a beekeeping riddle

[irerob]

[img][img]  Theres not really a practical reason to do this other than to try to figure out what happened.
I did splits about 3 weeks ago. Friday i heard a deafening roar in my apiary I heard it from almost a 1oo yards away. Thinking some thing was after the hives i ran to see a HUGE cloud of bees it looked like they may of been coming from one of the weaker splits. thinking they may be getting robbed Went to the shed to get an entrance reducer and hope for the best. When I got back I saw the nicest swarm of bees hanging about 8 feet off the ground in a nearby branch. I scooped them up and decided this would be a great time to make use of the top bar I made last year. I then checked the out side of the hives they all seemed to have normal bee traffic so my weak hive didn't abscend.
  The next day tyring to figure out how or why a weak hive would swarm and to make sure it wasn't going on in any of the other hives i did an inspection found nothing out of the ordinary in the hives other than extra empty queen cells, since i just did a split I didn't think it was out of the ordinary they were all empty some even looked like they were being taken apart.
I get into the hive that looks like it has swarmed that has a the old deep from the split and a new medium and it looks like they have rejected the medium for some reason it barley has any new wax on it at all.(plasticell) the brood chamber deep has enough bees to completely cover 9 of 10 frames at a time of day when all the foragers were out.

I have noticed no difference in the original hives behavior after the split and the new  swarm also seems to be very gentle . I mowed about 20 feet away from it yesterday and didn't even draw there attention.
Any ideas as to what happened. how can a hive swarm and be just as strong as before?
Is it possible the bees took part of a swarm in and rejected the other half? I estimate the swarm weighed between 5 and 7 pounds.
http://img203.imageshack.us/i/sam0300g.jpg/
http://img535.imageshack.us/i/sam0323v.jpg/
http://img96.imageshack.us/i/sam0327

[MacfromNS]

Are you sure they came from yours?

[AllenF]

It don't sound like they came from your hives.   Your bee's scent may have brought them in.  Have you had a swarm in that tree lately?

[Highlandsfreedom]

Yup sounds like a free swarm from elsewhare.  Congrats.

[Buz Green]

Hope you bought some lotto tix.

[Jahjude]

Yeahman that definately sounds like a swarm from elsewhere!! U one lucky beek ;)

[bailey]

either a free swarm or during the split you got the old queen in one of the splits.
did this last year and had a really packed nuc for making a new queen which they did.
the old queen stayed in the split and the virgin swarmed out.
caught and hived her with no problem.

thats the only time i have seen what you describe.
bailey

[irerob]

Thanks for all the replies I was thinking they could not of built up that fast. It never crossed my mind my bees may have attracted another swarm.