Previous research has demonstrated the southern yellow bat (Lasiurus ega) to roost in the dead fronds of native palms (Sabal mexicana) and non-native palms (Washingtonia robusta). Roost use by the northern yellow bat (L. intermedius) is similar, with the addition of Spanish moss (Tillandsia spp.). Quantitative assessments of these roosting substrates, however, are lacking. My objective was to identify and quantitatively characterize the diurnal roosts of L. ega and L. intermedius in the Lower Rio Grande Valley of Texas. Through radio-telemetry from May – November of 2015, I located a total of 20 roosts in S. mexicana palms used by 8 yellow bats. Comparison of characteristics between roosts and randomly selected palms showed that yellow bats selected sabal palms with significantly taller, thicker frond skirts and smaller trunk diameters. A predictability model was subsequently constructed to aid in the management of roosting habitat for these species of yellow bats.