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When Do the Salmon Run?

Bald Eagle Biology

When they're chased!  When not swimming!

The Pacific Salmon spawn is highly variable, depending upon individual historic timing for a stream, the species and the geographic location.  Still not much help!

In general terms the earliest salmon runs are in the north and as the season progresses the runs are maturing and spawning farther south.  So the earliest runs occur in NW Alaska  -- some of the fish coming into the rivers as early as April and May, immediately after the rivers thaw. Then the peak spawn happens during the summer months and into the early fall.  However, by late fall in the north you are starting to get early freeze-ups, both preventing the salmon accessing the shallows and, more importantly, preventing the hatching fingerlings finding any insects upon which to feed.

So once the freeze ups start putting the dead and dying carcasses out of reach under the ice, the eagles are generally forced south.  This means that in the years of early and strong early freeze ups we get thousands more eagles forced early to our southern waters that are still open.  In most years the rivers around southern BC, and particularly our Harrison River complex, the heavy die-off is not available until late October or early November.  .. read more ..

 

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What Drives the Number of Nests in a Territory?

Bald Eagle Biology

Alternative Bald Eagle Nests - a Plethora in Some Areas - Not in Others- Why?

Here is a good Thesis topic -- but it needs a Sponsor!


In most of nature there are usually multiply reasons why some behavior or action takes place. 

Why do some eaqles  make several nests? In other active territories only one nest is ever found. Obviously some make a new nest to replace one that has been destroyed by the weather. The nest used for several years very successfully, simply rotted out and fell, partially or wholly to the ground.  In other cases the tree blew over.  In many of the urban areas the availability of strong cedar, Sitka spruce or

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Phoenix: Rising or Falling?

Bald Eagle Biology

by David Hancock

 

Quick comment on the diagnosis of Phoenix by the MOE (Ministry of Environment) avian pathologists for the British Columbia Animal Health Laboratory, Dr. Schwantje  and Dr. Vicky Bowes.

Their "preliminary findings from the necropsy performed on Phoenix. Phoenix was a female. She died from acute bilateral mycotic pneumonia."

This is sad but a very common disease of raptors and of young eagles.  Usually the problem organism is the fungus Aspergillosis.  This is a world-wide contaminant found literally everywhere that only becomes toxic when the host is under nourished or stressed.  I have seen sitting birds, in this case a ptarmigan, undergo a slight hormonal shift as the egg laying body hormones changed to incubation hormones and we believe the Aspergillosis in the bird's body took this shift as a threat and the Aspergillosis emitted a sudden toxic bloom of spores to insure it survived. Flowering is the plant's way to insure new life. The ptarmigan died within minutes still sitting on its eggs.

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Lifting Capacity of Eagles

Bald Eagle Biology

Eagles are predators but they have a very small lifting capacity.  Many times I have described our experiments and field observations on what eagles can lift. 

Generally a male can lift about 1.5 pounds and a female up to 2.5 to 3 pounds -- the latter if there is a good headwind.  However, this is not even lifting this weight for more than a few 100 yards and not necessarily up to a nest.

On the other hand, many a small cat, or parts of a road killed cat, can be lifted.  Eagles have great difficulty handling mink or cats because of 'fighting back' with sharp claws.  So a big 8 -10 pound cat is certainly beyond a bald eagle's capacity but parts of one, particularly cut by vehicle traffic, can and are lifted. 

We have the same frequent problem here but the predator is the coyote -- some live almost exclusively on cats. Raccoons take cats but a big cat can out-climb and out-fight or out-run most coons.

As you probably know cars take most cats.  I and a few close neighbors lose one or two of our barn cats each year. We see them dead on the road or their blood smear left when the coyotes got to them before I could even throw them off the road or bury them.  I recently wrote an item about road kills -- and the good source of food they are for eagles.  However, the other side is that eagles are often killed eating road kills and I spend a lot of time throwing kills off the road for this purpose.

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Bald Eagle US Legal Status Update

Bald Eagle Biology

Bald Eagle US Status Update -- from the Center for Biological Diversity.   (DH wrote this June 24, 2007  7:54pm)
((June 22, 2007))

It is always good to see something positive in the conservation field. Generally we humans continue on our destructive path: overusing and overpopulating the world -- our ecological footprint ever destroying the worlds natural resources that we depend upon. The Center of Biological Diversity has just correlated the latest estimates of breeding pairs of bald eagles for every southern state in the US. . 11,040 pairs for 2007. WOW!

In their Washington State data,
up from 100 pairs in the 1970's to over 835 pairs for 2007, I feel the British Columbia's population has done wonders in repopulation our southern neighbors territory. Lets hear a round of thanks!

When I started eagle surveys in the early to mid 1950's as I was logging time for first my private pilots license and then my commercial license, I could not find a single nesting pair of bald eagles down the entire coastline and adjacent San Juan Island between BC and southern Puget Sound around Seattle. I had over 100 nests in the adjacent BC southern Gulf Islands. And another 1000+ nests around Vancouver Island.

The Alaska bounty,
just ending in 1953, had had its incredible impact. As I have reported elsewhere many of the Alaskan commercial fisherman lived and wintered in the Washington State ports just south of Vancouver BC. For years, all winter long the fisherman had shot the "vermin" eagles, cut off their feet and legs, thrown them in the plastic pails on their boats, ready for turning in for $2.00 when they returned to Alaska in the summer fishing season. The bald eagle had been shot out of coastal Washington by the mid 1950's and had almost disappeared from the Lower Mainland / Fraser Valley region of Great Vancouver. In 1963-65 I could only find 3 pairs of nesting bald eagles in the Greater Vancouver area. Today, another sign of how they have come back so successfully, I have over 200 pairs in the same area -- and they produce almost twice as many young per nest as wilderness eagles.

Fortunately British Columbia did not offer the bounty. Unfortunately the "vermin" attitude -- the position that all predators or creatures not overtly useful, were therefore definitely negative, was continent-wide. All hawks, falcon, eagles, coyotes, wolves etc were the 'target focus" of all the rifle, ammunition and scope ads in every hunting magazine -- in the US and Canada. Now the gun and ammunition sellers have promote "fear of fellow humans" to continue gun sales. If you can't shoot eagles, shoot a religious extremist!

Eagles, the biggest and most vulnerable target suffered immensely. But every seal, sealion and orca was also pasted with bullets -- by sportsman and government fisheries officials as well. Persecution of predators was a national pastime and disgrace. Thank goodness for the attitudinal shift on the late 1960's -- the result of Rachael Carson's pesticide alert. Predators, who had suffered the most from loss of habitat, shooting persecution and then pesticide poisons working up through the food chain, began to be appreciated for their necessary role in the ecosystem. Most have responded very favorably. The bald eagle is a spectacular recovery story.

I have posted the Center of Biological Diversity summary map showing the southern states updated figures and the details for Washington State -- they give them for every state Check it out -- you all have lots to be proud of.

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Just think, what if we gave them back their trees along the shoreline (or artificial ones in the meantime!) and their waterways unpolluted -- no that's too much to expect so lets just be thankful for what the eagles have done with just by not being bountied --- and with a few souls truly loving and appreciating them.

Sure some of you are worried that without this extra protection, particularly to nest trees and habitat, some habitat will be lost. And this is true. But we should be protecting the habitat not just for eagles but to protect the entire ecosystem. Conservation is about preserving biological diversity -- the interrelationships that keep all living systems going. It is habitats that sustain ecosystems: not individual trees. Get out and protect the woodlots, the ponds, the forests , the beach and intertidal zones. That will protect the eagles and their food supply and nesting trees. It is totally counter productive to be thinking about one species. We are dependent upon communities of life. Get involved with you local governments and protect what little is left. Enough is enough.

Thanks to the Center for Biological Diversity for a great deal of effort to correlate the data pointing out a small step in the right direction,

david hancock

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