Every autumn, the chickadee roams a territory covering tens of square miles, gathering seeds and storing them in hundreds of hiding places in trees and on the ground. Over the harsh winter that follows, the tireless songbird, which weighs about 12 grams and fits inside the typical human hand, faithfully re-visits its caches to feed.

The chickadee's unerring spatial memory is remarkable enough, says Colin Saldanha, assistant professor of biological sciences at Lehigh University and an anatomist who has studied songbirds for six years. But it is what happens inside the tiny songbird's brain that Saldanha finds amazing. In the fall, as the chickadee is gathering and storing seeds, its hippocampus, the part of the brain responsible for spatial organization and memory in many vertebrates, expands in volume by approximately 30 percent by adding new nerve cells. In the spring, when its feats of memory are needed less, the chickadee's hippocampus shrinks back to its normal size.

By studying neurogenesis in the black-capped chickadee, Saldanha hopes to learn how hormones help guide the brain's development and reorganization. He is particularly interested in the role played by the hormone estrogen in the growth of the hippocampus. "We're looking at the ability of nerve cells and connections to make estrogen in the brain and asking if this ability is involved in brain reorganization," he says. "We are the first lab, I think, to look at estrogen-synthesizing neurons in the songbird hippocampus at the electron-microscope level. We may, in fact, be the only lab using this technology to investigate songbird spatial memory." >from *As autumn approaches, this chickadee's brain begins to expand. New nerve cells put fall foraging on fast track*. September 11, 2003

related context
> 'good' chemical, neurons in brain elevated among exercise addicts. september 26, 2003
> synaptic plasticity: how experiences rewire the brain. january 23, 2003
> neurogenesis: observed in human adult brain. march 6, 2002
> autumnal equinox. september 22, 2001
> neurogenesis in the adult human hippocampus. november, 1998

imago
> chickadee hippocampus expansion composition.
have you gathered your seeds?