Little bird finds a home amid all the noise in Dublin

A tree in Dublin’s St Anne’s Park, just opposite the famous Bull Island, became unsafe and had to be cropped. 
Little bird finds a home amid all the noise in Dublin

The City Council, in an inspired move, commissioned tree sculptor Tommy Cragg to transform the 10m high dead trunk into a celebration of wildlife. He has created a beautiful tableau of mammals birds and reptiles, now much admired and photographed.

The work also received the endorsement of an unlikely little creature. While the sculptor worked with his noisy chainsaws, a pair of tree-creepers arrived, inspected the tree and found a crevice in which they began building a nest. Everything was done to avoid disturbing the birds, but the work had to go on. To everyone’s surprise, the tree-creepers ignored the mayhem. Eggs were laid, incubated and hatched. All went well and, a month or so later, a brood of eager young fledglings took wing.

Tree-creepers are common in Ireland, wherever there are trees, but few people are aware of their presence. As the ‘tree of life’ nest shows, however, they are not shy of people. The wren is a distant relative, although the tree-creeper’s lifestyle is very different from that of wrens or any other small bird. To pursue it, the creeper has evolved extraordinary characteristics.

This little ‘tree mouse’, weighing the same as a two euro coin, scurries along tree trunks, always moving upwards, poking out insects and spiders from holes and cracks. To climb the North Wall of the Eiger, you need crampons, ropes and an ice pick. The tree-creeper’s toes, curved downwards like grappling hooks, are its crampons. Although songbirds have three forward-pointing toes, the tree-creeper has an elongated fourth one directed backwards, giving it purchase on steep inclines.

The feathers of the tail, like those of woodpeckers, are rigid and strong, forming a virtual third leg to buttress the bird as it climbs. The feet move parallel to each other. On reaching the tree-top, the creeper flies bat-like on short rounded wings to the base of another tree.

Worn-out feathers must be replaced. Growing new ones takes time, so the tree-creeper, when it sheds its tail feathers, retains the central pair until the others have been replaced. Moulting in late summer, when food is abundant, it grows the new feathers very quickly, minimising disruption to its daily routine.

The long thin bill serves as a tweezers. Inserted into holes and cracks, it locates and draws out prey. The bill curves downwards like a curlew’s; when the head is turned, the tip sweeps about in the nooks and crannies seizing insects and spiders.

Measurements of tree-creeper bills led to a surprising revelation; they can vary in size depending on the season. In an ingenious adaptation, the bird can alter the length and thickness of its bill to suit local conditions and the prey available. It was assumed that birds seen rubbing their bills against tree barks were simply cleaning them. In fact, they are wearing the bills down to reduce their thickness and length.

Of 56,726 tree-creepers ringed in Britain and Ireland up to 2002, only 157 later came to light, the lowest reporting rate for any of our birds. Ringing has shown the species is sedentary. Numbers fall during hard winters but, overall, the tree mouse is holding its own.

From the 1850s onwards, giant redwood trees were introduced to the great estates of Ireland. Their soft barks, protective blankets against forest fires during their thousands of years of life, provide luxury nesting and roosting accommodation for tree-creepers. A nest can be secreted behind the loose bark, which also provides warm snug sleeping quarters for individuals and broods on cold winter nights. The ‘tree of life’ is a Monterey cypress, a species which does not have a soft bark. It has lots of nooks and crannies however.

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