Winter wrens have a range of approximately 5,430,000 square kilometers with about 36,000,000 individuals. They are found in the temperate northern hemisphere, including Europe, much of Asia, and North America. There are some gaps in this range, including a large part of Turkmenistan. Winter wrens are most common in eastern and western North America and Eurasia. (BirdLife International, 2008; Drovetski, et al., 2004; Robinson, 2005)
Winter wrens are found in a wide range of habitats. They prefer deciduous forests, but they are also common in pastures, farms, scrub forests, coniferous forests, towns, and villages. They also occur on heath, grasslands, marshes, and in croplands. Winter wrens prefer thick vegetation close to the ground. (Mathevon and Aubin, 1997; Robinson, 2005)
Winter wrens are tiny brown birds with dark barring on their wings, tails, and ventral surfaces. They have a light stripe just above their eyes and their throats are lighter than the rest of their bodies. Juveniles are darker than adults and the sexes look the same. They have a narrow bill and a short tail which usually points upward. ("Cornell Lab of Ornithology: All About Birds", 2003)
Winter wrens have round, short wings with strong distal feathers. These features are adaptations to living in dense vegetation. Round, short wings require less effort and room to suddenly take off or stop and they are easier to maneuver within obstacles. Having heavier, stronger feathers at the ends of their wings protects them from breakage when they inevitably smack something in their crowded environment. (Dawson, 2006)
Winter wrens sexes can be distinguished during the breeding season by the presence of either a brood patch (female) or a cloacal protuberance (male). Age can be determined by the number of spots on their fourth primaries. (Peach, et al., 1995)
A species' average basal metabolic rate is influenced by several factors, including size and plumage color. Birds which eat mainly invertebrate prey generally have intermediate basal metabolic rates, compared to similar birds eating different diets. Temperate species average higher BMRs than tropical species and flighted birds are higher than flightless ones. Winter wrens average 0.60 kJ/h basal metabolic rate. (McNab, 2009)
Breeding season is mid-March to mid-August. Males either return each year to their previous breeding territory or remain on site year-round. Males in poor territories generally only keep one mate, but males in better areas can be polygamous. Males establish territories by singing and displaying and they defend these territories very aggressively against intruding males. Familiarity with their sites allows them to know the best places for resources and food. They build several nests on their territories, which can be used for shelter or by a mate forming a nest. Males build up to twelve nests, but average six. (Amrhein and Erne, 2006; Armstrong, 1956; Evans and Burn, 1996; Peach, et al., 1995)
Females are as not faithful to the same locations year after year. Unlike males, which defend territories, females rely on broader home ranges which they do not defend. They search in their range for a suitable male. Even when a female joins a male, only the male will defend the territory. (Armstrong, 1956; Evans and Burn, 1996; Peach, et al., 1995)
Males initially attract females with songs. When a female arrives, the male will give her a tour of all the cock nests in his territory. While giving her the tour, he displays in and around his nests. Females typically examine several nests before choosing and prefer males whose territories contain more nests. When a female chooses one, she will settle in and provide the nest with feathers and hair to make it suitable for brooding. If her nest is destroyed by a predator, she will usually abandon her mate and his territory and find a new mate. Polygamous males continue to try to attract females while his established mate or mates try to raise their broods. Males can have up to 9 mates. (Armstrong, 1956; Evans and Burn, 1996)
Older males often begin building nests earlier than younger ones, allowing them to build more nests. Females do not seem to mate selectively with older males, however, because too many factors determine how many nests a male has on his territory. Some males have more nest building ability than others and this ability can outweigh age benefits when it comes to accruing nests. (Evans, 1997)
Males build nests (called cock nests) of anything they find, including moss, feathers, twigs and grass. They often build it in a hole which may have been dug by the wren or found. They may also build on branches. Nests are domed and have an entrance hole. Males begin building cock nests up to a month before females begin laying eggs. Individual males vary widely in when they begin building, with the earliest building two months before the latest. After settling in to a nest site, females produce about 5 to 7 eggs, which are white with reddish brown spots. Eggs are 1.3 grams in weight of which 6% is shell. ("Cornell Lab of Ornithology: All About Birds", 2003; Evans and Goldsmith, 2000)
Females incubate the eggs and the young hatch at an altricial stage with some downy feathers. Raising the brood is generally the female’s responsibility, but some males help. Monogamous males spend more time on domestic activities, while polygamous males continue to spend time on singing and courting females. Some males don't care the their young at all, some males provide an equal amount of care as females. Males are capable of raising broods on their own. ("Cornell Lab of Ornithology: All About Birds", 2003; Armstrong, 1956; Robinson, 2005)
Winter wrens typically live only two years, but birds which survive longer than two years can still be reproductively active. Breeding males have been found up to 4 years old. The longest recorded lifespan in the wild was 6 years and 8 months. (Evans, 1997; Peach, et al., 1995; Robinson, 2005)
Winter wren populations may be sedentary or migratory. Migratory populations generally migrate short distances. When they migrate, winter wrens arrive at their wintering area in October and leave in March. In sedentary populations, males hold territories year-round. Males can intrude on and usurp each other’s territory at any time of the year, so territory owners must be on guard even in winter and autumn. (Amrhein and Erne, 2006; Drovetski, et al., 2004; Garson and Hunter, 1979; Murakami and Nakano, 2001)
In winter, during bad weather, winter wrens retreat to roosting sites. They may roost alone or in groups. Birds with good shelter and who roost in groups tend to survive winters better. Roosting groups can be quite large: one nest in Washington contained 31 birds. ("Cornell Lab of Ornithology: All About Birds", 2003; Armstrong, 1956)
Winter wren territories vary in size depending on situation. They range between 1 and 7 acres and average 2 to 3 acres in size. A wren in Iceland was so isolated from other wrens that he defended a territory of 60 to 90 acres. (Armstrong, 1956)
Male winter wrens use song to establish and maintain their territories. Their songs are variable and fast, using between 15 and 40 notes per second, and the entire song lasts 5 to 10 seconds. They are impressively loud. Winter wrens use ten times as much power to deliver their songs as roosters would if they weighed the same amount. They also use other calls, which are only one or two notes. ("Cornell Lab of Ornithology: All About Birds", 2003; Mathevon and Aubin, 1997)
Male winter wrens listen to the songs of other wrens in order to know who and where they are. Their songs are high-pitched, averaging around 5500 hertz, so they are subject to a lot of deterioration as they travel farther from the singing wren. To avoid some of this degradation, wrens choose high places from which to sing so their messages will travel farther with less degradation of the signal. These perches are generally 1 to 4 meters high. Winter wrens also use singing perches to listen for the songs of other males. Winter wrens seem to be able to understand and respond to even highly degraded signals from other male winter wrens. They can determine how degraded the song is, indicating to the listener how far away the singer is. Winter wrens react more aggressively when they know the singer is close rather than if they know he is far away. (Garson and Hunter, 1979; Holland, et al., 2001; Mathevon and Aubin, 1997)
Singing is most important just before and after dawn. This is the time when intruding males will attempt to steal territory so a defending male must be ready to meet his challenger with a song. Dominance is determined by who sings the best songs. Females listen to these contests and, if they like the intruder’s song, they may sneak off afterward and seek extra-pair copulations. Males who have defended their territory recently sing more than males who have not. However, they sing less in cold weather, especially after cold nights. (Amrhein and Erne, 2006; Garson and Hunter, 1979)
Winter wrens are insectivores that eat a wide variety of invertebrate prey. They hunt for food on the ground. In addition to insects and their larvae, they also regularly consume millipedes and spiders. If they are in riparian areas they may prey on aquatic invertebrates. Their small size allows them to forage in places where other insectivorous birds cannot successfully forage. ("Cornell Lab of Ornithology: All About Birds", 2003; Armstrong, 1956; Murakami and Nakano, 2001)
Domestic cats, which are ubiquitous anywhere humans exist, are major predators of native animals, including winter wrens. Northern harriers (Circus cyaneus) eat adult wrens. Nests are preyed on by many animals, including crows and jays and weasels. Interestingly, crows and jays destroy empty nests in addition to ones containing eggs or nestlings. (Clarke, et al., 1997; Evans and Burn, 1996; Maclean, et al., 2008)
Winter wrens have a few adaptations to counteract possible attacks by predators or nest parasites. Cryptic coloration makes them and their nests hard to find, and their habit of building several nests makes the real nest harder to locate. They also avoid nesting near established nests. Despite these countermeasures, cuckoos in Germany heavily parasitize them. (Armstrong, 1956)
Winter wrens are important members of the ecosystem because they eat insects and are food for larger predators. In addition to these roles, they are parasitized by both invertebrates and vertebrates. They suffer from feather mites of the family Proctophyllodidae, which includes the genera Proctophyllodes and Monojoubertia. They are subject to nest parasitism by common cuckoos, Cuculus canorus. ("Cornell Lab of Ornithology: All About Birds", 2003; Armstrong, 1956; Clarke, et al., 1997; Evans and Burn, 1996; Harper, 1999)
Because winter wrens are small, insectivorous birds, they are affected by cold weather more than many other bird species. Their population levels drop when temperatures are consistently too low. As a result they are used as indicators of changing climate. They may help to control pest populations in areas of human habitation. ("Cornell Lab of Ornithology: All About Birds", 2003; Armstrong, 1956; Murakami and Nakano, 2001; Robinson, et al., 2007)
There are no known adverse effects of winter wrens on humans.
With 36,000,000 individuals and no serious trends of declining populations, winter wrens are not considered a species of concern. Populations of winter wrens in Britain are increasing. (BirdLife International, 2008; Hewson, et al., 2007)
The Brothers Grimm have a tale about winter wrens. They say that one day all the birds gathered together in order to determine who ought to be king. Every type of bird showed up, including a tiny one that didn’t even have a name. They decided they would settle the matter by seeing who could fly the highest, so they all set off and began ascending. The little birds quit first, then the geese and swans, and finally the eagle was all alone. Seeing he was the highest, he relaxed and began sinking back down. As soon as he started to descend, the tiny, nameless bird popped out of his hiding place in the eagle’s feathers and began his flight. Since he wasn’t tired, he reached heaven easily, and then came back down to earth, crying out, “I am King!” the whole way. All the birds were upset that such a tiny bird had won the contest, so they changed the rules: the bird which got lowest in the ground won the monarchy contest. Most birds tried scratching their own holes, but the nameless bird simply crawled down into a mouse hole. As soon as he was down the hole, he cried out again, “I am King! I am King!” The birds were all horrified again, but they were too tired from all the flying and digging to do anything about it. They assigned the owl to watch over the mouse hole while the rest went home for the night. The owl gradually fell asleep and the tiny bird snuck out. Knowing he isn’t welcome, he hides in the brush to this day. The owl, so ashamed by his failure at guarding the mouse hole, now only comes out at night, and he takes out his frustration by eating mice. The other birds mock the little bird by calling him “King of the Hedges,” which in German is Zaunkonig, the common name for Troglodytes troglodytes. (Grimm and Grimm, 1806)
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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.
living in the northern part of the Old World. In otherwords, Europe and Asia and northern Africa.
uses sound to communicate
living in landscapes dominated by human agriculture.
young are born in a relatively underdeveloped state; they are unable to feed or care for themselves or locomote independently for a period of time after birth/hatching. In birds, naked and helpless after hatching.
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.
an animal that mainly eats meat
uses smells or other chemicals to communicate
having markings, coloration, shapes, or other features that cause an animal to be camouflaged in its natural environment; being difficult to see or otherwise detect.
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.
forest biomes are dominated by trees, otherwise forest biomes can vary widely in amount of precipitation and seasonality.
a distribution that more or less circles the Arctic, so occurring in both the Nearctic and Palearctic biogeographic regions.
Found in northern North America and northern Europe or Asia.
An animal that eats mainly insects or spiders.
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.
This terrestrial biome includes summits of high mountains, either without vegetation or covered by low, tundra-like vegetation.
the area in which the animal is naturally found, the region in which it is endemic.
reproduction in which eggs are released by the female; development of offspring occurs outside the mother's body.
having more than one female as a mate at one time
Referring to something living or located adjacent to a waterbody (usually, but not always, a river or stream).
scrub forests develop in areas that experience dry seasons.
breeding is confined to a particular season
remains in the same area
reproduction that includes combining the genetic contribution of two individuals, a male and a female
associates with others of its species; forms social groups.
living in residential areas on the outskirts of large cities or towns.
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).
Living on the ground.
defends an area within the home range, occupied by a single animals or group of animals of the same species and held through overt defense, display, or advertisement
living in cities and large towns, landscapes dominated by human structures and activity.
uses sight to communicate
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