See topography drawings at the end of this section.
Learning the topography of a bird is fundamental to understanding and describing the features that you see. It is important to stress that feathers on a bird are not haphazard, but are grown in organised rows or groups, overlapping like roof tiles. These feather tracts have specific standardised names illustrated on the front endpapers. Many birders confuse some of the terminology and the following lists some areas that most frequently cause problems.
Culmen, gonys and gonydeal angle The ridge along the top of the upper mandible of the bill is the ‘culmen’; hence, a bird may show a ‘strongly decurved culmen’. On the lower mandible, some birds, particularly gulls, have a distinct angle, about three-quarters of the way along towards the tip; this is the ‘gonydeal angle’. The ridge of the lower mandible between the gonydeal angle and the bill tip is called the ‘gonys’. Thus, the heavier-billed Great Black-backed Gull has a much stronger gonydeal angle than a Lesser Black-backed Gull.
Eye-stripe and supercilium The eye-stripe is exactly that: a stripe through the eye. When present, this is a dark line that usually extends from the bill back through the eye. On some birds, it extends just from the eye back, leaving the lores (the area between the eye and the bill) pale and unmarked. This may seem an insignificant difference, but unmarked lores produce a different facial expression – a rather pleasant, gentle, ‘open-faced’ appearance – whereas those species that have a line across the lores tend to look more ‘severe’. Species for which this difference is significant include Reed and Little Buntings, and Tawny and Richard’s Pipits. The supercilium is the pale line extending back from the bill above the eye and above the eye-stripe; as it is a Latin word, the plural is supercilia. The dictionary definition of the word is ‘eyebrow’ which is what, quite sensibly, it is called in North America. Some species have the supercilium extending only from the eye back, while others, such as Spotted Redshank, basically show only a fore-supercilum from the bill to the rear of the eye.
Crown-stripe Some species possess a pale stripe on the centre of the crown known as the ‘crown-stripe’; occasionally it may be more precisely referred to as the ‘median crown-stripe’. Some birds show a dark line on the side of the crown, immediately above the supercilium, and this is called, quite logically, the ‘lateral crown-stripe’. Common Snipe, Aquatic Warbler and Fire crest show both.
Eye-ring and orbital-ring Many birds show a ring pale of feathers around the eye known as the ‘eye-ring’. Whereas an eye-ring comprises feathering, the ‘orbital-ring’ is a narrow ring of bare skin immediately surrounding the eye. In some species, this may be swollen, colourful and very obvious, classic examples being the yellow orbital-rings shown by Lesser White-fronted Goose and Little Ringed Plover.
Chin and throat The ‘chin’ is the small area of feathering immediately below the base of the lower mandible of the bill. As such, it is not usually necessary to differentiate it from other areas of a bird’s plumage. The ‘throat’ is the large, triangular area of feathers between the chin and the upper breast.
Moustachial stripe, submoustachial stripe and lateral throat-stripe These three areas are often confused, but a recent development has clarified the position quite considerably. The ‘moustachial stripe’ is a dark line shown by many birds, most obviously pipits and buntings, which runs obliquely from the gape down and along the lower border of the ear-coverts. Many birds have another dark line below this, bordering the throat, properly referred to as the ‘lateral throat-stripe’. Between the dark moustachial stripe and the lateral throat-stripe is usually a pale area known as the ‘submoustachial stripe’. So, from top to bottom there is: (1) the dark moustachial stripe, (2) the pale submoustachial stripe and (3) the dark lateral throat-stripe. Note that the confusing ‘malar stripe’ is no longer in use.
Nape and hindneck The rear of the head, between the crown and the mantle, is called the nape (upper) and the hindneck (lower).
Mantle and back These two terms are often confused. The ‘mantle’ is the forward part of the upper side of a bird, immediately below the nape, whereas the ‘back’ is the lower part, sandwiched between the mantle and the rump. One complication, however, is that with adult gulls and terns, the whole of the grey area of the upperparts, which involves the mantle, back, scapulars, wing-coverts and tertials, is often referred to in its entirety as ‘the mantle’.
Tertials On the closed wing, between the wing-coverts and the primaries, are the ‘tertials’. They are in fact the three innermost secondaries that are elongated to cloak the bases of the primaries at rest; they often show contrasting pale edges or fringes (hence: ‘tertial fringes’). On some birds, such as gulls, the secondaries are often invisible at rest, but on others, such as warblers, the secondaries are visible immediately below the tertials. On some species, such as Icterine Warbler, the tertials and secondaries have contrasting pale fringes that form a rectangular ‘wing-panel’.
Speculum The iridescent speculum on dabbling ducks is on the secondaries and this area too is often readily visible at rest.
The open wing This can be divided into the flight feathers and the wing-coverts. The flight feathers comprise the primaries, secondaries and tertials. The feathers that overlay the primaries, towards the bend of the wing, are the ‘primary coverts’ (in fact comprised of lesser, median and greater primary coverts but, for identification purposes, these are not usually differentiated). The line of larger coverts overlying and immediately in front of the secondaries are the ‘greater coverts’, while the line of smaller coverts overlying the greater coverts are the ‘median coverts’ (not medium coverts). In front of these is a larger, more random looking area of small feathers: the ‘lesser coverts’. The large oval-shaped area of ‘shoulder’ feathers between the open wing and the mantle/back is the ‘scapulars’.
The closed wing What is less straightforward is how these feathers lie when the wing is closed. The first point to remember is that, at rest, the lesser coverts are largely concealed by the overlying scapulars and sometimes by the fluffed-up flank feathers, so that all that can usually be seen at rest are the median and greater coverts; on many passerines, these feathers have pale tips, which form two wing-bars. On many non-passerines, the scapulars are often the largest area of ‘non-flight feathers’ visible on the upper side of a bird at rest, although this depends to some extent on the bird’s posture. On swimming ducks, the wing-coverts are usually completely hidden by the scapulars and flank feathers.
Primary projection At rest, the visible primaries beyond the tertials are referred to as the ‘primary projection’. As a general rule, the longer the primary projection, the longer distance a bird migrates. In some species pairs, for example Willow Warbler and Common Chiffchaff and Icterine and Melodious Warblers, accurate assessment of the primary projection is one of the best ways to separate them. What you have to do is to gauge the length of the primary projection compared to the length of the overlying tertials. Thus, on a Common Chiffchaff, the primary projection is about half the overlying tertial length, whereas on the longer-winged Willow Warbler it is about three-quarters to equal. Some birds show no primary projection at all, their primaries being completely cloaked by the overlying tertials. The most obvious examples are larks, pipits and wagtails.
Remiges and rectrices ‘Remiges’ is a collective word given to the primaries, secondaries and tertials combined; as such it is a useful abbreviation when referring to those three feather groups, which comprise the ‘flight feathers’. ‘Rectrices’ is the equivalent term for the tail feathers, but is less frequently used.
