We’re gathering a large collection of bird community data across regions of North America where coniferous plantations are managed in ways that make complex, broadleaf, early-seral habitat scarce. Typically, this situation arises where conifers are planted and sprayed with herbicides to minimize competition between native early-seral plants such as shrubs and deciduous trees.
We are interested in whether there is a threshold in the amount of land around a plot with early-seral habitat below which bird populations decline. This has been observed in the Pacific Northwest (see graph), but has not been tested across a larger geographic area. Identifying thresholds is important for land management planning because it allows us to understand how much early seral habitat is necessary across the landscape for associated bird species.
We have accumulated several datasets with bird abundance and forest landscape GIS layers to test this hypothesis (see map) and are working toward integrating more data.