CHAPTER 7
Behaviour
GROUSE HAVE EVOLVED SPECTACULAR displays and ornaments that enhance them, such as the blackcock’s lyre-shaped tail and the ptarmigan’s red erectile combs. Many authors have described grouse displays and calls in detail,1 so here we confine ourselves to outlining their main features. Chapters 5 and 6 cover displays of blackgame and capercaillie, and in this chapter we note those of Lagopus lagopus and rock ptarmigan, drawing attention to their similarities. Much more attention has been paid to the spectacular displays of grouse than to any other aspect of their behaviour. It is at least as interesting, however, to see how they conduct themselves in the day-to-day business of coaxing a living from harsh environments.
This chapter emphasises such maintenance behaviour, the activities of making a living and daily survival. We note how birds of each British grouse species communicate with their fellows by calls and postures, including those of aggressive and sexual behaviour. We also summarise how these birds eat, drink, fly and care for their plumage. Where they choose to rest and roost is vital for their survival, and we discuss their reactions to enemies, including forming packs where they are safer from predators. Lastly, we describe their parental care, which differs greatly among the four species.
SOCIAL SYSTEMS OF BRITISH GROUSE
British grouse have two types of social system, these depending on the species. Cock and hen Lagopus lagopus and ptarmigan form pairs on large territories that are defended until chicks hatch. In contrast, blackcock and male capercaillie display at small territories on communal leks, and once serviced there, hens leave for their nesting haunts, where they incubate eggs and rear young without the help of guarding cocks.
There are, however, similarities between the territorial and lekking species. All four species often pack in winter. In spring, when red grouse hold well-spaced territories, occasionally two or three cocks (rarely up to five) contest where their territories meet at a corner, and the displays there resemble a lek.2 Cock red grouse also sometimes threaten one another like this when meeting off their territories. In a flock of male Alaskan rock ptarmigan loafing on the snow and feeding during their leisurely spring migration, RM saw some cocks defending small territories for a few minutes when hens appeared, again like a temporary lek. Hence red grouse and rock ptarmigan sometimes show lek-like behaviour.
Conversely, blackcock and cock capercaillie sometimes display off leks in a more spaced pattern, and blackcock can have an ‘exploded’ lek (see Chapter 5). Such instances bring to mind the social system of American woodland grouse, which is intermediate between the extremes of lekking (Tetrao) and monogamous territorial (Lagopus) behaviour. Cock ruffed and blue grouse defend display-sites on dispersed territories, but they do not form permanent pairs with hens. The drumming logs of ruffed grouse are often clumped along the edges of thick forest, and yearling cock blue grouse tend to clump around the territories of adult cocks.3
GROUSE CALLS AND ASSOCIATED POSTURES
Most grouse calls involve aggressive or sexual behaviour, while some signify contact (such as a hen calling her chicks) or warn of approaching predators. They include an extraordinary variety of sounds. Producing the calls requires an elaborate anatomical apparatus, including special throat pouches that help project sound.4
Many calls of Lagopus lagopus and rock ptarmigan have similar phrasing,5 but the latter sound different because of their low croaking pitch. Hens call in a higher pitch than cocks, as do immature cock red grouse when they start crowing at eight to ten weeks, before their voices break. Of Norwegian willow ptarmigan, it has been said: ‘According to musicians the hen calls with a high flute-like soprano, while the cock has a somewhat hoarse and metallic alto or mezzosoprano.’6 Hen rock ptarmigan give higher-pitched calls than hen Lagopus lagopus, sounding like cooing doves or squealing puppies.
The same call can vary somewhat between countries – for example, Norwegian cock willow ptarmigan sound harsher than red grouse.7 The songs of adjacent cocks also sound different to a good musical ear. At Glenamoy, P. J. O’Hare could tell unerringly which cock, invisible in the dawn twilight, gave each song.
Some publications illustrate calls by sound spectrographs that show timing and frequency,8 but most readers find this obscure. Calls have usually been described with words, although these are unstandardised and seldom indicate stressed syllables. The International Phonetic Association (IPA) has devised a set of symbols to indicate pronunciation, stress and tone in human speech.9 These cannot represent musical calls, however, far less the weird pops, clicks and shuffling calls of blackcock or capercaillie. None the less, IPA symbols are better at describing the calls than unstandardised words, where possible – Table 17 shows some examples.
TABLE 17. Some calls in Lagopus lagopus and rock ptarmigan, expressed phonetically.10
| LAGOPUS LAGOPUS | ROCK PTARMIGAN | |
|---|---|---|
| Alighting song | ‘a:,ka,ka,ka,ka,ka…… | ‘a:,ka,ka:………ka,ka,ka |
| ko’wa,ko’wa | ||
| Flushing song | as above | ‘ar,a·,ka,ka: |
| Ground song | k ,k,k,k,krr | ko’wa:k |
| Attack | ko’wa ko’wa ko’wa | kwa kwa kwa |
| Attack intention | ko’we:,ko,ko | ko’wa ·,o |
| Threat | krau krau krau | cock krrr, hen ki’a |
| Escape | kkk | k^k^k^ |
| Sexual chase | kk kk kk | ko’wa ko’wa ko’wa |
| KEY TO PHONETIC SYMBOLS | ||
| (after the International Phonetic Association) | ||
| a fat | ^ sun | |
| e day | u do | |
| i see | ‘ main stress on next syllable | |
| o bone | , secondary stress on next syllable | |
| pot | · half-long vowel | |
| : long vowel |
Note
In a paper by Johnsen et al. (1991) on Norwegian willow ptarmigan,
AW helped by using IPA phonetics for some calls.
Calls that warn against predators are very alike in Lagopus lagopus and rock ptarmigan, while those of sexual display are less so, despite similar phrasing. In contrast, song in flight, flushing song and ground song are very different in the two species, perhaps because they have an advertising function for hens – an unattached hen often flies to a cock that has given one of these calls.11
Postures that accompany the main calls are so alike in Lagopus lagopus and rock ptarmigan12 that we describe them together here, but because blackgame and capercaillie show big differences we note these in chapters 5 and 6. None the less, there are similarities amongst all four species. Common to all is flight intention, with crouching legs and bobbing body, sleek feathers and invisible combs. Common, too, is the cock’s frontal aggressive approach to another cock, as he puffs his body feathers, droops his wings, struts, fans his tail and expands his comb, while at each shoulder he displays a large white spot. Common again is how he alters this frontal aggression to less aggressive courtship, with sideways dancing or bowing as he approaches a hen, drooping the wing next to her and twisting his fanned tail towards her.
During aggressive interactions
In his song flight or aerial beck, a cock Lagopus lagopus or rock ptarmigan rises steeply, sails momentarily, and then descends on rapidly beating wings with fanned tail and outstretched head. On alighting, he calls while jerking his tail up and down, with body feathers puffed out and wings drooped. The hen gives shriller becks, rises less high in flight, and seldom calls after alighting. A cock often makes a directional beck towards a neighbour, and this generally induces the neighbour to beck. On a windless day, a thunderclap or avalanche can induce cock Scottish ptarmigan to beck.
In calm air, aerial becks of cock Lagopus lagopus or rock ptarmigan can be heard 2km away, and singing blackcock at 1km. Singing capercaillie are much harder to hear, perhaps because part of the sound they produce is below the threshold of human hearing. To our ears, the exact location of a distant rock ptarmigan is harder to judge than in red grouse, and blackcock are yet greater ventriloquists. The clicks of a singing capercaillie, however, are easy to locate.
Less intensive than aerial becking is the ground beck of Lagopus lagopus or rock ptarmigan. A bird delivers it while standing with its throat puffed and vibrating (Fig. 98). The rock ptarmigan’s version is most machine-like: a snoring, ticking croak that lasts for several seconds and resembles the sound of a turning fishing reel. It is often heard when two cocks parade at a boundary, and sometimes in disputes between foraging cocks when Scottish birds are in packs.
Some calls involve attack, or the less aggressive attack intention, or the even less aggressive threat. In attack, a bird stretches its head forwards with inflated neck, while running with beak open, wings drooped and tail fanned as it chases a retreating bird, which it may grasp with its bill and beat with its wings. In attack intention, it does not run, but crouches with neck feathers less erect. In threat, it stands with upright head and neck.
These postures can lead to a fight, when the two birds jump in the air and spar on the ground while striking with wings, feet and bills (see Fig. 99). Usually they do not lose feathers and seldom fight longer than a few seconds, most encounters being ritual displays where one bird soon feels submissive and withdraws. Occasionally, however, serious fighting erupts, lasting up to about two minutes, when birds may lose feathers. According to one account, when Scottish ptarmigan ‘cocks fight on steep ground they often roll over and over, frequently up to 20 metres and rarely up to 50 metres, down steep hillsides and rocks’.13
In escape intention, a bird crouches as if ready to fly, sleeking the feathers on its head, neck and breast, showing no comb, bobbing its tail and body, and holding its wings slightly outwards and downwards. A cock often raises his crown
feathers, which makes him look more hen-like and tends to reduce the attacker’s aggressiveness.
Aggressive postures mostly involve cocks of the same species, but occasionally two species fight or threaten. In the few cases recorded, willow ptarmigan usually dominated rock ptarmigan, and red grouse dominated blackgame, but outcomes with red grouse and Scottish ptarmigan were fairly evenly balanced.14
Social contact and warning of predators
In the posture of social contact, a hen solicits for a cock or a parent calls to lost chicks. The bird stands high with raised neck and head, looking around and calling until the cock or lost chick appears.
A bird warns of a fox or raptor with a distinct call for each, while standing with erect body, neck and head. This alerts others, which turn to look at the calling bird, learn the predator’s location, and call in turn. On the appearance of a fox, red grouse and ptarmigan produce a wave of sound that follows the fox as it crosses an area.
During sexual behaviour
Sexual behaviour is similar in Lagopus lagopus and rock ptarmigan. Several calls accompany it, the loudest being a sharp single repeated call by cock and hen while he chases her on the ground or in flight. During the chase, he dives at her, trying to move her to his territory.
In winter, Scottish red grouse show sexual behaviour more often than ptarmigan, but it occurs among ptarmigan in every month of a mild winter. When birds are in packs on snow-covered ground, however, neither species shows it, except briefly on fine spring days.
A hen Lagopus lagopus or rock ptarmigan that is seeking a cock flies from one territory to another, courted by each cock in turn. When she leaves, he often pursues in an aerial chase and a nearby cock may join. On each territory, she decides whether to stay or leave. The cock bows, struts and waltzes around her with drooped wings and open beak, while dragging his primaries through heath or crusty snow with a rasping sound. He drums his feet in a rapid stamping, making a sound that is audible to human ears within 4m. Above his head rise his brilliant red combs, with sunlight shining through them. In another display he sits and rapidly wags his head from side to side, presenting his two combs to the hen in a rapid whirl of crimson.
In both species a hen ready for coition with a cock spreads her wings slightly. As he walks onto her back, she lifts her tail and twists it sideways as he makes
FIG 100. Marks of a courting rock ptarmigan cock in snow, showing footprints and wing marks. (Adam Watson)
contact for several seconds. He then jumps off and shows further courtship while she shakes her feathers vigorously.15 Captive hen willow ptarmigan lay fertile eggs for about eight days after separation from a cock,16 so just one successful copulation may suffice to fertilise a whole clutch.
INDIVIDUAL DISTANCE
Birds usually keep well apart, even when in packs. This ‘individual distance’ increases with body size, and among British grouse is smallest in ptarmigan and greatest in capercaillie. Most paintings of adult grouse show them almost touching, which is perhaps artistic licence. An exception is Keith Brockie’s realistic painting of two ptarmigan in snow.17
An observer can readily discern individual distance in feeding birds. Adult red grouse usually keep about 6ocm apart, maintaining this by brief threat or attack.18 Frequently a bird displaces another from food or from coming too close, by making brief threats or calls. When red grouse or Scottish ptarmigan roost in packs, individuals are seldom closer than 30cm and usually more than 50cm apart (Fig. 101).19 Staying apart while sleeping should reduce risks from predators because, if a predator attacks, it is less likely to find more than one bird.
As in poultry, adults of all four species relax their individual distance while bathing in sunshine, dust or snow, when nearby birds come so close that a few almost touch. Also, capercaillie hens in a harem competing for the cock’s attentions may touch while jostling for position. Another obvious exception is that hens brood their chicks, which red grouse and Scottish ptarmigan do until the poults are six weeks old. Thereafter, feeding poults may almost touch the hen, and the whole family roosts close together, often touching, until the chicks are fully grown.
EATING AND DRINKING
Feeding grouse walk across the ground or snow from plant to plant, biting shoots with a sideways action that is also used when they feed in bushes or trees. Rock ptarmigan remove twigs ‘with the tip of the bill and a quick sideways turn of the head. This lightning-like movement bends the twig at a sharp angle against the cutting edge of the bill and breaks it off with an audible snap.’20 Although red grouse and Scottish ptarmigan sometimes stretch up to reach grass seeds and often eat plants shorter than themselves, red grouse prefer to eat heather that is 20-35cm high,21 where they do not have to bend down or stretch up. They usually
FIG 102. Ptarmigan hen with well-grown chicks. (Stuart Rae)
avoid plants taller than 35cm – in other words, that are above the 30cm height of a standing bird’s head.
At all seasons, birds in the open do most of their feeding near cover. Rock ptarmigan do so within a few metres of boulders,22 while the other species feed near tall vegetation. Blackgame and capercaillie feeding on the woodland floor also keep close to cover, which includes live and dead standing trees, stumps, wind-thrown trees, juniper bushes, and branches on felled plots.
Feeding in snow
Grouse often scratch through light snow to expose food, typically down to 6cm, although in Britain they rarely dig to feed. In Scotland we have not known of a grouse digging more than 10cm for food, although depths of up to 30cm have been recorded in Icelandic ptarmigan.23 When deep snow covers all plants, red grouse and Scottish ptarmigan fly to exposed ridges, where they eat shoots projecting above drifted snow, and red grouse sometimes feed in bushes or trees. Scottish ptarmigan rarely descend to woodland, although one was seen eating buds on a gnarled birch on the morning after a storm.24
Norwegian rock ptarmigan ‘often follow the reindeer in the winter and dive into the holes made by these animals, thus obtaining a few berries’.25 In the Arctic, they feed where foraging caribou, reindeer or musk ox have scraped snow off plants, and Scottish red grouse and ptarmigan often eat heather that has been exposed by red deer.26
Monthly and daily routines
At Spyhill, John Savory counted the pecks of red grouse that were feeding mostly on heather. His lowest monthly figure was in November, when hens on average pecked 10,300 times per day, and from February they increased the rate each month to a peak of 30,500 in May before incubation.27 Cocks also pecked least in November, with 11,500 per day, but their peak was 19,900 in March, a month of much territorial activity.
On snow-free winter days in Scotland, adults of all four species eat for a minor part of the day. They usually have a feeding peak shortly after rising in the morning, but eat most intensively and hurriedly in late afternoon, resulting in a lower quality of food, as they stuff their crops before the long night. Apart from brief breaks to drink and defecate, incubating hens feed almost continuously during the short periods off their eggs, again taking food of low quality.
Selective eating
Feeding can be leisurely, however, resulting in the selective choice of high-quality foods, such as when gravid hens eat for much of the day in the few weeks before and during the period when they lay eggs. In spring, all four species obtain nutritious food by eating plants that start growing early, such as cotton-grass shoots, and blackgame and capercaillie later take the red flowers of larch. Hence birds take a greater variety of foods in spring and summer, with fewer heath plants than in winter, and more herbs, flowers, moss capsules, grass seeds and invertebrates.
In late summer, Scottish ptarmigan often move to hollows that were inaccessible at nesting time because of deep snow. The same happens in east Greenland, where rock ptarmigan eat freshly growing Alpine bistort on snow-patch hollows.28 From late July to October in Scotland, birds of all four species sometimes move to feed on berries and bog sedges, frequently at higher altitudes. Capercaillie that venture into the open to do this usually remain on slopes, where they can easily take wing into nearby woodland if disturbed. For capercaillie, higher altitude is often just a steep slope above a wood, but for blackgame it can be up to 1.5km away and 300m higher in altitude, exceptionally even into ptarmigan habitat.29
Grit and water
Birds of all four species frequently swallow rock granules, preferring quartz when available. Most of the grit stays in the gizzard, a stomach with a tough, leathery, corrugated lining that moves in strong contractions, powered by thick, hard muscles. The contractions combine with the grit to pulverise food coming down from the crop. All four species – and especially hens in spring – frequent roadsides and tracks to get grit. In deep snow, red grouse often, and rock ptarmigan occasionally, go to Scottish roads to eat grit that has been spread to give cars a good
grip. In Alaska and Canada, where deep snow can lie for months, spruce grouse frequent roadsides in September-October, swallowing large amounts of grit before the first snowfalls.30 Poultry and captives of all British grouse eat and excrete grit daily if they get it ad lib, but can retain it for weeks if there are no fresh supplies.
Although their food contains much water (for example, there is 50 per cent moisture in heather), birds of all four species drink daily at pools or streams, and pairs of red grouse in spring fly up to 1km from their territories to do so. Birds also take raindrops and dew off plants. In the 1930s, keepers put out dew-pans on dry eastern moors so that grouse did not have to travel far for water. Red grouse and Scottish ptarmigan often swallow hoar frost or snow, but in prolonged extensive snow they usually fly or walk to the few places with open water at springs, and drink copiously there rather than taking snow. To drink water is much easier than swallowing snow, and it costs far less in terms of heat loss.31
PLUMAGE CARE AND FLIGHT
Birds of all four British grouse species spend much time each day on plumage care. A bird preens with its bill, anointing it with oil from the preen gland at the base of the tail and then transferring the oil to the feathers (see Fig. 106). Plumage care also includes bathing in sunshine, water, snow or dust.32 A bird bathing in sun, snow or dust lies on one side, stretching the other wing and leg, fluffing its plumage so that bare skin and the inner parts of its feathers are exposed, and FIG 105. Hen red grouse drinking. (Desmond Dugan)
FIG 105. Hen red grouse drinking. (Desmond Dugan)
FIG 106.Preening red grouse. (David A. Gowans)
FIG 107. Red grouse hens bathing. (David A. Gowans)
often closing its eyes. At times, it kicks its feet and moves its wings and body to cast water, dust or snow onto the plumage, working this deeply into the feathers. A grouse flushed while dust-bathing leaves a rocket-like trail of dust as it takes off Often a bird gets so covered in dust that its plumage matches the ground around it. After preening or bathing, it usually sheds the water, dust or snow by shaking its feathers vigorously. Birds about to dust-bathe select bare, loose, dry soil for bathing, often on paths or tracks. Willow ptarmigan on an island off Newfoundland liked to dust in anthills.33 Blackgame and capercaillie are fond of the south sides of big old ‘granny’ pines on slopes, where ground that has been dried by the roots creates ideal dust-bathing conditions.
Flight in all four species involves several rapid beats followed by a brief sailing glide. If you are within 50m of a flying bird in calm conditions, you will hear a soft whistle as it beats its wings and a hum as it glides. Most flights are short, but birds can easily fly from one hill or wood to another. Red grouse will fly up to 5km from an eagle, and rock ptarmigan have flown from Greenland to Iceland.
RESTING
In all four British species, a bird rests while sitting or standing with head drawn in and body feathers slightly puffed out. It often closes its eyes momentarily, and sometimes tucks its head under one wing like a domestic fowl. In daytime, grouse rest most frequently around noon and in the early afternoon, as do diurnal birds generally.
During daytime in winter, red and black grouse and capercaillie often rest on snow underneath low branches of pines or spruces. There they usually sit on the snow without scratching a bowl, and the foliage overhead reduces heat loss by radiation. Such trees have been eliminated on most moors, but on moorland in mid- and lower Deeside, where scattered trees have colonised, red and black grouse often use densely foliaged stunted Scots pines and Norway spruces. Dense coniferous or deciduous cover up to 2m above ground level is critical for hazel grouse in Eurasia,34 and in Britain it affords useful shelter for woodland grouse. Many mature British plantations that would otherwise be a good habitat for woodland grouse are now too open because foresters have reduced cover by thinning uniformly, removing wind-thrown trees and ‘brashing’ (lopping off lower branches).
Rock ptarmigan often rest on the leeward side of boulders or snowdrifts, where they sit basking in sunshine. Sometimes they rest on or beside dark rocks or vegetated banks that are warm from sunshine. Red and black grouse and capercaillie also sunbathe on banks, and hen capercaillie often venture out of woodland to do so.
ROOSTING
All grouse species roost like poultry, staying silent and scarcely moving. On a bright night at full moon, especially when hoar frost or a dusting of snow adds extra light, cock red grouse will occasionally crow in calm weather. However, they do this far less often than cock pheasants in the same area.
When grouse are scarce, you can walk far without seeing birds, but their marks reveal their presence, such as fresh dung where they have spent the night. The greenish-grey winter droppings of capercaillie are harder to spot, for they resemble the colour of the understorey feather mosses and blaeberry. When a woodland grouse roosts on the ground, its droppings form a discrete pile, but when it has slept high in a tree they are more scattered and broken by the time they reach the ground. All four species roost in snow if it is deep enough (see Chapter 8).
Red grouse and ptarmigan
Whether Scottish red grouse and ptarmigan roost as singletons or pairs rather than in flocks in late autumn and winter varies with snow conditions, weather, and nearness to the coming spring. When deep snow lies, they mostly roost in flocks, especially on stormy nights, but also in snow-free conditions on nights with gales and heavy rain. Hence, in midwinter, on sheltered moorland the red grouse mostly roost alone or in pairs and small groups, whereas on the high Cairngorms there is usually snow and strong wind, so ptarmigan here roost mainly in packs even when it is mild. On lower moors, a few dominant cock red grouse roost alone on their territories even when snow covers most ground, especially on calm nights after they have been on their territories all day, a habit that probably increases their sense of ownership. Even cock ptarmigan can be found roosting alone in such conditions, especially when snow is just a dusting or a shallow covering. The frequency of roosting singletons or pairs increases towards the spring, whatever the snow conditions or weather, in correspondence with the frequency of territorial behaviour during the day.
At Spyhill, roosting red grouse at all seasons spent the night in short heather that was one to seven years old, using taller heather or recently burnt ground far less.35 Even when they do use tall heather, red grouse often choose tiny gaps and roost with their backs open to the sky. Sometimes they roost on the top of tall degenerate heather that has bent sideways to form a flat surface, the birds supported by it, centimetres off the ground. So, on frosty mornings, ‘Nearly every bird is white with hoarfrost all over its back, upper tail and crown but not over its breast and throat, which shows that it roosted with uncovered back.’36 Unlike the silvery-white spangles of hoar frost on plants or stones, that on the birds is a fine powdery dusting, giving them a pale ghostly hue even an hour after they rise in the morning. Although a bird under tall heather would reduce its heat loss, it would make an easier catch for a fox. Grouse are so well adapted to cold that in temperate conditions they do not need to make heat conservation their paramount concern. In contrast, an inexperienced person in ordinary clothing would die sitting in heather overnight during a frost.
Red grouse often choose to roost in wet areas with surface water where they would hear the splash of an approaching fox – such as at Glenamoy, on short vegetation surrounded by water. When hens have broods, they use small patches of short vegetation or bare gravel or peat, surrounded by taller vegetation. The same goes for ptarmigan, except that boulders tend to be beside their roost sites rather than taller vegetation. Brood hens of both species like to use human paths, where small patches of bare ground with nearby cobbles or vegetation afford shelter and cover.
Blackgame and capercaillie
In winter at Glen Dye, Bob Robel found that radio-tagged blackcocks usually roosted in tall heather or scrub.37 On rainy nights they often used trees, and when deep snow lay on the nearby moor they roosted amongst tall heather on the floor of mature coniferous woodland. On dry mild nights they slept on the moor, usually in groups of three to ten, each group scattered over an area of 0.5-2ha. In all seasons at Kerloch, black grouse (including hens with broods) roosted amongst tall heather where much of it had fallen over, leaving openings.38
Capercaillie roost mostly in trees, although moulting adults and hens with small chicks use tall heather or other rank vegetation, and older chicks use branches once they can fly up to them. An adult in a tree prefers dense cover such as Norway spruce, and stands on a thick branch fairly near the trunk or sits with its breast lying on the branch.39 In the Scottish winter, capercaillie often roost singly or in small groups.
PACKING
A grouse flock is traditionally called a pack, which can be anything from a small group to thousands of birds.40 Although grouse of all four British species are often solitary, and red grouse and Scottish ptarmigan often occur in pairs, unmated cock Lagopus lagopus and rock ptarmigan gather together even in midsummer, as do hen capercaillie that have no chicks. The biggest packs occur at high population densities in deep snow (see Fig. 18), and in Scottish ptarmigan when birds are mostly white and poorly camouflaged on days with mainly snow-free ground. Packs of up to about 5,000 willow ptarmigan have been seen during winter in America, and up to 1,000 red grouse in snow.41 The largest ptarmigan pack recorded in Scotland numbered 450 on a November day, when they flushed with a loud noise of wings and fluttered like snowflakes across a dark, almost snow-free corrie.42
In winter, blackgame packs in Russia sometimes numbered 200-500 at a time during the early 1900s, with up to 1,000 in birches, but more recently up to 200-300.43 The sexes tend to separate in Scotland and Finland, with packs mainly of cocks or of hens. Adult cock and hen capercaillie are often solitary in winter, but they and young cocks also form groups of usually less than ten, or larger packs when population densities are high or in cold winters. Some winter packs comprise mainly young and old hens, others mainly young cocks.
A pack of birds, all maintaining individual distance, affords each bird some room to select food, while more eyes and ears readily detect predators. Being safer, big packs often feed at greater distance from cover – red grouse occasionally feed on short heather so far from cover that birds do not take territories on it.
REACTIONS TO ENEMIES
A red or black grouse or Scottish ptarmigan flushes well ahead of a golden eagle flying near the ground, but stands on watch with head turned upwards if the eagle is high up.44 By contrast, it crouches motionless when a flying peregrine appears near the ground. These differences fit the facts that eagles usually kill on the ground or just above it as grouse take off, whereas peregrines kill flying birds.
Eagles do occasionally kill grouse in full flight by stooping at speed from a greater height, but they are seldom successful in this. In two incidents on the Cairngorms, a flying ptarmigan being chased by a golden eagle flew towards people, escaping from the predator because the eagle flew away on seeing the people. On both occasions the ptarmigan partly closed its wings, ‘dropped in a near-vertical twisting dive to within a few metres of the ground, and then ran to crouch among boulders only ten metres from me and my companions’.45 An early author wrote that a covey of red grouse being chased by a sparrowhawk came into a shooter’s butt during shooting.46
PARENTAL CARE
Hens care for eggs and for chicks until these finally become independent and leave the brood. After mating with hens, blackcock and cock capercaillie take no part in parental care. In contrast, male rock ptarmigan guard nesting hens at least until late in incubation and often afterwards, while cock Lagopus lagopus stay with hens and chicks until the young reach independence.
The hens sit tight during incubation, slinking silently off the nest when leaving to feed and on their return. Occasionally a hen stays too long, however, and is killed by a fox or eagle. John Phillips found a hen red grouse that had died on her nest as fire swept the moor, and under her featherless black, singed carcass lay a pathetic sight: a heap of day-old chicks dead but untouched by flame.47 In June 1999, two hen Scottish ptarmigan were found dead on their nests after a snowstorm late in the incubation period (Fig. 108).48
When a human or dog disturbs a nest or chicks, grouse show distraction displays, which often succeed in their goal of causing the intruder to overlook the nest or chicks. In the least vigorous displays, the bird flies heavily near the ground. In the most vigorous, it flaps in front of the potential predator, calling loudly and attempting to divert it away from the nest or brood.
Distraction display has been studied much in Lagopus lagopus49 and, to a lesser extent, rock ptarmigan. Both sexes of these two species participate in the behaviour.50
FIG 108. Incubating hen ptarmigan amongst snow. (Stuart Rae)
A hen ptarmigan usually shows stronger display than a hen red grouse, and can lead a man more than 400m before flying to her chicks. A hen or cock of either species will occasionally attack a man or predator coming near a nest or chicks. One male rock ptarmigan in Arctic Canada, ‘uttering his belch-like challenge, flew violently and repeatedly against Ian McLaren’s tent on the night of 8 June’.51 We think his sleepless night resulted from pitching his tent too near a nest.
Greyhens and hen capercaillie usually show less intense though not less frequent distraction display from nests or chicks than Lagopus lagopus or rock ptarmigan. Occasionally, however, they flutter along the ground in injury flight or heavy flight, and frequently fly slowly near the ground, effectively distracting a dog or human.
Biologists use dogs to find chicks so that these can be counted or caught for marking. When a grouse shows distraction display, even trained dogs usually lie down, refusing to seek chicks, and Vidar Marcström noticed that only a small minority of dogs will search for chicks while a hen is displaying.52 Our experience tallies with his, although a dog intensively conditioned by daily work with eggs and chicks can be trained to ignore a displaying hen. Whether a fox ignores her might also vary with experience. A fox was watched as it flushed a greyhen and later a hen capercaillie, and although both hens showed strong distraction display, the fox ignored this to seek the chicks, and caught and ate two from each brood.53
Hens brood chicks until they are well feathered. In torrential rain or hail, they shelter chicks even seven weeks old by standing over them with spread wings,54 and Lagopus lagopus then have an advantage because cock and hen share several chicks each. During intense downpours, red grouse often lead chicks to the verge of tracks or tarmac roads, where they dry out after the rain, a habit shared with lapwing, oystercatcher and golden plover.
GATHERING SCATTERED YOUNG
After a disturbed brood a few weeks old scatters in flight, parents of Lagopus lagopus or rock ptarmigan fly to follow the young and give contact calls, whereupon some chicks fly to the parents, and parents then fly to other scattered chicks that are calling. In red grouse, ‘cock and hen often separate to follow different chicks, and then gather the remainder from distances of up to 500m by calling’.55 The time to regroup varies with the number of chicks and how widely they scatter, but many broods up to six or seven weeks old will regroup within half an hour and almost all within an hour.56 Families with well-grown chicks usually fly together when disturbed, but any that flush later are likely to be followed by a parent.
Greyhens and capercaillie hens collect scattered broods in much the same way. On being flushed, they typically fly off, grunting alarm to their chicks, which hide by burrowing under tall vegetation. A hen then circles round to perch in a tree, watching until the danger has passed, and usually gathers her chicks within a couple of hours.
Beaters on a shooting drive disturb red grouse severely. Families usually stay together in flight, but many are shot before the survivors land beyond the butts. Usually they have half an hour’s respite while people collect shot birds and then leave for a second drive. During this time, and even before completion of the first drive, surviving parents fly to their original location and give contact calls. The surviving young fly in ones or twos to each original location, and after about an hour the families have regrouped.57
Combining of broods
In all four species, two or more broods sometimes flush from the same spot, especially at rich food sources. Two or three families of red grouse are occasionally so close in their first two weeks that they flush within a few metres, and we know of instances where a chick disturbed in such a situation was repeatedly in the ‘wrong’ brood subsequently. Fully grown broods of red grouse come together more often, but tend to flush as separate units when disturbed, although they may amalgamate once they are well on the wing. Such amalgamations occur mostly in years of high density and good breeding.58
This also applies to rock ptarmigan, for example at Eagle Creek in Alaska, where broods sometimes amalgamate at high density.59 Hrisey in Iceland supports an unusually high density of these birds, and hens and broods at about two weeks old form groups of two to four families, which gather into packs as the chicks grow.60 During years of high density and good breeding in Scotland, occasionally several hen ptarmigan with broods of different age form a loose group, along with cocks and broodless hens.61 In such a group, most broods are already well grown when they combine.
Amalgamations of broods are sometimes called crèches, but the usual implication of a crèche, whether avian or human, is that there are shared parental duties or some evidence of cooperative care by non-parents. This may involve a real parent that skips parenting for some of the time, but this has not been studied in grouse. In red grouse and Scottish ptarmigan, adults in such a group give warning of predators, but each respective brood hen accompanies her own brood.62
Behaviour common to Lagopus lagopus and rock ptarmigan
Parental behaviour has been observed and studied more in these two species than in greyhens and capercaillie, and we now outline it in more depth.
When a hen is laying or incubating or has chicks, the cock’s alarm calls warn her of approaching predators. In the weeks before hens lay eggs and until the end of the incubation period, a cock red grouse or Scottish ptarmigan with a hen often attempts to divert a man or dog away from her.63 He leads the intruder away in a widening circle, and returns to her after successfully foiling the average dog or person. When no danger threatens, he spends much time being vigilant beside her, staying alert while she feeds.64 In a Canadian study, male rock ptarmigan became less vigilant once their hens started to incubate.65
Behaviour specific to Lagopus lagopus
The Lagopus lagopus cock shows more care than the male of any other grouse species. He guards his hen against predators for a few weeks before she lays eggs and until the eggs hatch, and guards her and the chicks until the young appear fully grown, or sometimes even later. Frequently, he shows distraction display when his hen is disturbed from the nest, more so when she has small chicks, and sometimes when the chicks are older. Occasionally his display surpasses hers. He often shares parental duties, caring for part of the brood while they are feeding, collecting chicks after flushing, and brooding them. If his hen is killed, he will rear the brood. However, some British and Irish cocks leave their hens and young - at Glen Esk, for example, this happened more often in years when birds were in poor condition.
Only the hen incubates, though Hugh Allen watched extraordinary behaviour with captive pairs of willow ptarmigan in Norway, where two cocks drove hens off their nests, incubated and turned the eggs, and developed brood patches.66 One captive cock red grouse sat on eggs, and a second cock often sat beside the incubating hen with his head resting on her, and brooded her eggs when she was off feeding.67 These observations may imply that this species retains the capacity for a cock to incubate eggs if the hen dies. Wild cocks often rear chicks after their hens die. In one case at Kerloch, a stoat killed a hen while she brooded day-old chicks, whereupon her cock took over and reared some of them.
When a man or dog approaches a brooding hen, she remains motionless and then bursts out in distraction display, often calling and beating her wings as if injured. She attempts to lead one away, and frequently diverts attention enough for a person, dog or fox to miss her eggs or chicks.68 One Kerloch hen regularly showed such strong display, even when a neighbouring hen’s brood was being disturbed, that trained dogs became confused and sometimes failed to find any chicks, and perhaps this might confuse foxes too.69 Such staunch behaviour occurs only if a hen is in good condition. Hen red grouse flush more readily than this in years when they have heavy threadworm burdens, often doing so without any distraction display. This happened at Glen Esk in 1958 and 1959, when many hens were in poor condition and some emaciated ones died. We also noticed hens flushing more readily at Rickarton in 1986.70
At Glen Esk, a greater percentage of parents showed distraction display during years when birds bred well than when they bred poorly.71 In an English study, hens that showed more frequent display also raised bigger broods,72 and Norwegian willow ptarmigan that displayed had bigger broods than those not displaying.73 When Norwegian hens with downy chicks were implanted with prolactin, the hormone that makes pregnant mammals produce milk and fowls go broody, they showed more display than other hens, and flushed at closer range.74
Susan Hannon, Kathy Martin and students studied parental care in Canadian willow ptarmigan.75 Hens that shared a bigamous cock were more likely to lose nests than monogamous hens, and cocks that had become widowers reared smaller broods than widows or pairs. After some paired cocks were removed in an experiment, the remaining complete pairs raised bigger broods than hens that had been widowed at hatch.76 A Norwegian study showed that single hens suffered heavier mortality during incubation and in the two weeks after hatching.77 In short, cocks defend hens from predators and help them to rear families, resulting in bigger broods and fewer hens dying.
For an experiment at Churchill, Canada, mated cocks were removed at the onset of incubation, whereupon unmated cocks joined the widows and defended chicks that they had apparently not fathered.78 However, because more than half of the first nests failed and most of these failed widows then laid a replacement clutch, the formerly unmated cocks that had joined them became real fathers in the end.
Behaviour specific to rock ptarmigan
Cocks spend less time with their broods than Lagopus lagopus do. The least faithful are in the far north, such as Arctic Canada, where cocks usually leave their hens and territories shortly before the eggs hatch. On Hrisey in Iceland, cocks very seldom accompany hens with chicks, and only exceptionally show distraction display. Faithfulness in the far north can vary, however. Although no Svalbard cocks stayed with their families in one year, all stayed in a second year,79 a few at Eagle Creek in Alaska stayed, and cocks on Prince Patrick Island in Canada were seen defending hens with broods.80 Greenland cocks often return to the families when chicks are two-thirds grown and can fly strongly.81 By then the cocks, no longer starkly white, are cryptic in their dark autumn plumage, and so would not draw the attention of predators to the broods.
Scottish cocks are more faithful. A few show distraction display to a predator in the last week of incubation and more often when hens have small chicks. Sometimes they stay with the family until chicks are fully grown.
SUMMARY
Cock red grouse and rock ptarmigan sometimes show lek-like behaviour at places on or off their territories, and conversely blackcock and cock capercaillie sometimes display in a more spaced manner than on their leks. The calls of Lagopus lagopus and rock ptarmigan have similar phrasing, but sound different because rock ptarmigan croak. Postures that accompany aggressive and sexual behaviour are similar in both Lagopus species. In all four species, birds maintain individual distance from one another. Although most attention has been paid to displays, the birds spend most time resting, preening and eating. During autumn and winter, they tend to pack, with larger packs forming when birds are at high density or in snow. Cock Lagopus lagopus usually stay with their families until chicks are fully grown or later, while blackcock and cock capercaillie do not care for hens, eggs or young. Rock ptarmigan guard hens before and during incubation, but Arctic cocks usually leave just after hatching, whereas Scottish cocks often show later care, sometimes until young are fully grown.