Effects of housing growth on forest bird populations

Collaborators: Anna M. Pidgeon, Volker C. Radeloff, Roger B. Hammer, Christopher A. Lepczyk, Mike Mossman, and Nancy Braker

The objective of this project is to evaluate housing growth over time in the forested regions of Wisconsin and its effects on forest songbird populations at two spatial scales. The first scale of focus is the Baraboo Hills landscape in southwestern Wisconsin. In the late 1970's, researchers conducted an extensive survey of the avifauna of the Baraboo Hills and more recently, these study sites have been re-sampled, presenting a unique opportunity to evaluate changes in the bird community over a longer period than many local-scale studies. Using a GIS, data on housing, land cover, and landscape indices of fragmentation will be obtained by manual digitization of individual housing units and land cover classes from orthorectified aerial photographs from 1978 and digital orthophotos from 2001 using USGS topographic maps (1:24,000) as a guide. We will use regression modeling to relate measures of housing density, land cover, and fragmentation to census data of individual bird species, forest-interior and low-nesting guilds, as well as non-native and human commensal species. Because of its importance for long-term population survival, understanding how housing density is related to the reproductive success of birds is critical. To achieve this, we will measure pairing and nest success for low-nesting forest songbirds. At the state level, we will use a time series of decadal housing density change that was derived from U.S. Census data to relate to Breeding Bird Survey data available since 1966. It is important to link these two spatial scales to assess the extent, and at which scale, housing most affects the measures of songbird abundance and breeding success. We hope that our findings will help to evaluate current conservation efforts and reserve designs while identifying opportunities to further protect the diverse and unique assemblage of songbirds in this important region.

Acknowledgements:
This research is funded by the U.S. Department of Agriculture McIntire-Stennis grant, WI DNR State Wildlife Grant, the Wisconsin Bird Conservation Initiative, and The Nature Conservancy.