It isn't just people that congregate at my church. The lawn between the building and parking lot attracts Canada geese. For those of you unfamiliar with the species, or who are blessed to live in a region beyond their imperial ambitions, allow me to explain. Canada geese are evil.

They swoop in like alien invaders and occupy a community's grassy areas, especially golf courses, parks, and playing fields. At first their presence is viewed as benign, particularly as their little goslings add a storybook charm to the scene.

But these are not graceful swans or timid ducks. Draw too near and the birds extend their wings, lower their heads, and release an unholy hiss like a fell beast of Mordor. If the warning is unheeded, they will charge and attack with astonishing speed—something I witnessed firsthand in high school as a friend on rollerblades nearly lost his ear to a rogue goose. With their lifeless black eyes and taste for blood, Canada geese are the Great Whites of suburbia.

Why are they attracted to my church? I cannot say for certain. But the presence of these demon birds (I'm convinced they were the inspiration for Alfred Hitchcock's film) illustrates something about the spiritual enemy we contend with.

Like the unseen "powers and authorities" the apostle Paul says we strive against (Eph. 6:12), the geese are not always visible on Sunday mornings. But their presence is still felt by all as we dodge their copious droppings on the sidewalk.

Every week as we prepare to exit our minivan, my four-year-old daughter pauses and reminds us of the danger: "We're going to church. Watch out for poop." Indeed, I think to myself.

In many church communities, mine included, talk about spiritual powers is uncommon. Some have dismissed it as residue of an antiquated worldview, like believing the sun orbits the earth. Others avoid the topic because it may be uncomfortable for newcomers or associated with unflattering portrayals of Christianity in popular culture. For many reasons we may deny the role of evil spirits, and we may not acknowledge their opposition in our work. But like the geese at my church, even when they're unseen, we cannot deny the evidence of their presence.

Like the minefield of poop that is our church parking lot, our communities are littered with the debris left by destructive spiritual forces: domestic violence, addiction, pornography, injustice, racism, materialism, dishonesty, and abuse. If your community is soiled by any of these (and how could it not be?), you are engaged in a spiritual battle with unseen forces.

[To read the rest of this column, which first appeared in Leadership Journal, click here.