Bird size
Learn or brush up on small bird identification while you’re out in the field
ANY ATTEMPT TO master the identification of birds has to take size into account as a major factor. At the very least, it can help you to narrow any unknown species down to a much smaller pool of likely suspects. At best, it might help you to confidently separate two otherwise very similarlooking birds.
Look in any field guide, and you’ll see measurements given for each species. One is usually the wingspan, but it’s the other one that has the potential to cause confusion. This is the length of the bird, from the end of its bill to the tip of its tail. Simple enough, but you might already have spotted that there are a couple of problems with that. These are, simply, that it tends to exaggerate the size of any bird that has a long bill or tail, and it fails to give you any real idea of the relative bulk of the bird you’re looking at. So, a Long-tailed Tit, for example, can, in a field guide, be shown as roughly the same length (c.15cm) as a Yellowhammer, but that utterly fails to convey how tiny the tit’s body actually is compared to the much chunkier bunting. The next thing to remember is probably that most birds, seen in the flesh, are smaller than you imagine having previously only seen pictures. There are a number of possible reasons for this. One, of course, is that you quickly become used to seeing the birds through the relatively narrow, circumscribed view provided by your binoculars or scope – it’s easy to start to ignore the wider
context that you’re seeing them in. Another is that field guides tend to illustrate each species at roughly the same size, even if some do on occasion provide side-by-side comparisons in certain cases. The bird’s structure also plays a part. A lot of beginner birders expect waders to be larger than they actually are, because seen on the page, their long legs give the impression of something more heron or egret-like. In reality, they’re often tiny. Finally, and this is a pet theory of mine, we grow up with certain ideas of what a ‘standard’ bird size is. When I was a child, for example, the only gulls that made an impression on my consciousness were Herring Gulls seen on summer holidays, so once I started birdwatching I tended to think of them as an averagely-sized gull. And of course, they’re not. They’re really pretty big. So what can you do to be able to confidently use size as a factor in making identifications? Well, try following these seven easy steps, and you’ll be well on the way. 1 Use familiar birds as ‘yardsticks’ Start with a few species that you see regularly and well. In the average garden, you might choose Blue Tit, Chaffinch, Blackbird and Woodpigeon. Get their sizes clear in your mind, and then compare any species you don’t know to one or more of these. A Blackcap, say, would be somewhere in-between Blue Tit and Chaffinch, and a Mistle Thrush would be bigger than a Blackbird but much smaller than a Woodpigeon. 2 Use other birds in view as yardsticks As your birdwatching develops, you’re not always going to be in a situation where one of your regular yardstick species is visible. Let’s say you’re studying a flock of winter waders on the mudflats of an estuary, and wondering what that grey and white bird is. It’s standing, hunched, on the edge of a mixed flock of waders. Several of these, you can see, have bright red legs, and you can confidently identify them as Redshanks. Your mystery bird is just a little larger, but nothing like as big as the Curlew that’s also in your scope view (which can be identified by its unmistakable curved bill). So, using your field guide and a bit of deduction, you can start to edge towards identifying this as a Greenshank. 3 Using other objects as yardsticks If all else fails, and your mystery bird resolutely refuses to go and stand anywhere near any other birds, you might still be able to get some impression of size from a nearby object. It’s relatively easy with birds on your feeders, for example – you can compare them to the distance between feeder ports, or against the level of seed. But elsewhere it can be possible, too – everything from fences to flowerpots can come in handy for making an educated guess at a bird’s size. 4 Judge size against itself Some very similar, and similarly sized, species are best told apart by looking at the difference in size between certain parts of their anatomy. Willow Warblers and Chiffchaffs are close enough in size that it’s impossible to tell the difference in the field, and their plumages are very similar, too. But the primary feathers on a Willow Warbler (those at the tip of the wing) are longer, roughly equal to the length of the tertial feathers; on a Chiffchaff, the primaries are no more than two-thirds the length of the tertials, often less.
And on the closely-related Wood Warbler, assuming the lemon-yellow throat and white underparts don’t give the game away, the primaries are longer still, reaching way down towards the end of its short tail. Or take the Ruff, a wader that, in juvenile and winter plumages, seems to get mistaken for a lot of other things, or overlooked entirely (as well as being highly variable in size). At all times, though, careful watching will reveal a proportionately small head and a long neck. 5 Consider the bird’s posture Some birds look every centimetre of their given size, while others seem to do their best to disguise their true dimensions. Take the way that egrets and herons ‘hunch’ their shoulders when at rest – Great White Egrets can appear Little, and Little can appear Cattle, if all other diagnostic features are impossible to make out. There’s also considerable variation of posture within a species. A perched, roosting Long-eared Owl can appear relatively dumpy, and, with its ear tufts down, might not look immediately different to a Short-eared Owl. But when disturbed, it adopts a very upright, sleek, elongated posture that’s not really like anything else. 6 Consider the bird’s location This might sound like stating the obvious, but waterbirds in particular can be deceptive because for much of the time, at least part of them is concealed underwater. A Great Northern Diver is a really big bird, but can appear much smaller because it often rides very low in the water. Waders, too, can look smaller than they should, because for much of the time the bottoms of their legs will be obscured by water or mud. And what about those birds that we typically see at a distance, or in flight, or both. Beginners are often surprised to find the Sky Lark is bigger than they’d thought, because they’re used to seeing it as a tiny speck overhead. 7 Consider the conditions Time of year can make a big difference to how big a bird appears. On the one hand, birds actually are bigger at some times than others – a Wheatear just arrived in the UK on its long migration in early March will be thinner than a well-fed individual towards the end of summer, and resident birds ought, by rights, to be thinner and smaller as the winter goes on, too, because they’ll have been finding less and less food. But winter also means that birds take steps to beat the cold. An obvious one is fluffing their plumage out, making a small bird appear chunkier than it is.
A perched, roosting Long-eared Owl can appear relatively dumpy, and with its ear tufts down might not look immediately different to a Short-eared Owl. But when disturbed, it adopts a very upright, sleek, elongated posture that’s not really like else