This time of year is tough enough – but the giant nest invader makes huge demands

These are days of rapid growth. Many birds emerge from the egg, bald, blind and utterly helpless.

At this early stage in their lives they are completely dependent upon their parents for food and warmth. Thus those parent birds are driven to search for and deliver a constant supply of food, most of it in the form of invertebrate life. The nature of the weather also plays its part and long periods of rain may shorten the odds on the continuity of that vitally regular supply of food and thus the survival of some or indeed all of the brood.

Those “hard working” parents must therefore take advantage of the long hours of daylight available in midsummer to continue to forage late into the evening and resume during the wee small hours.

The result of this dedication is a remarkable transformation, from those helpless, blind chicks into little balls of feather, bright eyed if not perhaps bushy tailed, in a few short days. The wide-open beaks of young birds, with their brightly coloured inner mouths, stimulate the parent birds into ever more frantic searching for more and more food.

Of all our native birds, the most startlingly colourful mouth belongs to a young cuckoo.

Furthermore, young cuckoos grow at the most remarkable rate, soon dwarfing their foster parents and thus reminiscent of Topsy, who, we were told, grew and grew and grew. Cuckoo parents, as we know, take absolutely no interest in the welfare of their off-spring, simply laying eggs in other bird’s nests and relying utterly upon the unfortunate hosts to just get on with the arduous job of rearing what soon becomes the single, monster, alien chick! As early as next month the parent cuckoos will begin their journeys back to Africa, leaving the next generation to the tender mercy of foster parents and their offspring’s migratory journey to chance!

Perhaps cuckoos are the exception to the rule with dedication clearly not a primary instinct! The cuckoo egg hatches after just 13 days of incubation, usually a day or so earlier than those of its foster parents. The young cuckoo also emerges blind and bald yet, instinctively, it immediately begins to expel as many of the “natural” eggs of its foster parents from the nest as it can, manipulating them on to its concave back and heaving them overboard. And if any do manage to hatch, the resultant chicks quickly go the same way. Strangely, the foster parents seem almost hypnotised by their fast growing chick and indifferent to the tragic demise of their own young as they now focus entirely on this single, rapidly growing youngster.

That ever-wide open, gaping chasm of a beak, a hallmark of this chick, simply impels them to find more and more caterpillars. Oddly enough, that brightly coloured gape sometimes mesmerises neighbouring birds too. I once watched in amazement when a starling hurtling back towards its own nest with a beak full of insects was so enchanted by that colourful interior that it found itself involuntarily making a diversion. Instead of feeding its own young, it found itself stuffing the contents of its beak into that extremely receptive, cavernous cuckoo beak.