While the rest of the pages of this magazine are all about the hard work put in by birds in finding food and surviving day to day, here we look at one species that seemingly does not do much at all
Dominic Couzens on the relaxed life of the Grey Heron
If you would like to know what this article is primarily about, the answer is, well, nothing. Or at least, doing nothing. This is an aspect of bird behaviour that is very rarely written about. Since birds tend to be highly active creatures, seemingly always flying about or feeding or fighting, we sometimes forget that they do come to a halt sometimes, and not just to sleep. At times in their lives birds just loaf, or lounge, or gaze at their navel (okay, they don’t have a navel) for hours on end. And this time isn’t merely incidental, but important. One bird that lounges a lot is the Grey Heron. Much of the time, though, we don’t realise that it is doing it. Herons, as you know, are patient fish-catchers, using the act of standing still as a foraging technique, maintaining position passively, hoping that a fish, or frog or small mammal will appear at their feet. They will then reach down and grab it. However, have you noticed how often you see a heron by the waterside, perhaps on a log sticking out of the water, or on a high bank? Those are the moments when we might say to ourselves: “How does it expect to catch anything while standing there?” Or you might see a group of Grey Herons, all in the same place, perhaps on an island in a lake, or in a damp field, standing in statuesque posture as if part of a sculpture park, and you assume they are all at least looking out for food. Those are the moments they are emphatically not doing anything of the sort. They are not foraging. They are doing nothing. Few birds stand idle in quite the way that Grey Herons do. They often retract their neck and appear to raise their shoulders, like a person caught in a downpour lifting the collar of their raincoat. They also assume a wild-eyed look that can appear hilariously fed up, as if they were stuck in a queue at customer services. Of course, it is quite wrong to assume that they are fed up or angry. Nobody knows what they are thinking. However, one thing might surprise you; for the most part they have chosen to be where they are. Daytime ‘roosts’ of Grey Herons have been studied by, among others, the eminent scientist Professor Tim Birkhead. He studied a gathering of Grey Herons in a field in Yorkshire. The most remarkable of his results is that many individual herons spent almost all the daylight hours stationed there, doing nothing. There were asleep for only 6% of the time, and for nearly 77% of the day they simply stood still, perfectly awake. Some arrived shortly after first light and didn’t depart until dusk. The obvious question thrown up by this is: when did the birds keep themselves alive by feeding? Although there is much individual variation, the answer is that they principally foraged
at dawn and dusk. Almost certainly some hunted by night – who knows, perhaps by moonlight? However, most herons are thought to roost by night (usually in tall trees rather than on the ground), which leaves remarkably little time to find food and a great deal of down time. However, fish are highly nutritious and if a hunter strikes almost immediately, it is set up for the day. If a heron is able to catch its ideal-sized prey, which is around 15-20cm long, then it is perfectly satiated for hours afterwards. The same applies to Cormorants, which also spend inordinate amounts of time loafing. This, at least, answers the question about herons being fed up at their daytime roosts. Their stomachs are full, so yes, they are literally fed up! A heron simply standing still, then, is actually a contented heron, full of food, at a site of its choosing, safe if vigilant. In contrast to the time budgets of small birds, which sometimes have to spend all the daylight hours in winter incessantly foraging simply to stay alive, the Grey Heron’s schedule is remarkably relaxed.
There are exceptions, of course. Not all individual herons will find what they need so quickly and have the luxury of clearing their diary. First year herons, just a few months old, tend not to spend as long in daytime roosts as adults, suggesting that they spend more time foraging. Other studies show that these youngsters make more frequent foraging trips. Full adults tend to have their own territories, which they will defend, and soon become expert in hunting in familiar surroundings. They can choose the most profitable times and exact locations, based on their own previous experience, and also ensure that they are free from interference from young upstarts. Such birds dominate in what we might call the post-feeding roost. On the other hand, when the weather is particularly bad, with rain, wind and cold, nobody has it easy, so the daytime roost can be virtually empty. Notwithstanding their relatively settled station in life, there is one activity that does excite the interest of loafing herons, and that is preening. On the chilly Yorkshire field studied by Birkhead, birds spent about 17% of their time working on their plumage. That is nearly a fifth of their time at the day-roost, a percentage of grooming time that nudges towards the stratospheric levels seen in, for example, Love Island contestants. And on the subject of preening celebrities, herons also lay claim to an impressive, almost Kylie Jenner-esque range of hair/feather-care products. High on this list is powder-down. This comes from paired groups of down feathers that occur in dense patches on the breast, flanks and rump, and these, in contrast to other avian feathers, grow continuously. As they grow, however, the keratin at the tip disintegrates, forming a very fine powder, with some particles no bigger than a micron in thickness. This powder is water-resistant and has a consistency similar to talc. The herons distribute the powder-down around the body with the bill in the normal preening process. The powder mixes with grease and other impurities on the plumage, making it coagulate into lumps that are easy to remove. The other must-have preening product is effectively a specialised comb. Herons cannot make it to Claire’s, so this accessory has to be on their body. If you’ve ever seen a heron scratching, that is the clue, because the comb is on their feet or, more specifically, on the claw of their front middle toe, their longest. The lower edge is serrated or, to be technical, pectinated. If you combine the built-in comb with the effects of powder-down, you have a very effective cleaning system. However, it does take time to keep the feathers in the best possible condition. Many of us are familiar with the sight of a heron standing in a ‘bored’ posture some distance from the water. We often assume that it is having an unprofitable time and would rather be somewhere else. This, though, is quite wrong. Such as bird is more likely to be highly satisfied and whiling away the hours without concern. So, as you can see, sometimes it takes nothing to tell a story.