A Trackpack is basically a backpack placed on your bird where you can mount a transmitter. You never have to take it off, and its nearly invisible because the bird preens it into its feathers.
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With the leg mount.. it can get in the way of those feet, With the tail mount, you run the risk of your bird getting caught in somthing and pulling out a deckfeather.
As far as I know, the only drawback to using the backpack, is its heavier, and reduces mobility.
However, the weight is distributed evenly to the back and I dont see it being any diffrent then wearing anklets,jesses,chaps etc..
It isnt a hinderance at all, i know a lot of ppl that use it on merlins with no ill effect at all. My dad has had one on his merlin since trapping and it ignored it after a day. You have to be able to put it on correctly which requires using medication in most cases. It has also been used on female sharpies and one female kestrel that i saw personally. Small female kestrels and also tiercel kestrels and sharpies have too narrow of a space in between their shoulders in flight for it to be used. Im going to use either a 1.8g or 2.3g leg mounted transmitter from holohil on my musket sharpie.www.holohil.com. They really work well from all the ppl i have talked with and in personal applications. They are saferly for large falcons because of the even distorbution of weight. A leg mounted 7g transmitter in the end of a stoop can be 40-50g because of g forces, when mounted on the back, it is just added to the birds weight. Wolf, did you check the shipping prices as well. I know northwoods has a shipping chart based on the $amount instead of weight(stupid). It might be cheaper from marshal with shipping.