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The blue jay is one of the loudest and most colorful birds that exist, but its cunning as a predator is enviable. Not only does it feed on almost everything in its path, but it is quick and skillful, as the biologist at the University of Cincinnati George Uetz has proven.
It has long been proven that the extravagant courtship dance starring wolf spiders made them easy prey for birds and other predators. His suspicions were verified when he and his colleague Dave Clark of Alma College joined the experiments with blue jays of Tricia Rubi of the University of Minnesota.
In his recordings, it is observed how spiders camouflage themselves among the leaf litter without predators being able to detect their presence. However, when males begin their courtship, waving their hairy front legs with the same enthusiasm as an orchestra conductor, they are quickly caught by these birds.
According to Uetz, the male inevitably succumbs to the call of females, whose pheromone trail is irresistible. The suitor then bounces, shakes his legs on the leaf litter and generates vibrations that can reach a considerable distance. This unequivocal dance, along with its thick fur, is the best indicator that the male enjoys excellent health. “The exhibits and decorations show male quality and thus guarantee a offspring with the same qualities, explains the biologist.
The problem is that birds also see in them an exquisite delicacy. “In addition,” he says, “blue jays are animals with excellent visual acuity and an ability to differentiate highly developed color, so it is not surprising that they detect spiders in motion.”
The study, published in Behavioral Processes, also indicates that female wolf spiders are very selective when choosing a mate. “The tufts on its front legs are very important. Its size and symmetry play an important role.” They are animals so small and with such a tiny brain, almost the size of a poppy seed, that it is hard to believe that they are capable of discriminating. “But they do.”