You might have purchased some hybrid plants at your garden center for planting. Hybrids are deliberately bred to take the best qualities of different species.
But sometimes this breeding occurs "naturally" and perhaps not with good results. Researchers have been studying "hybrid" chickadees. They are the offspring of northern black-capped chickadees and their southern relatives, Carolina chickadees. These two species began to mate in places where their separate ranges now overlap.
You may have learned that if you collected and planted seeds from your hybrid plants that they are infertile. The hybrid chickadees are also infertile and can't reproduce.
They are found only in a long, narrow strip of territory stretching from Kansas to New Jersey.
I first learned about this zone and the hybrid birds in a post by Michele S. Byers, Executive Director of the New Jersey Conservation Foundation.
The "hybrid zone" is a shifting line and the researchers have discovered it is a fairly accurate way of measuring the progression of global temperature changes.
The has moved north at a rate of about seven miles over the last 10 years. This matches the warming trend in winter temperatures.
In New Jersey, the hybrid zone crosses from Trenton to the Raritan Bay - the southern edge of the Piedmont region.
Hybrid chickadees can be hard to distinguish by sight, so blood samples are used. The hybrid songs are a mix of the distinctive songs of the parent species.
The hybrid chickadee can eat a wide variety of foods. If one food source disappears, they find another. But about 75% of animals and plants have little or no ability to move as the climate warms.
You might guess that all birds could easily adapt by flying to new places, but that's not the case. Rather than being "generalists", like the chickadee, many birds, butterflies and moths are "specialists," adapted over millennia to depend on specific food sources. If the food sources decline as the climate changes, populations of these species will diminish or disappear.
Changes in our climate is happening too fast for most species to adapt. Habitats also have to adapt but some sensitive habitat have plants that cannot adapt and so will simply collapse and disappear.
The hybrid chickadees may be like the "canary in a coalmine"providing an indicator and a warning of changes in the environment.