How strong are my two ten foot poles?
My estimate from the information given so far is that the nearly 18 foot high pole is not adequately anchored just by embedding the end of it in smallish block of concrete and a couple of U-bolts into a plank at ground level. (The block and u-bolt locations are smallish when you consider the overall pole lever arm length).

This thing should have a set of three guy wires coming down from about the 13 or 14 foot level that come down at angles to the ground and are anchored to their own piers of concrete in the ground. The bottom end of the guys would want to be out 13 to 17 feet from the bottom of the pole and spaced radially around the pole at 120 degree spacing. 

This procedure will ensure that a high force wind will not take down your bat house and crash it upon someone or some other property.