Yes Mona, thats the BAD news, I'm fairly confident that there are umteen ways in which Black Swallow-wort expands its range and invades new areas. Like I said in my blog, Cynanchum seeds have a kind of thin waxy coating, this is a natural design of nature to allow the seeds to survive various weather conditions. Float temporarily on water or resist drought.It plays a role in the dormancy and thus future emergence time periods of the seedlings ie inthat nature insures they dont all germinate at once. Nobody I'm aware of has studied wether this would allow the seeds to pass thru a bird or mammal after being ingested and then deposited elsewhere and survive. But in my opionion , they key mode is wind..for example..you have a huge area of distubed soil in drainage ditches along our roads,highways and railines..every time we get a heavy rain it washes away topsoil or loam and exposes fresh ground, it also buries seeds which have floated on the wind and landed there. These areas are perfect propagation grounds for BSW.Open sunny disturbed soil with plenty of moisture.One plant can produce thousands of wind bourne seeds, all it takes is a car,truck or train to pass by and get just one or a few stuck in the grill or whatever and go for a ride to a new habitat. When the vehicle stops the seeds falls to the ground and there you go.