Tuesday, 1 October 2019

Northern Short Tailed Shrew

Most species are primarily vermivorous and insectivorous, but some also eat small birds and mammals. The northern short-tailed shrew (Blarina brevicauda) ranges throughout the north-central and northeastern United States and into southern Canada.
Northern Short Tailed Shrew Diet
It eats insects, worms, snails, and other invertebrates and also may eat mice, voles, frogs, and other vertebrates. Because they prey on other vertebrates, shrews can concentrate DDT (and presumably other bio accumulative chemicals) to levels 10 times higher than either Peromyscus and Clethrionomys. Shrews are an important component of the diet of many owls and are also prey for other raptors, fox, weasels, and other carnivorous mammals.
Body size.
Short-tailed shrews are 8 to 10 cm in length with a 1.9 to 3.0 cm tail. The short-tailed shrew is the largest member of the genus, with some weighing over 22 g. Some studies have found little or no sexual dimorphism in size, while other reports show that males are slightly larger than females.
Metabolism.
Short-tailed shrews are active for about 16 percent of each 24-hour period, in periods of around 4.5 minutes at a time. The shrew's metabolism is inversely proportional to the ambient temperature, within the range of 0 to 25C. Sleeping metabolism is half that associated with normal, exploring activity.
However, the overall metabolism for shrews spending equal amounts of time sleeping and exploring as a function of ambient temperature. A linear increase in standard (near basal) metabolism with decreasing temperature that is similar to that for interrupted sleep. The thermoneutral zone, the standard metabolic rate of the short-tailed shrew is approximately 190 percent the metabolic rate predicted from body weight.
Habitat.
Short-tailed shrews inhabit a wide variety of habitats and are common in areas with abundant vegetative cover. Short-tailed shrews need cool, moist habitats because of their high metabolic and water-loss rates.
Food Habits
The short-tailed shrew is primarily carnivorous. Stomach analyses indicate that insects, earthworms, slugs, and snails can make up most of the shrew's food, while plants, fungi, millipedes, centipedes, arachnids, and small mammals also are consumed.
Small mammals are consumed more when invertebrates are less available. Shrews can prey on small vertebrates because they produce a poison secretion in their salivary glands that is transmitted during biting. The short-tailed shrew stores food, especially in the autumn and winter.
The short-tailed shrews cached most of the prey captured. Short-tailed shrews consume approximately 40 percent more food in winter than in summer. The shrew must consume water to compensate for its high evaporative water loss, even though it obtains water from both food and metabolic oxidation.
The short-tailed shrew's evaporative water loss increases with increasing ambient temperature even within its thermoneutral zone. Short-tailed shrews' digestive efficiency is about 90 percent.
Temperature Regulation and Molt
The short-tailed shrew does not undergo torpor but uses non-shivering thermogenesis (NST) to compensate for heat loss during cold stress in winter. The short-tailed shrew exhibits three molts.
Two are seasonal molts, the first in October and November replaces summer with winter pelage and occurs in first- and second-year shrews. The spring molt can occur any time from February to October. The third molt occurs in post juveniles that have reached adult size.
Breeding Activities and Social Organization
The short-tailed shrew probably breeds all year, including limited breeding in winter even in the northern portions of its range. In Illinois, males were found to be most active from January to July, females from March to September.
There are two peak breeding periods, in the spring and in late summer or early fall. The home ranges of short-tailed shrews in summer overlap both within and between sexes. Although females with young do exhibit some territoriality. Nomadic shrews are either young of the year or adults moving to areas with more abundant prey.
Home Range and Resources
Short-tailed shrews inhabit round, underground nests and maintain underground runaways, usually in the top 10 cm of soil. But sometimes as deep as 50 cm. In winter, nonbreeding home ranges can vary from 0.03 to 0.07 ha at high prey densities to 1 to 2.2 ha during low prey densities with a minimum of territory overlap. In the summer, ranges of opposite sex animals overlap, but same sex individuals do not; females with young exclude all others from their area.
Population Density
Population densities vary by habitat and season. In east-central Illinois, population density was higher in bluegrass than in tallgrass or alfalfa. In all three of these habitats, the short-tailed shrew exhibited annual abundance cycles, with peak densities ranging from 2.5 to 45 shrews per hectare, depending on the habitat. The peaks occurred from July to October (12.9/ha average for all three habitats), apparently just following peak precipitation levels.
In winter mortality up to 90 percent has been reported for the short-tailed shrew. however, mortality rates in winter may be closer to 70 percent, which is similar to the average monthly mortality rate he found for subadult animals. Several litters, averaging four to five pups, are born each year.
Similar Species
The masked shrew (Sorex cinereus) (length 5.1 to 6.4 cm; weight 3 to 6 g) is smaller than the short-tailed shrew and is the most common shrew in moist forests, open country, and brush of the northern United States and throughout Canada and Alaska. It feeds primarily on insects.
Merriam's shrew (Sorex merriami) (5.7 to 6.4 cm) is found in arid areas and sagebrush or bunchgrass of the western United States and is smaller than the short-tailed shrew.
The Smokey shrew (Sorex fumeus) (6.4 to 7.6 cm; 6 to 9 g), smaller than the short-tailed, prefers birch and hemlock forests with a thick leaf mold on the ground to burrow in. It uses burrows made by small mammals or nests in stumps, logs, and among rocks. Range is limited to the northeast United States and east of the Great Lakes in Canada.
The southeastern shrew (Sorex longirostris) is 5.1 to 6.4 cm; 3 to 6 g prefers moist areas. Found mostly in open fields and woodlots, its range is limited. to the southeastern United States. It nests in dry grass or leaves in a shallow depression.
The long-tailed shrew (Sorex dispar) is 7.0 cm; 5 to 6 g inhabits cool, moist, rocky areas in deciduous or deciduous-coniferous forests of the northeast, extending south to the North Carolina and Tennessee border.
The vagrant shrew (Sorex vagrans) is 5.9 to 7.3 cm; 7 ± g inhabits marshy wetlands and forest streams. Its range is confined to the western United States, excluding most of California and Nevada. In addition to insects, it also eats plant material.
The Pacific shrew (Sorex pacificus) (8.9 cm) is slightly larger than the short-tailed shrew. It is limited to redwood and spruce forests, marshes, and swamps of the northern California and southern Oregon coasts.
The dwarf shrew (Sorex nanus) (6.4 cm) is rare throughout its limited range in the western United States.
The least shrew (Cryptotis parva) (5.6 to 6.4 cm; 4 to 7 g) is easily distinguished from other shrews by its cinnamon color. It inhabits grassland and marsh; its range is like the short-tailed shrew but does not extend as far north.
The desert shrew (Notiosorex crawfordi) (Gray shrew) (5.1 to 6.6 cm) is rarely seen and is found only in the arid conditions, chaparral slopes, alluvial fans, and around low desert shrubs of the extreme southwest. It nests beneath plants, boards, or debris.


Wednesday, 25 September 2019

American Woodcock (Scolopax minor)

This inland member of the sandpiper family has a stocky build, long bill, and short legs. However, their habitats and diet are distinct. Woodcock inhabit primarily woodlands and abandoned fields. Whereas snipe is found in association with bogs and freshwater wetlands. Both species use their long bills to probe the substrate for invertebrates. The woodcock and snipe are similar in length, though the female woodcock weighs almost twice as much as the female snipe.
The American woodcock (Scolopax minor) breeds from southern Canada to Louisiana throughout forested regions of the eastern half of North America. The highest breeding densities are found in the northern portion of this range, especially in the Great Lakes area of the United States, northern New England, and southern Canada.
Woodcock winter mainly in the southeastern United States and are year-round residents in some of these areas. Woodcock are important game animals over much of their range. Woodcock are large for sandpipers 28 cm bill tip to tail tip. But the females weigh more than males. Most young are full-grown by 5 to 6 weeks after hatching.
Habitat
Woodcock inhabit both woodlands and abandoned fields, particularly those with rich and moderately to poorly drained loamy soils, which tend to support abundant earthworm populations. In the spring season, the male bird uses early successional open areas and woods openings, interspersed with low brush and grassy vegetation.
Thus, for singing displays at dawn and dusk. Females nest in brushy areas of secondary growth woodlands near their feeding areas, often near the edge of the woodland or near a break in the forest canopy. During the summer season, both sexes use second-growth hardwood or early successional mixed hardwood and conifer woodlands for diurnal cover.
At night, they move into open pastures and early successional abandoned agricultural fields, including former male singing grounds, to roost. During the winter, woodcock use bottomland hardwood forests, hardwood thickets, and upland mixed hardwood and conifer forests during the day. At night, they use open areas to some degree, but also forested habitats. Diurnal habitat and nocturnal roosting fields need to near be useful for woodcock.
American Woodcock Diet
Woodcocks feed primarily on invertebrates found in moist upland soils by probing the soil with their long prehensile-tipped bill. Earthworms are the preferred diet, but when earthworms are not available, other soil invertebrates are consumed. Some seeds and other plant matter may also be consumed.
During summer most, feeding was done in wooded areas prior to entering fields at night. But other studies have indicated that a significant amount of food is acquired during nocturnal activities.
During the winter in southern Louisiana, woodcock exhibited three feeding periods: early morning in the nocturnal habitat, midday in the diurnal habitat, and at dusk. However again in the nocturnal fields; earthworms and millipedes were consumed in both habitat types. Most of the woodcocks' metabolic water needs are met by their food.
But captive birds have been observed to drink. The chicks leave the nest soon after hatching but are dependent on the female for food for the first week after hatching. Moreover, American Woodcock molt twice annually. The prenuptial molt involves body plumage, some wing coverts, scapulars, and tertials and occurs in late winter or early spring. The complete postnuptial molt takes place in July or August.
Migration
Fall migration starts at the end of September and continues until December. But often following the first heavy frost. The migration may take four to six weeks. Some woodcock winter in the south Atlantic region, while those that breed west of the Appalachian Mountains winter in Louisiana and the other Gulf States.
American Woodcock are early spring migrants, leaving their wintering grounds in February and arriving on their northern breeding grounds in late March to early April. The dates of woodcock arrival at their breeding grounds can change from year to year depending on the timing of snowmelt. The spring and fall migration dates by States from numerous studies.
Courtship Display
From their arrival in the spring, male woodcock performs daily courtship flights at dawn and at dusk, defending a site on the singing grounds to attract females for mating. Often several males display on a single singing ground, with each defending his own section of the area.
Females construct their nests on the ground, usually at the base of a tree or shrub located in a brushy area adjacent to an opening or male singing ground. Females are responsible for all the incubation and care of their brood. The young chick leaves the nest soon after hatching and can sustain flight by approximately 18 days of age.
Range
The home range of woodcocks encompasses both diurnal cover areas and nocturnal roosting areas and varies in size depending on the season and the distribution of feeding sites and suitable cover. During the day, movements are usually limited until dusk, when woodcock fly to nocturnal roost sites.
In the Spring and summer diurnal ranges to be only 1 to 10 percent of the total home range. Movement on the nocturnal roost sites also is limited; however, during winter, woodcock is more likely to feed and move around at night.
Singing
Singing males generally restrict their movements more than non-singing males, juveniles, and females. The annual singing-ground survey conducted by the United States and Canada provides information on the population trends of woodcock in the northern states and Canada during the breeding season.
The singing-ground estimates to vary from 1.7 male singing grounds per 100 ha in Minnesota to 10.4 male singing grounds per 100 ha in Maine. Although this is appropriate for assessing population trends, flushing surveys, telemetry, and mark-recapture are better methods for estimating woodcock densities because there are variable numbers of females and non-singing males associated with active singing grounds.
The 2.2 singing males per 100 ha in a wildlife refuge in Maine, But summer densities of 19 to 25 birds per 100 ha in the same area. Woodcocks attempt to raise only a single brood in a given year but may re-nest if the initial clutch is destroyed. Survival of juveniles in their first-year ranges from 20 to 40 percent and survival of adults ranges from 35 to 40 percent for males to approximately 40 to 50 percent for females.
The adult survival rates 0.88 to 0.90 for both sexes between June and October in Maine, indicating that adult mortality may occur primarily in the winter and early spring. The lower summer survival rates for young woodcock between fledging and migration than for adults during the same months, with most losses of young attributed to predation.
Similar Species
The common snipe (Gallinago gallinago) is similar in length only 27 cm to the woodcock, although lighter in weight. Snipe are primarily found in association with bogs and freshwater wetlands and feed on the various invertebrates associated with wetland soils.
Snipe breed mainly in boreal forest regions and thus are found slightly north of the woodcock breeding range, with some areas of overlap in the eastern half of the continent. The breeding range of the snipe, however, extends westward to the Pacific coast and throughout most of Alaska, thus occupying a more extensive east-west range than the woodcock.
The American woodcock (Scolopax minor) breeds from southern Canada to Louisiana throughout forested regions of the eastern half of North America.
The American woodcock (Scolopax minor) breeds from southern Canada to Louisiana throughout forested regions of the eastern half of North America. 

The American woodcock (Scolopax minor) breeds from southern Canada to Louisiana throughout forested regions of the eastern half of North America.

The American woodcock (Scolopax minor) breeds from southern Canada to Louisiana throughout forested regions of the eastern half of North America.

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Tuesday, 24 September 2019

The spotted sandpiper (Actitis macularia)


The family Scolopacidae includes numerous species of shorebirds, e.g., sandpipers, tattlers, knots, godwits, curlews, yellowlegs, willets, and dowitchers. These are known as sandpipers tend to be small with moderately long legs and bills. Most sandpipers forage on sandy beaches and mudflats; a few utilize upland areas.
They feed almost exclusively on small invertebrates, either by probing into or gleaning from the substrate. Most species are highly migratory, breeding in the arctic and subarctic regions and either wintering along the coasts or in southern latitudes and the southern hemisphere; therefore, many are only passage migrants throughout most of the United States. Scolapids range in size from the least sandpiper (11.5 cm bill tip to tail tip) to the long-billed curlew (48 cm).
The spotted sandpiper (Actitis macularia) is 19 cm and very common summer resident of freshwater and saltwater bodies throughout most of the United States. These sandpipers are most often encountered singly but may form small flocks. Most winter in the neotropics. Females bird is approximately 50 g significantly larger than males (approximately 40 g).
Habitat
Spotted sandpipers breed along the edges of bodies of water. They usually in open habitats, from the northern border of the boreal forest across North America, south to the central United States. They require open water for bathing and drinking, semi-open habitat for nesting, and dense vegetation for a breeding strategy called polyandry.
Spotted Sandpiper Food
In coastal areas, spotted sandpipers search the beach and muddy edges of inlets and creeks, wading less frequently than most sandpipers; inland they feed along the shores of sandy ponds and all types of streams. But sometimes straying into meadows, fields, and gardens in agricultural areas.
Their diet is composed primarily of terrestrial and marine insects. While adult flying insects comprise the bulk of the diet, crustaceans, leeches, molluscs, small fish, and carrion also are eaten. Young feed themselves immediately after hatching, concentrating on small invertebrates. During insect outbreaks, sandpipers will forage in wooded areas near water, and they have been observed eating eggs and fish on occasion.
Partial prenuptial molt of body plumage occurs in March and April, while the postnuptial molt begins by August with the body feathers and ends anywhere from October to April with the loss of the primary flight feathers.
Migration
Spotted sandpipers generally migrate in small flocks or solitarily. They winter from the southern United States to northern Chile, Argentina, and Uraguay. They breed across North America, north from Virginia and southern California. In the spring season, females arrive at the breeding grounds earlier than males, by about 2 weeks.
Spotted Sandpiper Nests
The primary consideration for nesting sites is proximity to water, and it has been known to build their ground nests in such diverse conditions as depressions in volcanic rock and strawberry patches. Spotted sandpipers are polyandrous (i.e., a single female lays eggs for multiple males), with males supplying most of the incubation and parental care. Thus, reproduction is limited by the number of male’s present.
Spotted sandpipers lay a determinate clutch of four eggs. Females may lay several clutches in a year, often a dozen eggs per season. Egg-laying begins between late May and early June, and males incubate after the third egg is laid. Females sometimes incubate and brood when another male is not available. Parents brood small chicks and protect them with warning calls or by distracting or attacking predators. The female may store sperm for up to one month.
Sandpiper Range
Although a variety of vegetation types are used, nests usually are placed in semi-open vegetation near the edge of a lake, river, or ocean. The suitability of nesting habitat varies from year to year in some locations due to levels of precipitation and predators.
Females may lay one to six clutches for different males over one season, averaging 1.3 to 2.7 mates per year. Female mating and reproductive success increase with age, but male success do not. Lifetime reproductive success is most affected by fledging success and longevity for both males and females.
Spotted Sandpiper Call
The song or call of Spotted Sandpiper is very sweet of quick string of 10 weets in a similar style. The bird may give a pair of weet note when alarmed. Also, they give a sensible metallic spink to warn the chicks from predators. When they near the nest, they give a simple pink sound almost three times in a row followed by a brief paused.
Moreover, Spotted Sandpipers also use a courtship song among a mated pair that has a series of soft pips before the standard song. If they are staggered while incubating, they may let out a loud squeal.
You can listen the Spotted Sandpiper Call Here
Similar Species
1.     The solitary sandpiper (Tringa solitaria) is usually seen singly in freshwater swamps or rivers. Present over much of the United States during annual migrations, this average-sized sandpiper (18 cm) winters along the southeast and Gulf coasts.
2.     The western sandpiper (Calidris mauri) is a small sandpiper (13 cm), common on mudflats and sandbars, that winters on both the Atlantic and Pacific shores of the United States.
3.     The least sandpiper (Calidris minutilla), the smallest of this group (11 cm), is common in winter on salt marshes and muddy shores of rivers and estuaries in coastal areas across the United States.
4.     The semipalmated sandpipers (Calidris pusilla) are small birds (13 cm) seen in the United States primarily during migration and rarely wintering on Florida coasts. Most other members of the family Scolopacidae forage by gleaning.
The spotted sandpiper (Actitis macularia)

The spotted sandpiper (Actitis macularia)

The spotted sandpiper (Actitis macularia)

The spotted sandpiper (Actitis macularia)

The spotted sandpiper (Actitis macularia)

The spotted sandpiper (Actitis macularia)

The spotted sandpiper (Actitis macularia)



Read More – The Snapping Turtles (Chelydra serpentina)
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Monday, 23 September 2019

Facts of Bald Eagle

Bald Eagles have long rounded wings, large hooked bills, sharp talons, and are the largest birds of prey in the United States. They swoop down on their prey at high speeds, and their diet varies by species and considerably by habitat. In most species, the male is smaller than the female, but otherwise, the sexes are similar in appearance. This family also includes kites and hawks.
The bald eagle (Haliaeetus leucocephalus), is U.S. national symbol. It is a federally designated endangered species. Relatively common in Alaska, populations in the lower 48 States have been seriously diminished, although they are recovering in some areas. Bald eagles are most commonly sighted in coastal areas or near rivers or lakes.
Bald eagles are primarily carrion feeders. Perhaps Bald Eagle sound is not good in listening. Normally they emit a sort of high-pitched giggle or a weak scream showing the classics symbol of adventure. Habitually, Bald Eagle is a very romantic bird of prey, tend to pair for lifetime. They like to share parenting responsibilities with the female. You can listen Bald Eagle sound here 
Body Size
Females are significantly larger than males, but otherwise, the sexes look alike. Body size increases with latitude and is the sole basis by which the northern and southern subspecies are divided. Length from bill tip to tail tip averages 81 cm in the more northerly populations. There may be the reason those female needs extra food reserves to produce her eggs. This is scariest eagle is pretty much always the lady.
Bald Eagle Habitat
Bald eagles generally are restricted to coastal areas, lakes, and rivers. However, in winter areas it is not associated with water. Preferred breeding sites include proximity to large bodies of open water and large nest trees with sturdy branches (often conifers) and areas of old-growth timber with an open and discontinuous canopy.
In a study shows, more than 200 nests, found 55 % within 46 m of shoreline and 92 percent within 183 m of shore. During migration and in winter, conifers often are used for communal roosting both during the day and at night, perhaps to minimize heat loss. Mature trees with large open crowns and stout, horizontal perching limbs are preferred for roosting in general. Bald eagles reach maximum densities in areas of minimal human activity and are almost never found in areas of heavy human use.
Food Habits
Bald Eagle primarily carrion feeders eat dead or dying fish when available but also will catch live fish swimming near the surface or fish in shallow waters. In general, bald eagles can be described as opportunistic feeders, taking advantage of whatever food source is most plentiful. Also, it is easy to scavenge or to capture, including birds and mammals. In many areas, particularly in winter, waterfowl, killed or injured by hunters, and shore birds are an important food source.
Usually, eagles forage in an upland area in the winter season. when surface waters are frozen over, consuming carrion including rabbits, squirrels, and dead domestic livestock such as pigs and chickens. The Bald eagles is also famous in to steal food from other members of their own species as well as from hawks, osprey, gulls, and mergansers. This Bald Eagle may occur when there is a shortage of a primary food source, such as fish, and an abundance of other prey such as waterfowl being used by other predatory birds.
Some prey is important to a few populations; for example, in the Chesapeake Bay region, turtles are consumed during the breeding season, and at Amchitka Island in Alaska, sea otter pups are found regularly in bald eagle nests. In the Pacific Northwest during the breeding season, that bald eagles hunted live prey 57 percent of the time, scavenged for 24 percent of their prey, and pirated 19 percent (mostly from gulls or other eagles).
Because bald eagles scavenge dead or dying prey, they are particularly vulnerable to environmental contaminants and pesticides (e.g., from feeding on birds that died from pesticides, consuming lead shot from waterfowl killed or disabled by hunters. Bald eagles also are vulnerable to biomagnification of contaminants in food chains.
At the close of Lake Superior (WI), herring gulls, which were consumed by over 20 percent of nesting bald eagle pairs, were found to be a significant source of DDE and PCB intake by the eagles. The gulls contained higher contaminant levels than the local fish because of their higher trophic level.
Molt
Adult eagles molt yearly. In northern populations, molting occurs from late spring to early fall; in southern populations, molting may be initiated earlier. It is likely that the molt is not complete, and that some feathers are retained for 2 years. Young bald eagles generally molt into their adult plumage by their fifth year.
Migration
Bald eagles migrate out of areas where lakes are completely frozen over in winter but will remain as far north as the availability of open water and a reliable food supply allow. Areas with ice-free waterways, such as the Columbia River estuary in Washington and Oregon, may support both resident and migratory populations in the winter. The far northern breeding populations migrate south for the winter and often congregate in areas with abundant food, particularly the Mississippi Valley and the northwestern States.
Some populations of eagles that breed in southern latitudes (e.g., Arizona, Florida) show a reverse migration and migrate north in midsummer (following breeding), returning south in early autumn or winter. Bald eagles have been observed to nest successfully at 4 years of age, but most do not breed until at least their fifth year. Breeding pairs remain together if both are alive.
Nests of Bald Eagle
Moreover, Bald Eagle is famous for building a massive nest high in the treetops. Both male and female play their role to construct their home to cement their lifelong bond. The nests normally consist of grass and feathers and they used it year after year spruce it up with a whopping foot or two of new material. The nests on average is 2 to 4 feet deep and 5 to 6 feet wide.
Large stick nests (approximately 1.5 m across and 0.6 m deep) are built near water and most often in a large tree, but sometimes on rocky outcrops or even on the ground on some islands. In the absence of disturbance, the same nest site may be used for many years. In Florida, eggs are laid in late autumn or winter, while over the rest of the eagle's range, mating and egg-laying occur in spring.
Clutch sizes are larger in the north, and both sexes take responsibility for feeding the young. Young fledge at about 10 to 12 weeks of age; after leaving the nest, they are still dependent on their parents for several weeks and often return to the nest for food. After nesting, large groups will often gather at sites with plentiful food and resources, such as along rivers following a salmon spawn.
Bald Eagle Range
During the breeding season, eagles require large areas near open water, with an adequate supply of nesting trees. Distance from human disturbance is an important factor in nest-site selection, and nests have been reported to fail because of disturbance. During incubation and brooding, eagles show territorial defense of an area around the nest site. Following fledging, there is little need for nest defense, and eagles are opportunistic in their search for abundant sources of prey.
During winter, eagles roost communally in large aggregations and share a foraging home range. The population of 150 eagles that fed on meadow voles in a 250-ha flooded field for a 4-week period. This group also established a communal night roost in the vicinity.
Bald Eagle Population
Because population density depends strongly on the configuration of the surface water bodies used for foraging, few investigators have published explicit density estimates on an area basis; most report breeding densities along a shoreline on a linear basis. During the breeding season, 0.03 to 0.4 pairs have been recorded per km shore.
Eagles migrating south from their summer territories in Canada have aggregated in communal roosts of up to 400 eagles in a 40-ha area. In the winter, communal roost sites may also contain large numbers of eagles. A group of 150 eagles that roosted and foraged together in the Klamath Basin, and communal night roosts of up to 300 eagles in Oregon in late winter.
Not all adults in an area are part of the breeding population. Some pairs may establish territories and not breed, while others may not even pair. The percentage of adults breeding and the breeding success of those that do vary with local food abundance, weather, and habitat conditions.
The bioaccumulation of organochlorine pollutants reduced the reproductive success of bald eagles. Now, in many areas, these raptors are reproducing at rates like those prior to the widespread use of these pesticides. Eagles lay one clutch per year, although replacement clutches may be laid upon loss of the initial one. Very little is known about mortality rates of bald eagles.
The population models that adult survival is more important than the reproductive rate to the continued success of bald eagle populations. In captivity, bald eagles have lived for up to 50 years, and one wild eagle, banded and recaptured in Alaska, was estimated to be almost 22 years old. Upon loss of an initial clutch, bald eagles may lay replacement clutches if enough time remains. Moreover, the average life of bald is around 20 years, however, the oldest confirmed life span is 38 years of age.
Similar Species  
The golden eagle (Aquila chrysaetos) is similar in size (81 cm) to the bald eagle. Its range encompasses all but the southeastern United States. Small mammals, snakes, birds, and carrion are primary prey items, and golden eagles prefer mountainous or hilly terrain.












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