We heard frogs a lot in spring. A trio began calling as soon as the ice went out. Two tiny ones - chorus frogs and spring peepers - woke from a hibernation to quickly find open water and begin their calls.

These two diminutive frogs were joined by a slightly larger wood frog that added its "gluck-gluck" sounds to the early spring days and nights. These three set the pace for the breeding of local anurans. ("Anurans" is the term for both frogs and toads. It essentially means "amphibians with no tail.")

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A few weeks later, in about mid-May, we heard the next phase of the breeding season as the trill of toads with the "snoring" calls of leopard frogs. These were mixed with the high-pitch buzzer noise of gray tree frogs. Despite their lives on land, they all go to the water of vernal ponds to court and lay eggs.

Of these spring six, all but leopard frogs winter on land. Gray tree frogs continue to call while the other spring singers fade. It is not unusual to hear these tree frogs throughout June.

Last of our northern frogs to breed are the two summer singers: mink and green frogs. Both breed in larger bodies of water and during summer nights at lakes, we continue to hear the "knock-knock" of mink frogs and the "plunk" of green frogs. Their young will live over winter beneath the ice of lakes where the adults also spend the cold season.

The young of early breeding frogs have a different story. Eggs hatch quickly in spring and during the next several weeks, tadpoles develop to emerge from their aquatic youth in July. In late summer, when we think the frog season has passed, we might see the young hopping in woods, gardens and yards. But we now get an encore from the gray tree frogs.

Gray tree frogs are the only true tree frogs that live in the Northland. Though called gray tree frogs, they will often appear to be green in late summer.

Not only are they our singular true tree frog, they are the only ones that readily change colors. Patterns do not alter greatly, but they can be gray or green. I have noted that it seems to depend where they happen to be. When on bark, they are gray; on leaves, they are green. While picking blackberries, I have come across green ones sitting on leaves.

The young have developed in their wetland youth and emerged on land. Now they spread out seeking food and home sites. Apparently, the older ones need to tell the youth that some places are taken and so they call at this time.

These late summer days may be devoid of bird songs, but a few insects and these gray tree frogs call from the trees. Besides hearing their calls now, we may have another contact with these tree frogs. In their desire to find a place to feed, they climb up plants.

To many, our houses look like strange-looking trees and so they go up to find insect meals. From the point of view of the gray tree frogs, houses are good hiding and hunting sites. With the earlier sunsets now, we are more likely to be in the house after dusk. Our lights attract insects to the windows and the insect-eating frogs move in for meals.

We'll continue to see and hear this encore from gray tree frogs for a few more weeks until the chill and frost of September.