I also heard these birds calling while in the park.
two seen digging at Black Locust trees in the front yard
Dryocopus is a genus of large powerful woodpeckers, typically 35–45 cm in length. It has representatives in North and South America, Europe, and Asia; some South American species are endangered. It was believed to be closely related to the American genus Campephilus, but it is part of an entirely different lineage of woodpeckers altogether (Benz et al., 2006)