Bye-bye Baby Bluebirds!

Text and photos © 2015 Adele Wilson, author of Bonding with the Barn Swallows

I don’t know why I get so attached to baby birds, but I’ve been that way all my life.  The baby Bluebirds left the nest box on Wednesday, July 22^nd, and I haven’t seen them since.

I really didn’t see the babies at all except for their little heads peeking through the nest box hole the last few days during which they were in the box.  During that time, the parents had been extremely busy feeding larvae and full-grown insects to the babies through the box's entrance hole.

From my observations during the times that I had opened the nest box, I knew that the female had laid her last egg on June 21st.  The day the last egg is laid is generally said to be the day that the female begins incubating her eggs.  According to Cornell Lab of Ornithology, the average incubation period for Eastern Bluebirds is 14 days, but I had read that this period can be anywhere from 12 to 14 days.  The day that the first egg hatches is said to be the end of the incubation period.

Again, according to Cornell, the average number of days that Eastern Bluebird nestlings stay in the nest is 17 days, but I had read that it can be anywhere between 17 and 21 days, most likely 18.  When the babies leave the nest, they are said to “fledge”.  Therefore, the number of days that the nestlings stay in the nest is called the “fledging period”.

Also, in some cases, the female might begin to incubate on the day before the last egg is laid.  That would hasten the hatching date by one day.

Using all of this information, including the variability of the day that incubation begins, the length of the incubation period, and the number of days that the young stay in the nest (the fledging period), I had estimated that the babies would leave the nest (fledge) on Thursday, July 23^rd, when they were 18 days old.

So, based on my estimation of the fledging date, I went out early Wednesday morning, July 22^nd, to take pictures of the nest box.  Hopefully, I would get some photos of the babies’ heads peeking out of the box, and, if I didn’t, I would have 24 more hours left to do so.

The morning of July 22^nd was beautiful and sunny.  The sunlight coming from the east was hitting the nest box nicely, and I had a full, clear view of what going on at the box.

Both Mama and Papa Bluebird were busy bringing insects to the box to feed their babies through the hole.  Mama and Papa, usually one by one, would first land on top of the box with a grasshopper, a grub worm, or some other type of live insect in their beaks and await clearance to fly to the hole of the box and feed the babies inside.

And I wasn’t disappointed in my hopes of being able to see the babies’ faces peeking out of the hole!  It was a memorable and gratifying experience.

But I don’t think it was so gratifying to the parent Bluebirds to have me out there taking pictures of the box when the babies were so hungry.  So I took as many pictures as I could during a 30-minute period while the angle of the Sun was almost horizontal to the nest box.

At one point, I realized that I was holding up the feedings.  Both Mama and Papa were perched on top of the box at the same time, both holding insects to feed to their young, as the photo below shows.

The babies were eagerly awaiting their breakfasts.  Most of the time, I would see only one baby’s face through the nest box hole.  Perhaps this was the first-hatched, and therefore the most fully developed, nestling, the one with the most strength to beg for food.

On one occasion I was able to photograph, through the hole, what seemed like the heads of three of the nestlings.  I was rather disappointed that I couldn’t see all four because Mama Bluebird had laid four eggs and I had observed four nestlings in the box a week previously, on July 15^th, which was the last time I had opened the door of the nest box.

On that day, July 15^th, I had estimated the nestlings, or at least the oldest nestling, to be 10 days old.  All of the Eastern Bluebird information sources say not to check the box after the nestlings are 12 days old for fear that it will cause them to fledge early and decrease their chances of survival.  So I chose not to open the nest box door again after July 15^th.

My calculation of the oldest nestling being 10 days old was based on the assumption that Mama began incubating her eggs on June 21^st and did so for 14 days until the first egg hatched, which would have been on July 5^th.

I had read that Bluebird eggs generally hatch within 24 hours of each other, but there might be a straggler that takes a little longer than that to hatch.  Yet, the eggs are said to all hatch within no more than 48 hours of the first egg hatching.

So, if the first egg had hatched on July 5^th, the babies, at least the oldest one, would have been 10 days old on July 15^th, the last day that I had opened the door of the box.  I did not photograph them on that day, but I tried to remember what they looked like.  I remembered how I could see their light-colored pin feathers and began searching on the Internet for photos of Eastern Bluebird nestlings.

Yes, according to the photos that I found of Eastern Bluebird nestlings of different ages, the nestlings did indeed look much like 10-day-old nestlings on July 15th!  That meant that on July 22^nd they would be 17 days old and on July 23^rd, 18 days old.

At the time, I was not giving a great deal of attention to Cornell’s exact estimation of incubating and fledging time periods.  Instead, I was trying to assess an average of the time periods given on different websites.

Most of the websites said that baby Eastern Bluebirds fledge when they are 18 days old, which would be on July 23rd.  Therefore, on the morning of July 22^nd I would have at least another 24 hours before the 17-day-old babies would leave the nest.

Wrong I was!  On the evening of July 22^nd, there were no parent Bluebirds anywhere near the nest box.  If the babies were still inside, they would be starving because 17-day-old babies need to be fed several times an hour.

I checked the box on the morning of July 23^rd and found a crumpled-down nest that looked gross and unsanitary.  I had read stories about having to remove dead babies from the nest box, but, fortunately, I did not find any.

That meant that all four babies had been alive at the time they exited the box.  I would love to have seen the fledging of the babies, but I don’t think the parent birds would have permitted their babies to leave the box with a human in sight.

There is a chance that a predator (mainly a cat) could have attacked the babies while they were flying from the box, but I am having faith that did not occur given the parents’ defensiveness and vigilance that I had witnessed over the past two weeks.

On the morning of July 24^th, just before I put out my trash for our weekly pickup, I removed the nest from the box and sealed it in a plastic bag to put into my trash.  I then proceeded to scrape out the debris from the box, sprayed the inside with a 10% bleach solution, and scrubbed it with a brush.  By the time I had again sprayed, scraped, and brushed several times, the box was as clean as a new box. 

I left the box open to dry in the sun for the remainder of the day.  By evening, the box was dry and fresh, smelling like natural wood (the box is made of cedar), with no trace of the scent of bleach remaining.  So I closed the door of the box to prevent it from getting saturated with dew overnight.

After thinking that the babies had fledged one day early and that perhaps I had caused them to do so by my photographing the box on the morning of July 22^nd, I reviewed Cornell Lab of Ornithology’s timetable for Bluebird nesting.  To my surprise, I discovered that the babies had fledged RIGHT ON TIME!

As previously stated, Cornell gives an Eastern Bluebird incubation period of 14 days and a fledging period of 17 days.  Since 14 plus 17 equals 31, and 31 days added to June 21^st equals July 22^nd,, in light of Cornell’s average incubation and fledging periods, the babies fledged on the exact day that they were supposed to.  Excellent work, Cornell!

Bluebird babies are said to be unable to feed themselves for the first two weeks during which they are out of the nest.  The parents are said to take the babies into trees to protect them from predators, with the parents continuing to feed insects to the babies for the next two weeks.  Eventually, the parents teach the babies to hunt for insects by themselves.  The photo to the left shows what a baby Bluebird looks like when it is out on its own.  I took this photo during the summer of 2013 when I first observed baby Bluebirds near my yard.

So, perhaps by August 5^th or so, I will see the babies around, perching on the fence with their eyes on the ground, hunting for insects in the manner that their parents have taught them.  In the meantime, I am wondering if the Bluebird parents will nest again this summer.  Will they use one of our two now-clean nest boxes to do so?  Time will tell.

You can stay tuned to discover whether I see the babies again and whether their parents nest again in one of our boxes.  To follow this blog, you can enter your email address on the upper right of the page.

If you have found this story interesting, you might want to check out my book, Bonding with the Barn Swallows.  Its 117 photos include close-ups of the baby Barn Swallows that were hatched on my porch during 2011 and 2012.  There are also photos of the parent swallows guarding the nest and feeding their young.  As an extra bonus, the book includes photos of five different juvenal Barn Swallows, just ten days after fledging.  You will be amazed at their varied markings.  The book describes how one special male Barn Swallow communicated to me by his body language on the utility wire and how, only two days later, I discovered what he was trying to tell me.  To find out more about the book and read a preview, just click on the image to the right.