Pleistocene Blue Jays (Cyanocitta cristata)

When I was attending 3rd grade during the 1970/1971 school year, Perry Harvey came home with me everyday after school.  On occasion he could be reckless.  One unfortunate day he swung a baseball bat at an oak tree, and the bat rebounded, struck him in the head, and knocked him out cold; taking the old cliché “knock yourself out” to a literal reality.  Another day he made the mistake of picking up a baby blue jay that had fallen out of its nest.  Every blue jay in the neighborhood screeched and dive-bombed us.  He put the blue jay down, and the birds chased us into the house in a scene reminiscent of the Alfred Hitchcock classic The Birds. Like some other species of birds, blue jays practice communal defense.

YouTube video of a blue jay attacking a gardener.

Blue jays are intelligent birds from the corvid family which also includes crows and magpies.  They are well adapted for living in the temperate deciduous woods of eastern North America and have probably occupied that habitat for many millions of years.  However, I have been unable to find any studies of blue jay genetics, and I don’t know how long they have existed as a distinct species.  It seems likely they diverged from the common ancestor of the gray, Florida scrub, and Stellar’s jays before the beginning of the Pliocene over 5 million years ago.  Fossil remains of blue jays dating to the Pleistocene have been found at 3 sites in Florida, 1 site in Georgia, 1 site in Alabama, 1 site in Tennessee, and 3 sites in Virginia.

Blue jays played an important role in the spread of oak, beech, and chestnut trees north following the ends of Ice Ages.  Nuts and acorns are a major part of a blue jay’s diet, and they often carry excess food to distant locations where they hide them for later use.  A scientific study concluded blue jays were the sole reason oaks, beech, and chestnut were able to colonize deglaciated territory so rapidly after the end of the last Ice Age.  Squirrels invariably bury acorns and nuts so near the roots of the parent tree that they could not have been the agent of dispersal.  But blue jays carry nuts as much as an half a mile away.  Without blue jays there would be no oak or beech trees in eastern Canada and northern New England today.

Reference:

Johnson and Webb

“The Role of Blue Jays (Cyanocitta cristata) in the Post Glacial Dispersal of Fagaceous Trees in Eastern North America”

Journal of Biogeography 16 1989

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Tags: blue jays, post glacial expansion of fagaceous trees