Watch for the first arriving monarch butterflies. They are following the development of milkweeds on which they lay their eggs.

Woodland wildflowers such as large-flowered trillium, columbine, jack-in-the-pulpit, and wood anemone abound. Black-capped chickadee young are fledging. The big warbler migration is on: Birders in such places as Frontenac State Park and the Cannon River area can see and hear close to 22 species of these tiny songsters into June. It's possible to observe up to 32 warbler species for the birder who has time to make several trips around the state.

An experienced birder can identify each 5-inch warbler by sight and sound. Each has its own unique song and patterns of color, plus females look different from males.

One animal is quite now and once you learn its call you will hear them across most of the state. They feed on insects and other small wildlife, such as slugs, spiders, and centipedes. "They" are the American toad.

Soon after emerging from their underground hibernating spots, male American toads head for grassy ponds for breeding. When that water is reached in April or early May, they begin their mating trilled calls. Each trill is high-pitched, has a whistle quality, and continues on the same note for about 20 seconds. The call is so unique that it is worth obtaining a recording of it or finding someone to teach it to you.

The sound is made when the throat is puffed out, almost globular, but the actual sound is made by the air drawn in at the nostrils and passed back and forth from the lungs to the mouth over the vocal cords, the puffed-out throat acting as a resonator.

Females begin arriving at the breeding ponds a few days after the males and lay long strands of eggs, which are then fertilized by the males.

Contrary to popular superstition, you don't get warts on your hands by picking up a toad, but you will learn something about this remarkable amphibian. It feels cold to the hand because it is a cold blooded animal, which means an animal with blood the temperature of its surroundings.

Jim Gilbert taught and worked as a naturalist for 50 years.