Dominic Couzens marvels at this little bird’s party trick!
The Nuthatch is one of those birds that seems to re-emerge into our consciousness in the autumn, becoming obvious and noisy again after a summer when it seems to vanish behind the veil of canopy leaves. A Nuthatch might reappear at the bird table or the local patch, and you wonder where it has been, as if you were comparing your respective summer holidays with a colleague. Where once the tree trunks were empty, Nuthatches are now marching up and down them again, uttering their cheery whistling calls while holding preciously on, like human scaffolders. As far as we birders are concerned, they are back. They never went away. Most individuals, once adult, will never leave their territory. All this time, the Nuthatches have stayed put. Part of the reason for their reappearance is that, now autumn is upon us, their diet has changed. At the height of summer, they were almost exclusively feeding on invertebrates. They were the scourge of bugs and flies, and Tortrix moths, of bees, wasps and dozens of creatures that you and I have seldom heard of, which the Nuthatches took from the surface of the bark or unearthed from the ruts and fractures along their arboreal walkways. Now, the birds are switching to a diet mainly consisting of seeds and nuts, which often sends them right down on to the ground, where they will forage in the company of tits and finches. One Belgian study found that a Nuthatch’s height of foraging was positively correlated to temperature, high when it is warm and low when it is cold. So, the Nuthatches have come down to our level and are back on our radar. It is a time when we can enjoy their most famous party trick once again. Nuthatches are the only birds in the world that can hop down vertical trunks head-first (those Afro-indian oddities, the Spotted Creepers, can also do this but are now thought to be part of the nuthatch family). They can do this by keeping one foot above the other, using the upper foot as a pivot and, because their tails are short, they don’t overbalance. As far as I am aware, nobody is sure what competitive advantage this ability might give them over Treecreepers and woodpeckers, because Nuthatches
are also perfectly capable of creeping upwards, as the others do. Perhaps it enables them to forage from above? They have, after all, been recorded sallying from their head-down position on to the ground to catch an insect. Whatever the reason, Nuthatches are entertaining us once more with their dendrological high-jinks, and we are pleased to be reacquainted. And since it has been a while, it would be rude not to ask them how they have been during all this time of summer drift. After all, if you meet a friend on the street, it is polite to find out how their short break to Barcelona went. If you do ask, though, it could be one of those awkward moments when a trivial conversation becomes serious, even fraught and, worst of all, becomes longer than you want. You should probably know that, for a Nuthatch, the summer is a very difficult time. Behind the façade of the glinting, insect-rich woodland canopy lies a dark tale of awkwardness and woe. The tale begins shortly after the fledgling phase. It coincides with that time when the Springwatch cameras depart and the pretty broods separate and become juveniles, rather than cute, parent-fed adorable balls of fluff. Suddenly the wood is full of independent and demanding youth. It is a phase that occurs in every species, of course, but in Nuthatch society, the flush of new production ushers in a series of particularly pressing problems. There are fewer more difficult societies into which a young bird can take its first steps.
The problem revolves around territories. As mentioned above, Nuthatches adhere strictly to their territorial borders all year round. It is a matter of survival, and there isn’t much room to be flexible. Nuthatches live in pairs and use their territories for everything, including all the food gathering that they undertake during the year. They also store food away in hiding-places only known to them. Not surprisingly, individuals defend these borders vigorously. In the worse-case scenario, a given woodland can end up being saturated with Nuthatch territories, without an inch of room in between. What, then, is a youngster to do? It is new in a world of old borders. How does it integrate? It is a problem that has faced thousands of generations of Nuthatches. And incidentally, it has also perplexed scientists. It seems that the response differs between populations in different countries and in different types of woodland. One solution is to grow up fast. Phenomenally fast. Some youngsters in the Low Countries have acquired a territory and paired up within four weeks of becoming independent. Such precocious birds might be very fortunate and happen upon a vacant territory, into which they settle and pair up with a peer. Others acquire a territory by pairing up with a territory-holding adult which has lost a mate. For the latter that is a pretty blatant case of cradle-snatching. Does any other British bird, or any bird at all, allow a fledgling to cleave as quickly as that? A completely different solution is to do the complete opposite, and hardly grow up at all. In Germany, juveniles may briefly attach themselves to an adult pair and become part of a ‘pseudo-family’ for a few weeks, although these youngsters
do eventually move on and acquire a territory in the autumn, by hook or by crook, sometimes filling a vacancy and sometimes fighting to oust an incumbent. In Siberia, the same thing happens at first, but the attachment can last for months, or even years. The breeding pair simply tolerate the youngsters without any aggression, and the latter eventually move on to their own territory without generating heat.
But even these solutions don’t work universally. Some individuals simply try to blend in within the borders of several territories, avoiding conflict where possible with the incumbents and simply biding their time, waiting for opportunities to come along. Others wander the woodlands for a short time until, it appears, their patience runs out. Then, it is their fate to fight for a territory, or bust. There is also a halfway house that a youngster can fill between keeping a low profile and outright aggression, and that is to occupy the small vacant spaces between existing territories, which are easier to find in summer. Then, a bird can squeeze in between resident pairs and then hope to consolidate its territory into something workable over time. This puts a different complexion on the concept of a ‘gap year.’ However, between the lines of all these strategies is the real story of how fraught this all is. The reality is that, for every gain a youngster makes, there is likely to be some loss. The younger generation cannot integrate without making an impact on the status quo. Some adults will lose out, and will probably die if they lose their territory, or a part of it. On the other hand, where the adults win out, the youngsters eventually succumb. The rigid structure of the Nuthatch’s society makes these realities seem particularly stark. So the next time you meet a Nuthatch, you’d better just admire its acrobatics and not probe too deeply.
Nuthatch in classic ‘upside down’ pose
In the autumn, Nuthatches start reappearing at garden birdfeeders