Mid winter Wren.

Light from the kitchen window cut acutely into the morning, disturbing the slow rise of mid-winter. It planned to go from black to dark grey and back to black with minimum effort. The last frost lingered among mossy rocks; Robin tutted disapproval. Car lights of the 9-5 moved beyond the hedge into the globs of sleet. Wind tugged at gold on Silver Birch and Ash’s last leaf hung without expectation.

Shadow moved through shadow. Where logs dripped black on black, a thin probing bill. With many insect-eating birds changing their diet or migrating how do Wrens survive? What do they peck at in the first rays of light? Disappearing into the pile of logs the answer remains screened from view. It appears higher up. Bob, whirr of wings, on the ground it shuffles under Hazel leaves; they move, they are still.

Only one Wren set forth through the leaves where once there had been two.  Perhaps this was not the winter to start looking at Wrens.  Annual population growth is consistently correlated  with the number of frost days.  There is local variation showing adaption to colder weather; individual Wrens are heavier in colder regions. However as there are already more frost days this winter than the last two combined there will be more vacant territories next Spring.

B&W Wren with sunscreen effect

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How Do Wrens Measure Up?

Silently arriving together they demanded attention. Each bird took a different route; one picking under the leaves of the geraniums before the first frost flattens them; the second closer and easier to see, until it disappeared under a flower pot and out into the Hazel bush. At this point I claim them as ‘my’ Wrens. Knowing that one garden is not enough for their needs, does not defeat my possesiveness.

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Picture by Christopher Mercier

 
This is a common scene acted out in front of many household windows as Wrens are one of the top 20 most common garden birds. They are found in all other habitats too, with 7.7m territories across Britain the tic-tic of a Wren is never far away. Weighing about the same as a £1 coin (9g), the distribution map could be seen as a thin scattering of £14.4m.

wren distribution
Wren distribution from BTO BBS.

atlas wren distribution

If people know little about birds, they will still know that Wrens are small. The wing length is about that of the long edge of a custard cream with little difference between that of a male and female. The biscuit, for information, is heavier and tends not to move as fast around my garden. The biscuit is also paler in colour; the Hobnob being a better colour match did not have a suitable Wren metric.

wren trends

Population Trends

 
Wrens numbers drop after hard winters in Britain and so currently are doing well. This shift in climate is also being seen in its earlier nesting dates each year. The female lays 5-6 eggs which weigh 1.3g. Each egg represents about 14% of her body weight; you may wish to remember that next time you are in the bathroom.

laying date

Average laying date

 
Incubation last 2.5 weeks and there is another 2.5 weeks before the young Wrens fledge. About 26% of fledglings survive into the following year at which point they are able to breed. Many survive into a second breeding year, but these are short lives full of hustle and bustle. The longest lived birds hardly move far from where they were born, the greatest survivor being a 7 years old bird that lived its days on Bardsey Island.

fledgling per breeding attempt

Fledglings per breeding attempt

 
Some do have wanderlust and a small number of records of birds travelling within Britain up to 490km. Others have crossed the North Sea with a remarkable record of a bird travelling 909km from Falsterbo, Sweden to Northumberland in 13 days. However, the evidence does suggest that this species does have a tendency to stay local. This then, is part of their magic, here in your local birds is a genealogy traceable if one could only read the signs. Or more likely hear, as the song past from father to son that retains the essence of Wrenness through generations. It is this which isolates populations on islands and aids speciation.

Information taken from BTO Bird Facts