White Rock 2013 -- a different year!

Wednesday, May 01 2013 @ 02:30 AM EDT

Contributed by: davidh


What a difference a year makes.  All fall, winter and now spring has seen a series of disastrous happenings at the White Rock nest.  The big contrast is between the incredible cooperative effort the White Rock pair has exhibited during the past 3 seasons and this year. Each year the pair returned from migration in the same week in early October, then so cooperatively building the nest, even if Dad had to be repeatedly corrected on the way he placed branches and then with Ma laying her first egg on March 13 for the last 2 years we have had the cams running.  Their consistency has been so precise -- or coincidental!  Then comes 2013!

Not having marked birds makes the rest of the comments largely speculation -- but lets give it a shot! 
The 2013 breeding season started last fall with what appeared to be Pa arriving back from migration right on time in early October.  But no Ma for several days.  The viewers were quick to worry.  And then in comes Ma -- but not we believe the right Ma -- and Pa stood back not really accepting her.  The lack of greetings between the pair was apparent.  Then a few days later in comes a Juvie to replace the first adult female -- the one we thought was Ma.  This young lady was so obviously also viewed unfavorably by Pa. Then a few days later we had the "night fight" heard by many.  The next morning the lady in charge was a sub-adult wearing a few black feathers in the head and dark band on the tail.  Again Pa did not seem impressed with his newest lady.

There was some repair work to the nest but some period of little activity and no eggs.  After another exchange everyone thought Ma was back -- but she did not look quite right to many of us.  She was too large and bulky.  She seemed to intimidate Pa.  But to everyone's pleasant surprise the first egg appeared -- but 12 days later than in the previous two years.  Then the differences between this new female and the previous years' Ma really began to show themselves.  The new lady did not consistently sit the eggs -- she flew off the eggs for the first few nights.  And perhaps even more alarmingly, Pa was not sidling up to relieve Ma for incubation duties - something at which he had always excelled.  Pa did not seem to want to sit -- except on Ma!  This was definitely different.  While the female sat incubating, Pa would move in and copulate with the incubating hen -- sometimes repeatedly in a day. But a second egg appeared -- that seemed good.

No behavior of this pair was consistent with the behavior of last year.  The female was not sitting consistently and Pa did not seem to be at all interested in that duty.  After two or three days of this 'inattentive incubation' behavior I predicted the eggs would not hatch.  Eggs need consistent incubation and heating to first raise the egg temperature to initiate embryo development and then the development requires fairly consistent heat to maintain that development.  These eggs got neither. 

Then came disastrous April 28th -- the 34th day of incubation for the first egg, when the female gets up off the eggs and flies off.  Pa does not take over.  In comes a sub-adult, probably a female, with much different white in the head and tail patterns than any of the previous ladies of the year.  This lady then proceeds to grab at one of the eggs with  her bill and then finally picks up the egg with her right foot and moves it out of the nest cup.  With the egg in the talon she reaches down, punctures the egg and almost immediately pulls out a partially but poorly developed embryo -- and eats it! 

After picking at the embryonic remains a few seconds the invader is bowled over by attacking Ma -- who drives off the invader and stands around in obvious surprise at the changes -- she now has only one egg!  After a few moments she too picks at the embryonic materials, eats some parts and then leaves.  The "season of the females" was not a good productive year for the White Rock bald eagle territory.

So what happened?  Well who really knows?  It initially appears that possibly the original Pa did return -- the timing was similar -- but at some point, perhaps after the 3rd female came on the scene, he was replaced. Certainly his behavior with all the hens was considerably different but more different during the latter part of the season than last year.  He did not have the bond with any of the females so apparent in the previous years.  He showed no signs of being the partner in incubation -- that he so intensely pursued in the previous years.  Mounting the incubating hen was certainly different from previous years and something I had never seen or heard of.   I believe Pa either did not return to this nest for 2013 or was replaced during the nesting season.

The multiple females were interesting and exciting -- but certainly none were displaying effective motherhood traits. The final big hen did lay a couple of eggs but had very poor incubating habits. Without a cooperative male she could not be expected to effectively incubate eggs, let alone raise young. 

I was surprised to see that the "eaten embryo" was about 10 - 12 days incubated.  So at least the female mated -- with someone!  The mating of the incubating female by the male could not have fertilized the egg as this has to happen before the yolk enters the oviduct.  An egg that is laid cannot then be fertilized.

So, have we had the opportunity to witness a new pair taking over a territory from our previous pair?  Possibly.  Have they learned some lessons to improve their chances of success for next year?  Possibly.  As most of our viewers know, other cam-viewed nests have suffered similar blows in the past couple of years.  Maybe this less efficient behavior is more common than we think.  I suspect not.  Our White Rock territory just suffered some changes -- perhaps from the presence of so many eagles competing for this prime territory.  If you were more suspicious of how the world is turning for the worst, how we humans have over-exploited the resources, how the oil residues, pesticides and heavy metals have entered our one world ocean from the Danube, the Saint Lawrence, the Mississippi, the Ganges or the Yangtze Rivers, then you might think this was more indicative of nature's reaction to that which has already befallen our salmon, our herring, our orcas or..... 

David Hancock  

More Thoughts on Embryonic Egg Development

Embryonic development initiates when the temperature of the eggs gets to a certain level -- approaching the standard temp of about 99.5 degrees F or  37.5 degrees C  The following url give a wondrous visual opportunity to follow the development in a chicken egg -- that would hatch in 21 days, not the 35 days of the eagle:


From viewing that brief look at the eagle lifting up and swallowing the egg content I feel the content had about 10 - 12 days of development -- and then rotting deterioration.  This would equate it to about the 6 - 8 days of the chicken embryo. My reasoning for this is:  a) An infertile egg simply dries up in the shell under the heat of the incubating birds.  b) Usually the infertile egg does not go bad or look rotten in this period of time.  c) It is the fertile egg, the one undergoing cell division, bringing in oxygen and germs from the outside through the pores that sucks in bacteria that can take over and rot the egg once the embryo dies and is not growing.  So what I believe I saw on the video was a fertile egg that had initiated development but died. The dead embryo then starts to be attacked by bacteria and deteriorates.  What we saw the female take out of the broken shell appeared to me to have some "degraded" substance more like a dead embryo than an infertile yolk.

Having myself incubated thousands of eggs of perhaps 200 species of birds, these eagle parents were not doing what was required of them -- or what an aviculturist would do to artificially incubate them.  These parents had not yet learned the right lessons -- or more discouragingly -- may have lost those talents.

Here is the url to the egg depredation video by the sub-adult eagle -- and Ma's perturbed reaction. ????


So what will happen with the last egg -- still there Wednesday morning?  Well I would have said it would almost certainly be soon predated by a raven or crow -- now I have to add in "or eaten by an egg-eating bald eagle" -- something I had not seen before.  These cams sure show up some unexpected behaviors.  It is not long since we saw the Redding, California/Turtle Bay intruder land on the nest and in moments bend down and pull the head of the newly hatched chick and swallow it. 

Are these observations more normal than we had thought before our prying cams gave us these intimate views or are behaviors changing?  In the expanded populations of eagles in the recent years are we witnessing ways of eliminating competition, a version of the lion pride owner destroying the earlier pride owner's offspring?  Doubtful but possible.  Are we witnessing just the stress from competition for food?  We have more eagles and perhaps the seasonal food supplies are shifting and eating scraps or young from someone else's nest is simply fair game for a good dinner. 

From Depression to Optomism!

Egyptian vultures specialize in eating eggs, particularly using stones to break open Ostrich eggs.  Are we seeing a throwback to old DNA patterns in our bald eagles?  Or are some eagles simply showing that versatility that typifies a very successful predator/scavenger.  If a bird has the ability to identify so many different sources of food, from hunting huge to tiny mammals, birds, reptiles or fish and even insects and amphibians and then switching to eating carrion shapes and sizes barely differentiable as "protein", perhaps we have a super survivor in the making - a new crow, raccoon, a rat -- my goodness, perhaps eagles are evolving to replace us!  So something is good in all this!

David Hancock





Hancock Wildlife Foundation