Bird Communities and Habitat as Ecological Indicators of Forest Condition in Regional Monitoring

Ecological indicators for long-term monitoring programs are needed to detect and assess changing environmental conditions. We developed and tested community-level environmental indicators for monitor- ing forest bird populations and associated habitat. We surveyed 197 sampling plots in loblolly-shortleaf pine forests, spanning an area from Georgia to Virginia (U.S.A.) and representing a gradient in levels of anthropo- genic disturbance. Ninety of these plots were randomly selected from a sampling grid, permitting quantitative assessment of cumulative distribution functions for bird community and habitat parameters. Species were in- dependently classified into habitat assemblages indicating birds typical of disturbed habitat (e.g., shrubland, forest edge) and undisturbed habitat (mature forest). Relative abundances of these assemblages were used to form a bird community index—similar to the index of biotic integrity applied to aquatic systems—showing the effects of habitat disturbance on forest bird communities. Bird communities on the majority of the sample area (52-75%, 90% confidence interval) were dominated by disturbance-tolerant species. Sites dominated by mature-forest species were comparatively uncommon. Habitat assemblages appeared to be particularly useful tools for environmental monitoring; individual species abundance was positively correlated with assemblage species richness, and assemblage members showed consistent responses to variations in disturbance level. To a lesser extent, component species of nesting guilds showed this pattern of cohesive responses, but those of for- aging guilds did not. We also developed a habitat index based on habitat variables that predicted bird com- munity index values. Habitat and bird community indices were strongly correlated in an independent vali- dation dataset, suggesting that the habitat index can provide a reliable predictor of bird community status. The two indices may be used in combination, with the bird community index providing a direct measure of the status of the bird community and the habitat index providing a basis on which to separate changes in the bird community into local habitat effects versus other factors (e.g., landscape level effects, changes on winter- ing grounds).

[1]  D. Finch.  Population ecology, habitat requirements, and conservation of neotropical migratory birds , 1991 .

[2]  M. Willson,et al.  Avian Community Organization and Habitat Structure , 1974 .

[3]  J. Karr.  Biological Integrity: A Long-Neglected Aspect of Water Resource Management. , 1991, Ecological applications : a publication of the Ecological Society of America.

[4]  C. S. Robbins,et al.  Habitat area requirements of breeding forest birds of the middle Atlantic states , 1989 .

[5]  M. Morrison,et al.  The use of guilds in forest bird management. , 1984 .

[6]  T. E. Martin.  Nest Predation and Nest SitesNew perspectives on old patterns , 1993 .

[7]  T. E. Martin,et al.  Life History Traits of Open- vs. Cavity-Nesting Birds , 1992 .

[8]  Michael L. Morrison,et al.  Bird Populations as Indicators of Environmental Change , 1986 .

[9]  R. B. Root.  The Niche Exploitation Pattern of the Blue‐Gray Gnatcatcher , 1967 .

[10]  James R. Karr,et al.  Spatial and Temporal Variability of the Index of Biotic Integrity in Three Midwestern Streams , 1987 .

[11]  Sam Droege,et al.  The Summer Atlas of North American Birds , 1995 .

[12]  William D. Severinghaus,et al.  Guild theory development as a mechanism for assessing environmental impact , 1981 .

[13]  James R. Karr,et al.  Biological Integrity versus Biological Diversity as Policy DirectivesProtecting biotic resources , 1994 .

[14]  R. W. Mannan,et al.  Bird populations and vegetation characteristics in managed and old-growth forests, northeastern Oregon. , 1984 .

[15]  P. Ehrlich.  The Birder's Handbook , 1988 .

[16]  T. E. Martin,et al.  Avian Life History Evolution in Relation to Nest Sites, Nest Predation, and Food , 1995 .

[17]  E. Odum,et al.  Breeding Bird Populations in Relation to Plant Succession on the Piedmont of Georgia , 1956 .

[18]  D. Finch,et al.  Single-species versus multiple-species approaches for management , 1995 .

[19]  R. Szaro.  Guild management: an evaluation of avian guilds as a predictive tool , 1986 .

[20]  R. Sharitz,et al.  Integrating Ecological Concepts with Natural Resource Management of Southern Forests. , 1992, Ecological applications : a publication of the Ecological Society of America.

[21]  J. Karr.  Assessment of Biotic Integrity Using Fish Communities , 1981 .

[22]  D. Bradford,et al.  Bird Species Assemblages as Indicators of Biological Integrity in Great Basin Rangeland , 1998 .

[23]  Gerald J. Niemi,et al.  The Grinnellian Niche of the Wood Thrush , 1984, The American Naturalist.

[24]  Robert P. Brooks,et al.  Use of avian and mammalian guilds as indicators of cumulative impacts in riparian-wetland areas , 1991 .

[25]  J. W. Thomas,et al.  Ecological Uses of Vertebrate Indicator Species: A Critique , 1988 .

[26]  T. E. Lewis,et al.  Forest health monitoring: Southeast loblolly/shortleaf pine demonstration interim report , 1994 .

[27]  J. Verner,et al.  The guild concept applied to management of bird populations , 1984 .