One of these foods is the sap that wells up in active sapsucker holes. Although yellow-bellied sapsuckers excavate these shall reservoirs to provide food for themselves, a variety of critters such as other birds, squirrels, butterflies and even hummingbirds dine on the sugary sap found their excavations. Since the shrub also produces pollen, they attract the some of the few pollinators that also dine on pollen during the winter.