According to Robert Krulwich's blog on NPR, a small bird called the bar-tailed godwit grows up in northern Alaska, but every fall they fly nearly 7,000 miles to New Zealand. When the young birds mature and start to migrate, something wired in them also directs them to New Zealand. Though they are land birds, and cannot fish or rest on the sea, they will cross most of the Pacific Ocean, and fly all the way to New Zealand. Many of them are young, and have never done this before. How they do that, many of them never having been in the southern hemisphere, never having seen the southern stars, nobody seems to know. But they manage. One female, dubbed E7, because that was the code on her wireless transmitter, flew 11,680 kilometers (7,369 miles) in 8.1 days. Non-stop. The same homing signal that guides them over treacherous waters to New Zealand also navigates them back to their parents.

Similarly, humans also have "homing signals" for God and eternity. He has put eternity in our hearts.