Fig. (2) Venous partial pressure of oxygen (pO₂) from different ages of Titmice (Baeolophus spp.) both east (open squares) and west (filled squares) of the Balcones Escarpment and with and without administration of Midazolam. Juvenile titmice had lower pO₂ values after administration of midazolam (p = 0.01), based on an interaction of midazolam and age (p = 0.01, adj R²= 0.23).