Migratory birds are those birds listed as protected under the Migratory Bird Treaty Act (1918) (MBTA).
Currently, the U.S. Fish and Wildlife Service notes that some 836 species of birds are protected under the MBTA, of which 78 species are listed as endangered and 14 species are listed as threatened under the Endangered Species Act (ESA). An additional 144 MBTA species are listed on the Birds of Conservation Concern watch list, where populations are said to be declining precipitously.
Species protected under the MBTA include commonly hunted waterfowl, a wide variety of raptors, vultures, the California condor, crows, ravens, grackles, American woodcock and a large variety of seabirds.
Various causes of mortality to migratory birds include predation, disease, habitat loss and such anthropogenic causes as collisions with man-made structures (tall buildings, power poles, wind power turbines), poisoning (oil spills, pesticides), predation by feral cats, and “by catch” where sea birds are entangled in fishing nets and long lines.
Increased loss of habitat for migratory birds, notably waterfowl, due to pollution of soils, riparian environments, and aquifers can complicate environmental policy in the U.S. For example, the proposed construction of unlined wetland “ponds” in the Imperial Valley of California, where phosphate and selenium saturation of the soil within the mitigatory wetlands is estimated to occur in as little as 4-5 years. Contamination could result in violations of the “strict liability” language of the MBTA, which is currently being evaluated by the U.S. Fish and Wildlife Service and various environmental groups.
On December 19, 2010, the U.S. Fish and Wildlife Service banned lead ammunition for all take of migratory birds under the Depredation Order for blackbirds, cowbirds, grackles, crows and magpies in order to prevent alleged toxicity hazards to other wildlife. There is concern that the MBTA can be used like the ESA to promulgate more hunting and recreational shooting restrictions, including the use of lead ammunition.
Hunt for Truth is currently evaluating allegations regarding lead poisoning in migratory birds and upland game due to the ingestion of lead ammunition.