It’s May and the great caterpillar factories of eastern North America are in full production. You’ll hear their engines humming as they munch away in woodlots or mature trees. For songbirds, this is a sign the bounty that fuels the mating, nest-building and parenting is going on right now in our backyards. Join science writer and College Park resident Rick Borchelt for a look at some of the common birds that depend on these caterpillar factories in suburban landscapes. (Carolina chickadee photo courtesy Chesapeake Bay Program)