Effects of MTR on avian diversity and abundance, cerulean warblers as a case study

Background/Question/Methods

The coal mining technique of mountaintop removal-valley fill (MTR) converts a landscape of predominately mature deciduous forest to a landscape containing reclaimed grassland and scrubland habitats that surround remnant forest patches.  This paper synthesizes results from avian studies conducted in southern West Virginia on and surrounding 3 MTR mines.  We quantified richness and relative abundance of songbird populations in relatively intact forest landscape and in grassland, scrubland, and fragmented forest sites on the post-mining landscape.  Specifically for species that require forested habitats, we compared abundance of species in intact and fragmented forests.  We also focused on Cerulean Warblers (Dendroica cerulea), a species of conservation concern, because a high proportion of its core range occurs in forested areas of southern West Virginia. 

Results/Conclusions

Overall songbird richness and abundance were highest in reclaimed scrublands, lowest in reclaimed grasslands, and did not differ between intact and fragmented forests because increased abundance of edge and interior-edge species in fragmented forests balanced the loss of forest-interior species.  Grassland, edge, and interior-edge songbirds were more abundant on the post-mining landscape. Forest-interior species overall were significantly more abundant in intact than fragmented forest.  Specifically, Cerulean Warblers were more abundant in intact forest, had greater territory density, and occurred at a higher proportion of sample points.  Their territory density was 4.6 territories per 10 ha in intact forest and 0.7 territories per 10 ha in fragmented forest.  Abundance and territory density increased with increasing distance from MTR edge, although this edge avoidance did not occur with smaller-scale edges such as canopy gaps and roads.  Territory placement on ridges was greater than expected with 50% of all territories on ridges.  In general, Cerulean Warblers appear to be negatively affected by MTR from loss of forested habitat, particularly ridgetops where they occur in greater densities, and from degradation of remaining forests, as evidenced by lower territory density in fragmented forests and lower territory density and abundance closer to MTR mine edges.  The severity of the habitat loss and fragmentation will depend on whether MTR areas are reforested or if they remain in early stages of succession.  Non-timber post-mining land uses such as grazing or development will result in permanent fragmentation of forest habitats.  Reclamation techniques that emphasize reforestation may help ameliorate effects of forest loss and fragmentation.