Welcome to Frank's Field Notes, a semi-regular look at what’s happening across the Prairie Pothole Region during spring migration and breeding season.

Part field journal, part migration report, and part window into duck country, Delta Waterfowl Chief Scientist and President Dr. Frank Rohwer offers firsthand observations from the field on ducks, geese, weather, habitat conditions, and the annual return north.

Grebe Comparison

7/10/2026

Great photo that shows two very similar species

Title will be whatever Frank has for subject line

7/9/2026

This can just be a teaser sentence from the email Frank sends.

GPS Markers Reveal Amazing Movements

7/7/2026

We surgically implanted 30 Can hens with GPS transmitters

This Looks Bad - but I'll Always Take More Water

7/5/2026

This was a good week on the prairies. Lots of rain.

Happy 4th - Great Anniversary for a Great Country

7/4/2026

These beautiful guys have all left for northern molting areas.

A Great Mom

7/3/2026

For most prairie dabblers a clutch of 13 eggs is as good as it gets.

A ND Family of 4

7/2/2026

Trumpeter Swan numbers in Minnesota have increased dramatically; they are also expanding their breeding range out of Minnesota.

Who is most attractive?

7/1/2026

Older hens produce more kids in a season than younger females.

Good Looking in Photo or Art

6/29/2026

Duck stamps have raised over 1.3 billion for waterfowl conservation – a shining example of the North American Model of Conservation.

A Rare Anomaly

6/28/2026

This is a picture of a Canvasback nest with a runt egg next to a normal Can egg.

Got to Love Those Cute Kids

6/27/2026

Common Merganser female in Colorado.

The Good Looks are Going Fast

6/26/2026

Basic plumage males look so much like females that even professional ornithologist sometimes miss-label males in museums as females.

This Pic Makes Nest Parasitism Look Good

6/25/2026

Most parasitic eggs don’t hatch, but sometimes parasitism results in impressive broods.

An Unsolved Mystery - Ducks Wait to Molt

6/24/2026

Goose parents molt their flight feathers with their young, but ducks don’t.

Sharp-tailed grouse nest with fresh eggs

How to Estimate Incubation Stage on "Messy" Eggs

6/23/2026

Floating eggs to estimate stage is surprisingly accurate.

various birds photographed by Frank Rohwer

Great Delta Marsh Weekend

6/22/2026

The weekend at Delta Marsh allowed viewing of lots of ducks, but the diversity of other birds was also impressive.

How to Estimate the Stage of a Nest

6/22/2026

Candling means we look at the developing duckling inside the egg. This technique is decades old.a

Migration to Molt Feathers, not to Escape Cold

6/20/2026

Jim Fisher’s photo shows the lush green of the Manitoba countryside, which makes clear that this is a mid-summer movement.

Low snow winters - bad for ducks; good for pheasan...

6/19/2026

Yesterday I was the bearer of bad news about dry habitat and reduced duck numbers in North Dakota.

A Double Dose of Poor News

6/18/2026

Pilot/biologist field notes that simply describe what the federal crews saw when conducting the larger May surveys were released today (no data until August).