10 Fascinating Facts About Dragonflies

10 Fascinating Facts About Dragonflies

Contents

These Ancient Insects Have Truly Surprising Qualities

  • B.A., Political Science, Rutgers University

Prehistoric-looking dragonflies can be a little intimidating as they swoop about the summer skies. In fact, according to one dragonfly myth, the uncanny creatures would sew up the lips of unsuspecting humans. Of course, that’s not even remotely true. Dragonflies are essentially harmless. Even better, these large-eyed aeronauts love to feed on pests like mosquitoes and midges for which we can be truly grateful—but those aren’t the only interesting qualities that make them so fascinating.

1. Dragonflies Are Ancient Insects

Long before the dinosaurs roamed the Earth, dragonflies took to the air. Griffenflies (Meganisoptera), the gigantic precursors to modern dragonflies had wingspans of over two feet   and dotted the skies during the Carboniferous period over 300 million years ago.  

2. Dragonfly Nymphs Live In the Water

There’s a good reason why you see dragonflies and damselflies around ponds and lakes: They’re aquatic! Female dragonflies deposit their eggs on the water’s surface, or in some cases, insert them into aquatic plants or moss. Once hatched, the nymph dragonfly spends its time hunting other aquatic invertebrates. Larger species even dine on the occasional small fish or tadpole. After molting somewhere between six and 15 times, a dragonfly nymph is finally ready for adulthood and crawls out of the water to shed its final immature skin.  

3. Nymphs Breath Through Their Anus

The damselfly nymph actually breathes through gills inside its rectum. Likewise, the dragonfly nymph pulls water into its anus to facilitate gas exchange. When the nymph expels water, it propels itself forward, providing the added benefit of locomotion to its breathing.

4. Most New Dragonfly Adults Are Eaten

When a nymph is finally ready for adulthood, it crawls out of the water onto a rock or plant stem and molts one final time. This process takes several hours or days as the dragonfly expands to its full body capacity.   These newly emerged dragonflies, known at this stage as teneral adults, are soft-bodied, pale, and highly vulnerable to predators. Until their bodies fully harden they are weak flyers, making them ripe for the picking. Birds and other predators consume a significant number of young dragonflies in the first few days after their emergence.

5. Dragonflies Have Excellent Vision

Relative to other insects, dragonflies have extraordinarily keen vision that helps them detect the movement of other flying critters and avoid in-flight collisions. Thanks to two huge compound eyes, the dragonfly has nearly 360° vision and can see a wider spectrum of colors than humans.   Each compound eye contains 28,000 lenses or ommatidia and a dragonfly uses about 80% of its brain to process all of the visual information it receives.  

6. Dragonflies Are Masters of Flight

Dragonflies are able to move each of their four wings independently. They can flap each wing up and down, and rotate their wings forward and back on an axis. Dragonflies can move straight up or down, fly backward, stop and hover, and make hairpin turns—at full speed or in slow motion. A dragonfly can fly forward at a speed of 100 body lengths per second (up to 30 miles per hour).  

7. Male Dragonflies Fight for Territory

Competition for females is fierce, leading male dragonflies to aggressively fend off other suitors. In some species, males claim and defend a territory against intrusion from other males. Skimmers, clubtails, and petaltails scout out prime egg-laying locations around ponds. Should a challenger fly into his chosen habitat, the defending male will do all he can to chase away the competition. Other kinds of dragonflies don’t defend specific territories but still behave aggressively toward other males that cross their flight paths or dare to approach their perches.

8. Male Dragonflies Have Multiple Sex Organs

In nearly all insects, the male sex organs are located at the tip of the abdomen. Not so in male dragonflies. Their copulatory organs are on the underside of the abdomen, up around the second and third segments. Dragonfly sperm, however, is stored in an opening of the ninth abdominal segment. Before mating, the dragonfly has to fold his abdomen in order to transfer his sperm to his penis.

9. Some Dragonflies Migrate

A number of dragonfly species are known to migrate, either singly or en masse. As with other migratory species, dragonflies relocate to follow or find needed resources or in response to environmental changes such as impending cold weather. Green darners, for example, fly south each fall in sizeable swarms and then migrate north again in the spring. Forced to follow the rains that replenish their breeding sites, the globe skimmer—one of several species that’s known to spawn in temporary freshwater pools—set a new insect world record when a biologist documented its 11,000 mile trip between India and Africa.  

10. Dragonflies Thermoregulate Their Bodies

Like all insects, dragonflies are technically ectotherms («cold-blooded»), but that doesn’t mean they’re at the mercy of Mother Nature to keep them warm or cool. Dragonflies that patrol (those that habitually fly back and forth) employ a rapid whirring movement of their wings to raise their body temperatures. Perching dragonflies, on the other hand, who rely on solar energy for warmth, skillfully position their bodies to maximize the surface area exposed to sunlight. Some species even use their wings as reflectors, tilting them to direct the solar radiation toward their bodies. Conversely, during hot spells, some dragonflies strategically position themselves to minimize sun exposure, using their wings to deflect sunlight.

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Yellow-legged grandfather: dragonfly development features and characteristic habitats

Odonata: dragonflies and damselflies

Characteristics
These often brightly coloured, fast flying insects are well known and easily recognised. Dragonflies and damselflies are medium to large insects with body lengths ranging from 15-120 millimetres. They are often seen flying rapidly over streams and lakes, or through gardens at dusk, often following regular flight paths every day. Dragonflies and damselflies can be recognised by the following features:

  • Large compound eyes
  • 3 ocelli
  • Very small antennae
  • Mandibulate mouthparts
  • Two pairs of membranous wings of similar shape and size
  • Complex wing venation with many cells

Damselflies and dragonflies are very similar but can be separated by looking at their wings. In dragonflies the hind wings are slightly broader than the forewings and in damselflies both wings are more or less similar size. Wings are held horizontally to the body in dragonflies and vertically in damselflies when at rest.


Dragonfly


Damselfly

The nymphs of these insects are aquatic and bear only a slight similarity to the adults. They are wingless and have a broader more flattened body shape. Dragonflies have gills within their body while damselflies have 3 leaf-like gills protruding from the tip of the abdomen (see below).


Damselfly Nymph

Life Cycle
Mating usually takes place on the wing and the male will guard the female as she flies along the water surface depositing her eggs. The nymph spend almost their entire life underwater and moult up to 15 times before they are ready to emerge.

When fully mature the final instar crawls out onto overhanging rocks or vegetation where they shed their last nymphal skin and emerge as an adult ready to hunt and mate.

Development is dependant on the species and where they live. For most species development takes 1 to 2 years but some species that utilise temporary water bodies grow rapidly and develop into adults after a couple of months. Adults generally live for just a few weeks.

Feeding
Dragonflies and damselflies are carnivorous as both adults and nymphs . Nymphs feed on freshwater invertebrates catching them with specialised mouthparts that are able to spring forward and seize prey. Adults hunt by sight and prey on flying insects catching them on the wing with their legs.

Habitat
Dragonflies and damselflies are found all over Australia and although they need water to breed, individuals can be seen flying many kilometres from freshwater. Males tend to be territorial staying close by water to guard their hunting and mating grounds. They can often be observed perched on a favourite vantage point, usually a branch or rock protruding from the water or flying rapidly across their territory. When guarding their territory they will often fly rapidly after intruders chasing them away before returning to the same perch.

Females often roam further from water in search of prey. The nymphs are predominantly aquatic, although one species in known to inhabit wet leaf litter in northern Queensland. The nymphs of dragonflies and damselflies can be found in many aquatic habitats including either sluggish or fast running freshwater creeks, rivers, stream and lakes, and some species inhabit the more saline habitats of inland waters.

www.ento.csiro.au

Wild Bird Habitats

Ken Lund / Flickr / CC by-SA 2.0

What Is a Bird Habitat?

(noun) A habitat is a natural environment in which a wild bird lives, including all associated plant life, landforms, water sources, climate, weather patterns, and other wildlife. A healthy, diverse habitat is essential for birds to thrive.

Pronunciation

HAB-ih-tat
(rhymes with acrobat, copycat, and diplomat)

About Habitats

A habitat includes all four necessities for a bird’s survival: food, water, shelter, and nesting areas. These features can vary greatly between different types of habitats, however, which impacts which birds find which habitats useful.

  • Food: grains, seeds, fruits, nuts, nectar-producing flowers, and prey such as insects, fish, mammals, reptiles, amphibians, and other birds
  • Water: any source available for drinking or bathing, including rivers, swamps, lakes, streams, bays, estuaries, marshes, and oceans
  • Shelter: coniferous or deciduous trees, shrubbery, caves or rock niches, overhanging banks, brush piles, or snags
  • Nesting sites: hollow trees or snags, vegetation to support nests, burrows, nesting boxes, birdhouses, and suitable nesting material

In addition to having the appropriate features to support bird survival, a habitat also includes all the associated landforms (e.g., mountain ranges, coasts, plateaus, passes, and valleys), seasonal climate patterns, predators, and other wildlife.

Non-migratory birds occupy the same habitat year-round but may adjust their behavior to suit different seasons, such as changing their diet to the most abundant food sources throughout the year. Migratory birds change habitats seasonally, perhaps switching between two quite different types of habitats that may be hundreds or thousands of miles apart, or else seeking out similar habitats that meet their needs in different locations at different times of the year.

Types of Habitats

There are many different types of habitats across the globe, each of which can support different types of birds and other wildlife. The most familiar and widespread habitats include:

  • Forests: includes boreal regions, temperate woodlands, and tropical jungles
  • Grasslands: includes meadows, prairies, plains, and scrub regions
  • Deserts: with varying degrees of aridity and drought-tolerant vegetation
  • Wetlands: includes marshes, bogs, and swamps
  • Tundra: circumpolar regions with light and temperature extremes
  • Oceans:pelagic zones that include offshore islands and aquatic regions
  • Urban and suburban: regions associated with humans, including major cities

Habitats may be clearly defined or may have transitional zones where different types of habitats merge, such as woodland edges that are a transition between forests and grasslands. The type of habitat with the most diverse avifauna is the tropical forest, but multiple bird species and good birding can be found in every habitat.

The amount of habitat a bird requires for survival and growth depends on the species. Many species, while an individual bird may have a relatively small range, require large habitats for a healthy population to minimize competition for food sources and nesting grounds. At the same time, many species may occupy the same range because their food, shelter, and nesting needs do not overlap, and they do not compete individually. Instead, they share resources and use specific environmental niches that make the habitat more diverse.

Birders can make use of habitats as a clue to bird identification, particularly for birds with specific needs or habitat requirements. Habitat alone is not usually enough for identification but can be a critical part of determining which bird is which in any given area.

How Habitat Loss Affects Birds

Many birds are threatened by habitat destruction and fragmentation that eliminates the necessary undisturbed environments. Developmental activities that most impact habitats include:

  • Agricultural use, including clearing habitats for fields or grazing livestock
  • Logging and forest harvesting that removes mature vegetation
  • Expansion of urban areas for housing, industry, or similar developments
  • Implementing dams, canals, locks, or other structures that alter waterways
  • Infrastructure development that fractures habitats, such as roads, electrical lines, wind turbines, or similar structures

Habitats are also gravely damaged by polluting activities, such as oil spills or pesticide and herbicide runoff. Natural disasters can damage habitats as well, such as a fire destroying mature forests, flooding changing the water composition of coastal swamps, or a landslide changing the structure of a hill or valley.

Birds can adapt to habitat changes over time and may shift their ranges to more suitable locations. In some cases, habitat changes can even be beneficial, encouraging the growth of younger plants that may support different bird species. Rapid changes, such as caused by human actions, can have drastic consequences, however, and bird populations may plummet if their habitat is no longer suitable or there are no other locations to which they can relocate.

www.thespruce.com

Tree Frog

Tree frogs are not a distinct taxonomic group of animals, but rather, the term refers generally to frogs that spend most of their time in trees or higher vegetation. There are about 800 species of tree frogs, some of which are classified as tree frogs, which are aquatic or terrestrial. Aquatic tree frogs are generally smaller than terrestrial frogs, as their weight is usually supported by twigs and leaves.

Most tree frogs rarely descend to the ground, except to mate and spawn, but some tree frogs lay their eggs in trees, or vegetation in the trees, that contains water. Read on to learn about the tree frog.

Description of the Tree Frog

Tree frogs have the typical frog shape, with long hind legs and smooth, moist skin. One of the characteristic features of tree frogs is the disc-shaped, adhesive pads on their fingers and toes, which help them climb about in trees. They have forward facing eyes, which are often very large, to help them hunt their invertebrate prey, usually at night. Tree frogs can be found in a wide variety of colors, some of them very bright, although most are green, brown, or gray. Several species can change color to blend into the background as camouflage.

Interesting Facts About the Tree Frog

Tree frogs are a large and diverse group of amphibians. They have evolved to live a wide variety of lifestyles. This means there are several interesting facts about tree frogs.

  • Small Size – Most tree frogs are so small they can sit comfortably on the tip of your finger.
  • Teeth – Guenther’s marsupial frog (Gastrotheca guentheri) is the only frog that has teeth in their lower jaw.
  • Poisonous – Simply touching the yellow banded poison dart frog (Dendrobates leucomelas) can lead to heart failure.
  • Swallowing – Like many other frogs, tree frogs use their eyes to help swallow their food. They close their eyes very firmly which pushes the food item down their throat.
  • Flying Frog – The Costa Rican flying tree frog has webbing between its toes, which helps them glide between trees.

Habitat of the Tree Frog

Tree frogs live mainly in trees of forests that are in warmer climates, though some live in grasslands, marshes, or other aquatic environments.

Distribution of the Tree Frog

Tree frogs inhabit every continent except Antarctica. Approximately 30 species live in the U.S., and more than 600 species live in South and Central America.

Diet of the Tree Frog

Most tree frogs are herbivorous when they are tadpoles. As adults, they are generally insectivorous and eat small invertebrates, such as moths, flies, ants, crickets, and beetles. Larger species will also eat small mammals such as mice.

Tree Frog and Human Interaction

Some tree frog species secrete substances on their skin that are used by indigenous peoples as a hallucinogenic drug. Tree frogs are amphibians, meaning they are very susceptible to damage by water pollution and climate change caused by humans. They are also threatened by habitat loss from deforestation for agriculture.

Domestication

Although tree frogs are frequently kept as pets, they have not been domesticated.

Does the Tree Frog Make a Good Pet

Tree frogs are relatively easy to care for, but are sometimes considered uninteresting because they tend to be active at night (“nocturnal”), remaining hidden during the day. The natural behavior of the species needs to be considered when keeping them as pets: ground-dwellers should be given an enclosure with a large amount of floor space, whereas tree climbers should be provided with a more vertical enclosure with substantial plant material. Some countries require a permit to keep tree frogs as pets.

Tree Frog Care

Because tree frogs have moist skin, they can easily absorb toxins from human hands when they are handled. It is therefore often recommended that tree frogs not be handled, or that great care be taken with regards to hand washing. For some species, their food must be dusted with mineral/vitamin supplements, and some will only eat live food.

Behavior of the Tree Frog

Many tree frogs have brightly colored (blue, yellow, red) areas of their bodies, such as their feet, legs, or eyes. If they are threatened by a predator, they suddenly flash these colored areas to startle the predator, allowing the frog to leap away. Many male tree frogs are territorial, and advertise this with loud calling. Some species also advertise their territory by shaking the vegetation, which keeps other males away.

Reproduction of the Tree Frog

Most frogs have a life cycle of 3 stages. Eggs develop into larvae (tadpoles), which then develop into adults. The entire process is called “metamorphosis.” Tree frogs have a variety of reproductive strategies. Most of the species lay eggs – an average clutch consists of about 50 eggs, but some species lay up to 4,000 eggs.

Some species lay their eggs in a nest of foam, or on the leaves of the trees in which they live. When the eggs hatch, the tadpoles drop into the water below. Some eggs take only 4 – 5 days to hatch, but it may take years for the frogs to become sexually mature.

animals.net

Know This: Today’s Most Interesting and Important Scientific Ideas, Discoveries, and Developments

Today’s most visionary thinkers reveal the cutting-edge scientific ideas and breakthroughs you must understand.

Scientific developments radically change and enlighten our understanding of the world — whether it’s advances in technology and medical research or the latest revelations of neuroscience, psychology, physics, economics, anthropology, climatology, or genetics. And yet amid the flood of information today, it’s often difficult to recognize the truly revolutionary ideas that will have lasting impact. In the spirit of identifying the most significant new theories and discoveries, John Brockman, publisher of Edge.org («The world’s smartest website» — The Guardian), asked 198 of the finest minds What do you consider the most interesting recent scientific news? What makes it important?

Pulitzer Prize-winning author of Guns, Germs, and Steel Jared Diamond on the best way to understand complex problems * author of Seven Brief Lessons on Physics Carlo Rovelli on the mystery of black holes * Harvard psychologist Steven Pinker on the quantification of human progress * TED Talks curator Chris J. Anderson on the growth of the global brain * Harvard cosmologist Lisa Randall on the true measure of breakthrough discoveries * Nobel Prize-winning physicist Frank Wilczek on why the twenty-first century will be shaped by our mastery of the laws of matter * philosopher Rebecca Newberger Goldstein on the underestimation of female genius * music legend Peter Gabriel on tearing down the barriers between imagination and reality * Princeton physicist Freeman Dyson on the surprising ability of small (and cheap) upstarts to compete with billion-dollar projects. Plus Nobel laureate John C. Mather , Sun Microsystems cofounder Bill Joy, Wired founding editor Kevin Kelly, psychologist Alison Gopnik , Genome author Matt Ridley , Harvard geneticist George Church , Why Does the World Exist? author Jim Holt , anthropologist Helen Fisher , and more.

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Animal Diversity Web

More Information

Additional Information

Aythya valisineria canvasback

Geographic Range

Canvasbacks breed in the prairie pothole region of central North America, including the United States from Colorado and Nevada north through British Columbia, Alberta, Saskatchewan, Manitoba, the Northwest Territories, the Yukon, and central Alaska. Breeding populations seems to be moving farther northward in recent years. The winter range is from the coastal Pacific Northwest across central prairie states to the southern Great Lakes and south to Florida, Mexico, and Baja California. Largest winter concentrations of canvasbacks are found in Lake St. Clair, the Detroit River and eastern Lake Erie, Puget Sound, San Francisco Bay, the Mississippi River delta, the Chesapeake Bay and Currituck and Pamlico sounds in North Carolina. (Mowbray, 2002)

Habitat

In the breeding season canvasbacks are found in areas with small ponds, slow moving rivers, and dense vegetation. Most breeding occurs in the aspen parklands of central Canada, characterized by aspen woodlands, grasslands, and potholes. Canvasbacks prefer breeding in small lakes and ponds or marshes with dense emergent vegetation, such as cattails ( Typha ), bulrush ( Scirpus acutus ), reeds ( Phragmites communis ), and rivergrass ( Scholochloa festucacea ). During spring and fall migration and winter canvasbacks are found in aquatic areas with high densities of food availability, including estuaries, large freshwater lakes, coastal bays and harbors, and large river deltas. During migration they may also use flooded fields, farm ponds, and wetlands. (Mowbray, 2002)

Physical Description

Canvasbacks are sometimes called the «aristocrat of ducks» for their elegant appearance. Canvasbacks are the largest diving duck (Aythya) species. Males are slightly larger, from 51 to 56 cm in body length and 863 to 1,589 g mass. Females are from 48 to 52 cm in body length and 908 to 1,543 g in mass. Canvasbacks are distinguished by their large size and characteristic long, sloping profile and wedge-shaped head that is held erect on their long necks. Canvasback breeding plumage, which they keep for most of the year, is striking. Males have rich, reddish-brown heads and necks, black breasts, and white wings, sides, and belly. The rump and tail feathers are black. The feet and legs are dark grey and the bill is black. Female breeding plumage is much more subdued, but similar to males; the head and neck are brownish, the wings, sides, and belly are white or gray, and the tail and breast are dark brown. Non-breeding males and females, and immature individuals, are generally brownish overall. Canvasbacks are sometimes confused with their close relatives: redheads, greater scaup and lesser scaup. (Mowbray, 2002)

  • Other Physical Features
  • endothermic
  • homoiothermic
  • bilateral symmetry
  • Sexual Dimorphism
  • male larger
  • sexes colored or patterned differently
  • male more colorful
  • Range mass 863 to 1589 g 30.41 to 56.00 oz
  • Range length 48 to 56 cm 18.90 to 22.05 in

Reproduction

Canvasbacks are seasonally monogamous. Courtship begins during the spring migration and continues on the breeding grounds. Males and females generally remain with a partner during the season, although occasional males have extra pair copulations or abandon a first mate for a second. Females use courtship displays to assess male quality, especially male ability to compete for food and space. During the height of courtship, receptive females are periodically surrounded by 3 to 8 males in «courting parties.» There are a variety of courtship displays: the neck-stretch, incite behavior, a male sneak approach, kinked-neck, head-throw, and turning the back of the head. All are used to start and enforce the pair bond. (Mowbray, 2002)

Females choose the same home ranges for their nesting sites each year. Nests are started as early as late April, but nesting peaks in mid to late May and may continue into June. Pairs lay one brood per year, although they will re-nest if the first brood is destroyed. Nests are built in emergent vegetation above water, although they will occasionally build nests on land as long as it is in a protected area. They prefer medium to large sized, shallow wetlands with extensive emergent vegetation for breeding. Females lay from 5 to 11 smooth, elliptical, greenish drab eggs. Average reported clutch sizes vary regionally, but range from 6.6 to 8.3 eggs per nest. Clutch sizes may be affected by nest parasitism, with parasitized nests having smaller clutches. One egg is laid per day and the female begins to incubate the eggs a few days before the last egg is laid. Eggs are incubated for 24 to 29 days. Young are able to swim and forage soon after hatching. Young fledge at 56 to 68 days after hatching. In late August or September young canvasbacks form groups in preparation for migration. Canvasbacks are capable of breeding in the year after hatching. (Mowbray, 2002)

Females choose the same home ranges for their nesting sites each year. Nests are started as early as late April, but nesting peaks in mid to late May and may continue into June. Pairs lay one brood per year, although they will re-nest if the first brood is destroyed. Nests are built in emergent vegetation above water, although they will occasionally build nests on land as long as it is in a protected area. They prefer medium to large sized, shallow wetlands with extensive emergent vegetation for breeding. Females lay from 5 to 11 smooth, elliptical, greenish drab eggs. Average reported clutch sizes vary regionally, but range from 6.6 to 8.3 eggs per nest. Clutch sizes may be affected by nest parasitism, with parasitized nests having smaller clutches. One egg is laid per day and the female begins to incubate the eggs a few days before the last egg is laid. Eggs are incubated for 24 to 29 days. Young are able to swim and forage soon after hatching. Young fledge at 56 to 68 days after hatching. In late August or September young canvasbacks form groups in preparation for migration. Canvasbacks are capable of breeding in the year after hatching.

  • Key Reproductive Features
  • iteroparous
  • seasonal breeding
  • gonochoric/gonochoristic/dioecious (sexes separate)
  • sexual
  • oviparous
  • Breeding interval Canvasbacks breed once yearly.
  • Breeding season Canvasbacks nest from April to June, with a peak in mid to late May.
  • Range eggs per season 5 to 11
  • Range time to hatching 24 to 29 days
  • Average time to hatching 25 days
  • Range fledging age 56 to 68 days
  • Average age at sexual or reproductive maturity (female) 1 years
  • Average age at sexual or reproductive maturity (male) 1 years

Females build nests and continue to line them with plants and down feathers throughout the nest-building and incubation period. Male canvasbacks are protective of their mate and the nest, especially in the first week after incubation starts. After that time they begin to spend less time defending the nesting area from predators, other canvasbacks, and redheads. During incubation males abandon their mates and nests. Young are precocial at hatching and are able to swim as soon as their feathers dry. Females brood the young when the weather is cold, however. Within a day after hatching the female and her brood abandon the nest and move into larger bodies of water with abundant emergent vegetation. Females remain with their broods until close to migration. For broods that hatch late in the year, though, that may be at only 2 to 3 weeks old. Females do not feed their young, but they do protect them. (Mowbray, 2002)

Lifespan/Longevity

The oldest wild canvasback captured was 22 years and 7 months old, the next longest recorded lifespan in a wild canvasback was 16 years 11 months. Annual survival rates for adults have been estimated at 82% for males and 69% for females. Canvasback mortality is documented as a result of hunting, collisions, toxin ingestion, and exposure during cold weather. (Mowbray, 2002)

  • Range lifespan
    Status: wild 22.6 (high) years

Behavior

Canvasbacks are active during the day, they are highly social, and they migrate seasonally between breeding and non-breeding ranges. They migrate in loose V-shaped flocks and are one of the fastest flying ducks. They can fly up to 90 km/hour air speed (115 km/hour ground speed). They have to run along the water for some distance before they can take flight. Canvasbacks are efficient and powerful swimmers, with their legs positioned near the rear of their body. They may spend up to 20% of the day swimming and can dive to over 9 meters deep for 10 to 20 seconds.

Home Range

Canvasbacks maintain home ranges during the breeding season that vary in size. In one study, home ranges were about 73 hectares before nesting, increased to about 150 hectares before laying the eggs, and then declined to about 25 hectares when the eggs were laid. (Mowbray, 2002)

Communication and Perception

Canvasbacks are generally quiet ducks, although they do use a variety of distress calls and emit a variety of coos and rattles as part of courtship behaviors. They use visual signals in courtship, through their displays. (Mowbray, 2002)

Food Habits

Canvasbacks are omnivorous and opportunistic. In winter and migration they mainly eat aquatic vegetation, including buds, roots, tubers, and rhizomes. They may also take small snails and clams during this time. In the breeding season canvasbacks eat aquatic plants and animals, including seeds, buds, leaves, rhizomes, tubers, and roots and snails, caddisfly larvae ( Tricoptera ), damselfly and dragonfly nymphs (Odonata), mayfly nymphs (Ephemeroptera), and midge larvae (Chironomidae). Outside of the breeding season canvasbacks forage in small to very large groups (over 1000 individuals) and mainly in the morning and evening. These diving ducks can dive to more than 5 meters depth for 10 to 20 seconds, although they usually dive from 0.5 to 2 meters deep. They take food in a variety of ways, including diving, stripping plants with their feet or beaks, and grabbing prey from the water surface or air. In a dive they use their robust, cone-shaped heads to probe and excavate submerged plants. (Mowbray, 2002)

The scientific name of canvasbacks comes from their favorite winter food, the aquatic plant Vallisneria americana , or wild celery. (Mowbray, 2002)

  • Primary Diet
  • omnivore
  • Animal Foods
  • insects
  • mollusks
  • Plant Foods
  • leaves
  • roots and tubers
  • wood, bark, or stems
  • seeds, grains, and nuts

Predation

Canvasback eggs and young are preyed on by a variety of nest predators, including raccoons, striped skunks, red foxes, mink, ermine, American crows, black-billed magpies, common ravens, and California gulls. Adults and fledglings are preyed on by raptors as well as large terrestrial and aquatic predators, including: mink, coyotes, great black-backed gulls, bald eagles, great horned owls, black-crowned night herons, snapping turtles, and northern pike. (Mowbray, 2002)

When a female notices a predator near her nest, she silently swims away to distract attention. If the young are hatched, the female uses a warning call so that the young swim into thick vegetation. Outside of the breeding season canvasbacks form large groups to help protect against predation. Predation accounts for up to 60% of duckling mortality. (Mowbray, 2002)

Ecosystem Roles

Canvasbacks form large foraging groups in the non-breeding season, these large numbers of animals feeding on aquatic plants and animals can have a substantial effect on local aquatic ecosystems. Canvasbacks are infected by a variety of diseases and parasites, including renal coccidia ( Eimeria truncata ), malaria ( Plasmodium circumflexum ), blood parasites ( Leucocytozoon simondi and Haemoproteus nettionis ), parasitic trematodes (Typhlocoelum cucumerinum), bird fleas (Ceratophyllus), bird lice ( Austromenopon leucoxanthum ), and ticks (Ixodidae and Argasidae). In some areas canvasbacks are also parasitized by leeches ( Hirudinea ). (Mowbray, 2002)

Canvasback females may lay their eggs in the nests of other canvasback females, making them intra-specific nest parasites. Canvasbacks are also subject to nest parasitism by redheads (Aythya americana) and ruddy ducks (Oxyura jamaicensis). Male canvasbacks are important in protecting new nests from nest parasitism, they drive away other species aggressively. Because redheads often lay their eggs in canvasback nests about 1 week after incubation begins, aggressive encounters between canvasbacks and nest parasites at the nest often result in egg loss through breakage. Canvasback eggs are about five times as likely to crack as redhead eggs. Parasitized nests are more likely to be abandoned and ducklings from parasitized nests have lower survival rates than those from non-parasitized nests. (Mowbray, 2002)

Economic Importance for Humans: Positive

Canvasbacks are important members of healthy, aquatic ecosystems. They are also an important game species and are one of the best studied duck species. (Mowbray, 2002)

  • Positive Impacts
  • food
  • research and education

Economic Importance for Humans: Negative

There are no adverse effects of canvasbacks on humans.

Conservation Status

Canvasbacks are protected as migratory gamebirds in the United States, Mexico, and Canada. They are not considered threatened or endangered currently. Populations are affected by hunting pressure, habitat degradation, pollution, and collisions with cars or stationary objects. Hunting pressure is most intense during fall migration. In 1999 approximately 87,000 canvasbacks were taken by U.S. hunters. Because canvasbacks eat vegetation in aquatic sediments, they are susceptible to the toxins that accumulate in those sediments. This is particularly true in areas of high industrial activity, such as the Detroit River. (Mowbray, 2002)

Contributors

Tanya Dewey (author), Animal Diversity Web.

Glossary

living in the Nearctic biogeographic province, the northern part of the New World. This includes Greenland, the Canadian Arctic islands, and all of the North American as far south as the highlands of central Mexico.

uses sound to communicate

having body symmetry such that the animal can be divided in one plane into two mirror-image halves. Animals with bilateral symmetry have dorsal and ventral sides, as well as anterior and posterior ends. Synapomorphy of the Bilateria.

areas with salty water, usually in coastal marshes and estuaries.

uses smells or other chemicals to communicate

the nearshore aquatic habitats near a coast, or shoreline.

used loosely to describe any group of organisms living together or in close proximity to each other — for example nesting shorebirds that live in large colonies. More specifically refers to a group of organisms in which members act as specialized subunits (a continuous, modular society) — as in clonal organisms.

animals that use metabolically generated heat to regulate body temperature independently of ambient temperature. Endothermy is a synapomorphy of the Mammalia, although it may have arisen in a (now extinct) synapsid ancestor; the fossil record does not distinguish these possibilities. Convergent in birds.

an area where a freshwater river meets the ocean and tidal influences result in fluctuations in salinity.

A substance that provides both nutrients and energy to a living thing.

mainly lives in water that is not salty.

offspring are produced in more than one group (litters, clutches, etc.) and across multiple seasons (or other periods hospitable to reproduction). Iteroparous animals must, by definition, survive over multiple seasons (or periodic condition changes).

marshes are wetland areas often dominated by grasses and reeds.

makes seasonal movements between breeding and wintering grounds

Having one mate at a time.

having the capacity to move from one place to another.

specialized for swimming

the area in which the animal is naturally found, the region in which it is endemic.

an animal that mainly eats all kinds of things, including plants and animals

reproduction in which eggs are released by the female; development of offspring occurs outside the mother’s body.

mainly lives in oceans, seas, or other bodies of salt water.

breeding is confined to a particular season

reproduction that includes combining the genetic contribution of two individuals, a male and a female

associates with others of its species; forms social groups.

uses touch to communicate

that region of the Earth between 23.5 degrees North and 60 degrees North (between the Tropic of Cancer and the Arctic Circle) and between 23.5 degrees South and 60 degrees South (between the Tropic of Capricorn and the Antarctic Circle).

uses sight to communicate

young are relatively well-developed when born

References

Mowbray, T. 2002. Canvasbacks, Aythya valisineria. The Birds of North America Online , 659: 1-20. Accessed December 05, 2008 at http://bna.birds.cornell.edu/bna/species/659.

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