Yellow-bellied sapsucker (Sphyrapicus varius) habitat use, host tree selection, and time activity budgets in bottomland hardwood forests of East Texas

Yellow-bellied sapsuckers (Sphyrapicus varius) wintering in East Texas extensively use bottomland hardwood forest. Within these forests, sapsuckers select certain trees on which to construct sap wells, utilizing the high caloric value of phloem sap and consuming cambium and phloem material during sap well construction, and apparently avoid building wells on others. During winters of 2005--2006 and 2006--2007, yellow-bellied sapsucker habitat and host tree selection were examined in two bottomland hardwood forests located in the Angelina River floodplain. Habitat was measured using 0.04 ha (11.3 m radius) plots where tree species diversity (Simpson's Index), tree size, and tree density (trees/ha) were quantified around host trees, non-host trees, and random points. Habitat varied between study sites and among host, non-host and random plots within study sites (P < 0.05). Habitat surrounding host trees was generally characterized by fewer trees/ha, lower species diversity and species richness, and taller trees than random plots. However, host tree and non-host tree habitats were similar.;Morphological and physiological characteristics of host and non-host trees were measured including: total height (m), well(s) location (m) on trunks (lowest primary sap well band to highest sap well band), height to lowest limb, bark thickness, bark complexity, cell content and percent protein. Bark thickness and bark complexity varied (P < 0.001) between host and non-host trees. Furthermore, when trees were classified into DBH size classes, trees > 12 in and < 16 in DBH exhibited distinct variation in bark thickness and bark complexity that may induce selection and construction of sap well by sapsuckers regardless of tree health. This is the first study to demonstrate the importance of bark thickness and bark complexity to tree selection in yellow-bellied sapsuckers.;Behavior was quantified using time activity budgets of yellow-bellied sapsuckers. A total of 286 focal samples were recorded during the two wintering seasons. Behaviors were similar between study sites and sexes (P > 0.05), but varied (P = 0.008) between years. In general, sapsuckers behavior varied between diurnal periods and six week sampling periods. More time was spent foraging upon arrival to wintering grounds and in the morning diurnal periods. Deviation from monthly average low temperature was a significant (P = 0.038) covariate during the second study year, indicating increased time spent foraging during colder than average temperatures and increased time perching during warmer than average temperatures.;Selection of trees with thinner, less complex bark suggest sapsuckers use trees based upon morphological characteristics and evidence of previous use that may increase foraging efficiency. There have been contradictory results in other studies concerning tree health as a primary factor in host tree selection. In this study, despite differences in habitat, host tree characteristics and tree health between study sites, sapsucker host tree selection and behavior remained consistent.