How to Read the DuckCast Forecast

Start here: the score answers one question

The number on every region is the answer to how likely is a migration to be moving through here. It is not a count of birds on the ground, and it is not a prediction that you will shoot a limit.

That distinction decides how you use it. A high score on ground that is empty today means birds are likely to arrive. A low score where birds are already sitting does not make them leave. Most of the value is in the first case, because that is the one you cannot see from your truck.

Separately from the score, the radar check reads what was actually in the air over your region last night. That is the part that can tell the score it was wrong, and it is covered further down.

A fifth state, Freeze-Up, replaces the band entirely when local water has locked up during the season. It means the birds that were here have most likely already pushed south of you.

Which of the eight factors actually decide it

Every region page lists all eight with its own score and a sentence explaining it. The weights are fixed and public, so you can always work out why a number moved.

• 16%Cold front / temp trendforecast
• 16%Freeze north of regionmeasured
• 14%Wind direction + speedforecast
• 14%Season timingcalendar
• 12%Hunter reportsmeasured
• 10%Snow advance upstreammeasured
• 10%Local open water / holdingmixed
• 8%Crop harvest / field feedmeasured

How to tell whether new birds are actually coming

Look for three things at once. Any one of them alone is weak evidence.

1. 1

   Temperatures falling over the next 48 hours

   A front that drops the mean temperature eight degrees or more is the trigger the score reacts hardest to. A warming trend does the opposite: it settles birds in place, and the app says so in as many words.

2. 2

   A freeze or snow line advancing upstream

   This is the one most hunters skip, and it is the one that separates birds choosing to move from birds being forced to. Open the freeze line and read the upstream stations north to south. Water locking up above you is birds losing the option to stay.

3. 3

   Northwest winds building

   Migrating ducks ride a tailwind. A hard front with a northwest wind behind it carries birds a long way in one night. The same front with a south wind moves far fewer.

All three together is a push. Two of the three is worth watching. One on its own usually is not, and that is exactly the case where a score in the moderate band is telling you the truth.

Two scores, two different questions

The interesting cases are the ones where they disagree:

• High migration, low decoy. Birds are around but a flat calm bluebird morning will have them circling high and picking your spread apart. Hunt it anyway if you can hide, or wait a day.
• Low migration, high decoy. Perfect wind and a low grey ceiling with nothing to work. This is the morning to scout instead of hunt.
• Both high. Go.

Season timing gates everything else

A perfect front in September moves nothing, and the score says so. The season factor is 14% of the total on its own, and in the off-season it holds the whole number down no matter how good the weather looks. That is correct behavior rather than a broken app.

Timing is modelled per region, not per state, because within one state it can differ by two months. Missouri is the clearest example in the network: the mallard peak lands in late November in the northwest corner and holds into late January down in the Bootheel. A single statewide curve would tell a Bootheel hunter his season was finished six weeks before his best morning.

The radar check: the only part that watches birds instead of weather

Everything above infers birds from something else. The front, the wind, the freeze, the calendar, the crops: all of it is reasoning about conditions and concluding that birds probably moved. The radar check is the one place DuckCast looks at the birds, by decoding raw NEXRAD Level II volumes from the National Weather Service and measuring what was actually in the air over your region after sunset last night.

Two measurements, and it needs both

Reading reflectivity alone would call an August insect hatch a migration, which is exactly what it did before the second test existed.

1. 1

   The liftoff

   Nocturnal migrants leave the ground in a burst starting roughly half an hour after sunset. The card shows how much bird mass went up as a multiple of the pre-dark sky, so a reading of 8x means eight times as much in the air after dark as before it.

2. 2

   The airspeed

   Everything aloft drifts with the wind, but only birds add speed of their own. Subtract the wind at the altitude the birds are actually flying and what is left is how hard the targets were working. Insects come out near zero. Migrating birds run 10 to 40 mph.

What the card will tell you

The verdict is written in plain language rather than as a number, because the honest answers include several kinds of no:

• Solid or heavy bird movement. Both tests passed, with a compass heading. Birds lifted off and flew under their own power. This is the strongest single piece of evidence in the app.
• Nothing left the ground. A quiet sky. If the score was high, that disagreement matters.
• The sky filled up, but it was bugs. Plenty aloft, no real airspeed, never reached migration altitude.
• Something lifted off, unsettled. The two tests disagree, so the app says so instead of picking the answer you would rather hear.
• Rain hid the sky. Weather blocked the read. Not evidence either way.

Putting it together: choosing between two regions

This is the decision the app exists for. Rank the 90 regions by score, take the top two or three, then open each one and compare the factor breakdowns rather than the totals.

1. Prefer the region whose score is built on observed factors. Two regions both reading 8.2 are not equally good bets if one is carried by a forecast front and the other by a freeze that has already crossed its upstream stations and hunter reports flagging new birds.
2. Check last night's radar on both. If one region's sky backed its score up and the other's contradicted it, that is the most recent evidence you have and it beats everything else on the page.
3. Then read the decoy score. The better bird region with an unhuntable morning can be the worse choice, and the trip planner will show you which day inside your window is the strongest.

What the forecast cannot tell you

Worth stating plainly, because a tool that oversells itself gets trusted once.

• It works at the region level and never at the spot level. It cannot see your marsh, and by design it never collects or shows an exact location.
• It cannot see hunting pressure, whether the field you scouted got picked yesterday, or how the birds in your area have been behaving all week.
• Radar sees every bird in the air, not just ducks. Read it as evidence that a migration happened, never as a count.
• None of it replaces scouting. It narrows the search from a state to a region. You still have to find the birds inside it.

Common questions

What does the DuckCast migration score actually measure?

It measures how likely a duck migration is to be moving through a region, not how many birds are sitting there. A score of 8.5 or higher means the conditions that start and carry a migration are lined up. It is a forecast of movement, so a high score on ground that holds no birds still means birds are likely to arrive, and a low score where birds are already sitting does not make them leave.

Which factors matter most in the score?

Cold front and temperature trend and freeze north of the region are the heaviest at 16% each, followed by wind direction and speed and season timing at 14% each. Hunter reports carry 12%, snow advance upstream and local open water 10% each, and crop harvest 8%. Every one of the eight is shown on the region page with its own number, so you can see which ones are carrying a score and which are dragging it down.

What is the difference between the migration score and the decoy score?

They answer different questions. The migration score says WHERE birds are likely to be moving. The decoy score says whether tomorrow morning is actually huntable at that spot: wind in a workable band, cloud cover, precipitation, gusts and visibility. A high migration score with a low decoy score means birds are around but a bluebird sky will have them circling high and wary. A low migration score with a high decoy score means perfect conditions and nothing to work.

How do I tell whether new birds are actually coming?

Look for three things together rather than any one alone: temperatures falling over the next 48 hours, a freeze or snow line advancing across the upstream country, and northwest winds building. Any single one is weak evidence. All three at once is the push. The freeze line is the one hunters most often skip, and it is the one that tells you birds are being forced to leave rather than merely choosing to.

Does a high score mean I will shoot birds?

No, and nothing in DuckCast claims that. The score forecasts conditions, not results. It cannot see your spot, your decoy spread, your calling, how much pressure that marsh has taken, or whether the field you scouted got picked yesterday. It narrows down where to spend the day. Scouting still decides where to set up.

How does DuckCast use weather radar?

It decodes raw NEXRAD Level II volumes from the National Weather Service and reads how much bird mass lifted off after sunset, which way it tracked, and how fast it flew once the wind at flight altitude is subtracted out. Read it as a verdict on last night rather than a forecast: it tells you whether the sky backed the score up. Radar is species-blind, so it sees every bird in the air, not just ducks, and is never presented as a duck count.