Troglodytes troglodytes
winter wren

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, du Feu, and McMeeking, 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)

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, du Feu, and McMeeking, 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)

Home Range

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, Combridge, and Combridge, 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, Combridge, and Combridge, 1997; Evans and Burn, 1996; Harper, 1999)

There are no known adverse effects of winter wrens on humans.

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, Baillie, and Crick, 2007)

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)