Habitat Loss, Degradation, and Fragmentation
Birds and other organisms evolved in floristically and structurally diverse native natural communities that provide a wide variety of habitats and niche spaces, allowing multiple bird species to co-exist in the same area. When these habitats are converted to croplands, non-native grass pastures, urban areas, developed for energy, etc., many species are unable to find food, cover, and nest sites in the altered environments. Habitat conversion results in less suitable habitat being available, thus fewer birds can be supported. In addition to habitat loss, remaining tractCols of habitat are often smaller and more isolated, an outcome known as fragmentation. Fragmented landscapes tend to support more predators and nest parasites, causing a decrease in avian reproduction and adult survival.
Nearly all of the natural communities in the Central Hardwoods Bird Conservation Region evolved with periodic fires intentionally set by Native Americans or sparked by lightning. Fire acts as a thinning agent, leaving trees more widely spaced, or in the case of prairies and barrens, relegating them (trees) to areas where moisture accumulates like shallow wetlands and creek beds. The open canopy that results in woodland settings, in turn, allows more light to reach the ground and stimulate the growth of grasses and forbs. Fire suppression, which became popular in the mid-20th century, has allowed an unnaturally dense growth of trees to grow on woodland sites and effectively shade out the native grasses and forbs associated with a diverse understory. The bird species that have suffered the greatest declines across the Central Hardwoods in recent decades are those associated with grassland and open-woodland systems.
In the modern world, there are an ever-increasing number of barriers to bird flight, such as buildings, communication towers, and windmills that cause direct mortality to millions of birds each year from collisions. While it’s unrealistic to expect that we’ll stop building, there are ways to make these structures less deadly through proper siting, lighting, use of proper building materials, and other means. CHJV partner, American Bird Conservancy, has several programs devoted to finding ways to reduce the mortality to birds from collisions. Read more
The domestic cat is a beloved pet, but it’s also a major threat to birds. Introduced to the United States with European colonists, the number of domestic cats has tripled in the past 40 years. Today, more than 100 million feral and outdoor cats function as an invasive species with enormous impacts. Every year in the United States, cats kill well over 1 billion birds. This stunning level of predation is unsustainable for many already-declining species. To find out more about how keeping cats indoors is better for cats, birds, and people, click here.
Climate change can affect bird species in myriad ways. While the most obvious might seem to be as a result of changes in habitat structure over time, warming can also affect reproductive output and cause changes in the timing of food availability. While some forest types in the Central Hardwoods Region may be negatively impacted by climate change, some of the drier woodland communities in the region may prove more resilient. Read more