Wildlife management agencies in North America have a long history of using aircraft to monitor population abundance of ducks, geese, swans, and other migratory birds. While low-level, ocular surveys have been very successful and cost-efficient, they subject agency personnel to substantial risk. Ocular surveys, involving multiple air crews and observers, must include methods to minimize or estimate important biases such as detection, misclassification, flock-size estimation, and sample area determination.
Birds and Animals
Documenting bird and bat migration is challenging because migration activity is sporadic and nocturnal migrants (i.e., most aerial migrants) are difficult to observe. The FWS uses avian radar to monitor the timing, duration, and activity patterns of birds and bats as they move through the Great Lakes (https://www.fws.gov/radar). Each radar unit has a horizontal antenna that scans 360° just above the horizon and a vertical antenna that scans a vertical slice of the sky.
Several National Wildlife Refuges (NWRs) in Alaska have joined in a large-scale collaboration across the Northwest boreal forest to study Lynx (Lynx canadensis) through the peak and crash of the snowshoe hare (Lepus americanus) population cycle. Snowshoe hares make up 30–100% of a lynx diet. Lynx populations follow the snowshoe hare population with a 1- to 2-year time lag. The lynx and hare population cycles seem to radiate from central Canada such that the peak in central Canada occurs about 2 years prior to the peak in the Yukon Territory and Alaska.
During winter, bald eagles (Haliaeetus leucocephalus) tend to congregate around any open waters within ice-covered rivers and lakes in the upper Midwest in their search for fish. Open waters can range from a small stream or stormwater outlet a few meters across to many kilometers of open water such as along the Mississippi River. Ice formation rapidly changes from day to day depending on weather patterns, currents, and thermal inputs from power plants. Ice can form and thaw in a matter of hours.
Models of animal density commonly use coarse land cover categories that homogenize vegetation attributes, thereby limiting specificity of results. Alternatively, models including land surface phenology (LSP) metrics derived from Moderate Resolution Imaging Spectroradiometer (MODIS) imagery capture continuous data describing plant growth and senescence. LSP metrics may better discriminate the vegetation conditions influencing species habitat and distribution.
The Bear River Migratory Bird Refuge, located west of Brigham City, Utah, where the Bear River terminates into the Great Salt Lake, is a critically important feeding, resting, and breeding area for many species of migratory water birds. Established by Congress in 1928 to help conserve and protect the once vast, productive marshes on the Bear River delta, the refuge today faces many challenges including excess nutrients and sedimentation, invasive plants, and altered hydrology.
On the Kenai National Wildlife Refuge near Headquarters Lake is a small colony of Aleutian terns that nest alongside Arctic terns. Aleutian terns breed in small colonies along the Alaskan coast and in the Russian Far East. Unlike the Arctic tern and other more abundant seabirds, very little is known about the Aleutian tern. Recent analysis of historical survey data has shown a 93% decline of the Aleutian tern since 1960.
The western U.S. Gulf of Mexico coast provides important habitat for migrating waterfowl and shorebirds. The Gulf Coast Joint Venture (GCJV) uses bioenergetic models (i.e., models that incorporate species-specific population objectives, temporal residency, energy demand of birds, and foraging values of habitats) to translate fall–winter waterfowl population targets and summer–fall shorebird population targets into habitat objectives for this important region. These objectives are expected to represent landscape conditions needed to support desired population levels.
Wildland fires are an important natural disturbance in semi-desert grasslands, but they can pose a threat to natural resource values and private property. Predicting the spread and intensity of fires allows for the prioritization of areas to mitigate fuels and reduce fire hazard. Fire behavior models for grasslands fundamentally depend on topography, fire weather, and presumed fuel-bed conditions. National fuel model data products are available through Landscape Fire and Resource Management Planning Tools (LANDFIRE).
Monitoring the dynamic changes of glacial landscapes requires detailed topographic elevation data. In the late summer of 2016, the Kenai National Wildlife Refuge collected 75-cm multispectral imagery on over 4 million acres of the Kenai Peninsula. For the past several years an ecologist at the refuge has been collecting aerial photography and processing the imagery using Structure from Motion software.