Just remember that impact force goes up with the square of speed and that the certification standard is for a "single 4 lb bird" and the aircraft will be able to "continue for a safe landing". Add to this that above 1,000 ft. AGL you are most likely to be hitting larger birds such as raptors and waterfowl and you have a recipe for a disaster. Oh, and the last point is that with only tw exceptions all the large bird populations (greater than 4 lbs) are increasing in both numbers and average weight. Also be aware that many of these birds are not migrating long distances as they have done in the past and staying resident.
It is not safe to operate above 250 knots below 10,000 feet. If you do, you are rolling the dice.