Do­minic Couzens mar­vels at this lit­tle bird’s party trick!

Bird Watching (UK) - - Contents -

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.

De­fend­ing ter­ri­to­ries

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.

Avoid­ing con­flict

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

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