When you leave on a long car trip, you like to be sure there will be food along the way. Will restaurants will be open when you' re hungry?

You might say that migratory species need to count on the same thing. Scientists have long thought that hummingbirds time their migration to match the flowering plants. In other words, they follow "flower highways" that serve as nectar trails to fuel their flights. In the process of moving from one plant to another, hummingbirds are not only feeding; they are also pollinating.

Where are there flowering plants this spring? As a measure of plant growth-rates during this colder-than-normal spring watch the milkweed map. Then predict when your hummingbirds will arrive. Also, be ready with your sugar-water feeders for those early birds! Photo courtesy of Joann Ortiz.