These are young River Birches (Betula nigra). They get to be 50+ feet tall fairly quickly, have a beautiful multi-trunk form and peeling light brown bark. They do take quite a bit more water than many other trees, and must not be planted near sewer lines due to greedy roots. These trees are much larger now, and lightly shade the patio in the afternoon.

Now, I do recognize it as a Birch tree with dappled sun shade. Yes, it is thirsty tree--a problem in our area. Thank you also for your warning about its root system.