Image Credit: August Froehlich

Model Attributes
& Caveats

Please read: Important things to keep in mind when using any of the models

Please keep scale in mind: The results from this project provide guidance regarding the spatial distribution and factors affecting viability of stopover sites, and can be specifically incorporated into a wide range of plans and planning processes, including the Upper Mississippi River and Great Lakes Region Joint Venture; lake-wide conservation plans for Lakes Michigan, Huron, Erie and Ontario that have been developed by The Nature Conservancy; state wildlife action plans; and other regional plans that include protection of migratory birds, such as the Wisconsin Bird Conservation Initiative and Chicago Wilderness. The models produced with this project build upon stopover models developed earlier as we have incorporated results from new literature in these models. Yet, the regional models lack some detail provided in earlier work where local, fine resolution data layers were available. Users at any one site may find it most valuable to review both the Great Lakes regional model and more localized models when applying this work for conservation purposes. We suggest that the maps produced by the models and displayed on this web portal are best seen as a screening tool for choosing among options at larger spatial scales that should be complemented with local information on habitat quality when used to make conservation decisions.

Remember the resolution of the data: We aggregated raster data layers with a resolution of 30m (approximately 0.1 ha) pixels into 100 m (1 ha) pixels to approximate the minimum size of areas in which migrants move during any one stopover event. The most common, or majority, land cover was assigned to each 1 ha pixel; some fine scale ecological information is lost with this approach. However, this aggregation facilitated data analysis and summarization, is more consistent with the spatial scale at which conservation actions are implemented than a 30 m resolution, and is similar to the approach taken by Stralberg et al. (2011). However, we recognize that some areas < ha may be very important for birds under some circumstances and may not be identified as stopover sites with this approach if they have been aggregated with a “non-habitat” landcover type.

Habitat characteristics that we couldn’t “map” with GIS at the regional scale are still important: Although we considered both landscape and site influences on stopover habitat selection and use by migrants in our models, both of which governed the choice of spatial scale of analysis, the models are based on landscape features because there are insufficient data layers describing site features, such as vegetation structure or plant species composition, at a regional or more local scale.

Spring and fall migrations likely differ; these models are based on spring migrations: The attributes selected, and values for each attribute, primarily reflect migrant distribution in the spring when landbirds, and possibly other bird groups, are most concentrated near large bodies of water like the Great Lakes. However, it is likely that many important fall migration areas in our study area are captured by our models.

The complete report describing the stopover models is available here.

Setting Stopover Conservation Goals

Although very challenging to establish, articulating conservation goals, based on scientific, operationally realistic, and objective criteria, provides a foundation for estimating the magnitude of work and financial resources needed to achieve conservation results. Although goals are never perfect, they provide important guidelines to direct our work and, when accomplished, when to celebrate and when to focus resources on other conservation goals.

For landbirds, we set a goal of 40% of the landscape be in natural cover within 3 miles (5 km) of a site. The basis for this goal is that several studies, though not all, suggest that landbirds are more crowded, and gain less weight, where less than 15% of the landscape is in suitable habitat compared to landscapes with >15% of suitable habitat and especially with >40% suitable habitat. We think that the scientific literature is sufficiently consistent to articulate this goal to ensure the health of migrating landbirds. We recognize that this goal cannot be achieved everywhere, especially in highly developed urban and some agricultural areas. In these areas goals might focus on improving the quality of existing sites where protecting more habitat is unlikely or can be only be done at very small scales.

We have not yet set goals for shorebirds or waterfowl, as there is insufficient information for shorebirds and waterfowl to define criteria for establishing goals.

More research will improve our ability to establish goals but we now have, at least, a conservation goal to measure our progress toward providing safe passage of landbirds through the Great Lakes region.