Like birds , troodontids and dromaeosaurids did not retain small size throughout their evolutionary history , and had several separate size increases among different lineages .
They had several separate size increases among different lineages .
A 2005 study by Sankar Chatterjee suggested that the wings of Microraptor functioned like a split-level `` biplane '' , and that it likely employed a style of gliding , in which it would launch from a perch and swoop downward in a ` U ' shaped curve , then lift again to land on another tree , with the tail and hind wings helping to control its position and speed .