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Development of Bald Eagle Etiquette for the Chehalis Flats Harrison Mills.

Chehalis River + Eagle Point


Prepared for the ‘coalition of the concerned’ – The Chehalis Flats Protection Group!      Nov. 20, 2012

By  David Hancock,     Bald Eagle Biologist,    Hancock Wildlife Foundation.


Background of Chehalis Flats Bald Eagle Concerns: 

The Fraser Valley Bald Eagle Festival has promoted the presence of bald eagles in the Harrison Mills area for nearly 20 years.  Most recently David Hancock reviewed various bald eagle winter concentration areas in British Columbia and Alaska.  The historic evidence clearly shows that over time many different areas hold varying numbers of wintering eagles.  The region’s largest concentrations have regularly been at the Chilkat River in Alaska and the Squamish River system near Brackendale, BC.  More recently the Chehalis – Harrison River complex in Harrison Mills has wintered the largest concentrations ever known.


The reasons for these huge gatherings of eagles are largely two-fold:  weather conditions up north and salmon availability for the eagles throughout the area.  The food availability locally is driven by the incredible productivity of the Harrison River system salmon runs.  Historically we have seen that just having lots of spawned out carcasses does in itself not bring record numbers of eagles.  Normally the wintering eagles are dispersed all along the northwest coastal salmon rivers, feasting on the carcasses until they are eaten out or frozen under the ice.   On top of the influence of weather conditions is the prime numbers of salmon actually returning to the different rivers each season.  Fewer spawned-out salmon in the northern rivers simply means, regardless of impacting weather, that less poundage of salmon are there to feed eagles – or bears, gulls, wolves etc.

The past 15 years of gradual build-up in numbers of wintering eagles at Harrison Mills seem to be related to the general loss of spawning salmon in northern rivers – and of course due to the increasing eagle population.  Then in 2010 we had a world record for a gathering of eagles.  I counted individually 7362 eagles in a 3 kilometer section of the Chehalis Flats and probably several thousand more existed in the trees, soaring and spread southward to Harrison Bay.  This is almost twice the size of any earlier recorded gathering anywhere.  The point I wish to make here is that I suspect our big numbers of eagles here were the result of the collapse of most of the northern runs of chum salmon in the  fall of 2010 – from here northward throughout SE Alaska.  We were simply at the southern end of their potential migration -- dispersal arriHarr


pattern.  With fewer salmon carcasses to the north the eagles kept coming south.  We greeted them with our excellent Coho run. 

The 2010 build-up of eagles from early November through mid-December lasted until the Coho and small chum salmon runs were eaten out.  A week later, with the carcasses eaten up, the eagles left.

The importance of the fish and the Chehalis Flats alluvial fan are increasingly important to bald eagles.  The flats are the southern most of the large salmon spawning areas and not just offer one of the last great feasting areas for the eagles before nesting but an important resting and socializing place for the eagles to build up reserves for winter.  As might be expected the Harrison Mills area also hosts the world’s largest known night roost:  the cirque of hills and ancient lowland forest of cedar and Douglas fir surrounding Echo Lake, one kilometer west of the Chehalis Flats.  Each night and morning the eagles can be seen entering and leaving this ancient roost site.

The Chehalis Flats cut with the channels for spawning salmon, the surrounding shorelines of cottonwoods, the hills along both sides of the Harrison Valley from Mt. Woodside on the east to the Echo Lake cirque and night roost to the west, constitute one of the world’s greatest bald eagle habitats known. 

The Big Concern:   The incredible gathering of bald eagles during each fall and winter need not just food.  They need peace and quiet and rest.  A bioenergetics study done 20 years ago showed that bald eagles cannot sustain their body weight, no matter how much they eat in a day, if they have to undertake wing-flapping flight for more than 28 minutes a day.  They can soar almost effortlessly for many hours, in fact soar and glide for hundreds of miles a day.  But the challenge for this large scavenger – predator is to eat and rest.  The flats are the great feeding and resting grounds for the eagles.  We need to not disturb them on these flats.

The purpose of the note to the proposed ‘gathering of the concerned’ is to initiate some program to reduce human disturbance to the feeding and loafing eagles out on the flats.  From the eagles’ perspective, I see no problem at all with boat, kayak or fisherman traffic along the Harrison River main channel or humans walking along the commercial developments bordering the west shoreline.  These areas have large trees to let the eagles sit securely well above the passing humans below.

I have to admit that the “disturbance concerns” have been talked about for some years by Kathy S and Tom C.  However, until I saw, via our live streaming cams that show the eagles and the constant human access to the flats and the repeated disturbance to these feeding and loafing eagles, I was not as fully aware of the problem. Our camera moderators have created a file of these disturbances should they be needed.  These cams could also serve in the future to not just be an educational tool for the benefit of eagles, but as surveillance and monitoring tools for violations.

The disturbances are caused by many kinds of intruders but the most frequent and disruptive are the kayakers.  Some have even posted blogs that say how they got away from jet boaters by accessing the flats to flush the eagles for good close-up photos of the flying birds!  Indeed!  On one day, when the water was a little higher, we had Sea-Doos, helicopters, jet boats and punting hunters out on the flats. Dog walkers, cameramen with long conspicuous lens and fisherman add to the constant invasion of these eagle feeding and resting areas.

If may well be that a campaign that targets the outdoor sports clubs, the fishermen and hunters and the camera buffs, supplemented by posters at each launch or water access site would go a long way to solving this issue.  Some stronger words in access regulations may be needed or considered.

David Hancock,   Eagle Biologist

Hancock Wildlife Foundation, Director Fraser Valley Bald Eagle Festival.


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