Biology Reference Index Page


 Raptors: Biology & Conservation


General Conservation Issues


Bald Eagle Biology                           

 Life Cycle Summary


Chehalis-Harrison River Bald Eagle Congregation & Feasting Notes 


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Eagle Eggs: when and how they develop

Bald Eagle Biology

The question has come up from recent observations:  "Does egg laying immediately follow mating?"

Simply put -- No!  But of course we are dealing with live creatures so variability is expected.   As many people have now observed many of our bald eagles start to breed immediately upon their return to the nesting territory from the brief fall or winter flight north.

I have commented several times .......

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

Bald Eagle Biology

Prepared for the ‘coalition of the concerned’ – The Chehalis Flats Protection Group!     

Nov. 20, 2012    Updated Dec. 6, 2012

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

 Background of Chehalis Flats Bald Eagle & Fish Concerns: 

Fraser Valley Bald Eagle Festival for 20 years and in the past 7 years the Hancock Wildlife Foundation  have promoted the presence of bald eagles in the Harrison Mills area.  Most recently David Hancock reviewed various bald eagle winter concentration areas in British Columbia and Alaska and other North American sites.  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 to spawn 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 the next generation & Fish.


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Historic Review of North American Bald Eagle Gatherings and Numbers

Background of Counts:  In most northwest geographical areas the largest gatherings of bald eagles are associated with spawning salmon, oolachin and herring spawns and a few tidal bores, where fish are sometimes so disturbed by the fast turbulent waters that several thousand eagles occasionally gather to feast on the unorganized fish.  Over the years, due to changing river conditions and also due to public awareness, different areas can legitimately claim the seasonal, local or regional title for having the most eagles.

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The Bald Eagle Our Great Conservation Success Story.

Bald Eagle Biology

Bald Eagles are iconic.  They are big spectacular predators but prefer to be pirates and scavengers.  They are very territorial but gather by the thousands to share in and squabble over temporary and annual food surpluses like the spawned out salmon carcasses.  The bald eagle is the symbol of wildness but it has invaded our city parks and suburban areas where they can reproduce more successfully than in the wilderness.   The Bald Eagle is the American National Symbol – but most bald eagles live in and pass through Canada.  But we Canadians like to share so we invite you all to come to the World’s Greatest Bald Eagle Gathering Site – the Fraser River Bald Eagle Festival at Harrison Mills, British Columbia this fall.  Thousands of eagles will be here -- Will you? 

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World Record Number of Bald Eagles: at Harrison Mills, BC

Bald Eagle Biology

The Fraser Valley Bald Eagle Festival at Harrison Mills, at the confluence of the Chehalis and Harrison Rivers, has become the most famous and reliable place to see bald eagles in the entire world.  In December of 2010 7,362 bald eagles were counted in a small section of this area.  Over 10,000 were estimated to be in the normal Festival count area from Harrison Bay northward along the Harrison River to the Chehalis Flats.  This incredible world record aggregation of a large predator is an annual event.


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