Inconspicuous and rarely seen bird of rainforest canopy. Small and slender with a long tail; mostly dark gray with a broken white eyering, white belly, and white outer tail feathers. Inhabits canopy of tall forest, especially in regions with sandy soils, and also occurs in shorter-stature forests on white sand. Usually seen with mixed-species flocks as it forages actively in outer foliage, sallying for insects and gleaning from leaves, moving long tail from side to side, like other gnatcatchers. Thin and indistinct call notes are easily overlooked among calls of other species in flocks, but distinctive shape, active behavior, and long tail with much white should clinch identification. Distinguished from Tropical Gnatcatcher by uniform gray body plumage and lack of a black cap.