Archive for November 27th, 2009

Perhaps you’ve heard the expression An elephant never forgets, but did you know that chickadees have amazing memories? If you watch the birds that come to your feeder you will notice that some, like the American Goldfinches (Carduelis tristis), will perch on the feeder as long as they are able before being chased off by others seeking the perch. Black-capped Chickadees (Poecile atricapilla), however, don’t spend much time at the feeder. They grab a seed and fly. They may take the seed back to a safe branch to eat right away, or they may hide the seed for later.

Chickadees cache seeds under bits of lifted tree bark and in other safe hiding places for times when food is scarce. They may retrieve a seed a few hours later or a few weeks later. Unlike some animals that build up a large cache in a safe hiding place, chickadees are scatter-hoarders. That is, every seed is hidden in a different spot. A chickadee can cache as many as 100,000 food items in a year. The surprising thing is that it can find where it hid all those seeds with amazing accuracy!

Scientists have long been interested in this memory feat, not just zoologists, but psychologists and neurologists who study memory as well. Many experiments have looked at how chickadees relocate their caches. Generally, it has been found that they depend upon a hierarchy of visual cues to locate hidden seeds. The position of the hidden item relative to larger landmarks such as trees is the most important cue, with more localized cues such as a particular arrangement of pine needles next to the cache being less important.

Their amazing spacial capabilities are related to the hippocampus region of the brain. Surprisingly, the geographic location of birds can affect the size of this structure. For example, Alaskan chickadees have a larger hippocampus than do Colorado chickadees. It is hypothesized that birds living in more extreme conditions are more dependent on being able to locate their caches reliably and thus have a larger hippocampus. However, a finding that some European species such as starlings have a larger hippocampus than their North American relatives remains puzzling.

While it may not be true that a chickadee never forgets, these little birds are pretty cool!

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