Wren (Troglodytes troglodytes)



Wren © Mike Atkinson

Wren © Mike Atkinson

Some Wrens undertake altitudinal migration (Migration Atlas), leaving the highest ground, but surveyors for this Atlas found some birds in virtually every tetrad apart from the highest of all in the county (SK07A), lying above 500 m. Otherwise, many birds stay on or near their breeding areas. Typically of insectivores, many Wrens establish winter territories. Indeed, ensuring over-winter survival is so important to them that competition for territories may start in July (BTO Winter Atlas). There is little aggression during winter and many birds are unobtrusive. The odd bursts of winter song seem to be unrelated to declarations of territorial possession. As might be expected from a territorial species, half of the counts submitted by Atlas surveyors were of single birds. Some Wrens do gather into groups, especially in reedbeds and other habitats not used for breeding; these birds contain a majority of females, somewhat smaller than males, that have probably lost out in a contest for a territory.

As in the breeding season, Wrens find most of their winter food close to the ground, in ditches, hedges, crevices in walls and the like, which they search assiduously for insects, spiders and some seeds.

Habitat occupation in winter is determined partly by availability of food but especially by shelter from cold and winds. Atlas fieldworkers registered significant drops in almost every category of habitat code except for urban and suburban areas, but with substantial increases in the totals in hedgerows. To some extent birds flitting about in hedges might be more noticeable, with silent birds in woodland or scrub being quite inconspicuous, but there are some real differences in the type of hedges used: in the breeding season, the two categories of hedge (more or less than 2 metres in height) were equally occupied, but in winter there were significantly more Wrens recorded in short hedges. The BTO Winter Atlas noted that farmland hedgerows were commonly empty in winter, but that certainly is not the experience during this survey. The explanation for the disagreement may be winter temperatures, with the first national winter atlas collecting data during the relatively cold winters of 1981/ 82 to 1983/ 84, when the first winter had two ten-day spells of sub-zero temperatures, much colder than during this Cheshire and Wirral Atlas.

As a small resident insectivore the Wren is always vulnerable to hard weather. One way in which they try to keep warm overnight is by sharing roost sites, birds huddling together to minimise loss of heat. One such roost was reported during this Atlas, in house ivy near Mow Cop (SJ85U) where Alan Straw counted ten birds; the maximum at the same site had been 17 in 2003/ 04.

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