I'd give those eggs 21 days from the time the last egg was laid. Then I would candle a few (or even all of them) to make sure they aren't fertile.

Seven eggs have been reduced to three!? As I continue to monitor my bb box; I noticed on Sunday, 6/29, that the seven eggs are now three? I have seen both the male & female adult in and around the box usually in the morning. The nesting box seems to be empty most of the time. These eggs look fresh because they are gently laid on the nest where as the seven were sunk deep into the nest. The nest seems pest free and very clean. I am not sure what candling is? Is it ok for me to handle the eggs. I assume I can hold a light behind the egg and see if it is hollow or filled with a chick? Is that right. Would a standard flashlight work? Any comments about the mysterious change in egg count? I don't see any egg shells on ground surrounding box. Comments are appreciated. bjt in south carolina.

Yes Bjt that is candeling..you got it! 7 eggs is unusual, are you sure they were all Blue Bird eggs?Where are these birds and eggs? Can you tell us your set up? Try not to handel the eggs, get a spoon and gently lift the eggs from the nest. HOWEVER you may have some NEW egs in there! I would procede with caution! Come back here for answers from our really super experts!

PLEASE REALIZE THAT WILD BIRD EGGS ARE EXTREMELY FRAGILE. The oil on your hands can also be bad for them and could inhibit hatching.
The only reason I would handle wild bird eggs is if I am sure they are NOT viable (or they are HOSP or EUST eggs).
After a brood has fledged, and an unhatched egg is left behind, I might candle it just to see if the chick died in the egg, or it was not viable (fertilized), or if there was some damage such as a fine crack or puncture. Not that there is anything I could do about it, just curiosity, and I can do no harm to the egg at that point.
Bluebirds and other birds will sometimes remove eggs to start a new brood. Can you be 100% positive that these are, or are not, new eggs? You have to ask yourself some questions to determine if the risk is worth it.
Careful daily notes on a calendar can often be extremely helpful to determine the situation, and sometimes you have to let the birds decide; they know more about this than we do.
BlueBars

Seems to be more activity in and around the bluebird nesting box today. Male shows himself regularly; female was observed actually inside the box for a longer length of time. It was a cool, dry day today. I know I am more active during milder summer days; perhaps the BB are too. To give you some background: I put up 2 BB boxes 3 1/2 years ago when I moved to this property. That year one box was nested twice! How exciting! I nearly saw the fledglings leave as I watched the male swooping in and around the nest all day one day. Not surprised that I missed the little ones leaving. It was just too time consuming to observe the nest all day. I knew it would be special to see the fledglings leave but also knew it would be unusual to actually see this event. In the past three years: One year a wood pecker increased the hole so I replaced the box. BB visit the nest all summer but last year they were chased away by mockingbirds and never built a nest. This year the BB seem to be the only birds around other than some cardinals and occasional finch. We have had house sparrows in past years (I thoroughly cleaned out the box with Simple Green as suggested by Wild Birds Unlimited and they went away) I love monitoring BB but I see that observing their behaviour will teach me alot. I'll resist intervening and watch nature take its course. This is a great forum for gaining confidence in watching/protecting these little wonders. Thank you everyone; bjt in SC

If you are absolutely SURE about that 22 days I would candle them. Are you sure all 7 were laid in the same clutch? Maybe some of these were another females eggs and something happened to her and he found a new mate. Then a new female laid eggs in the same nest along side the old ones although it seems unlikely she would not make another nest on top. That's what they usually do. What were you told about Simple Green and hosps?
Cathy

Update: My original seven eggs disappeared! It appears that the two adult BB removed the original eggs. On last Thursday the nest was empty and I spotted a few broken empty egg shells in the yard. Over the weekend the female began laying more eggs! She also began incubating leaving the nest infrequently. This morning she was out and about, the male bird standing guard nearby. I took a quick peak and found seven new eggs! A mystery that I can not explain but very happy this pair are determined to grace our backyard box with little bluebirds. Expecting hatching around July 17th with the fledlings leaving around the 2nd week of Ausgust if all goes well. I'll post another message later... BJT of South Carolina

Answer for bbcathy: Simple Green diluted with some water is a good rinse for the bluebird box to chase away invading HOSP. I do this practice yearly as a maintenance to discourage HOSP. Two years ago I had a HOSP entering my BB box. Fortunately no BB were in the area at the time. One day I was in the Wild Birds Unlimited store in Charlotte. A gentlemen with overy 30 boxes on his property that he has been monitoring for several years was in the store. Considering his experience I told him of my hosp trying to occupy my BB box. He said to discourage this intruder any way I could. He said that though BB are not sensitive to human odor, he believes that they are to hosp odor. He suggested I clean out the nest of any nesting materials and rinse thoroughly with the Simple Green mixture. He also suggested I leave the hatch open for a few days. This practice seems to discourage the lazy hosp from returning. It worked! I will continue this practice at the end of the season every year just to discourage the hosp from ever returning. BJT in South Carolina

Do the HOSP not like the smell of Simple Green? Is that why they dont come back?
I want to try this!!

"...BB are not sensitive to human odor, he believes that they are to hosp odor." - not sure I understand what you mean by that.
Anyway, I personally would not depend on Simple Green, or any other odor to discourage HOSP. And leaving the box open will discourage all birds from returning. So I'm not sure that helps either.

There is so much mystery surrounding BB behaviour (or any other bird for that matter!) Discouraging HOSP is never a sure thing, but I considered the gentlemen's experience with 30 boxes over several years to be worthy of giving it consideration. BB are not repelled by humans as some species are. HOSP are lazy, opportunistic birds and will not hang around an area if a BB box hatch is left open. They'll move on fairly quickly to raid another nest. Though I would prefer to rid my area of all HOSP in a more definitive way due to their aggressive nature, this is the best way I have found to discourage them. BB that have bonded with the box, so to speak, WILL return to a clean box. And..... about 30% of the offspring will also return in subsequent seasons because they bond with that box for some unexplained reason. Obviously, if the hatch were left open for a long extended period, it would be difficult for any bird to build a nest. The recommendation given to me by the experienced birder was to leave it open a few days only. I hope that clarify's my previous statements.... Simple Green is a gentle, safe product effective in cleaning out the BB box at the end of a season whether you are trying to repell intruders or just leave it crisp & clean for the next generation.

Prior to leaving town for a week, the female BB was incubating. Upon returning yesterday, 6/20, I found one egg hatched! It has been difficult to monitor the nest with the female constantly on the nest or the male BB standing guard while she is out for brief periods. I'll leave them alone until the weekend then check again. I am concerned about the survival of seven hatchlings. Up to nature and the pairs ability to find food for the brood of seven! More postings to follow. BJT in South Carolina.

BJT I trap and dispose of hosps b/c they do so much damage to all cavity nesting birds. Once eggs are laid I would only trust a spooker to keep the hosps away. They are vile and if they really want that box persistent. They will peck you adult blues, and eggs or babies to death if they really want this box. Spookers are like a 24/7 babysitter for your birds and they are cheap and easy to make. Please visit www.sialis.org for more info on blues.
Good Luck
Cathy

Here is a link that might be useful: Spookers

Thank you bbcathy! I will check out info. on spookers as a way to keep HOSP off my BB! I'll also investigate ways to trap the hosp and dispose of them.

Apparently the incubation phase is over. I see both male & female BB sitting on top of the box together frequently. Alternating hanging onto the openning. The female rarely goes all the way in; I assume it must be very crowded in there! The male appears to be cleaning the nest as I observe particles in his beak as he reaches in and flys away with something white. The eggs that are going to hatch must be done. The female hangs on the front; reaches in; then flys away, I assume, to gather food. I am not sure how many of the second set of seven eyes hatched. I have tried to get a peek but the two birds are very busy and frequently around the box. I have chosen to stay away to not disturb them. It has continued to be a joy to watch them at work. I hope to get an opportunity by the end of the week to observe the number of little birds in the nest. I'll be VERY CAREFUL when I open the box to see. A neighborhood cat has spotted the nest; yesterday I walked out toward the nest and it ran away. I'll keep an eye out for him. I like cats, but, certainly do not want it to harm the BB. Thanks for all the helpful information. BJT in South Carolina

If the female rarely goes all the way in, the babies are probably old enough to reach up for food. And the white things are fecal sacs, removed to keep the nest clean.
If you do not know the age of the nestlings, it is probably NOT a good idea to open the box now. If they are 13 days or older, you could cause them to jump out before they can fly (= catfood). They should fledge around 17-18 days of age.
Have you visited http://www.sialis.org/index.html yet? There is a ton of useful info there.
BlueBars

Here is a link that might be useful: http://www.sialis.org/index.html

Thanks bluebars for the info.; I'll check the website again.

For bluebar: Here is what I found on www.sialis.org Don't monitor side/front opening boxes after bluebird nestlings are 12-14 days old, to avoid premature fledging. If you observe parents feeding the babies regularly during the day, that is generally a sign that things are okay.
If babies do prematurely fledge, and are unable to fly, try to capture them (throw a towel over them) and return them to the box. Stuff a sock in the hole until they calm down (maybe 15 minutes.) Sometimes they will jump right back out. If possible install a 1" hole restrictor so parents can continue to feed, but babies can not exit, and remove the restrictor when fledging would typically occur.
Also....
Typically monitors stop checking a bluebird nestbox 12-13 days (remember unlucky "13") after bluebirds hatch, to avoid premature fledging. That is one reason why it's important to keep good records, so you are able to calculate the age of nestlings. Note that some species like House Wrens are more prone to premature fledging when disturbed late in the nesting cycle.

Thanks for the reference....

From approximately July 8th to today, July 31st.... the process is complete..... all fledlings are gone. I observed the male BB yesterday & the day before fluttering in front of the box. I knew this was a sign the baby birds were ready for flegdling. Curious, noticing no activity this morning, I looked inside..... the nest was neat & clean... a bit of poo on the inside walls but the nest was completely clean. Neat little birds. Till the next nesting, I am signing off. Thanks for all your help. BJT from South Carolina....happy bluebirding to all!

BJT,

Now is your chance to put sparrow spookers on the box. Look at my post "Sparrow Proof" or "Successful nest transplant", I have photos and descriptions of how I "decorated" my nest box to keep sparrows away. It has worked very good so far, sparrows have not went near that box since I put the mylar and filament on it. They are around in the trees but I have not seen one near the box yet. I'm keeping my fingers crossed that they will stay away until the little ones fledge. (they are 11 and 12 days old today).

Ok, I am confused about something here. If the babies hatched on July 20/21st like posted above there is no way they could fledge on July 31st! That would make them only 10 days old, they couldn't fly at that age!

Donna

To dzyg, I am afraid you may be right. July 20 until July 31st does seem like an incredibly short time to hatch and fledge. All I know for sure: June 20th, seven eggs in nest. July 3rd: no eggs, none! July 8th, another seven eggs were spotted. July 20th, I observed a small bird in the box. I assumed this was an egg hatched, but now I am uncertain. It could have been the female holding very still & spreading her wings to protect her eggs. Wishful thinking on my part, I fear. The other fact I know, on July 31st I openned the box and the nest was clean! It is entirely possible that the second set of eggs were not viable and none hatched. I think I was in denial. Hoping so desperately that the seven eggs would produce. The eggs could have been removed by predators. I just don't know. It is a thought I did not want to think about. As of today, 8/12, I have had no activity in and around the box. No blues are anywhere to be seen. I truly miss them. Hoping for better times next spring......

sounds like the small bird may have been a WREN??