6
Play behaviour usually occurs in the period between fledging and dispersal, but it is also known to continue into adulthood. Generally, the time hatchlings spend confined to the nest and before they can leave it is relatively short: between 3 and 4 weeks on average. What makes Australian native birds very special indeed is that the period of time juveniles stay in their natal territory after fledging tends to be protracted whether or not they were raised by one parent or two. The length of juvenile dependence on parents or an entire group is significant in terms of developmental patterns and may foster extensive play behaviour over months. The longest periods of juvenile dependence have been recorded in cooperative species, with examples of juveniles staying with related or helping adults for 4 or even 5 years before dispersing and beginning to breed themselves. This juvenile stage has been well-studied in white-winged choughs (Boland et al. 1997a; Heinsohn 1991b, 1992; Heinsohn et al. 2000), in Australian magpies (Carrick 1972; Finn and Hughes 1995; Rollinson and Jones 2002; Kaplan 2008) and in kookaburras (Legge 2000, 2002). Notably, it has been shown that longer periods of dependence may dramatically increase the survival rate of offspring (Veltman and Carrick 1990).
Many avian juveniles of Australian parentage are thus privileged to have ongoing supervision, protection and the chance to learn and gather experience. The offspring of cooperative species have the added advantage that several adults may provision them and, with larger number of adults per offspring, they are better protected against predators and thus succeed at a substantially higher rate of survival into adulthood (Boland et al. 1997a; Beck and Heinsohn 2006). The question is why they need this protection over lengthy periods. For a long time, the understanding of development in birds was limited to physiological and other maturational processes. The maturation of the brain and the idea of learning were of limited interest, as long as birds were not thought capable of complex cognition. It is known that the larger the brain is, the longer it takes to reach maturity. Unlike the short period of transition between fledging separation from the nest and adults, as happens in most migratory birds, especially of the temperate and higher latitudes, growing up in Australia can be a slow and gradual affair, with implications for brain development, memory, and experience. One of the special facets of development is expressed in play behaviour and has been studied in many mammals, including humans, but less so in birds (Ficken 1977). The next chapter will explore aspects of learning while this chapter will delve into play behaviour – both of which have a special role in cognitive development.
What to make of play behaviour
Play behaviour sits uneasily in scientific research because at times it has been considered ‘untidy’ in its definitions and methodological difficulties. Some writers have simply stressed the structural elements of play while others have argued that play behaviour ought to be explicable by identifying at least one compelling function. The idea of play as a ‘program’ to hone future skills (i.e. for future functions) has been tested extensively in mammals since the 1980s. The results have been disappointing in a number of respects. Play was thought to make an animal more successful as an adult, but the results do not bear this out. As adults, cats are as good at catching mice whether or not they had played and practised target-catching with toys as kittens (Thomas and Schaller 1954; Caro 1980). Play fighting does not turn meerkats into dominant (i.e. breeding) adults (Sharpe 2005a) nor does it reduce their aggression (Sharpe and Cherry 2003). Also the social play of kittens fails to lead to stronger social bonds when they become adults (Sharpe 2005b). In other words, the idea that playing hones skills for later life, although still touted with great regularity in animal documentaries and magazine articles, is largely not supported by convincing evidence. Of course, it is very possible that play may have multiple functions (Bateson and Martin 2013), but tying down just one specific function has not always been easy.
This problem is not unique to studies in animal behaviour. In human development, entire journals have been devoted to understanding functions and future benefits of play behaviour for the individual. While there are claims made that play is important and that one type of play may be more crucial than another, causal relationships from one experience (as a child or as a juvenile) to another (in adulthood) are difficult to substantiate (Lillard et al. 2013). Indeed, Lillard et al. (2013) specifically tested ‘pretend play’ in children and they came to the conclusion that evidence did not support strong causal claims about the unique importance of pretend play for development. Yet the importance of environmental input, as play represents, ought to amount to something. James Flynn (2007), the foremost proponent of the environmental basis of intelligence, argued that intelligence depends not just on hereditary factors but substantially also on environmental ones. So how useful might play be in this respect?
Play behaviour is not a difficult area of research, but the possibility of identifying its future function – given the number of influencing factors, the dynamics and multiple variables in development – is statistically and logically difficult and perhaps even impossible because the variables interact and cannot be readily isolated one from another.
Perhaps one should begin with the easiest form of inquiry and this is the question of which species play at all. Next perhaps is the question how and when they play and whether there are simple or complex forms of play and, finally, whether there are factors that prove to be robust to show how play is actually useful. Much of that work has already been done, but largely for humans, primates and other mammalian vertebrates.
Who plays and with whom?
Play activity is usually categorised as solitary, object and social play. They may not be mutually exclusive. Humans, some species of mammals and birds are known to engage in social play. However, solitary play behaviour in juveniles and adults, while not ubiquitous, is very widespread across taxa.
There are species that play in all three categories but social play is the least widespread. Solitary or locomotor play has been identified in 13 of the 27 avian orders. To these belong waterfowl, fowl, gulls and allies, penguins, pelicans and allies, birds of prey, owls, parrots and allies, cuckoos, swifts and hummingbirds, woodpeckers and allies and the very large group of passerines (song or perching birds). While only half the classified orders are identified as solitary players, this phenomenon of solitary play is widespread because these orders encompass well over three-quarters of all extant birds. Solitary play may involve sudden bouts of running, lying on the back, hanging or swinging and it is usually confined to locomotion.
The category of play known as object play – that is, picking up any object such as a stone, a piece of grass or twig and interacting with it (such as throwing, pulling, dropping it) – has been observed only in 6 of the 27 orders and these currently include gulls, birds of prey, owls, parrots, woodpeckers and songbirds.
In the third category, called social play, the number of orders and species declines further. Social play requires at least two partners for a play session to occur. It may be highly structured or completely unstructured. Only three orders have been shown to engage in at least two, or all three, categories of play behaviour, including social play, and these are parrots, woodpeckers and songbirds (see Ortega and Bekoff 1987). Social play has been of particular interest to researchers because of its link to learning and to sociality and, of late, also because of the inferred complex cognitive dimension.
While three orders still suggests that even social play is widespread among birds, when checking at a species level of documented cases of social play behaviour, the number shrinks to a relatively small list of a mere 25 species (Diamond and Bond 2003). Evidence of social play has been found in 13 species belonging to parrots (Psittaciformes), 2 species of hornbills and 10 of corvids and allies (Passeriformes). Play behaviour by the New Zealand kea (Keller 1975; Diamond and Bond 1999) and the common raven Corvus corax has been known and well described for some considerable time (Gwinner 1966; Heinrich and Smolker 1998; Marzluff and Angell 2012) but Australian species tend to be underrepresented in studies of play, with the exception of play in Australian magpies (Pellis 1981a, 1981b; Kaplan 2008).
Listed in Diamond and Bond (2003) are some Australian species also known to play: the golden-shouldered parrot of Cape York (Collar 1997), the budgerigar (Engesser 1977), the apostlebird (Baldwin 1974; Chapman 1998), the white-winged chough (Chisholm 1948), and the satin bowerbird (Chisholm 1916). In this list there are major omissions of documented cases and others that still await documentation: namely the cockatoos, such as galahs, little corellas and many other parrots, including rainbow lorikeets, eastern rosellas, cockatiels and princess parrots. Australian ravens, likewise, engage in play behaviour. Some species, for instance galahs and corellas, even continue playing as adults. This may not be an omission by the authors but an omission in reporting such behaviour in relevant journals. One suspects that the list might be substantially longer and it is for want of confirmation and publication that we do not as yet have a complete picture of play behaviour in Australian birds. Possibly more orders, or at least more species, may eventually be found to show play elements or even complex social play behaviour. From observations in the field, one would suspect that cooperative species might well top the list of those species that engage in various levels of play behaviour, especially in social play.
It is worth noting that researchers on play behaviour proceeded to establish correlations between play behaviour and various other factors, with one being brain size and another average time of first reproduction. As mentioned before, brain size or body/brain ratios have been criticised as a measure (Healy and Rowe 2007) but the idea of relating incidents of social play to age of first reproduction is an interesting one and ought to be an inverse relationship: the longer individuals play the later individuals reproduce. White-winged choughs, apostlebirds, ravens and magpies certainly start breeding only years after fledging. Even more pertinent is the question of life expectancy. Both parrots as a group and corvids and allies in Australia are long lived; some cockatoos such as galahs and sulphur-crested cockatoos have life expectancies that are among the longest in the bird world (70±20 and 100±20 years, respectively) and even among mammals. Magpies and choughs are long lived (25–30 years) by comparison with bird species of similar size elsewhere. In other words, play behaviour may be a very important factor for the ability of the brain to develop cognitive abilities or, the opposite may also apply: play may simply be expressed in brains with greater cognitive ability.
Alternative approaches to explaining the riddle of play behaviour have examined brain activities in and during play behaviour. Most of the research in this area has been done on various strains of rats, known to play extensively. Importantly, there are developmental events in the brain of the juvenile rat that are co-timed with the peak of play behaviour. Pellis and Pellis headed one of their chapters in their book The Playful Brain (2009) ‘Playing for the Present’ and, indeed, by measuring events while play is performed, it is far easier to establish correlations between play performance and other criteria than it is to relate play to much later events (i.e. speculating about future functions). The focus on ‘what does play do while it is performed’ allows one to measure behaviour and brain activity rather precisely.
The most important finding in such tests was that play reduces stress as measured by levels of the stress hormone corticosterone (Meaney et al. 1991). This seems odd because one would imagine that social play with its thrills and mock risks (as in hide-and-seek and chasing) creates its own stress. Playing, especially play fighting, activates the same neuro-chemical pathways as stress (Siviy 1998) and somehow intercepts these pathways. Real stress in birds, measured in amounts of corticosterone in the blood, is very harmful especially when experienced over longer periods of time. Cam and Aubry (2011) have shown that exposure to stress in birds, especially during development, results in high levels of corticosterone, which, in turn, has been shown to have dramatic and negative repercussions for life history. In storks, also long lived, ongoing exposure to stress as juveniles was shown to lower their survival. Hence, reducing or eliminating stress in a juvenile bird by playing could thus have a direct effect on life expectancy, success in breeding and a number of other life-history events.
In the absence of stress, it has been shown that the juvenile brain of rats is receptive to enrichments and that a number of benefits flow from such experiences. For instance, rats reared with companions and various enrichment objects develop a larger brain than rats that grow up in austere surroundings (Rosenzweig et al. 1968). Enriched rats not only have more neural connections and a heavier cerebral cortex, but they also learn more quickly. Enriched rats perform better at a number of behavioural tasks too (Renner and Rosenzweig 1987). Behaviour is paralleled by physical evidence of changes in brain weight and structure by developing more dendrites and connections (Rosenzweig and Diamond 1969; Diamond et al. 1972). Moreover, the more a young rat plays, the more rapidly its brain grows (Ferchmin and Eterovic 1982). If juvenile rats can play or be exposed to novel objects for just 2 h per day over a 30-day period, this produces significant cerebral effects (Rosenzweig et al. 1968). Although the biochemistry of the developmental events is somewhat complicated and not all its interactions are as yet fully understood, the body of evidence for the interconnection between stress and brain development and life-history trajectories is robust and no longer a matter of any dispute.
Play can thus be shown to have a dual benefit: one of reducing stress as an instant effect (and therefore overall improving the general health and even immune system of an organism) and the other by increasing growth of the brain itself (i.e. contributing to optimal brain development). Hence the question is no longer what function does play have in terms of correlations with adult behaviour but what immediate effects and benefit does play behaviour bestow on the individual organism? Not only has it been shown in rats that growth of the brain is stimulated by play behaviour, but also that playing leads to faster reaction time and overall stress reduction at the time of playing. While most research has been done using mammals, it is clear that the few researchers who have applied the same principles to birds have arrived at similar conclusions. It is now considered a general principle for all vertebrates that stress may seriously compromise health and prevent optimal cognitive performance. Play thus offers not just a buffer zone against such negative outcomes but may, instead, optimise developmental potential.
Further, recent research has implicitly supported the findings on play behaviour and its relationship to stress and optimal brain development. Lendvai et al. (2013) found that bird species with larger brains relative to their body size, at any stage in their life history, had a lower baseline and lower peak levels of the stress hormone corticosterone than species with smaller brains.
Expressed differently, enhanced cognition is a viable alternative to stress responses. Stress, particularly if experienced at a chronic level, lowers life expectancy and influences decision making. Hence, there appears to be a good reason why, in circumstances of extreme stress, organisms either succumb or find more clever mechanisms to survive. Having a brain that deals better with stress seems therefore to be a very plausible adaptation.
These findings draw attention to very important biological principles: one is that the brain does not develop in isolation. The static view that an organism simply follows an inherent developmental plan and does so without any environmental contribution would be absurd. The examples of stress show that any living organism is a dynamic and interactive system. Organisms also respond to the environment and may make alterations according to circumstances or may be physically or physiologically altered by environmental events. Hence, the equation is not necessarily: ‘I have a big brain therefore I play’, but also: ‘I play and therefore develop a big brain’. Play behaviour has thus a place in any discussion on the cognitive complexity of birds.
Those species that have the luxury of having ongoing parental or group support and protection and have the developmental time to play have increased chances of survival and therefore of longevity than those who lack these conditions. Of course, there is a price to pay. As a result of lavishing so much attention and time on offspring, parents or groups can afford fewer offspring, investment is higher, and reproduction slowed down in some cases to the point that under certain environmental stress situations such species might be at risk of not replenishing their numbers. This is not so in budgerigars, identified, surprisingly, as having one of the largest relative brain/body weight ratios of any Australian birds. Budgerigars engage in play as juveniles and throughout adulthood and they are long lived relative to their size. Interestingly, there has been no record of extended juvenile play behaviour in palm cockatoos, yet this species is a prime example of longevity, of extremely slow reproduction (Murphy et al. 2003) (the slowest of any parrot, in fact, as already discussed in Chapter 2), but also a species with one of the biggest brain to body weight ratios.
There is a further general point to be made about social play behaviour. Very few adults play either with their offspring or with each other. The remarkable part about play is that, almost invariably, juveniles cannot mimic adults in this regard; it is something that is initiated by juveniles themselves. Although they may have observed aspects of many of the behaviours that they ‘play-act’, the sequences are different. In play fighting, any threats or punishments do not get carried out in earnest. In other words, the players (when more than one) seem to understand in advance that the other individual must not get hurt or any serious blows or detrimental acts must only be play-acted. True enough, accidents happen and play can get too rough so that one party experiences pain and may give a distress call. The important moment is the response of the perpetrator to allow the vanquished to get up and recover. When age differences occur, attacks may go only one way and the vanquished one might be vanquished too often and sustain minor injuries. That too happens but this is then no longer play behaviour but reflects social hierarchies or other specific idiosyncrasies and bullying behaviour. Hence, there can be a fine line between oppressive behaviour versus play behaviour.
Solitary play
Birds have been observed hanging and swinging from branches. Rowley called this behaviour in galahs ‘acrobatics’ and indeed the hanging, swinging, wing extensions and head movements are vigorous (Rowley 1990). Solitary play in other species may also involve acrobatics of some kind, such as feeding upside down (Fig. 6.1), swinging from a tree branch by either one or both legs is something many Australian birds do. Sitellas can hang upside down, and so can all honeyeaters, all parrots and all cracticid birds (magpies, currawongs and butcherbirds), riflebirds and quite a number of species of pigeon. Rainbow lorikeets are noted ‘swingers’. The best acrobat among the pigeons is probably the topknot pigeon, a species that used to roam the eastern seaboard in flocks of thousands but has become very rare now (Gilbert 1936; Frith 1957).
Acrobatic solitary play, whether in the air or on branches, is usually a prerogative of juveniles, as a self-engrossed sequence of movements or engagements with or without an object that can last for 1 minute to 5 minutes but if the object itself has sufficient attraction (as does a toy for cats), such games can last far longer. Magpies can be seen hanging upside down from branches or some other structure by one foot and swinging, and so do galahs and other cockatoos and I have also observed this in hand-raised noisy miners.
Fig. 6.1. Musk lorikeet acrobatics. Musk lorikeets have an attractive red beak, and red feathers over their beak and on ear coverts on an otherwise green-coloured body and some yellow. Here feeding and playing may go hand in hand. The flower would have been easily reachable by sitting upright. Instead, the bird is half rolled over another branch, just visible on its back, is twisted downwards and the head is entirely hanging down. Hanging from branches and either swinging or just hanging is a favourite pastime of most parrots in solitary play.
Object manipulation as play
Solitary and object play have been observed in birds far more often than social play. Of all categories, it is object play that is found most often in adults (Hall 1998). The more typical scenario is finding lone juveniles picking up a leaf or a stick, tossing it about, throwing it on the ground, jabbing or stomping on it or, if they find a short string, they will hold the string with their feet, roll on their back and also hold the string with their beak, without releasing the grip on their feet. I have seen such games on countless occasions in juvenile parrots (eastern rosella), galahs, magpies and noisy miners. Each game may only last a minute while the string seems to offer more possibilities and usually generates more sustained play. One juvenile magpie, hand-raised but released and roaming freely, had learned to untie my shoelaces and seemed to derive a special pleasure from doing so because the bird came running the moment it saw me and headed straight for my shoes and almost instantaneously started wrestling with the shoelaces, detaining me often for as much as 15 minutes. In a little experiment I conducted with this magpie, I put out the shoe by itself to see whether the magpie was equally attracted to the string pulling without the normally ‘attached’ human. The magpie approached the shoe and played with it for a while and even pulled the string of the shoelace just once but then left off rather quickly. It seemed therefore, that the object and the string pulling was not the only, or even the primary, objective of this juvenile’s game and what seemed to have started as object play had indeed evolved into social play.
Object exploration and play are common in young magpies and have been described in many species of Corvus. Some researchers have surmised that such play may be a process by which these birds develop their foraging skills (Pellis 1981a; Kilham 1989; Heinrich and Smolker 1998).
There are other forms of play in which the objects are not leaves or twigs but pebbles and stones. Jane Goodall, when she was still writing under her married name (Van Lawick-Goodall 1970), reported an instance of stone-dropping by a pair of black kites, which she thought could be play. To quote:
One bird picked up three stones in its talons, one after the other, flew some fifty yards with them, and dropped them at about 5-minute intervals: the second picked up and dropped two stones. All five stones were dropped from a height of about 60 feet. Unfortunately the observer, one of our assistants, did not immediately investigate: subsequently we found four of the five stones within an area of some five square yards at the bottom of a shallow grassy gully among some low bushes.
Galahs are said to have frequently dropped stones on to the iron roof of a country house in New South Wales, as reported by Chisholm (1971a). The same writer quoted a report of about 30 magpies that had apparently dropped stones onto a rooftop of a rural household that had made it a regular practice to provide food for the birds in the morning. The magpies took to this strategy only when provisioning of food was late and the owner then received a noisy reminder that it was feeding time! Many magpies need not resort to such labour-intensive strategies – when they have befriended property owners they often simply wander into their backyard and if the kitchen door is open may come right in. If it is closed, they might knock on the window. Kookaburras regularly provisioned by property owners will do the same, but their knocking on the window can be so forceful that even a slightly damaged window could break. Even brush turkeys will do so.
None of this stone-dropping in the context of food provisioning can be regarded as play because it has a very specific purpose, although the teasing by knocking and the dropping of stones might well have started as a game as was observed in the kites, quoted above. Presumably, however, the action was reinforced when the owner then appeared and in fact responded by putting out some food for them.
Some object manipulations seem to make little sense. For instance, rainbow bee-eaters have been observed tossing shiny pebbles into the air, not once but several times seemingly self-involved (Chisholm 1971b). Playing with sticks was mentioned in Chapter 2 because some of that, as in black kites, has apparently led to having a specific function, namely burning ground to secure more (singed) food for the kites. Presumably, a playful act with an object may occasionally also lead to insight of a function of the object not considered before. For instance, ravens dropping pebbles into a jar of water may have accidentally discovered that such action raises the water level and may put floating edible objects within reach of the beak.
Duncan Watson (1992) reported a detailed description of stone play. He observed a wild solitary kookaburra play with a stone continually for almost 3 minutes, dropping the stone, then flying to it and retrieving it, taking it to a branch and bashing it, then repeating the entire sequence, complete with head swipes from side to side (as if killing a snake). It is a wonderful description and still worth reading today. Apart from Pellis’s accounts of play behaviour in magpies, already cited, Watson’s was only the second detailed account of play behaviour of an Australian bird published in a journal. This is important because journals are now linked to international databases while books get listed in their entirety not revealing details within. Instances of specific Australian bird behaviour may thus miss detection in these bibliographical databases used for global statistical assessments.
Social play
Social games can be played among two or more individuals. In playful species, siblings of the same clutch typically play with each other (Fig. 6.2). Some siblings play peacefully together while others are very competitive. Older siblings often also play with neighbours and form playgroups that can be as daring as the exploits of street-corner gangs.
Fig. 6.2. Playing nicely together. These two black-backed juvenile magpies (1 month after fledging) were inseparable and always played with each other. Here they are facing each other and vocalising in short and soft sounds. The one on the left is about to preen the other just above the eyes and while the one on the right is standing still; it seems to show some concern about the beak being so near its eyes. The calls are subdued distress calls that disappeared once the tip of the beak of the other was actively preening.
White-winged choughs are rather unusual among birds in that the young reach sexual maturity only after 4 or 5 years. For the entire period of time, they interact with siblings and travel with parents and other group members for foraging excursions on the ground. After 3 months post fledging, they are usually expected to feed themselves on the forest floor but it leaves a good deal of time for the youngsters to engage with each other.
One of the games choughs play with each other is a game of ‘tag’ involving a small stick or a bunch of grass, which two youngsters have grabbed simultaneously and then each tries to wrest it from the other (Chisholm 1948). Youngsters also engage in a good deal of running and chasing each other as has been observed in common ravens (Marzluff and Marzluff 2011). Juvenile magpies have several months in which they strongly interact with each other in a playful way (Pellis 1981a, 1981b).
The most often observed behaviour among magpie juveniles is play fighting. Another is chasing – typically, the first magpie would collect an item, such as a leaf or a stick, and start running with it while another one (or often several) would be in hot pursuit of the leaf carrier (Pellis 1981b; Kaplan 2008).
Hide-and-seek
It is perhaps not so far-fetched to relate the capacity to form memories of hidden objects with a common child’s game: that of hide-and-seek. Clearly, hide-and-seek involves the complete disappearance or partial hiding of an object and requires a memory of the location of its disappearance, or at least an ability to recognise that partial exposure of an object hides a part of the known object. This has been studied extensively in chickens in the laboratory and will be taken up again in Chapter 11. Observed examples of such situations in the wild are rare and have not been systematically described. Indeed, it is even rarely found in the literature on children. Peskin and Ardino (2003) from Toronto University published a rare paper on this game. They specifically tested children’s ability to keep a secret and to play hide-and-seek. Results showed a high correlation between the two seemingly disparate tasks and levels of cognition. It seems that children take a good while before they fully understand the task: few 3-year-olds, most 4-year-olds, and almost all 5-year-olds could successfully play hide-and-seek.
Hence, to repeat an earlier point, conceptually, hide-and-seek is in a special category. As will be shown in Chapter 11, for objects or people to go out of sight and to recognise part of an object or body as something known and familiar (i.e. the complete visual ‘gestalt’) and, in addition, maintaining a memory as to where something or someone may be that has gone out of sight requires forming a memory and certainty called object permanence.
Taking the Peskin and Ardino (2003) study as a benchmark, it is easy to appreciate how extraordinary it is to see magpie juveniles play hide-and-seek. I regularly observed them play this game in several clutches and over at least a 10-year period. It is worth describing here in detail because of the strong evidence in humans that this is an activity that is cognitively complex and often takes children to the age of 5 before it is fully understood and sustained as a game (Peskin and Ardino 2003). It requires at least two individuals who understand that one has to hide and the other one is supposed to go after the first and find the one hiding. If the seeker does not find the hider, the hider is supposed to taunt the seeker by briefly giving cues of his/her whereabouts, such as rustling or showing the head or part of the body. In other words, the most important aspect of this game is to be able to trace the individual that has gone out of sight and imagine to where the body has gone. If tracing this is too difficult, part of the body should be shown (or a vocal clue given).
The games that I have observed in magpies qualify in every way as a typical hide-and-seek game. The first juvenile ran as fast as its legs would carry it and sought out some scrub and then hid behind the first tree or rock and then peeped to see whether the other juvenile followed. If not, it called briefly and if nothing happened, it showed itself again partially by stepping sideways or by bobbing up its head behind the barrier. At the play site, there was an area where the ground formed a natural trench. It was interesting to watch that this trench was used regularly for hide-and-seek games. In one year, there were three youngsters and they regularly ducked behind it, meaning any one of the three at one time (they kept swapping roles). As the season progressed, the birds got better at finding each other. After a month of playing I noticed that the hider no longer bobbed up or showed itself in its hiding spot but the seekers were also no longer running and searching but quietly and carefully stalking, slowly and silently approaching the hiding spot and then pouncing on the totally hidden bird. Both or all three tended to shriek when contact was made and the seeker usually pounced on the hider and a play fight would ensue. The fact that they kept playing this game among others throughout several months post fledging suggests that it gave them some sort of pleasure or thrill by evoking fear. The little shrieks would suggest that this was the case. Each game demanded heightened alertness and a knowledge of being aware that danger could be hidden or partially hidden and a memory of known things disappearing behind a barrier but still being there behind that barrier. Hence, in summary, it can be said without reservation that the repertoire of play in magpie juveniles is large and often innovative.
Play behaviour is certainly also known in many parrot species. In galahs and corellas it may extend into adulthood and persist throughout adulthood. Yet the Australian magpie’s variety of games well exceeds the performances even of galahs. The magpie juvenile is perhaps the most imaginative and extensive play-prone bird known, apart from New Zealand’s kea, and some of its tactics and game strategies have more in common with those of chimpanzees than with other birds.
One can say, perhaps, that awareness of things hidden behind barriers is a very useful knowledge to have obtained playfully because the few real risks of predation for magpies come in the form of ambush hunters such as goshawks and little eagles. It is also a display of imagination: a quality we normally tend to attribute only to humans (and then children of advanced age). Play also reduces stress, as has been discussed already. It leads to better health outcomes for adults and promotes better ‘brainpower’ and, as a recent study on bird brains and stress had shown (Lendvai et al. 2013): smarter birds stress less. Magpies are known as fearless fighters when defending their territories and their nest sites. Apart from skuas and common ravens, magpies are probably the most assertive birds known, taking on aerial predators several times their own size (discussed further in Chapter 10, Fig. 10.3). To launch such daredevil missions successfully may well be related to the many months of extensive playing as juveniles (Figs 6.3, 6.4). Fear tends to develop only with increased stress levels and, if these are well controlled thanks to periods of play during juvenile development, the individuals can think and act strategically. That is precisely what adult magpies do when confronted by raptors as a recent paper has shown (Koboroff et al. 2013).
There is little published evidence of play in aerial space. Aerial displays of territoriality, mating rituals and fights have been described in some detail since Armstrong (1942) but there is little information available on play-fighting in aerial space. In Australian magpies, aerial chase games can be seen regularly but such flights tend to be short and performed at lower height than flights with destinations. Magpies tend to turn around and then land in almost the same spot from where they had commenced the short aerial chase. Aerial play may be relatively rare but playful behaviour has been seen in wedge-tailed eagles, often in the context of courtship behaviour. One eagle may take a stick or a piece of carrion to the air, then drop it for the second eagle to catch mid-air. Among crows, aerial play has been observed just using a piece of paper that is dropped by one bird and caught by another and so forth (Marzluff and Marzluff 2011). In other aerial forms of play, an eagle might hover over a dog and lower itself to a low height above the dog, keeping just out of reach when the dog jumps, then allow the dog to settle and thereafter restart the sequence again (Olson 2005). Notably, these playful acts were usually carried out by adults.
Fig. 6.3. Aerial play in Australian magpies. (A) A tactical game in which one bird aims to get underneath the other one that is on a pretend flight from a pursuer and nip it in the belly, then the game changes and the pursuer becomes the pursued. (B) This aerial game may be a mere race among several contestants. However, the raised head of the last of the three birds indicates that this is the ‘catch my tail’ game. When adult, magpies will pursue aerial predators with considerable skill and speed.
Fig. 6.4. Play fighting in magpies. Five juvenile magpies about 5–6 months after fledging deeply involved in a social game of their own making. Brief flight jumps are accompanied by intense vocalisations. Posturing with outspread wings has the goal of jumping on top of the waiting juveniles who, in turn, get ready to fly up vertically to get in a position higher than the approaching birds. Note that the lower photo involves five magpies and they have clearly split into two teams for the purpose of this game.
A question arises as to what motivates the individual birds in the first place to start playing any game? Because there was no evidence that parents or other adults intervened or acted as mentors or demonstrators, games were entirely self-motivated and initiated by the juveniles among themselves. The play fighting in the magpies had all the elements of play fights in other species, such as dogs. There was a clear element of testing dominance and skill in overcoming the opponent. The loser rolled on its back and the winner was poised on top executing a few (gentle) stabs. When the winner was satisfied, it took itself off the body of the loser but the loser had to remain motionless on its back for some time. If the loser got up too soon the winner came back and had another go at the vanquished.
Play fights involving dominance and submissiveness in dogs and dingoes (Rogers and Kaplan 2000) are almost the same as in magpies. The fact that birds and dogs roll on their back as a gesture of submissiveness shows an interesting convergence here of social signals – crouching in dogs or rolling on the back in a submissive gesture also has a similar or even the same function in magpies baring the vulnerable abdomen and neck.
The question is also whether the playing birds enjoy themselves or, as we would now say: have ‘fun’. Interestingly, the journal Current Biology has devoted an entire issue to that question as a celebration of its own 25th anniversary. In doing so, the journal bravely opened the Pandora’s box of emotions in animals: another thorny subject that will be raised in Chapter 9. Importantly, here, Emery and Clayton (2015), answer the question cautiously in the affirmative, despite the absence of studies specifically dealing with this question in birds. However, such work has been carried out in mammals, chiefly rats. The researchers argue that essential ingredients in specific parts of the brain, such as endogenous opiates (e.g. encephalins), and neurotransmitters such as dopamine, are also found in the avian brain and they are essential preconditions for experiencing pleasure, although play fights may or may not need to be investigated separately.
Interestingly, such games that involve submission are widespread among species that form close-knit groups, have a clear hierarchy and thoroughly depend on one another for survival. Awareness of another member’s status is thus vital. It seems to foster awareness of one another in terms of communicating desires, acceptance of one’s status, but also in terms of support for each other. Keeping a ‘look out’ for other members of the team may require a memory of where they have gone if they have gone out of sight. Ravens have been found to be very good at finding things behind barriers and so have Australian magpies. Some of these issues will be taken up again in Chapter 11.
Suffice it to end this chapter with the conclusions that Ricklefs (2004) reached about the importance of play behaviour. He argued that cognitive abilities of birds should be assessed within the context of life histories (as considered in this book) and seen in the context of attributes such as brain size, rate of development, age at maturity and lifespan because:
Long life span may permit the extended learning periods that support experienced-based cognitive function. Play behaviour, which plausibly supports the development of motor and social skills, and, to a lesser extent, foraging innovations, are related to brain size (Ricklefs 2004).
The criticisms that brain size may not be a reliable, or the most crucial, measure have already been raised in previous chapters. However, his comments are important in showing that a seemingly quaint behaviour such as play behaviour may possibly tell us something important about the success of a number of Australian avian species and orders. The interrelationship between pleasure and play has yet to be convincingly demonstrated in birds, but hopefully it has been made clear in this chapter that there are many Australian birds that engage in play behaviour. Eventually this may be shown to be quite remarkable, because of the number of species and families involved and the wide distribution across non-songbirds and songbird families, especially in Australia.