Date: June 8, 2016
Source: Lehigh University
Class is in session for a group of chickadees at their temporary quarters inside an aviary in Lehigh's department of biological sciences.
Today, the students are beginning a 10-day lesson on spatial memory. A wooden board hanging on one of the aviary's walls contains 60 small holes, each covered with a ball of cotton. One of those cotton balls conceals a worm. One at a time, each bird must find the hole hiding the worm.
Over the next nine days, the test will be repeated daily, with a new worm hidden each day inside the same hole.
The experiment, says Michael McQuillan, is designed to measure each bird's ability to remember where it has stored food -- a trait vital for chickadees and other animals that scatter and hoard their food to survive in the wild.
It is also designed to shed light on speciation, the process by which new species arise over time.
McQuillan, a Ph.D. candidate in biological sciences, is particularly interested in hybridization, which occurs when parents from two different species mate. Their offspring, called a hybrid, may or may not become a new species.
McQuillan's chickadees include the black-capped chickadee, whose range covers Alaska, Canada and the northern United States, and the Carolina chickadee, which lives in the southeastern U.S. The two species of songbirds do not migrate and are similar, but distinguishable, in appearance. The black-capped variety is darker and larger, its tail is longer, and its black bib has sharper edges.
The ranges of the two purebred species overlap in the Lehigh Valley. The intermingling has led to interbreeding and produced hybrid chickadees, which McQuillan is also testing.
Hybridization occurs in about 10 percent of animals and 25 percent of plants, says McQuillan. Some hybrids thrive, but most do not. The mule, a cross between a horse and donkey, is valued for its strength and endurance but is unable to reproduce and thus to speciate. And roughly 60,000 years ago, says McQuillan, scientists believe human beings interbred with Neanderthal men.