Varied lifestyle for Irish coal tit

COAL tits are visiting my garden.

I’ve managed to ring several of them. Our area is fairly open and windswept, so what are these little tree dwellers doing here in the depths of winter? A report from the British Trust for Ornithology (BTO) on their Garden Bird-watch Survey suggests a possible explanation.

The coal tit’s glamorous relative, the blue tit, is especially well known, at least since 1929, when it started breaking open bottle caps to steal the creamy top of the milk underneath. Its large cousin, the great tit, though not as famous, is the most studied bird in the world. ‘Old King Coal’, however, is the Cinderella of the tits and keeps a lower profile. He’s sombrely attired in black white and grey but his pale cheeks and a white patch on the back of the neck are distinctive. The two-note ‘teacher teacher’ song is a familiar woodland sound in spring.

An accomplished little acrobat, a coal tit will ‘work’ a tree meticulously, combing the branches for insects. The pointed beak, a little pair of tweezers, is inserted in cones to extract seeds. The planting of conifers over the last century was a blessing, the tits repaying the forester by eating harmful insects. In winter, blue great and coal tits, and their long-tailed cousin, which isn’t actually a tit, gather into flocks to roam the countryside.

People in Britain monitor birds visiting gardens and report to the BTO. Seed-eaters, especially bullfinches goldfinches and nuthatches, are abundant this year. The rise in coal tit numbers is particularly dramatic. In a normal year, the species is found in about half of all gardens. This winter, it has turned up in three-quarters of them, more locations being visited than in the previous 17 years of the survey.

Dr Tim Harrison, of the BTO Garden Ecology scheme, suggests that the influx is due to a scarcity of tree seeds. Inclement weather in spring and summer led to crop failure. Unable to secure enough wild food, seed-eaters are visiting gardens hoping for handouts from people. Coal tits have an additional problem; they specialise in conifer seeds. Cones will open in dry weather, but if damp conditions persist, as in recent weeks, they remain closed and the birds can’t eat.

We must be careful when applying British results to Ireland, especially where coal tits are concerned. Parus ater hibernicus is a unique sub species found only on this island. Our coal tits have creamy yellow face patches whereas the cheeks of birds elsewhere are white. The bills of the Irish ones are said to be slightly larger.

Irish tits don’t migrate but northern European ones head south in the autumn. Although some continental coal tits reach Britain, there is little reliable evidence of stragglers arriving here. The ancestors of our coal tits probably came with the conifers at the end of the last ice age and the bird has been on its own here ever since. It’s likely, therefore, to have developed some ‘Irish solutions to Irish problems’.

The species is found from here to Japan but the Irish climate is milder than those tit encounters anywhere. Our winters are warmer, our summers cooler and wetter. Droughts are rare. These factors may have influenced the coal tit’s ecology and behaviour. Food, for example, is hidden when times are good. According to research elsewhere, an individual can remember the locations of stored items for about four weeks. Given our mild climate, is food storage less important here than elsewhere? Are Irish tits more forgetful? Although the variety of tree and the insect species is more limited here than in Britain, the range of birds exploiting them is smaller and competition between species is reduced. Britain has six tit species, twice as many as we have. Coal tits in Ireland, therefore, can afford a more varied lifestyle or, in ecology-speak, can occupy wider ecological niches, than their British counterparts. Not having to share the habitat with marsh and willow tits, their lifestyles may be less specialised. The life and times of the Irish coal tit would seem an ideal subject for an energetic young PhD student.

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Saturday, January 23, 2021

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