Nesting Bluebirds -- Bugs for the Babies!

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

The Bluebird eggs have hatched!  My estimation is that the hatching date was July 5^th.  That would be the date of the hatching of the first egg.  Bluebird eggs are said to hatch within twenty-four hours of each other, although the last-laid egg might take a little longer.  The general rule is that all of the eggs will hatch within 48 hours of the first egg hatching, unless any of them are infertile. 

If you are interested in knowing how I estimated the hatching date, you can read the Technical Section below.

There were four eggs in the nest, and now there are four Bluebird babies.  I do not check the inside of the box very frequently for fear of stressing the parent Bluebirds.  The last time I checked, which was on Wednesday, July 15^th, the babies had light-colored “pin feathers” on them.  Assuming a hatching date of July 5^th, the first-hatched baby was ten days old at that time.

I have not photographed the babies, but if you go to the following site and look at Figure 5, you can see approximately what the babies looked like on July 15^th:  http://www.wbu.com/chipperwoods/photos/ebluebird.htm.  Here’s another photo of 10-day-old Bluebirds:  http://www.sialis.org/images/series/ybb11thday.jpg.

As the babies grow larger, they need increasing amounts of food and higher frequencies of feeding.  Their food consists of bugs, more technically called insects, that the babies’ parents bring to the nest box.  On the right is a photo of Mama Bluebird with what might be a grasshopper in her beak.  She is preparing to feed at least one baby through the nest box hole when she feels that it is safe to do so.  The blossoms in the background are on a Mimosa tree.

Both parents have been diligently hunting for insects and bringing them to the box to feed to the babies.  The insects that Bluebirds eat are largely those that live on the ground.  A Bluebird will perch on a fence, a utility wire, or a building's roof and focus on the ground below.  Once it sees an insect, it will quickly swoop to the ground, capture the insect, and immediately return to its higher post to either digest the insect or save it to feed its youngsters.

The parent Bluebirds closely guard the nest box and for good reason.  We have roaming, feral cats around here that eat birds.  The parent Bluebirds probably also consider me to be a potential predator because they are extremely cautious about feeding their babies when I am taking pictures of them.

The photo on the left shows both Mama and Papa Bluebird on top of the box with insects in their beaks.  They are awaiting a safe time to feed their babies.

Mama Bluebird is more cautious than Papa Bluebird and likes to wait until I am out of the way before she feeds her babies.  I have very few photos, if any, of Mama feeding the babies though the nest box hole.

Finally, after a few minutes of both Mama and Papa Bluebird perching on top of the nest box, Papa Bluebird deemed it safe enough to feed his insect to the babies inside the box.  Mama stayed on top of the box awaiting her turn, as shown in the photo below.

The photo on the right, taken early in the morning, shows Papa Bluebird on top of the box holding an insect, a large one at that!  Since I was there with my camera, he was watching me to be certain that I would not interfere with his feeding of the babies.

I wondered how many babies that large insect would feed.  Interestingly, male Bluebirds are said to show preference for feeding the female babies instead of the males.  It is speculated that the Papa Bluebird would rather have the females grow up and be healthy because, unlike the males, they will not interfere with his breeding territory next spring.  Instead, the females will go off with their own mates into another territory.  In short, male Bluebirds compete for breeding territories, which are usually five or six acres in size, but they can sometimes range up to twenty acres.

Much of this information presented here can be found in the delightful book, Eastern Bluebird by Gary Ritchison, which I heartily recommend if you would like to find out more about Eastern Bluebirds.  The book is well illustrated with superb photos and contains a great deal of information.

After perching on top of the box and holding the huge insect in his beak, Papa Bluebird proceeded to feed the babies.  As the photo to the left shows, Papa landed on the front of the box and fed the insect to the babies inside. 

Immediately afterward, Papa actually went inside the box.  I was wondering what he was doing inside of the box, but a moment later I discovered what it was.

Papa Bluebird stayed inside the box for a short time and then exited from the box, flying away to hunt for another insect.  The photo below shows him flying from the box.  As to what Papa had been doing inside the box, the answer is shown in the photo.

If you look closely at the photo, you will see that Papa had something white in his beak.

Something white?  It was actually a form of a diaper.  It is called a “fecal sac” and is from one of the baby Bluebirds.  When the babies reach a certain age, it becomes the job of the parents to remove these sacs from the nest.

A parent will take the sac from the nest box and fly far away from the box.  The parent will drop the sac in a place where predators will not be able to associate the scent of the sac with the location of the nest box.  And that is what Papa Bluebird did.  I watched him fly across the adjacent field and out of sight with the sac still in his beak.

Technical Section

Estimating Eastern Bluebirds’ hatching dates is based on observations of the nest and certain knowledge of Bluebird behavior and breeding patterns.  It is necessary to know how many eggs are laid and when the female finishes laying them.  Here are my observations:

Afternoon of June 17th – no eggs in nest
Afternoon of June 21st – four eggs in nest
Afternoon of June 29th – four eggs in nest

Ornithological observations have shown that, once a female Bluebird starts laying eggs, she will lay one egg each morning.  This is also true of many other birds.  Bluebirds tend to lay their eggs well after sunrise, often between 8 and 10 a.m.

Also from observations, it is known that the female will usually start incubating her eggs either on the day that she lays her last egg or on the previous day.

Since no eggs were in the nest on the afternoon of June 17^th, the female had not yet laid any eggs.  However, on June 21^st there were four eggs in the nest, indicating that she had laid her first egg on June 18^th, her second on June 19^th, her third on June 20^th, and her fourth on June 21^st.

Since there were still only four eggs in the nest on June 29^th, the female stopped laying after she laid her last egg on June 21^st.  She therefore began incubating her eggs either on June 21^st or on June 20^th. 

For the purpose of my calculation, I assumed that the female began incubating on June 21st. That is because I did not notice the female peeking her head out of the nest box prior to the morning of June 21st. Peeking her head out of the box would have indicated that she had been in the box all night keeping the eggs warm. Instead, early each morning prior to June 21st, between about 6 and 7 a.m., I observed the male landing on top of the box, the female flying from the fence to the top of the box to join him, after which the male would enter the box with the female following him. The male would then fly out of the box, leaving the female inside. I interpreted this behavior as the male escorting the female inside the box to make sure it was safe to lay an egg.

Since the average incubation period for Eastern Bluebirds is fourteen days, I assumed that the eggs began hatching on July 5^th, which was fourteen days from June 21^st.

Based on the assumption that the oldest baby was ten days old on July 15th, I estimate that babies will start fledging (leaving the nest) sometime around July 23rd. This is based on the average fledging date for Eastern Bluebirds being the date when they are eighteen days old. However, this can vary up to twenty-one days. On the other hand, the material that I have read about Eastern Bluebird nesting in this region of the U.S. has indicated an average of 18 days.

Stay tuned to discover the fate of the babies!  And please pray with me that they will be safe once they leave the nest.  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 closeups 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 juvenile 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.

 

 

 

 

 

 

 

Two Nest Boxes, Two Bird Families: Bluebirds and Tree Swallows!

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

Yes!  Tree Swallows have claimed the second nest box!  After the original Tree Swallow nest in Box #1 was hijacked by Bluebirds on May 10th, we finally mounted a second box (Box #2) on May 19th. 

A pair of Tree Swallows claimed Box #2 on May 23rd and have now started building a nest inside of it.  The photo to the right shows the female Tree Swallow peeking out of Box #2 and holding straw in her bill, straw that she would be adding to the nest inside the box  The male is to the left, flying away from the box.

Sadly, however, this pair of Tree Swallows does not appear to be the same pair of Tree Swallows who were chased out of Box #1 by the Bluebirds on May 10th.

I felt so sorry for the female Tree Swallow who had been building a nest in Box #1 for 9 full days when she and her mate were chased away by the Bluebirds.  The female Tree Swallow and her mate kept hanging around my yard for several days thereafter, mating on the fence during the mornings.  I knew that the female was ready to lay eggs and hoped and prayed that she would find a place to lay them.

Back to Box #1:  The Bluebirds seem to be doing fine, and the female has laid five eggs!  The female is often inside the box incubating the eggs, but she sometimes takes breaks and leaves the box, especially during warm afternoons.

While the female is inside the box, the male brings her food and feeds her through the box's hole, just as if he is feeding a baby. This is an excellent way for him to practice what he will have to do once the eggs hatch!

A couple of mornings ago, I observed the female Bluebird peeking out of the hole of the nest box.  Soon the male came to the box and fed her through the hole.  To my surprise, when the male flew from the box, the female left the box and flew after him!  I wonder if she was chastising him for not feeding her often enough.

The size of the hole on a Bluebird nest box easily accommodates Tree Swallows as well as Bluebirds.  In geographical regions where both species breed, the two species commonly compete for nest sites. 

It is often recommended to mount nest boxes in pairs, one for Bluebirds and one for Tree Swallows.  The reason for this is that Bluebirds and Tree Swallows can coexist in the same breeding territory as long as they both have boxes in which to nest.  Also, the Tree Swallows can help defend both boxes from predators by swooping at any bird, animal, or even a human, that comes close to the boxes.

A pair of Bluebirds requires a radius of 300 feet for its territory and will chase away any other Bluebirds within that radius.  However, Bluebirds that are already established in a nest will not chase nearby nesting Tree Swallows away.

Tree Swallows defend a territory from other Tree Swallows, but only within a 100-foot radius.  They will tolerate Bluebirds in their territory because the diets of Tree Swallows and Bluebirds differ immensely.

While Bluebirds feed on insects and larvae on the ground, Tree Swallows feed on flying insects.  Thus, there is no competition for food within the same territory.

The photo on the right shows the male Bluebird, who has just captured some food.

The recommendation is to mount the two boxes, one for Bluebirds and the other for Tree Swallows, no more than five to ten feet apart.   We tried to do that, but were unsuccessful.

We were restrained by the parameters specified by Bluebird organizations and also by restrictions from our landlord.  Bluebird specifications dictate that, in order to help guard against predators (and we have plenty of roaming cats around here), a Bluebird box must be mounted on a pole and in an open area, preferably at least 20 feet from a building, fence, or tree.  Our landlord restricted us from being able to mount the boxes in the middle of the lawn.  The reason for the restriction was that this type of location would add complications to the chore of lawn mowing.

We received permission from our landlord to mount a box near the septic tank opening, which is about 25 feet from our building.  So that is where we mounted Box #1 on April 24th.

It took only a week for birds to claim Box #1, but the birds ended up being Tree Swallows rather than Bluebirds.  After Bluebirds hijacked the box from the Tree Swallows only nine days later, we decided that we needed to mount a second nest box, one for the Tree Swallows.  The photo to the left shows the two Bluebirds on Box #1 the day they hijacked the box.  The female Bluebird is peering through the hole to check the inside of the box.  The male on the roof looks like he is jumping for joy at having procured a suitable nest box!

We tried to mount Box #2 about 5 feet from Box #1 where it would have not interfered with lawn mowing.  However, a layer of rock about 6 inches below the surface of the ground prevented the driving of the pole far enough into the soil.

The only option at that point was to mount Box #2 along the horse pasture fence where our landlord had also given us permission.  To mount a nest box along a fence is not an optimal choice because predators can sometimes use a fence to gain access to a nest.  However, this is the only choice our landlord gave us based on avoidance of lawn-mowing complications.

We ended up locating Box #2 between two metal fence poles that are about 4.3 feet high and 8 feet apart.  The box is located 28 feet from a 11-foot high wooden fence post that serves as a lookout tower for several different species of birds.  We are hoping that the fence post is far enough away from Box #2 that a large bird cannot use the post to prey upon the birds using the box.

The photo below, from the morning of May 28th, shows Box #2 on the left, separated from the high fence post by three metal fence poles.

The photo below, from May 20th, the day after we mounted Box #2, shows Box #1 in the foreground on the right, with Box #2 in the background.  The two boxes are about 75 feet apart although in the photo they look closer.  This photo was taken three days before the Tree Swallows arrived and claimed Box #2.  I cannot identify the bird perching on top of Box #2 in the photo, but the Bluebirds from Box #1 are perching on the fence.  The male Bluebird is on the wire at the center of the photo, and the female is on top of the fence pole on the right.

While Box #1 is about 4.3 feet high, we mounted Box #2 a little higher.  The distance from the ground to the lower edge of Box #2 is about 5.3 feet.

The higher a nest box is from the ground, the lesser the chance that House Sparrows will use the box.  This is a matter of great concern because we do have House Sparrows in close proximity, and House Sparrows have been known to enter a nest box and destroy the young of the host species.

The day after we mounted Box #2, I noticed a House Sparrow hovering near the entrance hole of that box and perching on the fence next to the box.  To my delight, the male Bluebird from Box #1 immediately flew to Box #2 and chased the House Sparrow away!

Also to my delight, when the Tree Swallows arrived and began investigating Box #2 on May 23rd, the Bluebirds did not chase them away!  What I had read about Bluebirds and Tree Swallows peacefully nesting near one another had proven true.  To this day, the Tree Swallows are still guarding Box #2, and the Bluebirds have not bothered the Tree Swallows.

The photo below shows Box #2 on the morning of May 24th, just one day after the new pair of Tree Swallows claimed the box.  The male Tree Swallow is perching on the fence pole, while the female is inside the box, peeking out.

Optimally, we should have already had Box #1 mounted by early March when our local Bluebirds start choosing their mates and searching for nest sites.  But we did not get it mounted until April 24th. For one thing, my neighbor was mounting these boxes for me as favor.  For another, it took a great deal of time for us to decide upon a nest box design, plan its location, and gather the parts needed for mounting.  Besides, in early March it was likely that the ground would have been too frozen for driving a pole into the ground.

In early March, no Tree Swallows would have been on the scene.  That is because, while Bluebirds remain in this area all winter long, Tree Swallows are migratory and do not arrive here until early April.  Although Bluebirds tend to be feisty and defensive of their chosen nesting sites, they would not have had any competition from Tree Swallows during March.

If you don't want to miss the news about the hatching of the Bluebird eggs or whether the female Tree Swallow lays eggs in Box #2, you can follow this blog by entering your email address at the top right of this page.

If you have enjoyed these photos, you might want to check out the 117 photos in my book, Bonding with the Barn Swallows.  Many of them show closeups 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 juvenile 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.  The book is available at Amazon at:   http://www.amazon.com/gp/product/1494481464/ref=as_li_tl?ie=UTF8&camp=1789&creative=390957&creativeASIN=1494481464&linkCode=as2&tag=barnswalfrie-20&linkId=5WME3VAHNSX3EXHH