My Wild Goose Chase

Vertical Aerial Photography and Computer Analysis to Determine Aleutian Geese Population

Endangered Species Success Story

The Aleutian cackling goose, formerly known as the Aleutian Canada goose, was one of the first on the new Endangered Species List in the 1970’s with less than 500 birds. Today, population estimates are over 40,000. Geese typically roost offshore of Crescent City, CA and near Eureka, CA on the southern end of Humboldt Bay. During the day, they fly to surrounding fields and pasture land, feeding and fattening up for the long trip north to the Aleutian Islands in early spring.

The Humboldt Bay National Wildlife Refuge Complex contracted me to conduct an aerial photographic survey of the geese. Refuge Manager, Eric Nelson, and I designed a feasibility test to determine methods that would give a simple yet accurate way of counting the Aleutian Geese population with vertical aerial photographs.

The US Coast Guard, as a co-operative federal agency, flew us north in an HH65A helicopter using my vertical camera mount that has been used for thousands of other photographs with the Coast Guard, mostly for mapping surveys. We had planned to fly a prescribed set of transects over Tolowa Dunes State Park where geese typically would feed (see map diagram). As with many plans, methods were changed and improvised once over the flocks.

Initial plans called for three overlapping flight lines to take vertical photographs of geese flocks. However, it worked out better for testing to try different altitudes and just photograph a selected flock on the ground.

Geese from 1400’ are just visible with the naked eye. The red box represents the enlargement in the next images

Geese are recognizable by shape and color with shadows helping to differentiate from brown patches on the ground

The computer operator/photo interpreter “paints” dots over the geese in the enlarged area

By displaying just the dots in a software layer, geese can later be counted manually. Eventually, computer recognition software could be capable of marking the geese.

At initial altitude of 1500 feet we couldn’t see any flocks, except some that were flying in response to the first appearance of the helicopter. Dropping down to 800’, individual birds were easy to spot. However, it would take several photos to cover large flocks on the ground. Climbing to higher altitudes, the geese became accustomed to us, and our eyes became accustomed to the visual signature of far-away Aleutian Geese. At 1400’ we could now identify geese on the ground and the geese recognized that we meant them no harm.

Test Photo Shows Feasibility of Counting with Vertical Photos

One photograph was selected for testing methods to count geese on the computer. Images from the Hasselblad aerial camera have a size of 56 x 56 mm (about 2.25 inches on a side), producing a 120-megabyte digital photo file. The first photo shows the whole image, and captions below the others describe how the count was done.

Future Geese Counts Could Use Vertical Aerial Photography

This initial photographic test may be useful again when the Aleutian Geese return for the summer. Farmers and ranchers are increasingly concerned with the damage being done to property from the vast flocks of birds feeding on crops and dairy pastures. Accurate bird population counts will contribute to good management of wildlife along with local concerns. By using high-resolution aerial imagery, counts could be done quickly and accurately using both photography and computer image recognition methods.

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