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Blue
tit time Over the last few weeks we have been anxiously watching our nest box for signs of occupancy. A pair of blue tits has viewed the property but so far, no doubt wisely, has not moved in. Last year's brood failed - perhaps due to disturbance or perhaps to the wet stormy weather just at hatching time - leaving a handful of tiny naked corpses in the carefully constructed nest. This is a disaster for blue tits: unlike blackbirds, which can have three broods a season, they invest everything in a single clutch: all that effort and no next generation to inherit their genes. Long-tailed tits, those tiny pink, white and black birds with round bodies and long tails, have developed a clever strategy for such a contingency. Recent researches have discovered that if its own single brood fails, the cock bird will ally itself to the family of one of its brothers and help to raise the chicks. Sometimes young long-tails are attended by two such uncles, and, although a pair is quite capable of rearing their large family (up to twelve eggs can be laid), the young from extended families are significantly heavier on fledging and, therefore, better able to survive their first winter. Of course the uncles' apparently unselfish behaviour does have a genetic pay off, since siblings share a genetic inheritance. There's another gain too. Long-tail families stay together over the winter and roost together, so the uncles get a share of this snug communal huddle - important for such tiny birds' survival. As April ends we await the arrival of the bird which has developed a strikingly effective strategies for ensuring its stake in the next generation. The last week of April is the time when male cuckoos arrive on our local moors and advertise for their mates with their insistent, ringing call. Female cuckoos lay up to twenty-five eggs a season, each placed in a separate nest of its host bird - on our moors this is usually a meadow pipit. It only takes her a few seconds to nip in, lay her egg, seize and remove an egg from the clutch and off she goes. The pipits raise their huge and ever-hungry foster child and the parent birds are free to take an early flight back to Africa. [Back] |