Do English Springer Spaniels have strong chasing instincts?

YES. springers are made to hunt, and that's what they do. i have a 1 year old female and every time she goes outside she's on a trail. if she sees a cat or a squirrel or something she bolts.....as long as it moves, a springer will chase it. we have a neighborhood rabbit that hangs around in our yard and our dog chases it every time she's outside. we started taking her out on a leash and have her trained to sit and stay when she sees it, but she wants to chase it so bad that she literally shakes looking at it. and springers are smart, so if they see a cat in your neighborhood, they remember it's there and start looking for it every time they go out. springers are bred to track and chase....it's just in their instincts.