Species – Habitat Associations 

Background

The concept of habitat in ecology includes the geographic, biotic, and abiotic factors that determine the occurrence of a species at a given place and time. The habitat of a species can be defined by the relative presence or absence on the landscape of resources necessary for survival and reproduction of individuals. 

Why Vegetation Alone Isn’t Enough

While habitat for a given species is often thought of in terms of vegetation communities and physical habitat features, the resource needs of a species often require individuals to cross boundaries between these defined units. Studies show that vegetation communities are an imperfect surrogate for species distributions (Robinson 2012) so assumptions should not be made that conservation of special natural communities will adequately conserve all SGCN. In addition, in human-altered landscapes, some species may choose lower quality habitats over higher quality habitats, with the former functioning as ecological traps (Hollander et al. 2011). In these cases, the presence of a species in each habitat may not indicate successful reproduction or survival in that habitat.  

Big Picture and Fine Detail: A Smarter Path to Conservation

These caveats illustrate the importance of using both coarse- and fine-scale approaches to species and habitat conservation. Conservation of land cover types at a broad scale and focused protection of vegetation associations at the narrow scale should be one of the goals of any conservation strategy, but species-specific and guild-specific approaches should also be developed. A renewed focus on life history data for many species, especially invertebrates, is necessary to direct management decision-making. 

Species – Habitat Associations in Delaware 

A gap analysis of animal species distributions for Maryland, Delaware and New Jersey was developed by McCorkle et al. (2006). This effort developed habitat models and distribution maps for 363 animal species (206 birds, 69 mammals, 47 reptiles, and 41 amphibians). Bird habitat models and distribution maps were limited to those species that regularly nest within the project area. 

The gap analysis found that habitats supporting the rare to extremely rare species that were underrepresented in GAP status 1 and 2 (protected) lands include early successional habitats, vernal pools (non-tidal, isolated, seasonally flooded wetlands) with substantial upland forest buffers, forested wetlands, and freshwater marshes, forest interior, broad riparian and floodplain forests, and beach and dune habitats. The report also found that the most significant unprotected habitats for rare species were the large concentration of coastal plain ponds (i.e., vernal pools) and surrounding hardwood forests in the Blackbird-Millington Corridor of Delaware and Maryland (McCorkle et al. 2006).

For the 2025 DEWAP revision, species-habitat associations included in the previous DEWAP were reassessed, and assigned for new SGCN. Habitat associations were denoted as either Primary or Supplemental, depending on the degree of reliance of a species on the habitat at any life stage. 

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