제비 nest with three baby birds

I found this 제비 nest near a bus stop. I only happened to look up because there were many white-colored droplets in one spot. Their mother and father showed up later, and they were doing evasive maneuvers, not going directly to the nest. Only when I looked the other way around saw these birds delivering food to baby birds. I looked it up on the internet for the two pictures below. I remember seeing them when I was a kid visiting my grandparents house. They usually make nests under the roof. They are migratory birds and fly to warmer places when winter arrives.