What are the threats to Maine's wading birds and their habitat?
Small Populations
As Maine marks the edge of the range for many wading bird species, their populations are small and consequently vulnerable to habitat loss and alteration. For example, Great and Snowy Egrets, Glossy Ibis, and Least Bittern reach the northern extent of their range in Maine , where they nest in just a few locations.
Human Disturbance
In contrast, Great Blue Herons are among the more abundant and widely distributed of the wading birds. However, they often nest in the tops of dead trees where they build large stick nests. These colonies of 2 to 200 nesting pairs are frequently, but not always, located in places with limited human disturbance. Road construction, logging, and human presence within or near established colonies can result in loss of many young herons in a single nesting season and abandonment of the colony in future years.
Pollution
The diet of many wading birds includes fish, amphibians, and large insects placing them near the top of the food chain. Top predators, especially in aquatic ecosystems, such as herons and egrets are vulnerable to accumulation of environmental contaminants. Increased toxins can negatively affect feeding and breeding behaviors and result in a shortened life span and reduced productivity.
Lack of Information
Maine 's wading bird population is diverse and the factors that limit the growth and health of local populations are poorly understood. For many of the rail species we have only limited data on where they occur, let alone what levels of human disturbance can be tolerated before a site is abandoned. Although Great Blue Herons appear abundant, the numbers of colonies on coastal islands has declined in recent years. Whether the numbers of breeding herons on inland sites have increased to buffer this decline is unknown.
