MarkGelbart
Well-known member
My latest blog entry should be of interest to birders. It's about the kinds of corvids that lived in southeastern North America during the Pleistocene.
Today, only 3 species of corvids live in Georgia (USA), though ravens may also occasionally stray within the state boundaries. But based on fossil evidence and logical deduction, I've determined that 7 species lived in what's now the state boundaries, during the Pleistocene.
The extant species are the common crow, the fish crow, and blue jays.
The Pleistocene species that no longer live in Georgia include the raven, the magpie, the Florida scrub jay, and the Canada jay.
Ravens and magpies had an expanded range during the Pleistocene because they exploited megafauna carrion. Both have been found as fossils in Georgia and Alabama.
The Canada jays present day habitat was under miles of glacial ice during the Ice Age. Its range necessarily was depressed south. Fossils of Canada jays were excavated from a cave in middle Tennessee, much farther south than where they live today, and I assume they ranged into north Georgia during the last glacial maximum.
Florida scrub jays have a discontinous range--they live in central Florida and in the far west. At some time during the Pleistocene, these two populations would've had to have been connected. This probably occurred during a dry climate cycle when scrubby prairie habitat was more widespread than today.
For my blog entry I scanned a couple of illustrations of jays and crows from my favorite bird book--The Natural History of Birds of eastern North America by Edward Forbush. The book was written in the early twentieth century and has wonderful descriptions or rural settings, such as overgrown fruit orchards, that have long since been swallowed up by suburban sprawl.
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http://markgelbart.wordpress.com/
http://stores.lulu.com/GeorgiaBeforePeople
Today, only 3 species of corvids live in Georgia (USA), though ravens may also occasionally stray within the state boundaries. But based on fossil evidence and logical deduction, I've determined that 7 species lived in what's now the state boundaries, during the Pleistocene.
The extant species are the common crow, the fish crow, and blue jays.
The Pleistocene species that no longer live in Georgia include the raven, the magpie, the Florida scrub jay, and the Canada jay.
Ravens and magpies had an expanded range during the Pleistocene because they exploited megafauna carrion. Both have been found as fossils in Georgia and Alabama.
The Canada jays present day habitat was under miles of glacial ice during the Ice Age. Its range necessarily was depressed south. Fossils of Canada jays were excavated from a cave in middle Tennessee, much farther south than where they live today, and I assume they ranged into north Georgia during the last glacial maximum.
Florida scrub jays have a discontinous range--they live in central Florida and in the far west. At some time during the Pleistocene, these two populations would've had to have been connected. This probably occurred during a dry climate cycle when scrubby prairie habitat was more widespread than today.
For my blog entry I scanned a couple of illustrations of jays and crows from my favorite bird book--The Natural History of Birds of eastern North America by Edward Forbush. The book was written in the early twentieth century and has wonderful descriptions or rural settings, such as overgrown fruit orchards, that have long since been swallowed up by suburban sprawl.
*****************************************************
http://markgelbart.wordpress.com/
http://stores.lulu.com/GeorgiaBeforePeople
