Habitat and Host Tree Selection by Wintering Yellow-bellied Sapsuckers in East Texas

Abstract

Yellow-bellied Sapsucker (Sphyrapicus varius) foraging ecology has long been a focus of study, primarily due to their sap-foraging behavior throughout the year and speculation on how sapsuckers subsist by foraging on dormant host trees during winter. Wintering sapsucker habitat use as related to host tree selection is not clearly defined, particularly in the southwestern portion of its range. We studied Yellow-bellied Sapsucker habitat use and host tree selection in two bottomland hardwood forest sites in eastern Texas during winters, 2005–2006 and 2006–2007. Habitat surrounding overcup oak (Quercus lyrata) host trees was generally characterized by fewer trees/ha, lower species diversity and richness, and taller trees than random plots. Overcup oak host trees tended to be healthier than overcup oak non-host trees, but host trees had thinner, less complex bark than non-host trees, irrespective of tree size and health. Also, digestible cell and protein content was similar between host and non-host trees, irrespective of tree size and health. Selection of host trees with thinner, less complex bark suggest sapsuckers use visual cues to focus host selection upon bark morphology and evidence of previous use. Combined, wintering sapsuckers may increase foraging efficiency and maximize caloric intake by increasing energy gained/unit time foraging on already established, and presumably productive host trees. Despite similarities in habitat, health and cell and protein content between host and non-host trees, Yellow-bellied Sapsuckers selected healthy host trees with thin, less complex bark where stable levels of digestible cell content and protein over time provide a reliable, consistent food source throughout winter.