Amazing and Incredible

Sunday 6 October 2019

Wildlife Values of Conservation Trees and Shrubs

SHRUBS

CARAGANA (SIBERIAN PEASHRUB) (Caragana arborescens): Used for nesting by several songbirds and the seeds are occasionally eaten. Not a preferred food for browsing animals. It provides good cover. (Introduced from Siberia).

COTONEASTER (Cotoneaster acutifolia): Provides roosting and loafing cover for numerous songbirds and game birds, and some utilize the fruits for food (esp. catbird, mockingbird, and purple finch). Not a preferred browse for animals. (Introduced from northern China).

HONEYSUCKLE (Lonicera tatarica): Provides fruit, which is eaten by several songbirds. It also provides some cover for both bird and animal species but has little value as a browse source. Preferred nesting site for many songbirds. Prefers open, moist areas; good in fencerows. It provides food for songbirds, rabbits, quail, and turkeys. (Introduced from southern Siberia).

CHOKECHERRY (Prunus virginiana): All parts of the plant have some benefit to wildlife for winter food, but most important during summer and fall. Among the most important plants for wildlife cover and food. The shrubby, thicket-forming growth provides cover for songbird nesting, loafing, and roosting, and animal loafing and bedding. The fruit and foliage are relished by a great number of wildlife species, including songbirds, upland game birds, rodents and other small mammals, bears, and whitetail and mule deer. (Native to most of North America).

COMMON LILAC (Syringa vulgaris): Because of root suckers, it provides high-quality cover for numerous species of birds and animals. Little value for fruit or browses. (Introduced from Eastern Europe).

NATIVE (AMERICAN) PLUM (Prunus americana): Highly important as wildlife cover and food. The thorny, suckering growth when protected forms a thicket valuable for bird nesting, loafing, and roosting, and animal loafing and bedding. Twigs and foliage provide a highly preferred browse for whitetail and mule deer. Foxes are chief consumers of fruit. (Native over eastern two-thirds of central North America, including eastern Colorado).

SKUNKBUSH SUMAC (QUAILBUSH) (Rhus trilobata): Prefers moist, sunny, open areas, but will grow in dry locations. Good in the fence row, along roads, and canal/stream edges. Important fall and winter food for songbirds, woodpeckers, and deer. Emergency winter food for game birds. Fruit and buds are stapled food for sharp-tailed grouse. A good source of vitamin A. Bark and twigs eaten by rabbits, rodents, and deer. Provides high quality roosting and loafing cover for many bird species and is a preferred nest site for many thicket-nesting birds. (Native to western North America).

WESTERN SAND CHERRY (BESSEY CHERRY) (Prunus besseyi): Provides preferred fruit for numerous songbirds. Growth form creates good roosting and loafing cover for songbirds and game birds, and nesting cover for songbirds. Occasionally browsed by deer. Short-lived; notable decline in vigor after 5 years. (Native to northern Great Plains, including northeastern Colorado).

NANKING CHERRY (Prunus tomentosa): Utilized by a few songbirds as nesting cover and produces a fruit that is relished by many songbirds. Preferred browse for rabbits, other rodents, white-tailed deer, and mule deer. (Introduced, native to China and Japan).

EUROPEAN SAGE (Artemesia abrotanum): Good in semi-arid sites. Better for cover than for food, but is eaten by antelope, mule deer, and small mammals.

WOODS ROSE (Rosa woodsii): Good in fencerows, along roads, and borders for windbreaks. Especially good food during bad winter weather. Hips high in vitamin C. Important food to upland game birds and deer and excellent nesting/escape cover for songbirds and game birds. (Native to much of North America).

SILVER BUFFALOBERRY (Shepherdia argentea): Will sucker like native plum and form thickets. Thorny thickets create an ideal cover for numerous bird and animal species. Preferred nesting site for many songbirds. Some birds eat the fruit although it is not relished by a wide variety of species. (Native to northwestern North America, including Colorado).

GOLDEN CURRANT (Ribes aureum): Good cover for birds and small mammals. Good palatability to game animals. Preferred roosting, loafing, or nesting cover for several songbirds and has general use by many birds for food. A preferred browse of mule deer. (Native to western North America).

SASKATOON SERVICEBERRY (JUNEBERRY) (Amelanchier alnifolia): Will grow in dry, rocky areas. A high-quality plant for wildlife cover and food. Songbirds and game birds seek the sweet, juicy berries in early summer. Squirrels, rodents, and bears also eat fruit. Whitetail and mule deer browse twigs and foliage extensively. The shrubby growth provides cover for bird nesting, loafing, and roosting, and animal loafing and bedding. (Native to western North America).

FOURWING SALTBUSH (Atriplex canescens): Provides cover and food for songbirds and small mammals as well as forage for antelope, whitetail deer, and mule deer. A San Miguel County landowner reports that elk heavily utilizes the four-wing saltbush there as winter and spring browse, a large herd removing as much as a meter’s growth over winter. (Native to the western U.S.)

COYOTE (SANDBAR) WILLOW (Salix exigua Nutt.): Coyote and other varieties of riparian willows are very important as browse and cover for the big game, especially in fall and winter. Also important as food and cover for birds in winter, particularly ptarmigan. Especially valuable along trout streams as shade and cover, and as a secondary food source for beaver. (Native to North America).

GAMBEL OAK (Quercus gambeli): Also called shrub oak and oak brush. Very important for mast, browse, and cover. Acorns are eaten by many species, especially jays, wild turkey, squirrels, and bears. Important winter browse and mast for deer, bighorn sheep, and elk. (Native to parts of southwestern U.S., including Colorado, and northern Mexico).

ANTELOPE BITTERBRUSH (Purshia tridentata): Palatable and a very important browse for deer, elk, antelope, and livestock, except horses. Other species, such as rabbits and grouse, also utilize. (Native to western North America).

TRUE MOUNTAIN MAHOGANY (Cercocarpus montanus): Very important browse species for all big game ungulates and livestock. Provides cover and food (seeds) for small game birds and mammals. (Native to western North America).

NEW MEXICO FORESTIERA (Forestiera neomexicana): Taken sparingly by deer, almost unpalatable to livestock. Fruits are eaten by quail and songbirds. (Native to southwestern U.S., including southwest Colorado).

DECIDUOUS TREES

GREEN ASH (Fraxinus pennsylvanica var. lanceolata): Most common on prairie, preferring moist areas. Of moderate importance to wildlife. The winged seeds (samaras) are eaten by several birds and mammals including wild turkey and rodents. Whitetail and mule deer browse the twigs and foliage. The biggest benefit is shade. (Native to eastern North America, including watercourses in eastern Colorado).

HONEYLOCUST (Gleditsia triacanthos var. inermis): Has limited wildlife use but provides some songbird cover and is eaten by cottontail rabbit, squirrels, and deer. (Native to central U.S.)

BLACK LOCUST (Robinia pseudoacacia): Seed is eaten by bobwhite quail and squirrel. (Native to parts of the eastern half of U.S.)

SIBERIAN (CHINESE) ELM (Ulmus pumila): Little value as a food source for game birds or mammals. Not sought by birds or mammals as a source of quality browse or cover, although it is used for nesting (esp. English sparrows and orioles). Seeds are eaten by songbirds, game birds, and rodents. (Introduced, native to northern China and eastern Siberia).

Wildlife Values of Conservation Trees and Shrubs

COTTONWOOD: HYBRID AND NARROWLEAF (Populus deltoides var. noreaster, Populus angustifolia): Need moist areas. Buds/catkins are good food in winter and early spring. Bark, twigs, and leaves are eaten by rodents, rabbits, deer, beaver, and porcupines. Provide forage for browsing wildlife such as whitetail and mule deer up through the sapling stage. Provide important nesting and roosting habitat for various species of birds. (Hybrid native to eastern North America, narrow-leaf native to Rocky Mountain region of North America).

GOLDEN WILLOW (Salix alba var. vitellina): Moist, fertile sites needed. Good browse food for the big game, rabbits, and beaver. It provides forage for browsing wildlife such as whitetail and mule deer through the sapling stage. It provides important nesting and roosting habitat for various species of birds. (Introduced, native to Europe, North Africa, and central Asia).

HACKBERRY (Celtis occidentalis): Fruit important winter food for songbirds (esp. waxwings, sapsuckers, mockingbirds, and robins). Important for shade. About 45 wildlife species eat fruit, and deer browse on twigs and leaves. (Native to eastern United States, including plains of eastern Colorado).

RUSSIAN OLIVE (Elaeagnus angustifolia): Spreads quite well on its own (birds and deer distribute seed). Tolerates alkaline soil and hardy during drought. Berries are a choice food of many birds and an important winter food for waxwings, grosbeaks, and robins. Not a preferred food for browsing animals. Fairly low overall wildlife value - has been overrated in the past. Tends to take over riparian areas, so avoid planting in. (Introduced from Eurasia).

LOMBARDY POPLAR (Populus nigra var. italica): Limited wildlife value, some songbirds use for nesting (especially English sparrows). (Introduced from Europe).

ASPEN (Populus tremuloides): Very important browse in many areas for snowshoe hare, deer, and elk. Deer avidly takes fallen leaves in fall and early winter. Important food and building material for beaver. Grouse depend on buds for winter food. (Native to North America).

BUR OAK (Quercus macrocarpa): Very important to wildlife. Acorns are very (possibly most) important wildlife food, especially in winter. Almost 100 wildlife species use oak; quail, turkey, deer, bear, and squirrels are especially avid acorn eaters. Also, excellent wildlife cover. (Native to mid-western and northeastern U.S., and southeastern Canada).

CONIFEROUS TREES (EVERGREENS)

PINE: AUSTRIAN, SCOTCH, PONDEROSA, PINON, LODGEPOLE, LIMBER, & BRISTLECONE (Pinus nigra, P. sylvestris, P. ponderosa, P. edulis, P. contorta, P. flexilis, P. aristata): Pines are nearly as important as oaks. All parts of the tree are used and/or eaten. Pine seeds are especially important for food. Bark harbors insects that woodpeckers, sapsuckers, and nuthatches eat. (Austrian and Scotch pine introduced from Europe; Ponderosa and lodgepole native to western North America; piñon native to western U.S. and northern Mexico; limber and bristlecone native to the western U.S.)

JUNIPER: EASTERN REDCEDAR & ROCKY MOUNTAIN (Juniperus virginiana, J. scopulorum): Some food value to songbirds. Important escape and nesting cover for songbirds and game birds. Use caution near apple trees, as juniper is the alternate host for apple rust. (Eastern redcedar native to central and eastern U.S., Rocky Mountain juniper native to the western U.S. and Canada).

SPRUCE: COLORADO BLUE & ENGELMANN (Picea pungens, P. engelmannii): Little food value. Provide excellent nesting, roosting, and winter cover for numerous small birds. Deer will browse on blue spruce although it is not a preferred forage plant. (Blue spruce native to Rocky Mountains of U.S.; Engelmann spruce native to the western U.S. and Canada).

DOUGLAS-FIR (Pseudotsuga menziesii): Seeds used by squirrels, rabbits, and other rodents. (Native to western North America).

WHITE FIR (Abies concolor): Prefer cool, moist sites. Moderate wildlife importance mostly used for cover by mammals and game birds. Used for roosting and nesting by songbirds, seeds eaten by squirrels. (Native to western U.S. and Mexico).

Read More – The Snapping Turtles (Chelydra serpentina)

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Thursday 3 October 2019

Red Fox Facts (Vulpes vulpes)

Unlike the more social wolves, foxes and coyotes tend to hunt alone, although coyotes may hunt larger prey in pairs. Foxes and coyotes are primarily carnivorous, preying predominantly on small mammals. But they also may eat insects, fruits, berries, seeds, and nuts. Foxes are found throughout most of the United States and Canada, including the arctic, as are coyotes except for the southeastern United States. Foxes and coyotes are active mainly at night.

Red foxes (Vulpes vulpes) are present throughout the United States and Canada except in the southeast, extreme southwest, and parts of the central states. Red fox preys extensively on mice and voles but also feed on other small mammals, insects, hares, game birds, poultry, and occasionally seeds, berries, and fruits.

Twelve subspecies are recognized in North America. The dog-sized red fox has a body of about 56 to 63 cm in length, with a 35 to 41 cm tail. They weigh from 3 to 7 kg, with the males usually outweighing the females by about 1 kg.

Habitat

As the most widely distributed carnivore in the world, the red fox can live in habitats ranging from arctic areas to temperate deserts. Red foxes utilize many types of habitat cropland, rolling farmland, brush, pastures, hardwood stands, and coniferous forests. They prefer areas with broken and diverse upland habitats such as occur in most agricultural areas. They are rare or absent from continuous stands of pine forests in the southeast, moist conifer forests along the Pacific coast, and semiarid grasslands and deserts.

Food Habits

The red fox feeds on both animal and plant material, mostly small mammals, birds, insects, and fruit. Meadow voles are a major food in most areas of North America. However, other common prey includes mice and rabbits. Game birds (e.g., ring-necked pheasant and ruffed grouse) and waterfowl are seasonally important prey in some areas.

Plant material is most common in red fox diets in summer and fall when fruits, berries, and nuts become available. Red foxes often cache food in a hole for future use. They also are noted scavengers on carcasses or other refuse. Most activity is nocturnal and at twilight. In winter, foxes do not undergo hibernation or torpor; instead, they are active year-round. They undergo one molt per year, which usually begins in April and is finished by June. The winter coat is regrown by October or November in northern latitudes.

Breeding occurs earlier in the south than in the red fox's northern ranges. A mated pair maintains a territory throughout the year, with the male contributing more to its defense than the female. Pups are born and reared in an underground den, and the male assists the female in rearing young, bringing food to the den for the pups.

Pups first emerge from the den when 4 to 5 weeks old. Once considered solitary, red foxes now are reported to exhibit more complex social habits. A fox family, the basic social unit, generally consists of a mated pair or one male and several related females. The additional females are usually nonbreeders that often help the breeding female.

Range

The home ranges of individuals from the same family overlap considerably, constituting a family territory. Territories of neighboring red fox families are largely nonoverlapping and contiguous, usually resulting in all parts of a landscape being occupied by foxes. Territory sizes range from less than 50 to over 3,000 ha. Territories in urban areas tend to be smaller than those in rural areas.

Adults visit most parts of their territory on a regular basis; however, they tend to concentrate their activities near to their dens, preferred hunting areas, abundant food supplies, and resting areas. Territory boundaries often conform to physical landscape features such as well-traveled roads and streams.

Territory defense is primarily by nonaggressive mechanisms involving urine scent-marking and avoidance behaviors. Scent marking occurs throughout the territory; there is little patrolling of territory boundaries. Each fox or family usually has a main underground den and one or more other burrows within the home range.

Most dens are abandoned burrows of other species e.g., woodchucks, badgers. Tunnels are up to 10 m in length and lead to a chamber 1 to 3 m below the surface. Pup-rearing dens are the focal point of fox activity during spring and early summer. Foxes have some rest sites and usually forage away from the den.

One red fox family per 100 to 1,000 ha is typical. Red foxes have larger home ranges where population densities are low and in poorer habitats. Most young foxes, especially males, disperse before the age of 1, usually from September to March, with peaks in dispersal in October and November.

Foxes usually produce pups their first year, except in extremely high-density areas and in some years in northern portions of their range where they may delay breeding until the next season. Litter size generally averages four to six pups. The pups leave the den about 1 month after birth, and they are weaned by about 8 to 10 weeks of age.

Red foxes incur high mortality rates as a result of the shooting, trapping, disease, and accidents at roadkill. Two factors that tend to limit red fox abundance are competition with other canids, especially coyotes, and seasonal limits on food availability. Fecundity is higher in areas of high mortality and low population densities.

Similar Species

The arctic fox (Alopexlagopus) is smaller than the red fox (body length approximately 51 cm; weight 3.2 to 6.7 kg) and is restricted in its distribution to the arctic, found in the United States only in Alaska. This species primarily scavenges for food but also eats lemmings, hares, birds, and eggs as well as berries in season.

The swift fox (Vulpes velox) is smaller than the red fox (body length 38 to 51 cm; weight 1.8 to 2.7 kg) and inhabits the deserts and plains of the southwest and the central United States. It dens in ground burrows and feeds on small mammals and insects.

The kit fox (Vulpes macrotis) is similar in size to the swift fox and is considered by some to be the same species, although it has noticeably larger ears. It inhabits the southwestern United States and prefers open, level, sandy areas, and low desert vegetation. It feeds on small mammals and insects.

The gray fox (Urocyon cinereoargenteus) is similar in size (body length 53 to 74 cm; weight 3.2 to 5.8 kg) to the red fox and ranges over most of the United States except the northwest and northern prairies. It is inhabiting chaparral, open forests, and rimrock regions. Secretive and nocturnal, gray foxes will climb trees to evade enemies. They feed primarily on small mammals but also eat insects, fruits, acorns, birds, and eggs.

The coyote (Canis latrans) is much larger (body length 81 to 94 cm; weight 9 to 22 kg) than the red fox and is found throughout most of the United States (except possibly eastern), western Canada, and Alaska. It inhabits prairies, open woodlands, brushy and boulder-strewn areas, and dens in the ground. Coyotes share some feeding habits with the red fox but also scavenge and hunt larger prey in pairs.

Read More – The Snapping Turtles (Chelydra serpentina)

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Saturday 28 September 2019

The Northern River Otter (Lutra canadensis)

River Otter Facts

Mustelids have long, slender bodies, short legs, and anal scent glands. Throughout the family, the male is usually larger than the female. The more terrestrial species of this family occupy various habitats and feed primarily on small mammals and birds. Mustelids that live around lakes and streams feed primarily on aquatic species such as fish, frogs, and invertebrates.

The northern river otter (Lutra canadensis) historically lived in or near lakes, marshes, streams, and seashores throughout much of the North American continent. Currently, many populations along the coastal United States and Canada are stable or increasing, but this species is rare or extirpated throughout much of the midwestern United States.

The river otter dens in banks and hollow logs. Individuals range over large areas daily, feeding primarily on fish. Although otters have few natural predators, while on land, they may be taken by coyotes, fox, or dogs. Otters clean themselves frequently by rubbing and rolling in any dry surface.

Otters appear to undergo bradycardia while submerged and can stay underwater for up to 4 minutes. Because of its piscivorous diet and high trophic level, the river otter is a noteworthy indicator of bioaccumulative pollution in aquatic ecosystems.

Body Size

River otters measure 66 to 76 cm with a 30 to 43 cm tail. Sexual dimorphism in size is seen among all subspecies, and adult males (5 to 10 kg) outweigh females (4 to 7 kg) by approximately 17 percent. Full adult weight generally is not attained until sexual maturity after 2 years of age.

Along the Pacific Coast, there is some evidence that size decreases from north to south. The basal metabolic rate of otters and other mustelids weighing 1 kg or more. The Free-living metabolic rates would be expected to be three to five times higher.

Habitat

Almost exclusively aquatic, the river otter is found in freshwater, estuarine, and some marine environments all the way from coastal areas to mountain lakes. They are found primarily in food-rich coastal areas, such as the lower portions of streams and rivers, estuaries, nonpolluted waterways, the lakes and tributaries that feed rivers, and areas showing little human impact.

River Otter Diet

Otters usually are active in the evening and from dawn to midmorning, although they can be active any time of day. The bulk of the river otter's diet is fish; however, otters are opportunistic and will feed on a variety of prey depending on availability and ease of capture. River otters take different fish species according to their availability and how well the fish can escape capture.

Depending on availability, otters also may consume crustaceans (especially crayfish), aquatic insects (e.g., stonefly nymphs, aquatic beetles), amphibians, insects, birds (e.g., ducks), mammals (e.g., young beavers), and turtles.

River otters consume more waterfowl in the northerly latitudes than in the south, probably because of the ease of capturing the waterfowl during their molt in the north. Otters probe the bottoms of ponds or streams for invertebrates and may ingest mud or other debris in the process. Otters in captivity required 700-900 g of food daily.

Temperature Regulation and molt

Seasonal patterns in otters are not well understood. Otters are active throughout the year. The most intense activity levels during the winter. They undergo a gradual molt in spring and fall.

Breeding activities and social organization

Adult males are usually solitary; an adult female and two or three pups make up a typical family group. River otters breed in late winter or early spring over a period of 3 months or more. Birth of a litter follows mating by about 1 year; however, implantation is delayed for approximately 10 months, and active gestation lasts only 2 months.

Newborn otters are born blind but fully furred and depend on their mother for milk until 3 to 5 months of age. Family groups disperse about 3 months after the pups are weaned. Home range and resources. The river otter's home range encompasses the area needed for foraging and reproduction.

The shape of the home range varies by habitat type; for example, near rivers or coastal areas, it may be a long strip along the shoreline. But in marshes or areas with many small streams, the home range may resemble a polygon.

All parts of a home range are not used equally; instead, several activity centers may be interconnected by a stream or coast. Food has the greatest influence on habitat use, but adequate shelter in the form of temporary dens and resting sites also plays a role. River otters use dens dug by other animals or natural shelters such as hollow logs, logjams, or drift piles.

River otters appear to prefer flowing water habitats over more stationary water (e.g., lakes, ponds). River otters maintain distinct territories within their home ranges: females maintain a feeding area for their families, males for breeding purposes.

Individuals tend to avoid confrontation through mutual avoidance. Home ranges are most restricted for lactating females. Adult and subadult males have larger, more variable home ranges than females.

River otter populations show variable spacing in relation to prey density and habitat. This characteristic, along with their secretive habits and use of several den sites, makes it difficult to estimate river otter populations. Population density of otters often is expressed in terms of number per kilometer of waterway or coastline because of their dependence on aquatic habitats. Densities between one otter every kilometer to one otter every 10 km of river or shoreline are typical.

Otters generally are not sexually mature until 2 years of age. Adult females appear to reproduce yearly in Oregon (based on a pregnancy rate of almost 100 percent. They breed every other year in Alabama and Georgia. Litters usually consist of two to three pups, although litters as large as six pups occur. As adults, river otter mortality rates are low, between 15 and 30 percent per year.

Similar Species

The sea otter (Enhy dralutris) is 76 to 91 cm body and 28 to 33 cm tail; weight 13 to 38 kg, inhabits kelp beds and rocky shores from the Aleutian Islands to California. Its diet includes fish, abalones, sea urchins, and other marine animals.

Read More – The Snapping Turtles (Chelydra serpentina)

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Thursday 26 September 2019

The Herring Gull (Larus argentatus)

Gulls are medium-to-large-sized sea birds with long pointed wings, a stout, slightly hooked bill, and webbed feet. They are plentiful in temperate coastal areas and throughout the Great Lakes. Although these gulls habitually may feed from garbage dumps and landfills. But the most take natural prey.

Gulls nest primarily in colonies, although some of the larger species also nest solitarily. Many populations migrate annually between breeding and wintering areas. North American gull species range in size from Bonaparte's gull 33 cm bill tip to tail tip to the great black-backed gull is 76 cm.

The Herring Gull (Larus argentatus) is 64 cm, has the largest range of any North American gull, from Newfoundland south to the Chesapeake Bay along the north Atlantic and west throughout the Great Lakes into Alaska. Along the Pacific coast, the similar-sized western gull (L. occidentalis) is the ecological equivalent of the herring gull.

Both species take primarily natural foods, especially fish, though some individuals of both species forage around fishing operations and landfills. The increase in the number of herring gulls in this century has been attributed to the increasing abundance of year-round food supplies found in landfills.

However, birds specializing in garbage have such low reproductive success that they cannot replace themselves in the population. An alternative explanation of the species' expansion is that cessation of the taking of gulls by the feather industry in the late 1800s. This has allowed gull numbers to return to pre-exploitation levels.

Body Size

Adult females are normally 800 to 1,000 g significantly smaller than males 1,000 to 1,300 g in both the herring gull and the western gull. The chicks grow from their hatching weight of about 60 to 70 g to 800 to 900 g within 30 to 40 days. Once after which time their weight stabilizes. The Adults show seasonal variation in body weight.

Habitat

Nesting colonies of herring gulls along the northeastern coast of the United States are found primarily on sandy or rocky offshore or barrier beach islands. In the Great Lakes, they are found on the more remote, secluded, and protected islands and shorelines of the lakes and their connecting rivers. Smaller colonies or isolated pairs also can be found in coastal marshes.

The peninsulas, or cliffs along seacoasts, lakes, and rivers, and occasionally in inland areas or on buildings or piers. Gulls are the most abundant seabirds offshore from fall through spring. They are only found predominantly inshore during the breeding season in late spring and summer season. Herring Gulls forage predominantly offshore, within 1 to 5 km of the coast. In all seasons the number of birds feeding at sea outnumber those feeding inshore.

Inshore, Herring gulls forage primarily in intertidal zones but also search for food in wet fields, around lakes, bays, and rock jetties, and at landfills in some areas. In Florida, herring gull presence at landfills is restricted to the winter months December through April. They may consist primarily of first-year birds that migrated from more northerly populations (e.g., from the Great Lakes).

Herring Gull Diet

Gulls feed on a variety of foods depending on availability, including fish, squid, crustacea, molluscs, worms, insects, small mammals and birds, duck and gull eggs and chicks, and garbage. Gulls forage on open water by aerial dipping and shallow diving around concentrations of prey.

At sea, such concentrations often are associated with whales or dolphins, other seabirds, or fishing boats. In the Great Lakes, concentrations of species such as alewife occur seasonally when spawning. Gulls also forage by stealing food from other birds and by scavenging around human refuse sites i.e., garbage dumps, fish plants, docks, and seaside parks.

Individual pairs of gulls may specialize predominantly on a single type of food; for example, three quarters of a population of herring gulls in Newfoundland were found to specialize either on blue mussels, garbage, or adults of Leach's storm-petrel, with 60 percent of the specialists concentrating on mussels between 0.5 and 3 cm in length.

Diet choices may change with the age and experience of adult birds as well as with the availability of prey. Females take smaller prey and feed less on garbage than do males). Females to feed more on smelt (100 to 250 mm) and males more on alewife (250 to 300 mm) in the Great Lakes region.

Adult gulls sometimes attack and eat chicks of neighboring gulls or other species of seabird. Juveniles up to 3 years of age forage less efficiently than adults. In the Great Lakes, herring gulls' high consumption of alewife during their spawn may result in high exposures of the gulls to lipophilic contaminants that bio-magnify.

Metabolism

It is estimated an annual energy budget for free-living female herring gulls that breed in the Great Lakes and an annual energy budget for free-living juvenile herring gulls in the Great Lakes in their first year. Between September and March, the non-breeding season, they estimate that adult females require 250 to 260 kcal/day.

Following a dip in energy requirements to 210 kcal/day when the male feeds the female during courtship, the female's needs increase to peak at 280 kcal/day for egg production, then fall to approximately 210 kcal/day during incubation. The energy required to forage for food for the chicks is substantial, rising through July to peak in August at 310 to 320 kcal/day.

However, then declining again until September when feeding chicks has ceased. These estimates compare well with those derived from Nagy's equation to estimate free-living metabolic rates for seabirds. Except that the energy peaks required is to produce eggs and to feed chicks are not included in Nagy's model. The overview of seabird energetic and additional discussion to approaches and models for estimating metabolic rates of free-ranging seabirds.

Molt

Herring Gull chicks are downy gray with dark brown spotting and molt into a dark-gray or brown mottled juvenile plumage. At the end of the first year, portions of the plumage have paled, and by the second year, gray plumage develops along the back and top of wings. By their third year, young gulls resemble dirty adults, and they acquire their full adult plumage by 4 years.

The adult gulls, at least in some populations, begin their primary feather molt during incubation and complete the molt by mid-to-late fall. They molt and replace the large body feathers from mid-summer to early fall.

Migration

Herring gull populations along the northeast coast of North America tend to be migratory, while adult herring gulls of the Great Lakes are year-round residents. Along the western North Atlantic, most herring gulls arrive on their breeding grounds between late February and late April.

They remain until late August or early September when they leave for their wintering grounds along the Atlantic and Gulf coasts or well offshore. Therefore, the adult and older sub-adult herring gulls in the Great Lakes area are essentially non-migratory. Thus, in contrast to other fish-eating birds in the Great Lakes system that migrate south in the winter, herring gulls are exposed to any contaminants that may be in Great Lakes' fish throughout the year.

The post-breeding dispersal away from breeding colonies starts in late July and ends in August, with all ages traveling short distances. Great Lakes herring gulls less than a year old usually migrate to the Gulf or Atlantic coast, traveling along with river systems and the coast.

Herring Gull Nest

Herring Gulls nest primarily in colonies on offshore islands, and nest density is strongly affected by population size. Naturally, males arrive at the breeding grounds first and establish territories. Both sexes build the nest of vegetation on the ground in areas that are sheltered from the wind but may be exposed to the sun. Males feed females for 10 to 15 days prior to the start of egg-laying.

Breeding Activities and Social Organization

From the laying of the first egg until the chicks are 3 to 4 weeks old, one or both parents will always be present. Males perform most territorial defense, females perform most incubation, and both parents feed the chicks until they are at least 6 to 7 weeks old. All gulls are strongly monogamous; pair bonds can persist for 10 or more years and usually only are terminated by the death of a mate or failure to reproduce successfully.

Males may be promiscuous in populations with more females than males. Herring gull colonies often are found in association with colonies of other species, including other gulls. In some nesting colonies, gulls attack chicks of neighboring gulls and other species.

Herring Gull Range

During the breeding season, herring gulls defend a territory of several tens of square meters around the immediate vicinity of the nest. Their daily foraging range depends on the availability of prey and on the foraging strategy, age, and sex of the gull. Also, they are using radio telemetry on gulls in the Great Lakes.

This has demonstrated that some parents with chick’s forage at specific locations within one km of the colony. Whereas other parents make extended flights to destinations across a lake more than 30 km away. Similarly, gulls that feed at sea may range tens of kilometers from their nest whereas gulls from the same colony feeding in the intertidal zone may travel less than one km. Males typically range farther than females and take larger prey items. At sea during the nonbreeding season, gulls may range hundreds of kilometers during a day.

Population density. As described above, population density is determined by available nesting space, size of the breeding population, and quality of habitat. Small islands with good feeding areas nearby can have several hundred nests per hectare. In poor quality habitat, some pairs nest solitarily without another nest for several kilometers.

Herring gulls and western gulls usually do not start breeding until at least four years of age for males and 5 years of age for females. However, in a given year, 15 to 30 percent of adults of breeding age does not breed. Most breeding females produce three-egg clutches, but individuals in poor condition may lay only one or two eggs.

Herring gulls will lay replacement eggs if all or a portion of their original clutch is destroyed. Hatching success appears to be influenced by female diet, with garbage specialists hatching a smaller percentage of eggs than fish or intertidal (mussel) specialists. Predation, often by gulls of the same or other species, also contributes to egg losses.

Many herring gull chicks that hatch die before fledging, most within the first 5 days after hatching. Adult mortality is low (around 10 percent per year), and some birds may live up to 20 years. Subadult birds exhibit higher mortality of 20 to 30 percent per year.

Similar Species

1. The western gull (Larus occidentalis) (64 cm), found on the Pacific coast of the United States, is the ecological equivalent of the herring gull and is similar in size (53 cm); males range from 1,000 to 1,300 g and females from 800 to 1,000 g.

2. The glaucous gull (Larus hyperboreus) is larger (69 cm) than the herring gull and is the predominant gull breeding in the high arctic. Birds from Alaska are slightly smaller than birds from eastern Canada.

3. The glaucous-winged gull (Larus glaucescens) is similar in size to the herring gull (66 cm) and is the primary breeding species north of the Columbia River. This species hybridizes extensively with the herring gull in Alaska.

4. The California gull (Larus californicus) is smaller (53 cm) than the herring gull. This species breeds primarily in the Great Basin Desert and winters along the Pacific coast.

5. The great black-backed gull (Larus marinus) is the largest species of gull (76 cm) in North America and breeds from Labrador to Long Island.

6. The ring-billed gull (Larus delawarensis) is of average size (45 cm) and is the most common breeding gull in the Great Lakes and northern prairies.

7. Franklin's gull (Larus pipixcan) is a small (37 cm), a summer resident of the Great Plains.

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