By Donald Brightsmith
Originally Published in Bird Talk Magazine
January 2000
Each month in the pages of Bird Talk readers can find articles or products that help people keep their birds healthy and happy. Pet owners and breeders go to great pains to keep their birds safe from threats from teflon pans, to houseplants, to wild animals. While all of this is very wise and prudent for pet owners, we should not forget that parrots have evolved over millions of years under the constant threat of predation and this threat has help shaped many aspects of parrot life.
In the wild, parrots face the constant threat of attacks by hawks. Falcons like the Peregrine Falcon (Falco peregrinus)hunt in open areas and above the forest canopy diving through the air at speeds up to 200 miles per hour. The swift falcons can overtake even the fastest parrots in flight. Below the canopy of the forest, other species of hawks and falcons await. Forest-falcons and Accipiter hawks make a living darting through the understory of the tropical forests ready to pick off any unsuspecting parrots that venture into the dark forest interior. In fact it was repeated attacks by one of these forest hawks, the Northern Goshawk (Accipiter gentiles), that helped end recent attempts to reintroduce Thick-billed Parrots in Arizona.
Where parrots are forced to go to the ground to feed or drink they are exposed to an even greater variety of predators. Aerial predators such as the Black-and-White Hawk-Eagle or Roadside Hawks are known to take unsuspecting parrots as they descend to the river banks in South America to eat clay. At these times parrots may also be vulnerable to attacks by mammalian predators. Cats like jaguars and ocelots may catch unwary parrots. Even the relatively innocent appearing Brown-capuchin Monkeys (Cebus apella) have been known to catch and eat adult macaws as they descend to the river banks for their daily dose of clay. This constant threat of attack must have greatly impacted all aspects of parrot life, but how? What specific traits have evolved to deal with the constant threat of predation?
Parrots are extremely social creatures. When kept in captivity, isolated parrots often suffer from severe problems with symptoms that resemble depression and madness. Similarly, pairs may not breed well when kept in complete isolation from other birds. In the wild, many parrots are known to spend their lives in groups ranging in size from two up to thousands. Detailed studies show that even during the breeding season when females should be off incubating or brooding few parrots travel or feed alone. At night, many parrots also roost groups. Yet within these groups the birds are far from peaceful and sociable neighbors. For example, pairs of White-winged Parakeets (Brotogeris versicolurus) and others in this genus frequently fight amongst themselves as they protect their own personal space, favorite perches and favorite feeding sites. Similarly tussles among macaws and other parrots are frequent occurrences within large flocks. If the birds are so confrontational, why then are they so social?
The causes for flocking and sociality are many and complex, but the threat of predation is undoubtedly one of the most important. In many species of birds, not just parrots, flocking is known to have a variety of advantages. By traveling in a flock individual birds may benefit because the odds are that the attacking predator will catch one of the other flock members and allowing the rest to escape. In addition, birds in flocks are more difficult to catch than birds traveling alone. For predators, the most efficient attack strategy is to focus on one individual and pursue it until capture. This may be extremely difficult to do when a large group of parrots bursts from the top of a tree and swirls off through the air. If the predator gets distracted and switches targets mid attack the chance of success drop significantly. For this reason, even when attacked by a higly skilled predator, the entire flock may escape unharmed.
Another advantage of being part of a flock is that there are many eyes that can serve to detect predators. This is especially important during feeding. When parrots are feeding their must often climb to the tips of thin branches, or hang precariously to reach the ripe seed and fruits. These activities take great concentration and may leave little time to watch the sky for approaching predators. In many parrot species, birds will take turns acting as sentinels forgoing feeding for a short period to just scan the surrounding area for danger. This is especially well developed in species that descend to the ground to feed like the Hyacinth, Red-fronted, and Lear's Macaws. Sentinels are so common among ground feeders because being on the ground is doubly dangerous for these large birds. Mammalian predators may sneak up on feeding birds. Potentially more important is that when on the ground, parrots require much longer to get up to good flying speed compared to when they can just drop from a tree and zoom off with little effort. As a result, parrots must detect attacking predators much sooner when they are on the ground making sentinels that much more important.
As the day draws to a close and night approaches, many parrots continue to maintain their social tendencies. The day time feeding flocks coalesce forming even larger flocks that often run into the hundreds or more. These flocks may mill around during the fading light of the evening before settling down to roost together in the highest branches of tall trees. These preferred roost locations are often on river islands or in trees isolated in some other way from the surrounding forest. In these locations the birds settle in dense groups, often on relatively thin branches or palm leaves to pass the long dark night. The hawks and monkeys that hunt by day are replaced by an equally dangerous group of nocturnal predators that include owls, opossums, cats and vampire bats. By roosting in large groups on flexible perches, parrots rely on the fact that predators climbing through the roost tree or attacking a single bird will wake all the members of the roost, allowing them to flee to safety. While there may be other social benefits of communal roosting, predation is undoubtedly a vital force that has driven the evolution of this behavior.
From the proceeding discussion it is clear that traveling, feeding and even sleeping in groups is a very good way for birds to reduce the risk of predation. Over time individual parrots that abandoned the group living behaviors may have been eliminated by opportunistic predators. This form of natural selection may be part of the reason for the inherent "need" for companionship shown by many modern parrots. While it seems unlikely that a parrot kept alone in a cage with little social interaction consciously fears attack by predators, the millions of years of negative reinforcement of being alone has likely produced birds that are driven to seek companionship.