The Full Moon Myth: What 25,000 Hunt Days Say About Moon Phase and Duck Hunting

Updated March 2026 · Source: CDFW daily hunt check-station data, 2003–2026

Every duck hunter has an opinion about the full moon. Most of them think it kills the hunt — birds feed all night, sleep all day, and your decoys sit untouched. Twenty-two seasons of data say that's wrong. But the truth is more interesting than the myth.

Moon phase doesn't predict harvest — at all

We compared moon illumination against harvest residuals — the part of daily harvest that isn't explained by which refuge, which week, which season, or which day of the week. The correlation is effectively zero — no pattern at all.

Broken into eight lunar phases, there's no consistent pattern. Full moons, new moons, quarters — they all cluster around zero. No phase reliably produces better or worse hunting.

Ducks per hunter above/below expected, by lunar phase. Controlled for refuge, week, season, and day of week.

And it's not that we didn't have enough data to find an effect. With 25,000 hunt-days, even a tiny consistent pattern would show up clearly. If the full moon cost you even a fraction of a bird, we'd see it. We don't.

But clear-sky full moons are different

Here's where it gets interesting. When we separate full moon nights by sky conditions using ERA5 satellite cloud data, a signal emerges.

Full moon with clear sky (overnight cloud cover below 25%) produces slightly better hunting the next morning: +0.09 ducks per hunter above dark-night baselines. This effect survives Bonferroni correction — it's the strongest signal in our entire analysis.

Full moons with cloudy skies? Right at the baseline. No different from any other phase.

Ducks per hunter above/below expected, by moon phase and overnight sky conditions. Cloud data from ERA5 reanalysis (6 PM–7 AM).

The direction is the opposite of what most hunters believe. Bright nights don't hurt — they help slightly. The effect is tiny — about 11 trips per extra duck — but it's a real pattern, not a fluke.

The rice belt theory

Why would bright nights help? One plausible mechanism: on bright, clear nights, ducks fly from refuges to rice fields to feed. They spend the night in the rice, then return to the refuge at dawn — right when hunters are set up.

If this theory holds, the bright-night effect should be strongest in rice-growing regions (Sacramento Valley, San Joaquin Valley) and weaker elsewhere.

That's roughly what the data shows.

Bright night (full + clear sky) vs dark night (new moon) effect by zone. Dark green = rice-growing regions.

This is suggestive, not conclusive. It's a post-hoc exploration — we looked for this pattern after seeing the bright-night signal, which weakens the statistical claim. More work is needed to test the feeding-flight hypothesis directly.

How many trips to earn one more duck?

Even the strongest moon-related effect — clear-sky full moons — takes 11 trips to deliver one extra bird. Moon illumination as a continuous variable does nothing at all.

Why everyone "knows" the full moon is bad

The myth persists because it feels true. A slow morning after a bright night is memorable. A good morning after a bright night is attributed to something else — wind, cold front, lucky spot. And nobody's tracking their own data rigorously enough to separate signal from noise.

With 25,000 data points, we can. And the answer is: moon phase alone doesn't predict your hunt. If the moon matters at all, it matters when combined with clear skies — and even then, it's a slight positive, not the negative hunters expect.