Subdivision design and stewardship characteristics influence bird and mammal use of conservation developments in northern Colorado, USA
Due to rapid human population growth, accelerated rates of land conversion, and decreased public land acquisition, developing effective tools for conservation on private lands is increasingly important for global biodiversity conservation. One strategy is conservation development (CD), which clusters houses in a small portion of a property and preserves the remaining land as protected open space. Despite widespread use, the characteristics that make CD more or less effective at achieving biodiversity conservation are not well understood. We investigated CD’s ability to successfully protect animal populations by examining bird and mammal habitat use in 14 CD subdivisions (range: 14-432 ha) in Northern Colorado, USA. Using point count and camera trap data in an occupancy modeling framework, we evaluated the relative effects of 8 subdivision design (e.g. area, housing density, proportion of protected space) and 11 stewardship factors (e.g. mowing, livestock, native vegetation cover) on the probability of use by 12 bird and 8 mammal species.
We found that subdivision design had a greater overall influence on habitat use than stewardship; a majority (75%) of birds and mammals had at least one design variable in their top occupancy models. The proportion and total area of protected open space positively influenced habitat use by human-sensitive bird species such as the Lark Sparrow, Blue-gray Gnatcatcher, and Lazuli Bunting, and mid- to large- mammals such as the striped skunk, coyote, and mule deer. Housing density in the surrounding landscape positively influenced the probability of use by non-native and human-adapted species such the Eurasian-collared Dove, European Starling, and Northern Flicker, and decreased the probability of use for elk, black-tailed prairie dog, and American black bear. The stewardship characteristic with the greatest influence on bird and mammal occurrence was the percent cover of native vegetation in the protected open space, whereas localized disturbances such as dogs, recreation, or mowing in the open space did not have a strong effect on habitat use. By identifying characteristics that promote the persistence of sensitive animal species, this research enhances the ability for CD to balance the housing needs of growing human communities with the preservation of diverse and abundant animal populations.