The Grouse in Health and in Disease/Chapter III/Part II

by Committee of Inquiry on Grouse Disease

Part II. — Plumage Changes of the Hen Grouse.

The two changes of plumage in the hen Grouse are completed, as has already been explained, in the one case by the end of April or the beginning of May, and in the other case by July and August. Seasonal
changes of
plumage

The actual feather changes in both cock and hen are really very comparable in character, notwithstanding the difference as to season; and allowing for the difference of two months which makes the moult in the two sexes asynchronous, they may be described and explained in very much the same terms.

Mr Ogilvie-Grant was the first to draw attention to the exceptional want of agreement in the seasons chosen by the two sexes of the Red Grouse for their moult, and as in the cock's plumage he makes use of the Explanation of
terms. terms "autumn" and "winter-summer" or "winter" plumages, which have therefore been used here, so in speaking of the hen's plumages it will be well to adhere similarly to the expressions used by him, and to call them "summer" and "autumn-winter" or "autumn" plumages.

Exception may be taken, and indeed has been taken, to these names, as being inappropriate and inexact, but they are sufficiently exact for all practical purposes, and so long as moults and plumage changes are not completed in a week, but are spread over a period of several months, so long will there be some inexactitude in the terminology of these moults and plumages if they are named according to the months or seasons. It is immaterial so long as the term is sufficiently defined, for it is obviously impossible to use a term so exact as to require no definition.

The hen Grouse moults twice in the year, and wears her "summer plumage" as the breeding dress from April to July, and her "autumn" or "autumn to winter" plumage from August to March. These changes may be expressed in terms of comparison with the cock, as a case of plumage change in which the hen has two annual moults, exactly as has the cock, but both moults occur two months earlier in the hen than in the cock.

The hen's "summer" or breeding plumage is a very beautiful dress, variable to a considerable extent it is true, but yet having a general uniformity which becomes the more obvious as a greater series of skins in any particular phase of plumage is examined.

Opportunities for even seeing the hen Grouse, to say nothing of obtaining her skin, in the full breeding plumage are rare; and thus it happens Difficulty of
obtaining
specimens
of nesting
plumage. that, even in the large series of Grouse skins at South Kensington and at Cambridge, this phase is only poorly represented.

The Committee has been to some extent more fortunate, and has obtained a great many skins of hens in the summer plumage (see p. 54 and Appendix D), so that Points of resemblance can be noted at sight, and individual variations perforce take their proper places. It has been a marked feature in the whole collection of six hundred skins that as the series grew, and the general uniformity became more marked, the individual variations of which we were inclined to make much at first, became gradually relegated to their subordinate position.

Uniformity, albeit with endless minor variations, is the rule in the Grouse as it is in every other creature that leads an unprotected existence under natural conditions. How long it will continue in the protected, often over-protected. Grouse remains to be seen. It is possible that such variation as already occurs is to some extent a modern development ; but on this point there is at present insufficient evidence to amount to certainty.

Beginning once more with January, it may be said that in this month some hens, when examined on the under side, are hardly distinguishable by January. their plumage from some cocks (Pl. viii.). On the dorsum it is different, and a healthy hen in January is unmistakable owing to the terminal spots of buff which appear almost invariably, though occasionally in limited numbers, on the feathers of the back. In some healthy hens the chin is sometimes still pale buff in colour, owing to the persistence of summer-plumage feathers of the preceding year. The throat and fore-neck, on the other hand, are copper-red, but rarely so uniformly red as in the cock (Pl. xvi., Fig. 1). The copper-red feathers seem to begin on the fore-neck and proceed towards the chin, so that the chin often remains buff and black when the throat is already red. Except in very backward birds, which have been sick, the old and faded broad-barred feathers of the flanks are never found in January. The legs and feet are white and thickly feathered, and the claws are long and strong.

Pl. VIII.
(p.z.s. 1910. Pl. LXXXV)

Andre & Sleigh, Ltd.

female grouse, black type, in autumn-plumage.

Pl. IX.
(p.z.s. 1910. Pl. LXXXIVII)

Andre & Sleigh, Ltd.

female grouse, red type, changing from winter to
summer-plumage.

Pl. X.
(p.z.s. 1910. Pl. LXXXVI)

Andre & Sleigh, Ltd.

female grouse in full breeding-plumage.

In February the bird is still in the same plumage as in January. In a few forward birds the feathers of the summer dress are beginning February. to make their appearance on the back of the neck about the middle of the month.

In March the change from autumn plumage to spring breeding plumage is, in healthy birds, now quite unmistakable, though many birds are very backward owing to disease. All doubt as to the sex of healthy March. birds, whether from above or below, is now removed. The broad-barred buff and black feathers of the flanks are now appearing, and are most conspicuous and characteristic, while the whole of the lower breast and abdomen covered by the red-brown or red-black finely barred feather of September growth are still in excellent condition and remain unchanged (Pl. ix. The feathers of the chin, throat, neck, and upper breast are now mixed with broad-barred black and yellow feathers in forward birds; while in backward birds the throat and fore-neck may still be clad in copper-red feathers. The legs and feet are already looking worn and less well feathered, but the laws are long.

In April and in May, for the simple reason that many hen Grouse died of "Grouse Disease" in these months during the six years of the Inquiry, the proportion of skins of backward hens is large. The birds thus April and
May picked up dead carry one immediately back again to winter, for although they ought by this time to be putting the finishing touches to their spring plumage, hey are, in fact, but just succeeding in the belated effort to put on the autumn dress. They are thus a clear six months late, and afford the most misleading seasonal characters imaginable. Their legs and feet, instead of being worn and almost moulted clean, are at last, after a winter spent with almost naked legs, well-clothed with thick white feathers. The appearance of the legs therefore in the hens, as in the cocks, is totally misleading to the keeper or to the sportsman who considers bare unfeathered legs to be a sign of "Grouse Disease." This holds good for autumn only, and in spring precisely the opposite is the case, for in April, May, and June none but healthy birds have naked legs and feet. The general character of advanced and healthy birds towards the end of April and in May is that of a complete spring plumage. The whole of the upper parts are broadly barred with buff and black, and marked with conspicuous terminal whitish buff spots or bars (Pl. x. The under parts, again, are broadly barred with buff and black, from the chin to the throat and neck, over the breast and down the flanks, while the central lower breast and abdomen are still in the autumn plumage of the previous September (Pl. xi. and xiii.). White terminal spots may, of course, be present on the breast and abdomen. These are a local or an individual character which will be mentioned later in dealing with varieties of feather pattern and coloration. The flank feathers of the hen in the full spring plumage show much diversity of pattern. This diversity even in the same individual bird Change of
pigmentation
improbable has led to the belief that the pattern may be changed in an unmoulted feather from the autumn plumage arrangement of red-brown and probable, reddish-black finely barred with lines of black to a much bolder barring of buflf and black. It has been surmised, from the examination of singe feathers, that the change commences in the centre of the feather on either side of the shaft, and gradually produces another pattern of a totally different colour. But can this be possible in a feather which has long been fully grown, and which has presumably been long cut off from any blood or lymph supply, and which is as dead as if it had been shed? (Pl. xii.). It is almost certain that rearrangement of the pigment or of the pattern in this way is out of the question, and the reasons for this view have already been discussed.^[1]

The legs and feet of the hen Grouse in April and in May are very poorly feathered, and the claws are very long (Pl. xiii., Figs. 3, 5).

In June the legs and feet are almost bare, and the claws begin to drop off (Pl. xiii., Figs. 3, 4, 5). The precise date of this shedding of the claws is June. again really a part of the moult, and is, in consequence, equally dependent upon the health of the bird. Sick birds which have survived the spring mortality are always late in the shedding of their claws, and Shedding
of claws. equally late in the changing of their feathers. The claws are shed, both in health and in disease, but once a year, and the casting is synchronous as a rule with the disappearance of the autumn dress. The figures (PI. xiii.) by which this process is illustrated require but little explanation. The whole of the year's growth of horny black nail becomes loose on the soft and growing vascular matrix, and when quite ready to be cast can be easily pulled off like a little cap. The young nail beneath is at first soft, pink and vascular and very short, but soon hardens and deepens in colour, and in a month or two has grown to be a useful nail of horn. The transverse or circular groove which is

Pl. XI.
(p.z.s. 1910. Pl. LXXXVIII)

Andre & Sleigh, Ltd.

female grouse in full summer-plumage.

Pl. XII.
(p.z.s. 1910. Pl. NC)

Andre & Sleigh, Ltd.

female grouse, red type; feathers from flanks.

Female grouse, red type, feathers from flanks. Natural size.
Fig. a and c (from No. 1864). g and h (from No. 226), and k (from No. 632),
are varieties of the spring flank-feathers.
Fig b (from No. 575) is a flank-feather from a very black hen.
Fig d (from No. 1864) is an example of what is termed fine-barred dark-red
winter-plumage, with narrow blank bars or lines on rather dark rufous
chestnut, the latter being slightly bleached towards the tip.
Fig e and f (from No. 1864) and l and m (from No. 664) illustrates intermediate
stages of colouration, the feathers probably having broken through
the skin when winter-conditions prevailed, and having completed their
growth under summer-conditions.
Fig i and n (from No, 664) illustrate the reasoning upon which is based the
view just mentioned; of these two feathers there is no doubt that n was
being grown much later than i, and therefore more in summer-conditions,
producing summer breeding-plumage.

Pl. XIII.
(p.z.s. 1910. Pl. XCIII)

Andre & Sleigh, Ltd.

feet of red grouse: (1) new winter-feathers and nails; (2) full winter-plumage;
(3), (4), (5) and (6) showing stages in moulting of nails.

XIII Grouse, red type, feet showing winter-plumage.
Fig. 1. Right foot showing new winter feathers and new nails (No. 1177).
Fig. 2. Left foot showing full feathered winter-plumage.
Feet of grouse, showing replacement of nails.
Fig. 3. Right foot (No. 1148) with old nails ready to be shed.
Fig. 4. Right foot (No. 1148) in median vertical section.
Fig. 5. Left foot (No. 1167) 5a, old nails; 5b, new nails; 5c, shed nails.
Fig. 6. Right foot (No. 1185) with new feathers and new nails.

Pl. XIV.
(p.z.s. 1910. Pl. LXXXIX)

Andre & Sleigh, Ltd.

female grouse showing bare patch of skin and double
line of barred feathers on abdomen.

Pl. XV.
(p.z.s. 1910. Pl. XCL)

Andre & Sleigh, Ltd.

female grouse, red type; worn upper tail-coverts.

left at the point of detachment of the old nail is quite a useful indication of age in cases where there is a doubt as to a bird being over twelve months old or of the year. The presence of the groove showing that the claws have once at least been shed is conclusive proof that the bird is more than twelve months old.

In June there is another characteristic appearance in the hens, namely the bare patch of abdominal skin which results from the shedding of the abdominal feathers, grown in the previous September. The loss of these feathers Bare patch
on abdomen. leaves a naked patch of skin on the abdomen of a hen that has been sitting, and this patch remains naked for the next few months (Pl. xiv.). The general character of a June hen in health is that of the completed summer-nesting plumage, broad-barred buff and black over all the upper and under parts, excepting the abdominal area, the lower breast, wings, and tail. But it looks already somewhat faded and worn; and it is quite probable that in acquiring so perfect a plumage for sitting unnoticed on a nest built amongst the heather, the economic absence of the redder pigment in the feathers is in part a result of the acknowledged fact that for longer and more trying use, and for wear and tear in feathers, darker pigments are required, whereas for the short-lived and less exacting requirements of the summer plumage in the hen Grouse from April to June the buff and black feathers, with very much poorer wearing qualities, are found to be sufficient. The accompanying figures of a few worn-out and moulting feathers taken from a hen in summer plumage, show how distinctly better the black pigmented parts of the feather stand wear and tear than the yellow parts (Pl. xv.). Certain pigments have a value, therefore, of a very practical nature apart altogether from the aesthetic point of view of attractiveness, or the rather hypothetical view of assimilation to surroundings for purposes of safety or to assist in obtaining food. He would be unwise, however, who denied that all three factors play a part in the very beautiful nesting plumage of the hen Grouse.

It very occasionally happens that the hen Grouse, instead of retaining the redder plumage of the previous autumn's growth on the abdomen until it drops off during incubation, grows an almost universal spring plumage This patch
sometimes
absent. of buff and black broad-barred feathers covering the lower breast and abdomen as well as the remainder of the body from head to tail. A skin showing this condition is preserved in the National Collection, and there is an almost equally perfect specimen in the Committee's Collection, No. 919.

The more usual procedure is that the abdominal patch of autumnal plumage is lost during incubation, and is then quickly replaced by a renewal of the Peculiar
growth on
abdomen.autumnal feathers when the spring plumage is also being shed. There remains, however, in the majority of birds, a very quaint abdomen. growth of belated spring plumage, consisting of buff and black-barred feathers in two lines down each side of the centre of the naked patch, as though, for some occult reason, the intention to grow "spring-plumage" feathers upon this area had never been altogether lost. This peculiar persistence of belated intention shows itself as a patch of yellow feathers made up of the two lines of feather growth in the midst of a much broader area of the autumn red pigmented feather which one would expect to find all over the abdomen (Pl. xiv.). It is conceivable that a small persistent remnant such as this, having no obvious connection with the surrounding plumage at the time, or with the habits of the bird, or with the seasons, may yet have something to do with the third or lost "eclipse" plumage which is still to be found in the grey plumage of the Ptarmigan, but is almost completely lost in the case of the Red Grouse

In July the summer plumage of healthy hens is much worn out, frayed at the edges, and very definitely faded, and the feathers are already July. dropping out. On the chin, throat, and fore-neck, new red feathers of the autumn plumage, looking rich and dark, are already making their appearance. The back is as it was, but faded, and the flanks are still conspicuously broad-barred with buff and black; but the abdominal bare patch is now growing new autumn-plumage feathers with great rapidity from the centre outwards. The primaries and secondaries have now commenced to moult. There may be in July, in the hen, as many as six or eight old primaries in each wing with frayed tips, still to be renewed.

Precocious young birds of the year can still at once be distinguished from hens in moult, because in the former the dark red-brown black-lined autumn Distinction
between
young and
old birds. plumage is on the flanks, while the broad-barred buff and black, and rather worn-out chicken feathers are in the centre of the abdomen. In the adult the distribution is reversed. The broad-barred buff and black feathers of the spring plumage are on the flanks, and the redder fine-barred autumn-plumage is appearing in the centre(compare Pl. xii.). Figs, a, c, g, h, k, and n, with Fig. d.). In skin No. 284 there seems to be an unusual compromise in a very backward hen, owing to disease. The compromise is between the

Pl. XVI.
(p.z.s. 1910. Pl. XCIV)

Andre & Sleigh, Ltd.

heads of: (1) (2) female grouse; (3) (4) male grouse; (5) ptarmigan, showing supra-orbital combs.

Pl. XVII.
(p.z.s. 1910. Pl. XCVI)

Andre & Sleigh, Ltd.

head of blackcock, showing supra-orbital comb.

broad-barred and the winter plumage with its very fine black cross-lines (PI. xii., Figs, e, f, l, and n).

The legs and feet in July are naked, and the claws are very small; but the feathers are already showing through as small white points, not to be confused with broken shafts, which occasionally result from wear and tear in woody heather.

The plumage of the hen Grouse in August is well known. It has already been pointed out how, owing to the sudden increase of observation, and owing to the sudden arrival of opportunities for examining an enormous August. number of birds over the whole country during this month, there has sprung up an idea that disease amongst Grouse has a recrudescence in the autumn. But this is not the case. There are probably fewer diseased No
autumn
outbreak
of disease.birds on the moor in August than there are in July. In July, however, they are never shot, and therefore not investigated, but in of August they are carefully picked out of every bag, and, owing to the general interest in the question of disease, are almost always noticed, and in a large proportion of cases publicly notified. Hence the idea that disease makes a new start in August and September. As a matter of fact, however, these wasted birds are almost certainly convalescent. They have been diseased, and they are still suffering from disease, but thanks, in the majority of cases to their sex (for the bulk of the sickly autumn birds are hens), they have avoided actual death in the two highest mortality months, April and May. Once tided over these fatal months, the food and general conditions of life improve, the weight of the cock goes up, and the balance is again in favour of recovery for him; and although with the hen the exigencies of incubation and the cares of the family continue to handicap her until June and even July, she then rapidly begins to put on weight, and in August and September is once more on the way towards complete recovery. Many sick-looking "piners" are shot upon the moors in August, but it should be remembered that in that month they are recovering from disease, and not growing worse; while in September many that were not up to the average weight the month before will be practically normal and probably indistinguishable from healthy birds, were it not that their serious indisposition of the preceding months has put them behind their fellows in the matter of feather change.

In August, therefore, the Committee's collection of skins contains a large number of examples of hen birds showing deferred moult and belated growth of feather. The normal healthy hen Grouse in August has already put off most of the broad-barred spring plumage feathers of her nesting dress, and is very much like the cock bird in appearance, with the same dark, red-brown vermiculate or fine-barred plumage underneath, white-flecked or not as the case may be, and with a mixture of old and new feathers above. The legs and feet of a forward hen are already showing quite a fair growth of white feathers, and the nails have all been shed. The claws are therefore short and rather soft, and the transverse sulcus or groove at the point of detachment is clearly marked. In the wings there may still be a number of primaries to be changed.

In the convalescent "piner," on the other hand, the case is often very different. She has still a most deplorably bleached and weathered breeding plumage on her, with worn-out feathers, frayed or ragged, often with saw-toothed edges, showing the unequal effect of wear and tear on the pale buff pigmented and black pigmented parts. The bird in this belated plumage has quite naked legs and feet and long unshed nails, or may at the most be just showing the points of a new growth of feathers through the skin; and in this state she is conspicuously shabby and ill to look upon in comparison with the splendid plumage recently acquired by her healthy sisters, and by the now almost universally healthy cocks. But the point above all others to be remembered in this connection is that this hen is convalescent, and still has a couple of months of good food and good weather, as a rule, in which to complete her convalescence before the winter comes.

If the spring outbreak of disease has been severe — that is, if the general conditions of the preceding winter and early spring months have been such Different
effect of
disease
in cocks
and hens. as to conduce to a heavy and widespread infection of the Grouse with the larval Trichostronqylus — then both cocks and hens will be equally infested. But the breeding season and the concomitant needs of the two sexes are, from April onwards, quite distinct from one another.

The result of this is that there is often a large mortality of cocks in April and in May, and a much less marked mortality of hens, probably in the proportion of seven or eight cocks to one hen, but definitely occurring in the same two months.

There is no great mortality from Strongylosis in any other months of the year and after May, the cocks are suddenly relieved and rapidly recover, so that by August there are almost no sick cocks; the hens, on the other hand, have still two very trying months to face, and although, thanks to the abundance of food, probably most of them succeed in struggling through, yet by August they have only just been freed of their more pressing cares and disabilities, and so a very great number are still found to be in very poor condition. The moment the disabilities are removed, however, they begin to recover, and it is this point which has so constantly been overlooked. Sick birds in August are convalescent, and however many there may be, it is not a sign of a new outbreak of disease, but a sign that the past spring infection was a heavy one, though less fatal than it might have been.

At the end of their own specially critical periods, the cocks have at any rate June, July, August, and September in which to pull themselves together by means of good food assisted by good weather; whereas the hens, at the end of their own specially critical period, have August and September. Hence the preponderance of sick-looking hens when the shooting begins, and the widespread, but erroneous, belief in a recrudescence of disease in autumn.

To return to the further consideration of the hen's change of plumage in September, her finest feature is now undoubtedly the clean new growth of bright red, or dark red or even black and white-flecked feathers of September. the breast and abdomen, with their narrow but even blacker markings. The whole of the feathers of this tract have now been shed, but they grow again so quickly that no bare skin is visible save in the middle area of the abdomen quite low down, where, as has been already pointed out, the new growth is of belated feathers coloured as in the spring plumage, and therefore quite different from those around them. There is still, as a rule, no accession of new red feathers on the chin or throat of the healthy September hen, or at the most but a feather or two. But in the sick hen there is still often a sprinkling of the old red feathers of the preceding autumn plumage, very faded, amongst the faded buff and black feathers of the belated spring plumage. On the back of even forward hens there is still a mixture of old and new plumage, and the scapulars are often faded to something like black and white, and are badly frayed at the ends. The wings have now almost completed their moult, but there may still be a primary or two to change, even in very forward birds. The legs and feet are rapidly becoming feathered for the winter, though in backward birds which have been sick they are still quite bare, and now, of course, this feature may truly be taken to be a sign of sickness and disease, though in a convalescing bird.

In October one may find a very backward bird with as many as three worn-out primaries in either wing to change; but, as a rule, the wing is October. perfect, the primaries and secondaries and their coverts all completely new, and in the tail the rectrices are full grown. The legs and feet are now also fully feathered, though the thickness of the growth increases as the winter cold comes on. On the back the bird now looks fresh and richly coloured, from head to tail, but a close search will always disclose a number of spring-plumage feathers which have still to be thrown off. Underneath, the rich red-copper colour is gradually replacing all the previous buf on the chin and throat. The change "hangs fire" a little on the neck and upper breast, but it is still progressing, whereas on the lower breast and belly the rich red or darker winter plumage with its beautiful fine black cross-lines and pure white flecks is a very striking feature.

There are, in the Committee's collection of skins, a number of examples showing the result of disease in deferring the moult; many of these birds, even in October and November, have made no effort to get rid of the old, faded and completely worn-out spring plumage. The majority of these birds have been so diseased in spring that they have not bred at all. The ovaries have throughout the season shown no development, and there are no signs, even in the earlier months, of the shedding or development of ova or of any increase in size of the oviduct. They have been true barren hens. In some cases (e.g., in No. 1247) there appear, in November, feathers of three separate plumages. There are the faded spring-plumage feathers of the current year, but mixed up with them here and there are new feathers of the autumn plumage coming, and here and there exceedingly old worn feathers of the autumn plumage of the year before. No. 1225, an October hen, shows exceedingly well how the bare, broody patch of the abdomen grows delayed broad-barred buff and black feathers instead of the fine-barred darker autumn-plumage feathers which surround the patch. These broad-barred feathers appear in two parallel rows, breaking through the skin of the broody patch on either side of the medial line; this growth is also well shown in a specimen at the British Museum of Natural History (Pl. xiv.).

In November the chief alteration is the completion of the autumn moult and the assumption of the autumn plumage. The feathers of the upper parts have black middles, and are barred with rufous-chestnut and November. ornamented with the characteristic white or buff-coloured terminal spots.

In December the hen is in full autumn-winter plumage. On the legs and feet she is well and thickly feathered; and on the under side the chin and throat are dark red, as well as the fore-neck, marked with December. broader black bars than upon the lower breast and abdomen, where the marking is "of the finer type, and the colour distinctly of the redder and darker autumn plumage.

1. Vide pp. 37–40.