Monday, 19 January 2015

The Silver Birch

Brrr...  Several successive night of temperatures at or below freezing point appear to have brought nature to a shuddering halt - but of course that is a completely false impression. Birds were out and about in our local pocket park earlier today, with crows, magpies, blue tits, great tits, long tailed tits, robins and wrens noted, plus the gulls ever wheeling overheard. These were noted quite casually as I strode along but no doubt other species would have been seen had I stopped and stood quietly for a while.

In fact I did break stride for a while to look at the delicate tracery of a birch tree's branches and twigs against the background of a brilliant blue sky.

A closer look reveals the female cones from last autumn together with the male catkins seemingly ready to scatter their pollen to the four winds. The seeds within the cones form an important source of food for finches, with goldfinches in particular being regularly seen suspended from the twigs as they feed.

The cones are, of course, structurally quite different from those of conifers such as pines or larches. The seeds within conifer cones are naked in that they are not enclosed within an ovary. The seeds of birch are contained within an ovary and strictly speaking the 'cones' are simply short, broad catkins.

It is difficult to overstate the importance of birch for wildlife. It is Britain's second most common broadleaf tree (only oak being commoner) and, apart from its value to birds, the birch supports over 300 species of insect. It seems probable that the status of birch owes much to amenity planting; it is fast-growing, reasonably tolerant of urban pollution and, of course, is one of the loveliest of our trees. Its delicate grace belies the fact that it is as tough as old boots and, as the last Ice Age retreated, birch was one of the pioneer tree species which moved in to colonise the newly available areas.

It seems that, in Northamptonshire, its familiarity is almost entirely due to amenity planting. As far as I can establish, John Clare makes no mention of it in his writings, suggesting that in his day it was quite a rare - or at least uncommon - tree.

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