Spotlight on Zoo Science
June 19, 2007

Seeing Green: A Suspicious Sign of Climate Change

Seeing green jays where they shouldn’t have been inspired National Zoo scientist John Rappole to begin a study of how climate change may be altering the avifauna of Texas.

Some scientific findings emerge only after years of dogged effort; others pop up as if by accident, taking scientists by surprise—and opening up new lines of inquiry. Take one Zoo scientist’s recent experience.

In February, ecologist and ornithologist John Rappole started a six-month sabbatical to write a book on Texas wildlife for the University of Texas Press. The book is to focus on vertebrates—mammals, birds, reptiles, and amphibians. As a bird specialist and co-author of the 1994 Birds of Texas, Rappole figured writing about the birds would be the easiest part of the project.

Rappole’s sabbatical home is at the Welder Wildlife Foundation, a 7,800-acre wildlife refuge in the Coastal Bend region of Texas. Soon after he arrived in south Texas, he set up a bird feeder so he could watch his favorite wildlife while working.

green jay

Green jays are about the size of blue jays and enjoy a diet of insects, spiders, small vertebrates, seeds, and fruits. (Photo here and above left by Bill Draker.)

To his surprise, among the first avian visitors were green jays (Cyanocorax yncas)—a species that shouldn’t have been there at all! The northern end of this subtropical bird's range is supposed to be—once was—60 miles south of Welder, near the town of Kingsville, Texas.

Professional and amateur ornithologists have thoroughly documented Texas’s bird life, says Rappole, so, "Until I saw the green jays, I thought no new research would be needed. But it turns out that's not the case at all.” Texas green jays do not migrate and studies show they are remarkably sedentary, so this observation caused him to rethink his book project.

Distribution of green jays in North and South America.
Green jays have an interesting disjunct distribution. They range from south Texas to the coasts of Mexico and into Honduras and then aren’t found again until northern South America. It’s possible the jays in South America are a separate species but these birds have not been well studied in any part of their range.

great kiskadee
buff-breasted hummingbird
The great kiskadee (Pitangus sulphuratus), top, and the buff-bellied hummingbird (Amazilia yucatensis), below, are among about 80 species whose range may be expanding. (U.S. Geological Survey/Photos by Chan Robbins.)

Talking to bird watchers about his find, Rappole heard that perhaps 80 species of birds native to south Texas and northeastern Mexico, including, in addition to the green jay, such species as the great kiskadee, buff-bellied hummingbird, white-tipped dove, and tropical parula, may have moved north or east within the last 30 years. Rappole hopes to confirm that these species are truly resident by finding nests and young beyond these species’ former known range.

Rappole suspects that these range shifts are due to climate change. Climatologists have reported a warming and drying trend across the region over the past 30 years, although just how these changes might be affecting bird ranges is unknown. "That's something else that will take a little research to find out," says Rappole.

Discovering whether some mammals, reptiles, or amphibians have similarly changed their ranges in Texas will be an even bigger challenge.


Rappole, John H. and  Gene W. Blacklock. 1994. Birds of Texas: A Field Guide (The W.L. Moody, Jr., Natural History, No. 14). Texas A&M University Press.

John Rappole’s latest book is Wildlife of the Mid-Atlantic: A Complete Reference Manual. 2007. University of Pennsylvania Press.

Related Information

external linkGreen Jay Species Account

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