Sharp-shinned Hawk numbers declined during the DDT pesticide years (mid-1940s to 1972), but rebounded after DDT was banned. Sharp-shinned hawk populations declined in the 1970s due to eggshell thinning caused by pesticide contamination in their prey. Sharp-shinned hawk (Accipiter striatus) Although pesticides no longer play as large a role in the decline of sharp-shinned populations today, the species is still affected by other factors, like the loss of habitat. Collisions with plate glass doors and picture windows are responsible for the deaths of many sharp-shinned hawks annually. The glass reflects the surrounding woods and cannot be readily distinguished by a hawk chasing prey or seeking cover.
Grasshopper sparrows have steadily declined as dry, grassy uplands and farms have reverted to forests or have been replaced by developments. Grasshopper sparrow (Ammodramussavannarum) As with other ground-nesting birds, high populations of predators like raccoons, skunks and feral or free-roaming housecats have also contributed to this species' decline.
Long-eared owl populations are mainly limited by the loss of habitat due to land development, forest thinning and the conversion of softwood forests to hardwood forests. In Connecticut, because of changing land use practices and the decline in farming, fields have either been overtaken by development or they have reverted to forests. Long-eared owl (Asiootus) They are also affected by the decline in suitable nest sites, predation and the decrease in prey abundance.
When passenger pigeon populations declined in the late 1800s, upland sandpipers became an additional gamebird. Upland sandpipers experienced a population decline due to overhunting. The birds have not been able to regain their former numbers. Upland sandpiper (Bartramialongicauda)
American bittern (Botauruslentiginosus) The decline in American bittern populations can be attributed to a loss of habitat. The marshes and swamps upon which this species depends have been drained and filled. They have been used for roadway, housing and commercial developments. There has been only one observed Connecticut breeding location reported in the last decade.
It is estimated that in urban areas, changes in roofing substrate from pea stone to rubber and PVC may also be a factor in their decline. Common nighthawk (Chordeiles minor) Although causes of decline are unclear, they may include habitat loss, pesticide use on breeding and wintering grounds, and migration hazards.
Northern harrier (Circus cyaneus) The Northern harrier’s decline is due to loss and destruction of habitat. Reviving harrier populations depends on the conservation and protection of large areas of inland and coastal marshes, wet meadows, upland heaths, and grasslands through land acquisition or landowner agreements.
Humans are directly responsible for the decline in the population of sedge wren. The destruction of ideal wetland habitats has hurt this species. Sedge wren (Cistothorusplatensis) The bird has been considered a very rare migrant and sporadic nester in the state since the 1960s. Nationwide Breeding Bird Survey results from 1965 to 1979 reflected a continental decline in sedge wren populations.
The marked population decline is presumably due to urbanization. The Horned lark is the only true lark native to North America. Population decline can be attributed to the disappearance and alteration of grassland ecosystems. Horned lark (Eremophilaalpestris) The use of mowed areas around airstrips has allowed the Horned Lark to colonize regions where no other suitable habitat may exist nearby, such as heavily forested areas.
The decline in Peregrine falcons is directly attributed to the effect of pesticides, particularly DDT, on breeding populations. Peregrine falcon populations declined rapidly between 1950 and 1965 throughout the United States and parts of Europe. By 1975, the entire population of peregrines in the eastern United States was considered to be extirpated. Peregrine falcon (Falcoperegrinus) In 1997, peregrine falcons successfully nested on the Travelers Tower; the site of the last known nesting in the 1940s. Since that time, there also has been a report of a successful nesting in Bridgeport.
Common moorhen (Gallinulachloropus) Degradation and loss of deep water marshes with emergent vegetation pose the greatest threats to Connecticut’s moorhen populations. Much of this habitat loss is associated with the draining and filling of wetland areas for urban and suburban development. The popularity of Connecticut's aquatic resources for recreation has also contributed to the decline of the wetland areas once used by the moorhen.
The bald eagle was first declared an endangered species with the passage of the federal Endangered Species Act in 1973. The decline of the Bald eagle is due to loss of habitat and nesting trees, food contamination by pesticides, and illegal shooting. Bald Eagle (Haliaeetusleucocephalus) Contamination of food by the organochlorine pesticide DDT is widely accepted as a major reason why populations of eagles, along with many other raptor species, declined in the mid-20th century. Populations eventually began to recover due to the ban on DDT use, successful reintroduction programs of fostered chicks and fledglings, and habitat and nest protection measures.
The chat population declined in northern Connecticut through the 1930s and 1940s. It was considered a rare nester in all but the southern regions of the state. Chat population numbers have dropped drastically throughout much of the species' eastern range. The chat is a bird of successional habitat, overgrown fields and abundant thickets. Populations of chats declined as farmlands and pastures were reverted to forests or were developed for human occupation or commercial use. Yellow-breasted chat (Icteriavirens)
Because high marsh habitats have been heavily exploited, black rail populations have suffered. Marshes have been used as haying and grazing areas, and then as areas to be filled for development. Although high marsh habitat is now protected by wetland laws, it has been reduced to a fraction of its former size. Black rail (Laterallusjamaicensis) Predation by cats, dogs, raccoons and skunks may also be a factor limiting black rail populations. The difficulty in locating the black rail may still be responsible for its perceived scarcity.
A decline in farming causing a loss of open woodlots through forest succession have reduced the amount of standard habitat for the red-headed woodpecker in Connecticut. The introduction of the European starling had a detrimental affect on Red-headed woodpecker populations. Competition for suitable nesting cavities with the non-native European starling has contributed to the decline in populations. The aggressive starlings often take over cavities excavated by woodpeckers. Red-headed woodpecker (Melanerpeserythrocephalus)
Pied-billed grebes tend to nest in low numbers, which perpetuates a very small population. Wetland degradation and loss has also resulted in a very small population. Pied-billed grebe (Podilymbuspodiceps) The species is declining throughout New England. In New Hampshire, they are classified as endangered, while in Massachusetts they are threatened. Vermont lists the pied-billed grebe as a species of special concern and Rhode Island considers it to be extirpated (locally extinct). The pied-billed grebe was never a common, abundant nester in Connecticut.
The disappearance of farmlands and open fields and the increase in residential and commercial development have caused populations of vesper sparrows to decline. As with many ground-nesting birds, high numbers of predators, such as raccoons or skunks, have also contributed to the decline of this species. Vesper sparrow (Pooecetesgramineus) Vesper sparrows were considered abundant nesters throughout Connecticut in the mid-1800s, but populations have been scarce in Connecticut since the early 1900s. A successful vesper sparrow nesting has not been confirmed in the state of Connecticut since 1984.
The king rail was never common in Connecticut. The species has been considered a rare nester. The king rail is protected under the Migratory Bird Treaty Act of 1918. There are federal migratory game bird hunting regulations. King rail (Ralluselegans) Although the king rail is not uncommon in all areas, degradation and loss of freshwater marsh habitats have resulted in a decline of localized populations.
Roseate tern productivity has also been affected by increased human recreation and disturbance in coastal areas. Increased human activity on or near coastal barrier islands have greatly reduced available nesting habitat for the roseate tern population in northeastern North America. Roseate tern (Sterna dougallii) Historically, the roseate tern population suffered losses due to the millinery trade. Predation by great black-backed and herring gulls, owls and nocturnal-feeding mammals has caused a decline in tern populations. Many traditional nesting sites in southern New England were abandoned during the 1940s and 1950s when great black-backed and herring gulls rapidly expanded their nesting ranges. These large, aggressive gulls stake out nesting territories in early spring before the terns return from their wintering areas. Gulls have taken over most of the outer islands preferred by nesting terns.
Not only has foraging habitat been reduced, but the increased use of rodent poisons has resulted in a smaller food base. Natural nest sites in hollow trees are often limited, and human disturbance of the nest during incubation may cause nest abandonment. Barn owl (Tyto alba) The barn owl occurs in low numbers in Connecticut, probably because grasslands and farmlands are declining. Land use changes, particularly the decrease in the number of farms, have contributed to the decline of this species. One common cause of mortality is predation of young barn owls by raccoons. Other mortality factors include exposure to harsh weather, electrocution by power lines, predation by dogs and great-horned owls, and accidental entanglement in farm and industrial machinery.
The courtship calls and displays of Blue-winged warblers and Golden-winged warblers are very similar. Interbreeding results and hybrids, instead of pure-bred Golden-winged warblers are produced. A decrease in farmland, the ideal habitat, has reduced the Golden-winged warbler population. Golden-winged warbler (Vermivorachrysoptera)
Sources • http://www.ct.gov/dep/search • http://www.allaboutbirds.org/NetCommunity/Page.aspx?pid=1189