Great little dogs, Dave.  I've had a couple of JRTs over the years and most recently a pair of littermate rat terrier/beagle mixes, Bonnie and Clyde.  I haven't encouraged them on birds as I have a pointer for that, but they are great squirrel dogs and will take on just about anything as shown below. 
 
Fred
		 
		
		
		
			
		
		
		
		
		
		
		
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