As I walked out of my apartment this morning I noticed two geese standing on the rooftop of the building across the street; each one on opposite corners, as guarding soldiers, protecting their territory. These birds migrate every winter, and yet, they always come back with a sense of pride and confidence, as if their recent trip has made them more secure, and confident in themselves.

And so, I asked myself, why do these birds migrate south every year? I always thought I knew the answer, until I decided to do a bit of research.

It turns out those migratory birds in North America trace back to ancestors that lived in the tropics. Over time, these birds expanded their ranges until a small proportion eventually made it to North America. So the question I should ask myself is why do they fly north for the summer?

Believe it or not, this question is paramount to me, at this point in my life, because migration carries a very deep cost, for both birds and humans. It’s easy to discount the effort required to fly to and from the tropics, given the convenience of modern air travel, but the journey for these birds takes a huge amounts of time and energy, as well as exposing the bird to unfamiliar environments and predators. The time, energy, and risk involved in migration have severe impacts.

Did you know that migratory birds are twice as likely to die in any given year, compared to tropical non-migration birds? So why do they do it? The answer, if you think about it, is very simple: The benefits outweigh the costs. Since relatively few birds come to North America, migrants have easy access to plentiful insects, plants, and nesting grounds. With plentiful food and territory, migratory birds produce many more offspring each summer than their non-migratory counterparts.

In general, migratory birds do not live as long as non-migratory tropical birds but produce more offspring each year. So, the birds that graced me this morning with their “at attention” posture do so for extra payoffs, but at enormous cost.

This is why they can stand so poised, in the early morning hours, looking down with pride, because unlike many of us, they are not afraid to take these types of risks, because they know that in the end is not about how long you live, but how well you live.