Species of birds that exhibit this dual residency are called neotropical migrants . The yearly migrations of many of these birds, often covering thousands of miles over ocean and other inhospitable terrain, rank among the most incredible wildlife journeys known. Neotropical migrants appear to be among the bird species most threatened by human caused changes in the environment. Many of these species are unable to adapt to the clearing of forests and brushlands for residential and commercial development, grazing for livestock, and farm crops. A number of the migrants are vulnerable to nest parasitism by the brown-headed cowbird, a species of blackbird which is attracted to domestic livestock and grain.
Programs are also in place along the Texas coast to preserve essential habitats for migrating birds.