Issue At Hand

Evaluating population trends requires baselines. In North America, the earliest population data available for evaluating bird population changes are those from the late 1960s. At this time, however, forests of the northern Great Lakes region were undergoing rapid change as they rebounded from widespread logging around the turn of the 20th century. It is expected that bird populations were undergoing similarly rapid change.

What We Hope to Accomplish

We propose pre-Euro-American settlement as an alternative baseline for assessing changes in bird populations, and develop a method for assessing the availability and quality of bird habitat at this time period.

How We Go About It

We construct bird-habitat relationships based on published accounts and regional datasets. Models of these relationships are then applied to widely available vegetation data from the presettlement and current periods. Using this technique, we evaluated changes in breeding bird habitat of three forest birds: the Pine, Black-burnian, and Black-throated Green Warblers.

What We Found

The overall habitat quality has degraded since the presettlement period for the species we examined. Sources of habitat loss and degradation include loss of conifers, especially eastern hemlock and eastern white pine, and loss of large trees. The spatial distribution of habitat has also shifted among regions. Species range expansion has accompanied forest incursion into previously open habitats and the replacement of native forests with pine plantations.