from what I can see of the bark and the leaf shape I think it is a species of Prunus, probably a cherry. If you upload some more detail photos of leaves, bark and any fruit I might be able to get closer to species.
I concur with Jen for now.
...and failing photos, a description of the flowers / ftuit (maybe last year's fruit in the vegetative litter under the tree) / bark / anything unusual (eg. scented buds).
Please could you also check the leaves for a pair of tiny possibly red glands near where the blade meets the stalk.
Cherry it is.
Good call Jen.
Keep an eye out for flowers in the spring (pink or white). If they are 'double', ie. composed of a much larger number of petals than normal, chances are they won't set fruit - hence your not noticing them.
(From what I can see, the tree should be old enough to flower.)