The diet of the Vulnerable Yellow-bellied Glider (Petaurus australis unnamed subspecies) in north Queensland includes sap obtained from Eucalyptus resinifera (Small-fruited Red Mahogany), this being a critical resource obtained from a small percentage of trees. Past logging might have depleted resources for the gliders. In the Sawmill Gully area of Tumoulin Forest Reserve, an area temporarily reserved for the gliders, we show that most E. resinifera are less than 70 cm in diameter. Smaller size classes are all well-represented including saplings, but very few trees are greater than 1 m in diameter, suggesting that the forest is recovering from logging. Thirty-two glider sap-trees in the area had a mean diameter of 60.4 cm with a strong preference by gliders, relative to availability, for trees more than 60 cm in diameter. Recruitment of more E. resinifera to larger size classes may increase options for gliders, but more logging may deplete them.