I read that the pulse rate is 44 per minute, the same as for many other FAA approved pulsing lights on both aircraft and ground systems. Apparently the FAA feels that this rate provides the earliest recognition at the farthest distance. Some new pulsing units however have a daytime pulse rate that's twice as fast, with the 44 pulse rate still being required at night, because the 88 pulse rate is said to take longer to recognize at night.
The US Department of Agriculture is also presently conducting studies with birds to determine the effectiveness of pulsing landing lights on approaching aircraft, in shattering the birds from the aircraft's flight path. They are conducting the research on a variety of species, and are also testing a variety of pulse frequencies.
I've only read that testing is on going, as I haven't read anything about any results yet. The speculation I read suggests they might possibly recommend a different frequency to the FAA, or possibly several different frequencies depending on what bird species are prevalant at a given airport. Of course all of this depends on the results of the research.
It would be interesting to be flying an approach into your local coastal airfield, select "seagulls" on the landing light panel, and watch the seagulls perform TCAS RAs in deference to your approaching aircraft.