Today we'll begin following a pair of Eastern bluebirds that
started their nest at the beginning of May.
Actually, it would be more
precise to say that the female started the nest. Among bluebirds, the
females are the ones who handle nest construction. Typically this
takes 4 or 5 days.
After all the eggs are laid, the female begins to incubate them. At night she stays on top of them constantly, and may leave them for 30-45 minutes at a time during the day.
When an egg hatches, the chick begins chipping away in a straight line at the largest diameter of the egg. In this video, we can see the progress of the first egg hatching. It's a relatively slow process; to show it we've sped up the video in certain parts. As the chick emerges from the shell, the mom stays on the nest to provide heat.
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The female bluebird originally lays one egg per day. But they all
usually hatch on the same day or within a day of each other.
Here we see chick 2 hatching from the egg on the right. His
sibling, who hatched about 8 hours ago, is flopping around at the top
of the nest. For the first couple of days, they barely have the
strength to move their heads.
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Max / min temperature for the day: 57 F (13 C)
/
45 F (7 C)
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If you looked at the previous clip of egg 2 hatching, you might
have asked "Where is the eggshell from egg 1, which hatched earlier?"
This clip shows us the answer.
Here we see the mother eating eggshell 2. Female bluebirds either
eat the leftover eggshells or carry them out of the nest. By eating
them, they can recapture the calcium that they lost in manufacturing
the egg.
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Even though the male bluebird does not incubate the eggs, he generally
remains near the nest during incubation. This male was an
exception. During the incubation period, we never saw him near the
nest or anywhere nearby.
But once the chicks hatched, he reappeared. In this clip we see
him bringing an insect (possibly a grub). It almost looks like he
sticks around to make sure that Mom feeds it to the chicks!
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Max / min temperature for the day: 69 F (20 C)
/
42 F (5 C)
Precipitation: 0 in
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At this point all the eggs have hatched and there are 5 chicks.
They are all huddled together for warmth because they can't
regulate their body temperature yet.
When the parent arrives with food, we see that 3 of the chicks are
strong enough to lift their heads and open their mouths wide. This is
important, because the gaping mouth is often what triggers an adult's
reflex to feed the chick. The nights are still cold at this time of year, so
it's important that
these chicks are well-fed as quickly as possible.
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Max / min temperature for the day: 70 F (21 C)
/
39 F (3 C)
Precipitation: 0 in
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The chicks are covered with soft down and the most recognizable
parts are their eyes (still not open) and their beaks.
Here the male bluebird delivers food. According to one study, males spend 29%
of their time hunting food and delivering it to the chicks.
Typically, they hunt by perching above a grassy area and spotting
ground-crawling insects.
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Max / min temperature for May 11: 75 F (23 C)
/
44 F (6 C)
Precipitation: 0 in
Max / min temperature for May 12: 62 F (16 C)
/
34 F (1 C)
Precipitation: 0 in
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The chicks are much more active. They are still in the stage
where they usually poop as soon as they eat, and this clip shows that in vivid
detail. :-) We also see the mom working hard to retrieve the fecal
sac (we've covered this topic before) and remove it from the nest.
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Max / min temperature for May 13: 63 F (17 C)
/
28 F (-2 C)
Precipitation: 0 in
Max / min temperature for May 14: 71 F (21 C)
/
48 F (8 C)
Precipitation: 0 in
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It rained today after a long while, so earthworms are on the menu
today.
As we see here, it's not so easy for a chick to eat a worm that's longer
than its own body! But Mom apparently is a firm believer that
no food should go to waste, and diligently ensures that the chick eats
the whole thing.
(If you're having trouble seeing the worm, keep your eye on the chick at the lower left.)
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Max / min temperature for May 15: 70 F (21 C)
/
46 F (7 C)
Precipitation: .16 in
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At 7 a.m. this morning, the chicks are mostly asleep when a house
wren drops by. You can see that it's a house wren by its tail
markings and the fact that it's much smaller than the entrance hole.
House wrens compete for nest cavities with bluebirds,
and can be real trouble for young chicks. They commonly kill helpless
chicks or simply shove them out the nest hole and leave them to die on
the ground. In this case, however, perhaps the chicks are too big for
the house wren to easily handle. We see the wren examining the nest
and the chicks, but it never pokes at them. I also wonder if perhaps
the wren was seeking warmth. It was a cold morning.
Another interesting thing we see here is that the chicks never
even move when the wren enters the nest. This is particularly
noticeable since one has its head up crying about 2 seconds before the
wren enters. Perhaps the parents gave a warning call (though you
would think that if the parents saw the wren enter they would have
chased it off more actively). And when the mom arrives
about 30 seconds after the wren leaves, one chick is quick to pop up
its head. So it would appear that somehow the chicks knew to lie low
only when the wren was there.
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Max / min temperature for May 19: 66 F (18 C)
/
37 F (2 C) (
Precipitation: 0 in
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The chicks are larger and more coordinated now. Their eyes have been open
since day 12. They still huddle for warmth, but the huddle moves all
around the nest box. As a result, the cup-shaped nest has now been
trampled down to a flat surface. They spend a lot of time flexing
their wings, whose feathers are coming in nicely. Each chick also has
tufts of down above each eye, like little antennae.
Here we see them lunging towards, and almost out of, the entrance hole
when the adults deliver food.
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Max / min temperature for May 21: 66 F (18 C)
/
37 F (2 C)
Precipitation: .1 in
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The huddle of chicks now always stays close to the hole, and the
chicks compete hard for who gets the food delivery. Here we see the
first chick who has figured out how to get a leg up by hopping onto
the wall of the nest box.
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Max / min temperature for May 23: 61 F (16 C)
/
39 F (3 C)
Precipitation: 0 in
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At first light this morning there were only 3 heads instead of the
5 that were there the night before. At first I thought 2 had fledged,
but after looking closer, I realize that instead they expired during
the night. The remaining three are actually standing on their
bodies. You can see some of the bodies if you look closely, but for
the most part they've already been trampled underfoot.
This seems gross and sad, but nestling mortality is a
hard fact of life. If the spring nights get too cold, or the adults can't
find enough food, some of the chicks will die. In this case, I think
the problem lies with the food supply. It's been drizzling for 3 of the 4
previous days, which I imagine makes it hard to for the adults to find flying
insects and tough to spot crawling insects.
As for the remaining chicks, they are taking turns sitting in the nest
hole, usually for about 5 minutes at a time. I guess they're checking
out the outside world, and working up the nerve to leave the nest.
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Max / min temperature for May 25: 51 F (10 C)
/
46 F (7 C)
Precipitation: .3 in
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The morning began with mom and pop bluebird fluttering around the
nest calling to the chicks. Sometimes too they would sit on top of the
nest and call. It sure seemed like they were trying to encourage
the chicks to fly. Also, for the first time ever they became
defensive towards me. I was about 15 feet away
from the nest when one flew straight at my head.
This clip begins with the two strongest chicks leaving the
nest. Each warmed up for this adventure by doing a lot of flapping
inside the box before launching. Note also that upon the first
departure, the remaining chicks seem to take it quite in stride and
stay calm. I'm not sure if they receive any vocal signal from the
parents to stay put for awhile.
Sadly, the last remaining chick was quite weak, and never flapped
his wings. You can see in this clip that he can barely swallow when a
worm is delivered, and unfortunately he expires just after noon.
As I mentioned in the prior day's entry, I think the parents may have failed
to gather enough food in the preceding days.
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Max / min temperature for May 26: 57 F (13 C)
/
51 F (10 C)
Precipitation: 0 in
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