Weekend birding

Thomas and I attended a birding festival over the weekend, which included a guided hike with experts.  This was fantastic as we are relatively new to birding.  We learned some identification tips and were just in awe of the knowledge/experience of the group leaders.  As we were walking, our guide would stop and say something like, "I heard a Cerulean Warbler in those trees" so everyone would look and sure enough, a Cerulean Warbler would appear.  How can people know so many bird calls?

We didn't take any good pictures of the birds, but here are a couple from the surroundings:

This made us laugh -- some geese were not heeding the "no hiking beyond this point" sign:

A mallard pair were in our backyard; hopefully they will not attempt to build a nest as they would have a treacherous walk to water with their young: