During nesting season, some birds will nest close to larger birds, the idea being that the bigger birds' presence will discourage other bigger birds from raiding their nests. The little ones get a bit of nest defense on the cheap, thanks to the big ones.
But how cheap is it, really? Researcher Rhea Esposito, from from the Cary Institute of Ecosystem Studies, wanted to know whether the smaller birds paid a food cost, losing out on meals to their larger neighbors.
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A trio of corvids -- those super-sharp birds whose intelligence and problem-solving skills have been well documented -- in Jackson Hole, Wyo. made for the perfect test subjects. Magpies in the area tended to nest near bigger crows, which offer tough defenses of their own nests against even bigger ravens.
Do the magpies pay a food penalty for the indirect protection?
Esposito held what she termed "Cheetos challenges," tests of breeding pairs based around the orange snack loved by people and, apparently, magpies and crows.
In the first challenge, she set out Cheetos near the nests of breeding pairs of both birds and then let the fun begin.
For sheer speed of approach it was magpies all the way (video below). They descended upon the curly treats some 20 seconds faster than the crows. The crows, for their part, tended to exercise more caution around the new, possibly suspicious items.
However, once the crows realized the strangely colored items were a tasty snack, they became quite the thieves, stealing the treats from nearby magpie nests.
"Because it's the nesting season, they are often close enough to see neighboring Cheetos piles. So crows would learn that there is food at the nearby magpie nest, as well as their own nest. Crows steal more often than magpies by a factor of three," said Esposito, who performed the tests while a graduate student at at the University of Louisiana at Lafayette.
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The tests got tougher. Eventually the Cheetos were hidden inside logs and could only be extracted if the birds tugged on a string tied to them. Once again, magpies were quicker on the draw, averaging about 1 minute faster than the crows at solving the puzzle and scoring the snack (Esposito acknowledged she was more interested in ecological questions than those of corvid intelligence. "These puzzles were very simple for corvid abilities. They have solved much harder problems in the lab," she said.)
In another test, where Cheetos were placed equidistant from nests of both magpies and crows, some 279 feet (85 meters) away, the birds found them at about the same rate and in the same amount of time. But a pattern Esposito had seen in earlier tests was once again present: The crows let the magpies explore the snack first before swooping in, driving away the smaller birds, and taking the treat themselves.
In time, Esposito noted, the poor magpies abandoned all hope. They didn't even bother to land and check out the Cheetos.
So, then, the answer to the question underpinning the tests would seem to have been "yes." There is no such thing as free protection. "Crows are about twice the size as magpies. That's why they are great as nest defenders. But there is a cost," said Esposito, who presented her findings at a recent Ecological Society of America gathering.
VIEW PHOTOS: Top 10 Most Intelligent Animals
Creatures both big and small made the list of the top 10 most intelligent organisms on the planet, proving that bigger isn't always better when it comes to brains. The new list, created by neuropsychiatrist Jon Lieff, includes animals that have been widely known for their smarts, as well as some surprising entries. Boston-based Lieff, who is a past president of the American Association for Geriatric Psychiatry, specializes in the interface between psychiatry, neurology, and medicine. Such interdisciplinary research is leading to a better understanding on how human and other mammal brains age, which may shed light on treatments for common disorders, such as dementia. Included on the list are bees, which Lieff said use symbolism and abstract concepts to solve problems in their daily lives. "They have a kaleidoscopic memory of every flower for miles, and learn from wise elders where the best flowers are," he told Discovery News. "Bees self medicate in their hives in different ways, and engineer the very complex honeycomb structures that are the most efficient possible for honey storage."
Do not let their squishy tentacles fool you. Octopuses are extremely intelligent, according to Lieff, who explained that they spread cultural information, mimic others and communicate using colors, patterns and flashing. "They have advanced spatial learning capacity, navigational abilities and use creative predatory techniques," he added. "They manipulate objects as well as the human hand does."
Elephants have highly evolved social capabilities and often show wise, compassionate and loving behaviors, Lieff said. Elephants have amazing memories and can remember friends and enemies for a half century or more, depending on their health and lifetime. (Elephants in the wild can live to about 60, and the oldest known elephant on record -- in captivity -- reached the age of 86.) "In captivity, elephants have become excellent artists," Lieff said. "Elephant communication is elaborate involving many different vocalizations, and they 'speak' to family five miles away. Elephants are extremely collaborative, consoling and cooperative, and deeply mourn their dead."
Ants are the ultimate team players, but they display great individual intelligence as well, according to Lieff. The insects can navigate long distances with ease, remembering their lengthy routes. "Ants care for their family similar to many mammals and show altruism for comrades," Lieff said, mentioning that ants are the second society on earth (after termites) to develop agriculture. Human-established agriculture evolved much later.
Dolphins continue to astound researchers. These marine mammals in captivity can remember the communications of their fellow tank mates for at least 20 years, according to Lieff. "They also immediately notice themselves in a mirror, and are very creative in inventing new ways to fish," he continued. "They wear sponges on their noses to protect themselves near rocks. They have advanced social relations with humans, such as herding large schools of fish toward fishermen wading in the water with nets. When the fish are about to come in contact with the nets, the dolphins signal the fishermen by slapping the water."
Birds are among the smartest of animals, with two groups making this particular list. The first are crows. "Crows are aware of themselves and are able to use counting and analogies," Lieff said. "They can solve higher-order, relational-matching tasks spontaneously. They use tools better than most (non-human) primates, molding wire into a hook and using three different tools for one task." He added that studies reveal crows understand the Archimedes principle, which holds that the upward buoyant force exerted on a body immersed in a fluid, whether fully or partially submerged, is equal to the weight of the fluid that the body displaces. This knowledge allows crows to manipulate water levels to access food.
Curious and playful, cockatoos are also incredibly smart. Lieff explained that cockatoos use multi-step techniques to solve problems, such as figuring out how a complex cage lock works. For example, Lieff said one clever cockatoo figured out a lock that required removal of a screw, followed by removal of a bolt, then turning a wheel 90 degrees before finally shifting a latch sideways. Other cockatoos that watched this happen quickly repeated the successful maneuver. A quick search at YouTube also reveals that cockatoos "completely disprove the notion that animals can't dance," Lieff said.
Lizards do not get a lot of recognition for their intelligence, but Lieff believes it is time they did. Anole lizards, in particular, continue to impress researchers with their cognitive skills. Anoles demonstrate counting, advanced learning and problem solving, he said, adding that their memories are extraordinary. In captivity, these lizards can "invent techniques that they don't use in the wild. They can use multiple different strategies (to solve puzzles) and can unlearn incorrect approaches, rapidly reversing course."
Dogs are so loyal to humans that they often don't get credit for their own intelligence. "From a purely cognitive vantage point, dogs have learned up to a thousand different words," Lieff said. He added that "service dogs demonstrate creativity and high intelligence" in saving others. Canines can also accurately read human emotions.
Rounding out the list are whales, which demonstrate elaborate communication techniques and cultural exchange. "They work together for creative fishing techniques, with each whale in a designated role," Lieff said. For example, he explained three whales sometimes line up in a row while beating their tails together. This creates waves that can knock a seal off an ice perch. Whales also swim beneath a school of fish in circles, blowing air bubble "nets," which trap the fish. This requires a lot of team organization, as some whales do the diving while others make calls in order to herd the fish. Such teamwork is passed on to other generations.
Missing from this Top 10 list are humans and other primates, which clearly excel at social communication, cooperation, tool making and much more. But can a species measure with complete accuracy its own intelligence compared to that of other animals? It's near impossible, since that judgment can only be based on the particular animal's values, brain structure and way of thinking.