker, M.C.: Shorebird food habits in the Eastern Canadian Arctic. Condor 79, 56–62 (1977)Google Scholar
  2. Baker, M.C., Baker, A.E.M.: Niche relationships among six species of shorebirds on their wintering and breeding ranges. Ecol. Monogr. 43, 193–212 (1973)Google Scholar
  3. Beaver, D.L., Baldwin, P.H.: Ecological overlap and the problem of competition and sympatry in the Western and Hammond's flycatchers. Condor 77, 1–13 (1975)Google Scholar
  4. Brown, J.H.: Geographical ecology of desert rodents. In: Ecology and evolution of communities (M.L. Cody, J.M. Diamond, eds.), pp. 315–341. Cambridge, Mass.: Belknap Press 1975Google Scholar
  5. Brown, J.H., Liebermann, G.A.: Resource utilization and coexistence of seed-eating desert rodents in sand dune habitats. Ecology 54, 788–797 (1973)Google Scholar
  6. Cody, M.L.: Competition and the structure of bird communities. Monogr. Popul. Biol. No. 7. Princeton, N.J.: Princeton Univ. Press 1974Google Scholar
  7. Cohen, J.E.: Food webs and niche space. Monogr. Popul. Biol. No. 11. Princeton, N.J.: Princeton Univ. Press 1978Google Scholar
  8. Colwell, R.K., Futuyma, D.J.: On the measurement of niche breadth and overlap. Ecology 52, 567–576 (1971)Google Scholar
  9. Connell, J.H.: Diversity in tropical rain forests and coral reefs. Science 199, 1302–1310 (1978)Google Scholar
  10. Custer, T.W., Pitelka, F.A.: Correction factors for digestion rates for prey taken by Snow Buntings (Plectrophenax nivalis). Condor 77, 210–212 (1975)Google Scholar
  11. Custer, T.W., Pitelka, F.A.: Seasonal trends in summer diet of the Lapland Longspur near Barrow, Alaska. Condor 80, 295–301 (1978)Google Scholar
  12. Davidson, D.W.: Foraging ecology and community organization in desert seed-eating ants. Ecology 58, 725–737 (1977)Google Scholar
  13. Diamond, J.M.: Niche shifts and the rediscovery of interspecific competition. Am. Sci. 66, 322–331 (1978)Google Scholar
  14. Ellis, J.E., Wiens, J.A., Rodell, C.F., Anway, J.C.: A conceptual model of diet selection as an ecosystem process. J. Theor. Biol. 60, 93–108 (1976)Google Scholar
  15. Emlen, J.M.: Ecology: an evolutionary approach. Reading, Mass.: Addison-Wesley 1973Google Scholar
  16. Hansen, S.R.: Resource utilization and coexistence of three species of Pogonomyrmex ants in an Upper Sonoran grassland community. Oecologia 35, 109–117 (1978)Google Scholar
  17. Herrera, C.M., Hiraldo, F.: Food-niche and trophic relationships among European owls. Ornis Scand. 7, 29–41 (1976)Google Scholar
  18. Hespenheide, H.A.: Prey characteristics and predator niche width. In: Ecology and evolution of communities (M.L. Cody, J.M. Diamond, eds.), pp. 158–180. Cambridge, Mass.: Belknap Press 1975Google Scholar
  19. Hill, M.O.: Diversity and evenness: a unifying notation and its consequences. Ecology 54, 427–432 (1973)Google Scholar
  20. Jarman, P.J.: The social organisation of antelope in relation to their ecology. Behaviour 48, 215–266 (1974)Google Scholar
  21. Lack, D.: Population studies of birds. Oxford: Clarendon Press 1966Google Scholar
  22. Lack, D.: Ecological isolation in birds. Cambridge, Mass.: Harvard Univ. Press 1972Google Scholar
  23. Leigh, E.G., Jr.: Population fluctuations, community stability, and environmental variability. In: Ecology and evolution of communities (M.L. Cody, J.M. Diamond, eds.), pp. 51–73. Cambridge, Mass.: Belknap Press 1975Google Scholar
  24. MacArthur, R.H.: Species packing and what competition minimizes. Proc. Natl. Acad. Sci. USA 64, 1369–1371 (1969)Google Scholar
  25. MacArthur, R.H.: Geographical ecology. New York: Harper and Row 1972Google Scholar
  26. MacArthur, R.H., Levins, R.: Competition, habitat selection, and character displacement in a patchy environment. Proc. Natl. Acad. Sci. USA 51, 1207–1210 (1964)Google Scholar
  27. MacArthur, R.H., Pianka, E.R.: On optimal use of a patchy environment. Am. Natur. 100, 603–609 (1966)Google Scholar
  28. Marti, C.D.: Feeding ecology of four sympatric owls. Condor 76, 45–61 (1974)Google Scholar
  29. May, R.M.: On the theory of niche overlap. Theor. Popul. Biol. 5, 297–332 (1974)Google Scholar
  30. May, R.M.: Some notes on estimating the competition matrix, α. Ecology 56, 737–741 (1975)Google Scholar
  31. May, R.M.: Models for two interacting populations. In: Theoretical ecology. Principles and applications (R.M. May, ed.), pp. 49–70. Philadelphia: W.B. Saunders 1976Google Scholar
  32. May, R.M., MacArthur, R.H.: Niche overlap as a function of environmental variability. Proc. Natl. Acad. Sci. USA 69, 1109–1113 (1972)Google Scholar
  33. M'Closkey, R.T.: Niche separation and assembly in four species of sonoran desert rodents. Am. Natur. 112, 683–694 (1978)Google Scholar
  34. McNaughton, S.J., Wolf, L.L.: Dominance and the niche in ecological systems. Science 167, 131–139 (1970)Google Scholar
  35. Menge, B.A., Sutherland, J.P.: Species diversity gradients: synthesis of the roles of predation, competition, and temporal heterogeneity. Am. Natur. 110, 351–369 (1976)Google Scholar
  36. Pianka, E.R.: Sympatry of lizards (Ctenotus) in Western Australia. Ecology 50, 1012–1030 (1969)Google Scholar
  37. Pianka, E.R.: Niche overlap and diffuse competition. Proc. Natl. Acad. Sci. USA 71, 2141–2145 (1974)Google Scholar
  38. Pianka, E.R.: Competition and niche theory. In: Theoretical ecology. Principles and applications (R.M. May, ed.), pp. 114–141. Philadelphia: W.B. Saunders 1976Google Scholar
  39. Pianka, E.R.: Reptilian species diversity. In: Biology of the reptilia, vol. 7 (C. Gans, D.W. Tinkle, eds.), pp. 1–34. New York: Academic Press 1977Google Scholar
  40. Rogers, L.E., Buschbom, R.L., Watson, C.R.: Length-weight relationships of shrubsteppe invertebrates. Ann. Ent. Soc. Amer. 70, 51–53 (1977)Google Scholar
  41. Rotenberry, J.T.: Components of avian diversity along a multifactorial climatic gradient. Ecology 59, 693–699 (1978)Google Scholar
  42. Rotenberry, J.T.: Dietary relationships among shrubsteppe passerine birds: competition or opportunism in a variable environment? Ecol. Monogr. (in press)Google Scholar
  43. Rotenberry, J.T., Wiens, J.A.: Nongame bird communities in northwestern rangelands. USDA Forest Serv. Gen. Tech. Rept. PNW-64, 32–46 (1978)Google Scholar
  44. Schoener, T.W.: Theory of feeding strategies. Ann. Rev. Ecol. Syst. 2, 369–404 (1971)Google Scholar
  45. Schoener, T.W.: Resource partitioning in ecological communities. Science 185, 27–39 (1974)Google Scholar
  46. Schoener, T.W.: Competition and the niche. In: Biology of the reptilia, vol. 7 (C. Gans, D.W. Tinkle, eds.), pp. 35–136. New York: Academic Press 1977Google Scholar
  47. Selander, R.K.: Sexual dimorphism and differential niche utilization in birds. Condor 68, 113–151 (1966)Google Scholar
  48. Simpson, E.H.: Measurement of diversity. Nature 163, 688 (1949)Google Scholar
  49. Sims, P.L., Singh, J.S., Lauenroth, W.K.: The structure and function of ten western North American grasslands. I. Abiotic and vegetational characteristics. J. Ecol. 66, 251–285 (1978)Google Scholar
  50. Sokal, R.R., Rohlf, F.J.: Biometry. San Francisco: W.H. Freeman and Co. 1969Google Scholar
  51. Stander, J.M.: Diversity and similarity of benthic fauna off Oregon. Unpubl. M.S. thesis, Corvallis: Oregon State UniversityGoogle Scholar
  52. Watson, A. (ed.): Animal populations in relation to their food resources. Oxford: Blackwell Scientific Pub. 1970Google Scholar
  53. Werner, E.E., Hall, D.J.: Competition and habitat shift in two sunfishes (Centrarchidae). Ecology 58, 869–876 (1977)Google Scholar
  54. Wiens, J.A.: Pattern and process in grassland bird communities. Ecol. Monogr. 43, 237–270 (1973)Google Scholar
  55. Wiens, J.A.: Climatic instability and the “ecological saturation” of bird communities in North American grasslands. Condor 76, 385–400 (1974)Google Scholar
  56. Wiens, J.A.: On competition and variable environments. Am. Sci. 65, 590–597 (1977 a)Google Scholar
  57. Wiens, J.A.: Model estimation of energy flow in North American grassland bird communities. Oecologia 31, 135–151 (1977 b)Google Scholar
  58. Wiens, J.A., Dyer, M.I.: Rangeland avifaunas: their composition, energetics, and role in the ecosystem. USDA Forest Serv. Gen. Tech. Rept. WO-1, 146–182 (1975)Google Scholar
  59. Wiens, J.A., Rotenberry, J.T.: Bird community structure in cold shrub deserts: competition or chaos? Proc. 17th Intern. Ornithol. Congr. (in press)Google Scholar
  60. Wiens, J.A., Ward, J.F., Rotenberry, J.T.: Dietary composition and relationships among breeding bird populations on US/IBP Grassland Biome sites. U.S. IBP Grassland Biome Tech. Rep. No. 265, 1–92 (1974)Google Scholar
  61. Yeaton, R.I.: An ecological analysis of chaparral and pine forest bird communities on Santa Cruz Island and mainland California. Ecology 55, 959–973 (1974)Google Scholar
  62. Zimmerman, J.L.: The territory and its density dependent effect in Spiza americana. Auk 88, 591–612 (1971)Google Scholar

Copyright information

© Springer-Verlag 1979

Authors and Affiliations

  • John A. Wiens
    • 1
  • John T. Rotenberry
    • 1
  1. 1.Shrubsteppe Habitat Investigation Team, Department of BiologyUniversity of New MexicoAlbuquerqueUSA

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