Thursday, April 07, 2016

Is the last egg going to hatch?

The last egg in the Original Decorah nest
As of this morning, the unhatched egg in Decorah is somewhere between 49 and 42 days old. Can it still hatch? Eagle eggs have hatched as late as 44 days after they were laid. If this is the last egg, we still have roughly two days in which hatch could occur. However, eggs have never hatched this far apart in Decorah before. Given the dates, it is possible that we've seen the hatch of eggs number two and three instead of eggs number one and two as we initially assumed. Roughly 3% to 12% of bald eagle eggs fail to hatch based on the studies I read, although some sources put the number a little higher, at 10% to 25%.

So why wouldn't the egg hatch? Eggs fail to hatch because they are either infertile or nonviable. Infertile eggs occur when the ovum is not fertilized before it begins its journey down the female's oviduct. We know that bald eagles copulate frequently before and during egg laying, which helps assure that sperm is present in the right place (the infundibulum) at the right time (when the ovum arrives).  Since female birds don't have a way to reject or stop the egg-laying process once it begins, incomplete, poorly timed, or insufficient copulation can result in unfertilized eggs.

A nonviable egg occurs when an embryo fails to develop properly and dies. This is mostly likely to happen within the first three days of incubation (embryonic organs fail to develop) or the last three days immediately prior to hatch (major organ failure becomes apparent or hatch starts but cannot be completed). Non-viability can happen for a number of reasons, including:
  • Insufficient incubation. Incubation is fairly complex! Eggs must be kept at the proper temperature and humidity and turned regularly. Freshly laid eggs can spend time in the zone of suspended development (roughly 28.4 to 80.6°F) with no harm to the egg or embryo, but eggs must remain between about 99 and 104°F once development starts. Time off the eggs regulates humidity and helps keep pores from clogging. Turning or rolling the eggs prevents the developing embryo from sticking to the side of the egg, brings it into contact with fresh 'food' and important nutrients supplied by the yolk and white, and assures proper development of the membranes that exchange gas and protect the embryo from contaminants. 
  • Piercing or cracking of the shell. If the egg shell is pierced or cracked before the embryo is fully developed, it will die. This can happen if the egg is jostled too vigorously, stepped on, or damaged or destroyed by an intruder - something that has been documented in many species of birds. 
  • Insufficient nutrition. Given all that we've seen the eagles eat, this doesn't seem to be especially likely in Decorah. But if a female bird is insufficiently nourished before she begins laying eggs, her eggs won't have the nutrients needed to nourish the developing embryo. 
  • Bacterial or chemical contamination. Although the embryo is protected by a shell and layers of membrane, contaminants can sometimes make their way into an egg and impede or kill the embryo inside it. 
We aren't going to attempt to retrieve the egg if it doesn't hatch - at least not while the birds are in the nest. Without opening the egg, we have no way of knowing why it failed. On one hand, the eagles spent a surprising amount of time off the first two eggs. On the other, studies in some species of birds indicate that infertility is more common than non-viability. Infertility is also more likely to prevail in first and last-laid eggs, which is unsurprising given the importance that timing plays in fertilization. 

What will happen to the egg? Different species do different things, but bald eagle eggs are commonly buried under layers in the nest, where they presumably break and decompose. Eggs may also be pierced or trampled as siblings grow and become more active. We will look for the egg if we go into the nest this fall. If we find it intact, we will turn it over to the USFWS for study. 

Will the next eaglet to hatch be called D26 or D27? This is confusing to followers who have seen nothing but production success. However, peregrine falcons aren't always successful and we don't count production until after banding. A falcon that makes it to fledge but dies soon after is still considered in production counts, but a falcon that dies before banding is not. If this egg doesn't hatch, the next living eaglet will be called D26. 

It's hard to believe that we could have an unhatched egg after so many years of success. How many times have we been worried about something only to have it all turn out right? But eggs don't always hatch and even excellent parents like our Mom and Dad experience failure. I'm glad we have D24 and D25 to watch this year and I look forward to studying the dynamics and rearing of two siblings, even though I wish there were three.  If we have a chance, we'll retrieve the egg for inspection and we will also review the video record to determine how much time was spent off the first egg.

Note: While I included contaminants on the list of things that can cause eggs to fail, my guess would be that this egg failed due to infertility (statistically more likely according to what I could find) or incubatory failure due to cold exposure.

41 comments:

Sheri said...

Thank you for this information! It really puts it into perspective how amazing it is that this pair has done so well for so long!

Blake Fisher said...

That is good information. Thank you for posting it. It does seems that the egg is not going to hatch. Like you said, infertility makes sense. It's kind of a shock, as I've never seen an egg not hatch since I started watching in 2009. Hopefully, we will be surprised with a hatch. At least we have to hatchlings.

anonymous said...

I want to help others find the link to here but got told I cannot do it. How can they find that link?

Prof. Catherwood, O.D. said...

Thank you for this very informative article. I've seen other sites with egg or nestling failures, but they never provided much more than a one-sentence explanation of how this is to be expected sometimes in nature, let alone such a thorough review of the possible causes that you've given us here. Thanks again.

Blake Fisher said...

They won't let anyone but moderators post links in chat. They said it's in the rules, but I didn't see it. Anyway, the link for this blog shows up in a message that is automatically generated every 10 minutes. The user name says JollyGiant (something like that), but it is actually a "bot" which I think comes from the word "robot". It is a message that they set up to run automatically every 10 minutes. They have another one with 4 links to interesting videos.

Shanda said...

So glad to finally get an answer to my question. I'm new here, and although I watched this pair 2 or 3 years ago, I have never seen an egg hatch. I thought sure I saw the egg move last Sunday, but now I know I imagined it. (I wasn't aware of the higher resolution option then.) I'll be interested to see how the egg gets disposed of. I don't have emotional attachment to this stuff, I just find it fascinating to watch.

Unknown said...

I actually believe that the non-viable egg was the first one laid based on the hatch dates of the other ones. If the first hatch was actually the 2nd laid it was right on time at 37 days as was the 2nd to hatch if it was the 3rd egg laid.
Just wanted to put this out there for you to consider.

Edward Hoover said...

Guess it is not uncommon this year, as Pittsburgh's Hays nest eagles laid 3 eggs, and only 2 hatched. Hanover PA eagles laid 2 eggs, one hatched but the eaglet only lived 2 days, and the 2 nd egg is way past hatching date. Stuff happens.

Ann Breidenstein said...

As you mentioned regarding the amount of time off the first two eggs, I only noticed time off the first laid egg which seemed like such a long period of time and was concerned - nervous about it.

Thank you for the explanation!

Keeping fingers and toes crossed that we'll see D26 very soon!

Ann

Mary Snyder said...

Didn't anyone see what looked to be a square hole in the last egg with cracks on the rest of the egg? It looked just like the last two eggs did at first sign of life.

MsRARAUL said...

Thanks for the information, let's hope the D26 for the next year.

Patch Davis said...

Decorah eagle watchers are VERY SPOILED, in that every egg hatches and every eaglet fledges every year. This is definitely not the usual case in nature. These parents are the VERY BEST and we are privileged to be able to share their success every year!

Ann Cathcart said...

Thank you for this great information! I have been watching this couple for six years and always look forward to the magical time of pipping and hatching. This event is a celebration in the miracle of all life and also a reminder that mother nature has her own plans.


Rexianli Gaming said...

Lets still hope that D26 will hatch!

Laura Pietila said...

Sadly, this confirms my wonderings. I remember one day before the second egg was laid, egg 1 sitting alone in the nest for 45 minutes on a cold, windy day...and being concerned. When first peep was so late, I wondered if it wasn't egg 2 and have been waiting hopefully for the last one to hatch. I also felt like there were a number of times when all the eggs sat uncovered for a bit longer than past years. What would (or could) cause that change in the eagles' behavior from past years when the eggs were rarely left alone?

LaKat47 said...

I haven't seen this discussed. Could the size of the nest have anything to do with only two eggs hatching? Though I am sad to see an unhatched egg, I am somewhat relieved because I could never see room for three fully grown eaglets to get enough wingersizing or runway practice on the nest at this size.

Olga ScrapShopping said...

thanks for the article. I hope D26 will hatch for next 2 days.

Michael Audette said...

Thank you for the very informative commentary. It's much appreciated.

Salvage Rocks said...

What if it was not even incubated? And why would you guys give it to a different group? Why not find out yourselves? Email me at PURPLEGUY198766@GMAIL.COM the answers.

Salvage Rocks said...

R.I.P. Bunny kins!

Sharon Jones said...

there is a small black feathery object in the lower right-hand corner. Could be the other chick and she might have pushed it out...or a dead bird brought for food?

Grandma said...

I have been away for a week and found the female eagle in the N2B nest this afternoon when I returned --- with the two eaglets sitting a small bit away from her. I was shocked to see her turning the third egg and still incubating it. Several questions: Has she ever laid an unhatched egg before? I think you wrote about this question before but I'm getting dizzy trying to find the answer to that. Is there any understanding about how long the female will continue to incubate the unhatched egg -- and how will this impact her normal life??

Jess098 said...

Looks like a duck head or another bird species I have been looking too.

Sharry Hebert said...

Thanks for the information on the unhatched egg. Please let us know what you find out if you do retrieve the egg.

Jeanie Ciruzzi said...

Thank you so much for this post. We have been watching daily & have wondered what happened to the third egg & a possible why. We have been watching the eagles for the past 3 years & They are just amazing parents! THANK YOU SO MUCH AGAIN!!They truly are the highlight of my day.

Pat L said...

Is this discussion about the egg in north nest?

Christine said...

I thought at one point we could see that 3rd egg moving rhythmically--as if breathing or the eaglet "pecking" from the inside. I remember someone commenting on that.

Sharon Marz said...

I just saw an active Eaglet pip in the third egg, approximately 7:05 pm EST It looks as if this nest will have a third Eaglet by morning. I thought I saw a hole in it this morning but wasn't sure because it is so dirty. I wonder how this baby will do with its siblings being so much older?

Sharon Marz said...

This third egg that is actively hatching must be the last egg laid and today is the 37th day. I am happy that it it going to hatch!

Blake Fisher said...

Pat, this blog was started to answer questions about the third egg at the N2B nest. I see people are now posting about the third egg at the Decorah North nest. I'm glad to hear that there is a pip. When I looked earlier today, I just saw a dirty looking egg.

TaeGron Fury said...

Where in the world is it now?!?

Sharry Hebert said...

As of April 27, 2016 it appears the unhatched egg is gone? I do not see it any longer in the next.

Pat L said...

The third egg at Decorah North Nest hatched over the weekend (4/23-24/2016). It would be nice if there was a chat/blog for the north nest. We're getting great images, applause, applause for the people who are monitoring and controlling the camera. Love the zoom shots of the chicks when mom/dad are feeding.
Pat

Sharry Hebert said...

Did you notice what happened to the eaglelet after it hatched?

Pat L said...

Hi Sharry. Eaglelet is in the north nest. I was watching all 3 this afternoon.

Mary-IVT said...

That's interesting. Our Macaws laid 3 eggs for the first time this year. Only 2 were viable. We heard momma bird calling out in little cries. Then she quit laying on the egg and then pushed it aside on the day it should have hatched. She didn't even fuss at all when my husband reached in to take the egg to candle. There was no development in the egg on candling and on emptying no sings of fertilization or early development. We think she was calling out to the baby as the others peeped before hatching and the daddy helped one baby out of the egg. This is all so fascinating. To watch the eagle babies and see the similarities. Thanks for the great view. Our 2 are doing great. We set up our own little macaw cam so we could observe the activity without disturbing, wonderful.

Blake Fisher said...

Lisa, this blog is about an unhatched bald eagle's egg in Decorah, Iowa. Need I say more?

Sharry Hebert said...

It looks like something has happened to D24 and D25, per the live cam, as of 5/17, 7:45am. Any knowledge what has happened?

Sherl said...

Thank you for the biological analysis of the failure of the third egg to hatch. I too have watched this pair for 4-5 years and have always been amazed that three eaglets were fledged each year. Providing the nourishment needed to grow three birds from egg size to full size eagles is a tremendous demand. Being next to the hatchery is a blessing - or really good judgement by the parents. I choose to believe that what we learned this year is about the miracle of life. It doesn't always work perfectly, but when it does it is miracle that we should be thankful for.

Lynne Anspach said...

Did the siblings leave

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