The Grouse in Health and in Disease/Chapter IV/Part I

by Committee of Inquiry on Grouse Disease

CHAPTER IV

food of the red grouse

By Edward A. Wilson and A. S. Leslie.

Part I. — Observations on the Food of Grouse, based on an
Examination of Crop Contents.

During the period of the Inquiry the contents of several hundreds of loaded crops have been examined by the Committee with a view to ascertaining the various foods eaten by Grouse; the percentage compositions have Methods of
examination. been tabulated, as well as the total weight of food in the crops at examination, the various hours of the day, and by these means the Committee have come to several unexpected conclusions.

Table I. (p. 68) shows how the three hundred and ninety-nine specimens of crop contents examined are distributed as to locality and as to date, during the three years 1906, 1907, and 1908.^[1] It is natural that by far the greater number should have been supplied during August and September; but the remainder are fairly evenly distributed.

Table II. (p. 69) is drawn up to show the average weight of the crop contents of birds killed at different hours of the day, from 6 a.m. to Time of
feeding. 6 p.m.

In the last right-hand column of Table II. will be found a general average for the twelve months, and it will be seen from the figures given that Grouse feed from morning until night, but that full crops are more commonly found in birds killed in the afternoon and evening, both in winter and summer, than in the morning and forenoon.

When a Grouse is in health the gizzard invariably contains food undergoing a grinding process throughout the hours of sunlight, even in the longest summer day. The crop, it is true, is often found very full towards evening, and rarely so before noon; but this is only because in the evening the bird feeds more heavily in order to store up food for the hours of darkness, while

TABLE I. — Crop Content; Material Examined.

	Jan.	Feb.	Mar.	Apr.	May.	June.	July.	Aug.	Sep.	Oct.	Nov.	Dec.
Aberdeen								1		1			2
Argyll	3	2	1	2	1			1	3			10	23
Arran	1	1	1	1									4
Ayrshire								2	5				7
Banff												2	2
Caithness	1	2	1				5	1		3		7	20
Dunbarton	1	1	3	1	3			6	12	1	5		33
Dumfries	2	2	2		2	4	2	2	1		2	5	24
Haddington			1										1
Inverness	7	5	3			1	3	38	15	1		9	82
Kincardine		1		1									2
Kirkcudbright				1						1			2
Lanark		1										1	2
Midlothian	2		1		1							3	7
Moray		1		2	1							2	6
Mull	1												1
Peebles				1					1			1	3
Perth		3	3	3	1		2	2	1	1		5	21
Ross	3		4	1		6		1	3	7		2	26
Roxburgh				2	1					1	5		9
Selkirk				3	3					1			7
Sutherland		1	1					1			1	1	5
Wigtown												1	1
Cumberland		1	1	1		1		10				2	16
Derby	1	1			3							2	6
Durham	1										1		2
Lancashire												2	2
Northumberland	4	4	2	1						2		2	15
Westmoreland	2	3	2	2	1							2	12
Yorkshire	1	6	5	7				2	4	7	1	3	36
Ireland										1			1
Wales	2	4	3	1								5	14
	33	39	33	30	16	12	12	67	44	27	15	71	399

Total number of crop contents examined=399

during the daytime he seldom eats more than the digestive processes can deal with at the time. Hence during the early part of the day the food passes rapidly from the crop to the gizzard and on to the digesting tracts of the gut proper, and the crop is left almost empty. This has given rise to the view that Grouse only feed once a day, and that in the evening. Heather (Calluna vulgaris), as is well known, is the ordinary food of the

TABLE II. — Weight in Grains of Crop Contents in which the Hour of Collection was given
from April to November inclusive.

Hour of collection.	Weight of crop contents of each Bird in Grains. (April to November.)	Weight of crop contents of each bird in Grains. (December to March.)	Average Weight, in Grains.
			Apr. to Nov. Average.	Dec. to Mar. Average.	Combined Average for 12 Months.
6 a.m.	1	10, 10	1	10	51⁄2
7 "	8	No specimen	8	No specimen	8
8 "	No specimen	20	No specimen	20	20
9 "	1, 8	10	41⁄2	10	71⁄4
10 "	9	No specimen	11	No specimen	51⁄2
11 "	18, 2, 16, 27, 20, 14, 3, 13, 24, 40, 28, 36, 43, 34, 11	5	22	5	131⁄2
Noon	12, 14, 2, 11, 18, 6, 7, 15, 21, 7, 1, 6, 15, 24	120, 10	111⁄3	65	38
1 p.m.	18, 36, 62, 29, 32, 2, 3, 5, 13, 13, 18, 12, 19, 9	No specimen	19	No specimen	19
2 "	26, 45	70, 60, 20	351⁄2	75	551⁄4
3 "	50, 173, 98, 213, 334, 27, 7, 12, 17 26, 18, 14, 2, 6, 8, 28, 52, 24, 48 31, 1, 5, 68, 31, 32	110, 100, 80, 180, 358, 200 369, 50, 380, 250, 320	53	217	135
4 "	15, 1, 4, 246, 50, 17, 32, 50, 43 50, 46, 8, 4, 2, 43, 3	339, 429, 239, 369, 429, 599 280, 280	36	3701⁄2	2081⁄4
5 "	8, 1, 1, 2, 1, 254, 66, 18, 5, 32, 23, 17 7, 23	150, 210, 200	321⁄2	1862⁄3	1091⁄2
6 "	37, 93, 114	10, 349, 290, 20, 409	81	214	1471⁄2

adult Red Grouse. But twenty or thirty other plants are also eaten, often in great quantities, and it is a well ascertained fact that Grouse that have never set eyes upon a sprig of heather will live and flourish for years. Yet the importance of heather in building up the birds for the approach of winter cannot be exaggerated, and there is little doubt that in a bad heather year all the young birds suffer, while even in a good heather year the later broods will be permanently handicapped as regards physique and disease-resisting power if they have missed the best food months.

The most noteworthy fact brought out by Table II. is that Grouse appear to require a larger quantity of food in the winter months from December to March, than in the spring, summer and autumn months from April to November.^[2]

It is, of course, true that in a bad heather year Grouse may find substitutes for their staple diet. Of these substitutes blackberry is undoubtedly the most Substitutes
for
heather. valuable, as may be seen by reference to Tables III. and IV.;^[3]- but in many districts blackberry does not grow upon the moors, and in no case is it so reliable a winter food as good heather. Other substitutes for heather are rush-heads, crowberry, bog myrtle buds, seeds of P. tormentilla fern leaves, bog cranberry leaves, flowers of Erica tetralix and Erica cinerea, moss spore capsules, sheep sorrel leaves and seeds, insects, and oats. On pp. 83–87 will be found a list of the vegetable foods eaten from time to time by the Red Grouse, with illustrations of some of the plants referred to.

TABLE III. — Showing the Percentages of Various Foods found in Crop Contents of Grouse
from April to November inclusive.

April.

May.

June.

July.

Aug.

Sep.

Oct.

Nov.

Calluna (Heather) shoots, fresh and green
Calluna (Heather) shoots, brown but living
Calluna flower-buds, flower and seed-heads

47 46  0

93

69½ 12   ½

82

82  0  0

82

31½ 21½  0

53

59½  1  0

66

63¼  0 16¼

79½

31 11 28

70

24 15 33

72

Blackberry (V. myrtillus), stalks and leaves

 4

 6

 6

20

 0

 4½

 9

22

Various, including Erica, Crowberry Fern, Sorrel, etc.

 3

12

12

27

34

16

21

 6

The summer substitutes for heather, while interesting as showing the wide range of the Grouse's diet when many varieties of food are available, cannot be considered of great importance to the health of the adult bird, for if the

PLATE XXIII

types of heather.

Old heather valueless as food for Grouse.

Young short Heather valuable as food for Grouse.

heather is good, and the supply sufficient, the stock will be well nourished and healthy, even on a moor where there are no berries or other miscellaneous kinds of food.

Heather then is the essential basis on which the Grouse depends, and the importance of the plant is so great that it may be permitted to give a short description of the phases through which it passes during the seasons of the year.

Beginning with the months of early spring, it will be seen from Table III. that in April the Grouse's diet consists of an equal quantity of fresh green heather and of brown "winter" heather. The former is more nutritious than Winter
heather. the latter, but even the brown winter heather is better than nothing, and is to be distinguished from withered dead heather which Grouse never eat.

The fresh green heather so desirable for the food of Grouse does not necessarily represent the young shoots of the spring growth, for these do not generally appear till May, but rather the evergreen foliage which the plant carries upon its lower branches throughout the winter. No one who casually examines a Grouse-moor in midwinter can realise that the dull brown weather-beaten scrub conceals on its more sheltered twigs a luxuriant growth of vivid green shoots: these green shoots are far more Shoot
versus long
heather. numerous on short close heather than on the long overgrown heather so common on many moors, for as the plant increases in height it becomes more open in its growth and more susceptible to the blighting effects of frost and cold winds.

In cases where the heather has attained a height of several feet the shelter is so greatly reduced that it is sometimes difficult to find any green shoots at all in winter unless the weather has been unusually mild; such long overgrown heather is of practically no value as winter food for Grouse (see Pl. xxiii., Fig. 1). This type of long and apparently luxuriant heather is very common on the west coast of Scotland, and in many districts in the central Highlands, and probably accounts for the fact that these districts carry a comparatively small stock of Grouse. In other districts the heather seems to have developed a short, close habit of growth — to the uninitiated it would appear to be stunted and poor; yet it is in the districts where Dwarf
type of
heather. this dwarf type of heather is common that Grouse appear to thrive in the largest numbers. The hills are covered with a close carpet of vegetation having a smooth level surface which may be compared to a well-clipped yew hedge — this level surface forms a canopy of shelter from frost, while the stems of the heather are so short and stiff that they are little affected by the wind. If this type of heather is examined, it will be found that immediately below the weathered canopy there is a rich growth of bright green shoots even in the most severe winter (see Pl. xxiii., Fig. 2).

There is no doubt that it is on the moors which have a large proportion of this short, close-growing heather that the largest stock of birds can be carried over the winter. But it is only on a special class of ground that this type of heather is found to grow naturally; it is usually associated with dry, hard soil, good natural drainage, a rocky subsoil, and only a shallow layer of peat on the surface; it is uncommon in districts with a heavy rainfall.

Even on the best ground there is a tendency for the heather to grow too long and bushy; but this tendency can fortunately be controlled by artificial Heather
culture. means. In another part of this Report the subject of heather burning is fully described,^[4] and it is only necessary here to state that, for purposes of food, heather ceases to have any value after it has been allowed to become rank.

With the advent of May comes a great change in the condition of the heather plant. In this month every twig breaks out into green shoots, Young
growth in
May. even the oldest and most ragged stick heather will produce young growth the kind most valuable as food for Grouse; but it is now too late for this tardy recovery to be profitable, for the days of famine are past, and there is sufficient food to feed ten times as many birds as there are upon the ground. Even in this month of plenty, however, the close, short heather of from 4 to 8 inches in height is superior to the straggly forest of overgrown plants, for there is an ever present risk of a late spring frost, when the tender young shoots will require all the shelter they can get.

The appearance of the young growth is marked by an immediate change in the diet of the Grouse. On referring again to Table III., it will be seen that the consumption of fresh green heather shoots rises suddenly to 69¹⁄₂ per cent, while that of the dry winter heather drops to 12 per cent. At the same time the proportion of miscellaneous foods is more than doubled, owing doubtless to the fact that every moorland plant is throwing off its winter sleep and bursting into appetising young buds.

Just as the first flush of early pasture is more nourishing than the later growth, the first heather shoots of spring probably contain a larger percentage of nutritive food than at any other time of the year, and it is doubtless due to this cause that Grouse make such rapid growth in size and Young
growth
very
nourishing. strength between the date of hatching in May, and the opening of the shooting season some ten or twelve weeks later.

It is in the month of May also that the young heather plants first begin to appear on the black ground, where the old heather has been burned. The length of time that elapses between the date of burning and the Growth of
young
plants. growth of the new heather varies. If the roots are not too old, and have not been destroyed by the fire, the new growth will spring from them within a year; on some ground this always occurs. If, however, the roots have been burnt out, or are too old to send forth new shoots, the ground must lie waste for years, until a fresh growth of heather springs from wind-blown seed or from the seed lying dormant in the soil or blown on to it.^[5]

It is usual to suppose that the first shoots of the young heather as they appear above the ground are greedily eaten by Grouse. Observation has shown that this view is not strictly correct, for the adult birds will Adult
Grouse do
not eat
seedling
heather. never feed on the immature plant so long as they can find plenty of close-growing heather of the type described on p. 72. This is fortunate, for otherwise the first growth might be very severely checked on a moor carrying a heavy stock of birds. Sheep, on the other hand, are very fond of the tender young shoots, and are often most destructive Sheep do to seedlings which have not had time to secure a firm roothold.

While the adult Grouse does not eat the very young heather, there is no doubt that the chicks prefer it to the shoots of the more mature So do
Grouse
chicks. plant; but the amount eaten by them in the days of their infancy is so small that they cannot make any material impression on the growth of the plant.

In June there is a continuance of the favourable conditions which commenced in May. It will be seen by reference to Table III. that in this Heather in
June. month the consumption of fresh green shoots of heather rises 82 per cent., while that of brown winter heather drops to zero.

In July the consumption of heather drops to its lowest for the year — only 53 per cent.; this is doubtless partly due to the ripening of In July. blaeberry leaves which occurs in this month. The consumption of blaeberry stalks and leaves has risen to 20 per cent., while the quantity of berries eaten is shown by the increase of "various" to 27 per cent. The unexpected increase in the consumption of brown winter heather is puzzling, but might be accounted for by an abnormal period of cold weather or blighting wind causing a "set back" in the new growth, and driving the birds to feed more largely on the old shoots. This view is supported by the fact that the birds have also Exceptional
character
of
July
figures. eaten an abnormal quantity of blaeberry stalks and leaves, whereas in the following month, when the heather has presumably recovered from its temporary blight, the consumption of brown winter heather and blaeberry leaves and stalks drops at once from 47 per cent, to 1 per cent. The figures for July shown in the Table are probably exceptional, and do not represent the normal proportion of foods eaten in that month; but they are interesting as showing the elastic manner in which the Grouse can adapt himself to varying conditions.

In August the figures for the consumption of heather appear to have become normal, and the fact that this is the great berry month of the year In August. is shown by the increase of "various" to 34 per cent., the largest amount in any month. Berry feeding is, of course, irregular, for berries only grow in certain localities, their consumption cannot therefore be gauged Berries. by the examination of specimens obtained from moors where no berries are obtainable. Berries are not an essential item in the diet of the Grouse; but it is well known that where they are to be obtained Grouse will flock to them in large numbers, often deserting the heather altogether for a while, and congregating in vast packs upon the berry ground. The blaeberry fruit does not as a rule grow in such profusion as that of the clusterberry or Scottish cranberry, and does not seem to be so attractive to the Grouse, though its leaf and bud are much more generally eaten at all times of the year.

The August figures are interesting as showing the first indication of heather blossom in the diet. First in the bud, afterwards in full bloom, and lastly in Heather
flowers
and seeds. the form of fully ripened seed, the flower of the heather is an important item of food. There is an old saying that when the "stoor (i.e., pollen dust) is on the heather in August a good Grouse season is sure to follow, and the experience of the Committee tends to confirm this belief. In a year when the bloom is early and luxuriant the pollen rises in clouds when disturbed, covering boots and gaiters with a soft yellowish dust, and sometimes even interfering with the breathing of the dogs. This condition is usually followed by a fine harvest of well-ripened heather seed, and the importance of heather seed as a form of food may be seen at a glance from the figures given in Tables III. and IV.

It is often stated that in seasons when the corn has ripened well and early, the stock of Grouse in the following spring is healthy and vigorous, and the breeding season a good one; from this it has been argued that the same weather which has resulted in a good crop of grain has also produced A good
grain year
usually in
good
heather
year.a good crop of heather seed. This factor too may have something to do with the difference in the numbers of Grouse which moors in different parts of the country are capable of carrying. It is well known that the number of Grouse on a moor does not depend upon the area of heather land, for in the thinly-stocked moors of the west of Scotland the heather growth is stronger than in the south of Scotland, where in many A good
grain district
usually
a good
Grouse
district. districts there is a larger stock of birds. Even in Yorkshire, Lancashire, and Derbyshire the ground does not appear to be better suited for the growth of heather than in Scotland, yet in these counties the stock of district birds is proportionately much greater. The difference is partly to be accounted for by the fact already noted, that the heather in the north of England is of a better quality, that is to say with many more stalks to the acre, than the rank growth of the west of Scotland, but it has also been suggested that in the former country the normal weather conditions are more favourable to the ripening of the heather seed. Again, in Caithness, where the grain always ripens well on account of the long hours of daylight in the summer months, the stock of birds which the ground can carry is unusually large.

In September, October, and November, the tendency to revert gradually from summer to winter diet is well exemplified by the figures in Table III. Throughout these three months the consumption of the heather seed increases steadily, In September,
October,
and November.while "various" drops from 16 per cent, in September to 6 per cent, in November. In October we find the item of "brown winter heather" reappearing in the list, and in November we have a sudden increase in the consumption of blaeberry stalks and leaves, due probably to some temporary check suffered by the heather similar to that indicated by the figures for July.

Turning now to Table IV. (p. 76) we find that in the four winter months the diet becomes more restricted. "Various" practically disappears, and Whiter
food. its place is taken by a larger quantity of heather shoots, while heather seeds and blaeberry stalks still keep their place in the list. One or two points are worth noting. In the first place, the sudden drop in the consumption of heather seed from 20¹⁄₄ per cent, in January to 2¹⁄₂ per Heather
seed not
eaten after
January. cent, in February and 2¹⁄₃ per cent, in March is interesting as showing that once the seed has fallen to the ground it is no longer eaten by Grouse, though it may be valuable for the reproduction of the plant.

TABLE IV. — Showing the Percentages of Various Foods found in Crop Contents of
Grouse from December to March inclusive.

December

January

February

March

Calluna (Heather) shoots
Calluna (Heather) seed-heads

592⁄3 per cent. 27 "

862⁄3

64 per cent. 201⁄4 "

841⁄4

751⁄2 per cent. 21⁄2 "

78

97 per cent. 21⁄3"

991⁄3

Blaeberry stalks and buds (Vaccinium myrtillus)

 10 per cent.

 13¹⁄₄ per cent.

 15"

 ...

Various, including Crowberry leaves (Vaccinium vitis-idæa), Bog Cranberry Leaves (Vaccinium oxycoccus), Crowberry Leaves (Empetrum nigrum), Erica, sorrel, fern, and other grean leaves

3¹⁄₂"

2¹⁄₂"

7"

 ²⁄₃"

Another point is that both in this and the preceding Table, the figures relating to the consumption of blaeberry stalks and leaves are misleading Blaeberry
eaten
largely
where procurable. because they are the result of averaging the crop contents of a large number of birds — many of them sent from localities where blaeberry is unknown. Were the crops of individual birds recorded it would be found that those coming from moors where blaeberry is common would show almost as large a consumption of that plant as of heather. Blaeberry forms as much as 30 per cent, of all foods taken by Grouse in Derbyshire, 22 per cent, in Yorkshire, and 11 per cent, in Inverness and Dumfriesshire, and very little in any of the other counties.

In special cases these averages are departed from, especially when the heather crop has been a failure. Thus some December specimens from Lancashire showed the remarkable average of 80 per cent, of blaeberry stalks and buds, with only 17¹⁄₂ per cent, of heather shoots and 2¹⁄₂ per cent, of heather seed, but in this case the heather-seed crop in Lancashire was reported as very bad. In the same year the heather-seed crop in Peebles and Merioneth was reported as exceptionally good, and the December specimens from both these counties showed the proportion of 50 per cent, of heather shoots and 50 per cent, of heather seed, but no blaeberry.

Probably the consumption of other foods, which are classed under "various," and have already been enumerated, varies in the same way chiefly with local relative abundance, as, for example, in Perthshire, where "various" rises to 53 per cent.; Ayrshire, where it reaches 47 per cent.; and Derbyshire, where it reaches 40 per cent, of all foods taken.

Individual taste plays a large share in the food statistics of Grouse. One may find, for example, one bird eating largely of fern leaf, another of bog myrtle buds, another of nothing but rush heads or tormentilla seed. In one case, where two birds were killed with a "right and left" in a Grouse drive it was found that one had filled his crop with heather shoots, the other with blaeberry leaf buds, yet both birds had come off the same beat. Occasionally one finds that even an adult bird has eaten scores of small black gnats. The flower of Calluna is varied occasionally by the flower of Erica tetralix, or ripe cluster berries, or spore capsules of several mosses, or leaves of the cloudberry.

The interest of Table IV. centres on the first item, "Heather Shoots," for the figures prove conclusively, if proof were required, that, except on Heather
shoots the
solo diet
in February
and
March. favoured moors where blaeberry abounds, heather shoots and nothing but heather shoots constitute the diet of the Grouse during February and March — the fact that the February column shows 7 per cent. of March "various" was due to one bird's crop being almost entirely filled with crowberry leaves, a quite unusual diet; the "various" consumed by other specimens examined for that month only amounted to ¹⁄₃ per cent.

It is obvious, therefore, that in February, March, and April the question of food becomes a critical one, for if the heather fails the Grouse must suffer either by direct starvation, or what is much more dangerous, by being forced to crowd too closely on to the few small areas where good winter heather is to be obtained.

Although we have no evidence from any one of the hundreds of Grouse crops examined that true frosted heather is ever eaten, the heather which actually filled the majority of the winter crops varied greatly in its value as a food. It could often be seen that the birds had been hard put to it to fill their crops at all, perhaps from stress of weather, or possibly because of excessive or deficient burning or an overstock of sheep, or for some other less obvious reason.

The mere fact that the crops of many birds contain old heather is enough to prove that birds sometimes find great difficulty in collecting a meal of wholesome food. The vast majority of winter crops contain, as we have already said, good dark green or dark reddish brown winter heather, sound wholesome food with a minimum of dead woody tissue. But now and again one finds a crop full of old woody growth of which the food value must be very small. And though the cause of this may sometimes be that the bird is a weakling and has been driven off the better feed to live upon whatever it can find elsewhere, yet this inferior food is sometimes found in the crop of a bird which is evidently no weakling. It may then be due to the fact that the moor has been left long unburned, and that all the heather within reach is old and rank. Or the moor may have been over-burnt from every point of view except that of the grazing tenant. In such a case large tracts of young heather are burned again and again, often by runaway fires, to bring the land to grass and kill the heather. In this the grazing tenants of parts of the borderland and of the north of England have been very successful, and heather in many places is a thing of the past, the moors being now almost all white land. Scattered through this, where the tussocky grass has had its way for many years, is a thin growth of useless straggling heather of little value as food for bird or beast.

For the purpose of drawing up Tables III. and IV. two hundred and eighty-seven specimens of Grouse were examined, and the specimens were fairly evenly Tables III.
and IV. distributed over the months from April 1906 to March 1907. The specimens represented birds from no fewer than twenty-seven different counties, so that the results may be regarded as conclusive, so far as concerns the particular period under review.

In case, however, of the period selected being abnormal, Table V. (p. 79) was prepared to show the crop contents for two complete years, viz., 1906 and 1907. Table V. In this Table the figures for the corresponding months are placed together, and an average is struck for each month. It will be seen that these averages show the same general tendencies as are seen in the former Tables, and confirm the view that the figures given in Table III. for July and November 1906 were abnormal, and probably due to exceptional circumstances.

The total number of specimens examined for the purpose of drawing up Table V. was four hundred and thirty-six, including the two hundred and eighty-seven already included in Tables III. and IV.; but in 1907 specimens were not quite so well distributed as in the earlier period. This remark specially applies to May, June, and July 1907, when only one specimen was received for each month as against a monthly average of fifteen in 1906.

TABLE V. — Comparison of Monthly Averages of Crop Contents covering Two Years.

		Jan.	Feb.	Mar.	Apr.	May.	June.	July.	Aug.	Sep.	Oct.	Nov.	Dec.
Calluna heather shoots	1906 1907	64 89	751⁄2 72	97 81	93 64	811⁄2 100	82 100	53 95	601⁄2 38	631⁄4 63	42 51	39 701⁄2	54 592⁄3
Calluna heather flower and seed-heads	Av 1906 1907	761⁄2 201⁄4 10	733⁄4 21⁄2 9	89 21⁄3 2	781⁄2 0 0	903⁄4 1⁄2 0	91 0 0	74 0 0	493⁄4 51⁄2 14	631⁄5 161⁄4 21	461⁄2 28 24	543⁄4 33 191⁄2	565⁄6 23 27
Blaeberry stalk, bud, and leaf	Av. 1906 1907	151⁄8 131⁄4 1⁄2	53⁄4 15 19	21⁄6 0 15	0 4 21	1⁄4 6 0	0 6 0	0 20 0	93⁄4 0 12	185⁄8 41⁄2 0	26 9 1	263⁄4 22 10	25 21 10
Various	Av.	11⁄2	31⁄2	11⁄3	9	6	6	16	35	131⁄2	221⁄2	3	22⁄3

The results of this Table have also been given in the form of a chart for purposes of comparison.^[6]

The strain upon the vitality of the Grouse in the winter months is intensified by the fact that a greater bulk of food is required by More food
required
in winter
than in
summer. each bird per day than is required during the summer

But few would have rated it at five times the value, and yet, from a comparison on the afternoon crops of the winter with those of the summer, this appears to be the case. Thus the average weight of food found in a Grouse crop from December to March, between 3 p.m. and 6 p.m., is 250 grains, whereas the average weight of food found in a Grouse crop from April to November, between 3 p.m. and 6 p.m., is only 50 grains.

The fact that more food is required in winter to maintain the body temperature would, of course, partly account for this increase, even Reasons
for this. if the heather had the same food-value. But as heather certainly has an inferior food-value in winter, the amount taken must be increased <noiwki />

CHART SHOWING
PERCENTAGE CONSUMPTION OF VARIOUS FOODS EATEN EACH
MONTH BY THE RED GROUSE

in a far greater proportion. No doubt the necessity for provision during the longer hours of night-time has some effect in the overfilling of the crop in winter, but this would not account for crops being heavier in March, when the days are comparatively long, than in November when they are short.

The interesting fact remains, and is amply proved by the figures, that more food is required by the Grouse in winter than in other seasons of the year; and as in winter the proportion of Calluna to all other foods is as seven to one, it is obvious that a very great advantage accrues to a Grouse on a moor in which young and comparatively nourishing heather is abundant during the winter months, i.e., on a well-burned moor, well covered with young heather of a varying number of seasons' growth.

To put this conclusion in other words; whereas in summer a certain area of heather will support a bird comfortably, many times this area will be required for the same bird in the winter, so that the capacity of a moor, as regards the question of stock, must be gauged mainly by its Grouse-feeding value during the winter months.

If we consider this generalisation with reference to moor management we shall see that a moor carrying its full tale of birds in the summer becomes automatically and unavoidably overstocked in the winter unless the stock is heavily reduced by shooting, for not only is there less food available, but the birds require a much larger quantity of food to keep them in health.

Migration of birds in winter obviously complicates the question. In the case of a moor on high ground, which often loses all its birds in winter, probably natural conditions regulate the stock of birds automatically Effect of
migration.during spring and summer. But on the adjacent low-lying moors the case is more serious; for the ground has to supply not only more food than is needed for its own stock in summer, but in addition an increased seasonal demand made upon it during the winter months by hundreds of undesirable immigrants from the higher ground. Such low-lying moors must always run the risk of being dangerously overstocked in the winter.

In certain parts of the country oats form a regular seasonal change in the dietary of Grouse, and this form of food must now be considered.^[7] Oats.

Very few birds with corn in any part of the alimentary canal were submitted for examination; but so far as these specimens show, oats are an unsuitable form of food for Grouse. As is well known. Grouse often visit the stubbles and corn-stooks in very large packs in the autumn — in September, October, or November, according to the season and locality. They seem to know that they are out of place, and finding themselves with a wealth of food all round, away from their normal surroundings, are eager to fill themselves as full as possible in a very short space of time, aware, by instinct or experience, that they may be disturbed at any moment. One consequence is, as the examination of birds has shown, that they eat as much husk as grain, instead of picking and choosing as Partridges do, in a quiet and leisurely manner. This difference in the crops of Grouse and Partridges that have been feeding on the same ground is very noticeable. The one is filled to repletion with indigestible and exceedingly irritating husks and a comparatively small amount of grain, while the other (the Partridge's crop) contains grain only.

The result in the Grouse is that the whole alimentary canal, from one end to the other, is soon in an irritable and inflamed condition. The gizzard does what it can to work up the husks and grain into a milky paste, but the microscope shows that this paste is to a large extent composed of siliceous spicules and small spines of an almost glassy hardness. This damages the delicate mucous lining of the intestine. The result of the passage of this irritating food is, first, an extra flow of digestive juices, secondly, an increased activity on the part of the walls of the intestine, both as to movement (peristalsis) and secretion from the stimulation produced by this form of food. Thirdly, comes a point at which mucus is thrown out in large quantities to protect the gut, and this continues and increases until the actual cells themselves are shed, and the protection breaks down. Finally, the intestine becomes inflamed to the extent of ulceration, and this state will continue and increase so long as the cause continues to act.

Such irritation to the intestine of even a healthy Grouse, which already has to deal with worms of at least two kinds, is bound to have an evil effect if continued for any length of time; moreover, in places where the corn is left out owing to bad weather, or for other reasons, there is the additional aggravation that the birds may be filling themselves with wet and sour grain, not one whit the less irritating as regards the husk, which cannot be softened by wet; and no doubt the consequence of this is in some seasons noticeably bad.

Corn in moderation is probably not unwholesome as a food, and were it possible to feed one set of Grouse with clean grain, and another with such stuff as the birds pick up for themselves on the stubbles, there is no doubt that the former would rapidly improve in condition, and the latter go steadily downhill. Such an experiment is not practicable.

To recapitulate, the following may be given as a fairly accurate account of the monthly dietary of the Red Grouse for the year: —
January, Calluna shoots (64 per cent.) and Calluna seed-heads (27 per cent.).
February, Calluna shoots (75 per cent.) and the stalks and buds of blaeberry and leaves of cowberry.
March, Calluna shoots (97 per cent.) and blaeberry stalks and buds.
April, Calluna shoots (93 per cent.) and very little besides.
May, Calluna shoots (82 per cent.) and rather more "various."
June, Calluna shoots (82 per cent.) and "various."
July, Calluna shoots (53 per cent.) and an increasing amount of "various."
August, Calluna shoots (60 per cent.) and some Calluna flowers and "various."
September, Calluna shoots (63 per cent.) and 16 per cent, of Calluna flowers and "various."
October, much less (42 per cent.) of Calluna shoots, and nearly 30 per cent, of Calluna flowers, and some "various."
November, still less (39 per cent.) of Calluna shoots, and 33 per cent, of Calluna flowers and seed-heads, and the rest "various."
December, a rise in Calluna shoots to 60 per cent., but still 27 per cent, of Calluna seed-heads.

List of Vegetable Food eaten from Time to Time by the Red Grouse

Calluna vulgaris, the staple food of Grouse, is known generally as Heather. Grouse eat the shoots, flowers, and seed-heads. See Pl. xxiii., p. 71.
Vaccinium myrtillus, Blaeberry, Blueberry, or Blue Whortleberry. Grouse eat the stem, buds, flowers, and berries. See Pl. xxiv., p. 86, Fig. 1.
Vaccinium oxycoccus, Bog Cranberry. The leaf and the berry are sometimes eaten. See P;. xxiv., p. 86, Fig. 2.
Vaccinium vitis-idæa, Red Whortleberry, Clusterberry, and (in Scotland) Cranberry. Leaf and berry are eaten. See Pl. xxiv., p. 86, Fig. 3.
Arctostaphylos uva-ursi, Red Bear Berry. See Pl. xxiv., p. 86, Fig. 4.
Rubus chamæmorus, Cloudberry, or (in Cumberland) Noops. The leaf is eaten, and so are the berries. See Pl. xxv., p. 87, Fig. 1.
Empetrum nigrum, Crowberry, Crakeberry or Lingberry. The top shoots, tight leaf buds, and berries are eaten. See Pl. xxv., p. 87, Fig. 2.
Erica cinerea, Purple Bell Heather. The flower alone is eaten, but while it is out it is eaten in fair quantities. See Pl. xxv., p. 87, Fig. 3.
Erica tetralix, Cross-leaved Heath. Flower-heads are eaten in quantities, but leaf-shoots are avoided. See Pl. xxv., p. 87, Fig. 4.
Salix repens, Dwarf or Creeping Willow, a low, straggling shrub from 2 inches to 1 foot in height. Foliage and young shoots more or less silky white. The plant has small oblong leaves, and bears small catkins in spring, followed by silky seed vessels. Found on sandy ground. Where it occurs the leaves and young shoots are greedily eaten.
Myrica gale, Bog Myrtle, or Sweet Gale, an erect shrub, 2 or 3 feet high, fragrant when rubbed. It has long, narrowish pointed leaves, slightly toothed near the tip, and often downy beneath. It bears small catkins before the leaves are out. Always found in boggy places. The buds are eaten in winter and early spring, but sparely.
Eriophorum, Cottonsedge or "Cotton Grass," two or three species of similar habit. A rush-like plant, bearing in summer, after the flowering period, conspicuous, white, cottony tufts, either solitary or in clusters of two or three or more. Grouse are very greedy for the flower of this plant in spring, and the tender shoots are also said to be useful when they first appear. The plant is then known by gamekeepers as "Blackhead" or "Mosscrop." It is found in marshy ground.
Rumex acetosella, Common Red or "Sheep" Sorrel. A slender plant, from 3 or 4 inches to 1 foot high, often turning red. It has long, more or less arrow-shaped leaves, very acid to the taste. The red-tinged green flowers are in terminal clusters on an erect stem, and are seen from spring to autumn. The plant grows in dry pastures, and on open heaths. The seeds are greedily eaten.
Juncus squarrosus, Heath Rush, a small rush about a foot high, growing in drier situations than most rushes. The flower and seed-heads are very freely eaten.
Luzula campestris, Field Wood Rush, a small rush with soft, flat, grass-like leaves, fringed with silky hairs. It grows in dry places.

The flower and seed-heads are eaten. The following additional list of plants, upon which Grouse are said to feed, is given in a pamphlet on "The Improvement of Grouse Moors," by the Rev. E. A. Woodruffe Peacock, who has examined the contents of many crops and gizzards of the Grouse.
Potentilla tormentilla, Tormentil.
Trifolium minus, Suckling Clover.
Galium saxatile, Heath Bed-straw.
Pedicularis palustris, Marsh Lousewort.
Pedicularis sylvatica, Heath Lousewort.

The seeds of the following plants are greedily eaten, and are most useful as late autumn and winter food: —

Alopecurus myosuriodes. Mouse-tail Grass.
Molinea cærulea, Purple Melio Grass.
Atriplex patula, Common Orache.
Cerastium triviale, Chickweeds and other moor cerastia.
Polyganum avicilare, and P. persicaria, Persicaria, and Knot Grasses of all species. The flower-heads are also eaten.
Viola lutea, Yellow Violet.
Pteris aquilina, Bracken Fern.

In their season, too, Grouse are very fond of capsules of the moor mosses, such as the Great Golden Maidenhair Moss (Polytrichum commune), and the smaller fungi.

For the purpose of reference the following plates and detailed descriptions are given of some of the moor plants most commonly confused on account of the variety of names by which they are known.

plate xxiv

Fig. 1
The Blaeberry (Vaccinium myrtillus), known
also as the Whortleberry, Bilberry, Whinberry,
Blueberry, or "Whorts" in various districts, a low
branched shrub 6 to 18 in. high, growing often in
large green patches. The flowers which appear in
April, May, or June, are flesh-coloured, and the
berries, which are black with a purple bloom,
ripen in July and August; they are agreeable to
the taste.

Fig. 2
The Cranberry

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1. In addition to the 399 crops tabulated some 1,100 other crops were examined — these were obtained mainly from diseased birds in April and May, and from shot birds in August and September.
2. Vide also p. 79.
3. Vide pp. 76, 79 and 80.
4. Vide chap. xviii. pp. 392 et seq.
5. Vide chap. xviii. p. 400.
6. Vide p. 80.
7. Vide also chap. i. p. 25, and chap. viii. pp. 178–180.