Dusky wood swallow -Artamus cyanopterus

It is apearantly classed as a common bird but it is the first time I see them,and only because this immature bird hit our house window and suffered from a temporary concussion . This gave me time to take some shots befor it recovered and went on its way. Then I noticed that our entire lawn area had maybe more then a 100 wood swallows searching for insects.
From several species of wood swallows this is the only one which displays a white streak along the leading edge of the wings . The beak is bluish with black at the tip.The chest feathers were a mousy brown which is the typical coloration of immature birds. So it was easy for me to identify this species.