Sunday, June 23, 2013

An Intelligent Murder of Crows

It was very late. I couldn't get to sleep and began cruising COMCAST for something to watch and found a PBS Nature show, A Murder of Crows. I learned some fascinating things.

New research has shown that crows can make and use tools, can recognize 250 distinct calls, and not only can recognize human faces but can pass down, through generations, that recognition.

Crows are social birds that mate for life and raise their young for up to five years. And they learn from each other’s misfortunes. When one is killed in a farmer’s field, it’s not uncommon for them to change entire migratory patterns so that no crows fly over that field for as long as two years.

CROWS MAKE AND USE TOOLS: For example, they use twigs to pry insects from wood or from inside long slender flowers. Crows are shown (in the program) using twigs to obtain other twigs that would allow them to obtain food - sequential tool use. Using tools to act on non-food objects – for example, to make or retrieve other tools – is considered to be a hallmark of human intelligence.
Crow using a stick to get a longer stick to get some food

CROWS HAVE OVER 250 CALLS: Calls are complex and vary by species and also regionally, sort of crow dialects. Not only the call but the tone and level of sound change the meaning of vocalizations – loud when defending territory or hungry and quiet, almost purring, to show affection. Distress calls bring other crows to their aid, as crows will defend other crows not known to them.

Univ. of Seattle researchers don masks to test crows recognition
CROWS KNOW WHO YOU ARE: Crows recognize individual human faces, and hold grudges against people who have been mean to them in the past. They have the ability to recognize individual human faces and pick them out of a crowd up to two years later. If a "dangerous face" is recognized by a crow, a call of warning is sent out among the crows. In a generation later,  the same face sends out caws of warning. Univ. of Washington researchers used masks in experiments that revealed that crows do not forget.

You can view the full episode online at PBS: A Murder of Crows -  it's not available through NetFlix yet.

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