......and right on time. Our hummingbirds arrive every year on March 10th. We could set our watch by that very fact. We have a feeder right outside our living room window and it's been in the same spot for many years. Last Wednesday, March 9th, I brought the feeder inside, cleaned and sterilized it, and filled it with nectar, (just a mixture of sugar and water that I boil for a few minutes to prevent fermentation). After letting it cool I placed it on the shepard's hook where it belongs. The next afternoon my husband came and tapped me on the shoulder and told me our little friends had arrived, right on time. How do they know?