We still find them interesting today. The monarch butterflies are special. They are three to four inches long. They are found in the United States and in a part of Canada. They migrate in colonies.
Birds avoid monarchs because the caterpillars are born on milkweed plants.
The caterpillars eat the milkweed which is poisonous to the birds. There is another butterfly that copies the monarch, but does not eat milkweed plants. The birds still avoid the Viceroy butterfly just because it looks like a monarch. Some scientists think monarchs moved more north as the milkweed plant moved north. Monarchs can not be in cold weather.