NATURE, START YOUR ENGINES

by Whit Gibbons

March 13, 2016

As we hover around the spring equinox, get ready to experience the full joy of our natural heritage. As my son says, "Nature, start your engines."

A recent trip to our woods and stream gave clear evidence of the upcoming transition to be seen over the several weeks of spring, with its fickleness of whether to be cold, warm, rainy or windy.

This particular day was on the cool side as we explored the landscape looking for whatever we could find of interest. Surprisingly, considering the temperature, we found two small, sluggish harmless snakes and a few lizards under boards we had set out for just that reason - to find snakes and lizards.

Most reptiles remain inactive during cool weather except on clear days when they can bask in the sun. But warm-blooded mammals and birds can be active during cold weather, and reproduction often starts in winter or early spring.

One advantage for smaller species is to get ahead of the inexorable advent of warm weather, when predatory reptiles emerge from cold weather dormancy.

Later that day, my grandson Parker decided he would climb up and check the wood duck boxes along the creek. These large boxes are nailed to trees facing the water and have a large circular opening so that ducks can enter, lay eggs, and incubate them to hatching. A hinged door on the side can be opened for a look inside.

The first two boxes led to high fives, because one had 10 wood duck eggs and the other had 17! The third box had its own surprise. A gray squirrel jumped out and ran up the tree when Parker opened the door. After feeling around inside he came out with the second surprise - two eyes-still-shut baby squirrels.

Because a warm spell was on the way, and we often find large ratsnakes (which eat duck eggs) in the boxes, I wondered about this cycle of life phenomenon, the dynamics of the arms race between wood ducks and ratsnakes. To get a science-based answer, I got in touch with Bobby Kennamer, a friend and colleague at the University of Georgia's Savannah River Ecology Lab.

I have described Bobby before as having conducted the most impressive long-term ecological studies on ratsnakes and wood ducks ever published in the scientific literature. His field credentials include capturing wood ducks for more than 35 years and counting nearly 50,000 eggs.

According to Bobby, a wood duck hen lays about an egg a day, for about 12 to 14 days. He noted that the box with 17 eggs is "almost certainly the work of more than one female," whose eggs will be incubated unknowingly by the first occupant of the nest.

Egg incubation does not begin until a female lays almost all of her eggs, at which point she sits on the eggs at night. Bobby said, "When the clutch is complete, full incubation is initiated during both day and night," with the female taking morning and evening feeding recesses.

Once rat snakes enter the spring-time scene, they patrol woods, swamps and streams searching for open tree cavities that might have nesting birds or squirrels.

A duck box with a big hole is a well-defined lure for a big ratsnake, which can eat as many as ten eggs. The hen will fly away, but the snake may stay in the nest box for up to several days while it digests the eggs.

Once the female wood duck figures out that a ratsnake predator has invaded, "she will generally abandon the nest, even though there may still be uneaten eggs remaining in the box."

Nature's race is underway, with squirrels and ducks in the starting lineup, but as soon as warm weather sets in, the snakes won't be far behind, looking for their first meals. Nature's race track is a lot longer than any of NASCAR's and a race for us to marvel at as spectators for many weeks.

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