Summer of the Robins

Camille, an American robin
American robins (Turdus migratorius) are familiar birds, found nearly everywhere—in urban and suburban parks and gardens, on farmland, and in wilder forests and even subalpine meadows. We enjoy hearing their cheery songs and watching them search for squirmy bits of food, but let’s face it: They’re taken for granted. To truly appreciate and respect a bird or anyone else, we need to discover how they live and love, and how little we know about them. Here’s a glimpse into a portion of the life of a charming bird and several of her babies, whom she raised almost directly under my gaze. They taught me how little I knew.


As I puttered around my garden on the afternoon of July 4th
I savored the quiet time and hoped for a mildly noisy evening for the sake of wild birds and other animals who intensely fear our fireworks and live for peace and quiet. As I approached my front door, the sound of wings fluttering in a nearby Camellia shrub stole my attention and I glimpsed someone quickly wing their way into a small nearby tree. Whom had I disturbed? A quick scan revealed none other than a shy American robin, perched on a branch, apparently waiting for me to leave. But curiosity got the best of me, so I back tracked a few steps and hid behind a native currant shrub to learn what this beautiful bird was up to. A few minutes later she returned to the Camellia and this time I could see that her bill was full of grass. Grass? That’s right: Nesting material! As my eyes focused, I realized that she was perched on the edge of a nest, to which she was adding the finishing touches.

Like a statue I stood for a few moments longer as she arranged the bits of grass. As soon as she flew off I ran inside inside to tell my husband, Rick, the exciting news: “A robin is building her nest right under our bedroom window!” We raced upstairs to the bay window that overlooks our front yard, and there—only 5 or 6 feet from the window—it was: A perfectly round little nursery, created with mud and grasses and such. We were astonished, elated, and honored that this nest had fallen into our proverbial laps, providing us with a rare opportunity to peek into the life of an enchanting bird. She had obviously been working on her nest for quite a few days, but we hadn’t even noticed. And that’s the way she wanted it.

Nest construction
Though I’ve discovered quite a bit about the black-capped chickadees and Anna’s hummingbirds who raise their young in our yard nearly every year, I knew little about robin family planning. To learn about their breeding habits I turned to books and websites and found that American robins are very busy birds. Typically, they have 2 or 3 broods during their breeding period, and I suspect that this female was on Number Three since it was already July. I’d seen a robin collecting nesting material in our back yard in April, so two previous nests were certainly possible.

According to several accounts I read, female robins may begin a new nest soon after the previous brood has fledged. When this happens, the male takes on their care while she efficiently finds a new nest site and constructs it by herself (robins don’t reuse nests but may reuse materials or build a new nest atop an old one). After reading about Dad’s duties I went to our back yard, camera in hand. Sure enough, there was Big Daddy in our bird bath, teaching Junior how to take a proper bath. Afterwards, they both left, but Junior returned ten minutes later, eager to practice this new (and no doubt thrilling) activity on his own. (Learn how to tell male, female and juvenile robins apart here.)

Big Daddy & Junior

Reportedly, robins build their nests from the inside out, pressing dead grasses, mosses, feathers, and twigs into a bowl shape using their wing’s wrist. The nest is then strengthened with soft mud (which explains the mud I’d noticed in the bird bath!), and finally lined with fine, dry grass. For two days we observed her from the closed window as she brought more grass and pressed her breast onto the inner sides of the nest to smooth and contour it. Upon completion it measured about 6.5 inches wide by 4 inches high, with a 4.5-inch inner diameter. During the days of July 6 and 7 she sat in her nest for short periods and the suspense (as to when she’d lay her first egg) was killing us. Finally, mid-morning on July 8 I noticed the first egg, and it was a most brilliant greenish-blue—the quintessential “robin’s egg blue.”

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Why blue?
There have been many theories. According to Tim Birkhead, author of The Most Perfect Thing: Inside (and Outside) a Bird’s Egg (Bloomsbury, 2016), Erasmus Darwin (grandfather of Charles) surmised that blue eggs offer protection from predators due to cryptic coloring: When seen from below, through their “wicker nests,” the blue eggs blend into the blue sky. “This is wrong at several levels, including the fact that … [their] nests are lined with mud and impossible to see through; and that he assumed that the main predators would see the nest from below,” writes Birkhead. Three later explanations—camouflage and conspicuousness, avoiding brood parasites, and individual recognition—have been tossed around, but a more recent one, thanks to technological advances in measuring color, makes the most sense to me: According to a study published in 2016 in The American Naturalist, birds like robins who typically nest in somewhat open nests within forests or other leafy places (where light levels are moderate) evolved towards having darker eggshells because the pigment protects the egg’s interior from dangerous UV radiation, but also allows the eggs to absorb more light, causing them to heat up more quickly, leading to faster embryonic development. Shorter incubation periods mean less risk of egg predation, but will likely be disastrous if climate change, which leads to more hot days during birds’ breeding periods, is allowed to continue. The blue-green color itself comes from biliverdin, a pigment that’s applied in the shell gland (aka uterus) just before delivery.

My biologist mind was spinning with more questions that weren’t answered in Ornithology 101, such as: How is eggshell formed? What is the real purpose of turning the eggs? Do the chicks breathe the same way as mammals do inside the womb? I’ll get to those, but also about this time I decided Mama robin should have a name. “Robbie” was just too banal for such a beautifully plumed bird whose dark eyes suggest a wonderful gentleness. I settled on “Camille” (French pronunciation: kah-MEE), after the Camellia shrub, but also because the name means pure and perfect.

Making eggs
I’ve always been fascinated by the self-contained life support systems called eggs and got to wondering about the shells. I knew that creating eggs is immensely draining on a female’s energy reserves and that extra nutrients are essential. I also knew that eggshells were made of calcium carbonate, but didn’t know that calcium is the most difficult mineral for many birds to obtain and that most female birds (other than birds such as raptors who eat bone by consuming whole prey) need to actively seek extra calcium.

No one knows exactly how birds know which foods are high in calcium, but they must ingest it during the evening hours prior to laying an egg so that a chalky solution of calcium carbonate can be applied to the membrane that envelops the embryo soon after it reaches the uterus. Birkhead notes that “most small birds seem to rely on calcium-rich snail shells that they find on the ground.” Robins may also eat arthropods like millipedes (often found in decaying leaves and other dead plant matter) that have a calcium-rich exoskeleton. Whether they use shells or skeletons, this is yet another reason to leave natural materials on the soil and to not use poisons. Without adequate calcium, birds may produce fragile, thin, or otherwise defective shells—with disastrous results—or fail to produce eggs at all. In case you’re wondering, avian eggshells are hard when they are laid, not soft.

Incubation
American robins typically lay three to five eggs; most common is four. Incubation, which is done by moms only (male robins don’t have a brood patch), lasts for 12-14 days. The day after Camille’s first egg was laid, another followed, but incubation was sporadic those first two days. Full incubation usually doesn’t begin until the last or second-to-last egg is laid so that all will hatch on the same day or thereabouts. With the addition of the third egg, laid on July 10, she began devoting nearly all of her time to incubation, quietly and secretively leaving only to grab something to eat and stretch her wings. She was rarely off the nest for more than 30 minutes, much less during slightly chilly mornings. We wondered whether she’d produce a fourth egg, but July 11 brought no more, so three it would be. On that day I heard a robin’s call outside the window around 7:20 AM and saw Camille return to the nest around 8:00. About an hour later I noticed what I believe was a male robin on our neighbor’s rooftop while she was off foraging. I imagine her call had something to do with this, but I don’t know whether it occurred on a regular basis.

Whenever she returned after foraging I noticed that she would do a little dance in the nest. Contrary to sources that state that robins turn their eggs with their bills, Camille always used her feet when we watched her. Turning eggs is essential for successful hatching, but is reportedly critical only during the first few days of incubation. Turning encourages the flow of nutrients and such within the egg, promotes the development of an embryo’s external blood vessels, and ensures that the embryo is positioned correctly with respect to the yolk and albumen (so that it can make full use of the albumen). Moms also position eggs so that no obstruction will prevent hatching.

Escaping the shell
According to Birkhead, hatching is complicated: Since they can no longer depend on the oxygen that comes through tiny eggshell pores and into blood vessels that line the inner shell, embryos need to do several things before the main event: Start shutting off that blood supply at their umbilicus and take it into their body; draw what’s left of the yolk into their abdomen (to use as food for the first few hours after hatching); and puncture the membrane of the “air cell” that’s inside the egg at the blunt end. As soon as they puncture it, they can use their lungs—for the first time—to obtain the oxygen and energy needed to come into the world.

These tiny creatures imprisoned in shells are impossibly weak and equipped with only a little egg-tooth on the tip of their bill—powered by a feeble neck muscle—to crack the shell. To learn how they actually break out, I consulted my dust-covered college ornithology textbook by ornithologist Sewall Pettingill, who described how an embryo “scrapes and presses the egg-tooth against the inside of the already weakened shell until a crack results,” a process known as pipping. Zooming in on some photographs we took revealed that there were tiny cracks in the eggs many hours before hatching, so it isn’t a quick, simple operation. “From a star-shaped crack, a fissure develops, usually around the larger end [of the egg]. Muscular action of the embryo, chiefly in the legs and neck, forces the shell apart at the circular fissure,” Pettingill explained.

Day 0 First hatchling

On the 12th day of incubation (July 22), all three chicks broke free of their shells. The first one hatched very early (perhaps well before dawn; we first noticed him/her at 7 AM, already gaping for food). The second hatched sometime between 10:30 and 11:30 AM, and the third at twilight, probably between 8:40 and 8:50 PM (the eggshell was still in the nest at 8:55, and because the parents remove (or eat) broken shells quickly because they’re sharp, it must have happened just minutes earlier).

As you can see in the photos, the chicks began life utterly helpless: Blind, nearly naked, and so weak they could barely hold their heads up. Needless to say, we were completely in awe, fascinated at their wondrous and fragile beginnings. In this photo you can see the egg-tooth at the end of one’s bill on Day 1.

Day 1

Growing up
Camille, like most bird moms, was completely devoted and attentive to her young. When she wasn’t foraging for food or feeding them she would brood them—that is, cover them with her body—and this went on until toward the end of the the nesting period when their bodies filled up the nest and daytime temperatures were high. During their first few days in particular, she showed great concern. Her comings and goings were secretive (as they had been during incubation), flying or hopping incrementally for short distances rather than flying quickly to and from the nest.

Several sources state that both parents feed the young, but we never saw anyone but Camille feeding her babies. Perhaps Big Daddy had his wings full with the previous fledglings or they had an agreement, or it’s possible he helped out at dawn while we were still asleep (although I have doubts about the latter). Rick did notice him perched atop our roof one afternoon, so he may have been assisting her by keeping an eye on the nestlings at times. But we never saw him after that, so I hope it was just their way of doing things and not that something terrible happened to him.

Nest activity was a whirlwind of frequent feeding, pooping, and incredibly fast growth. Aging the nestlings is done simply by day number, with hatching day designated as Day 0, the first full day as Day 1, and so forth. On Day 1 we filmed Camille bringing a huge earthworm to the nest, big enough to strangle a chick. When she couldn’t get it in their gaping mouths, everyone gave up and fell asleep with the mangled worm draped over and around them. And then she got on top. Adult robins may eat beetles, caterpillars, spiders and snails (as well as fruit such as serviceberries when insects and other arthropods are scarce), but Camille fed her babies mostly worms early on, although she did actually shove a huge moth down a tiny throat on the first day as well. That’s when I started watering the garden more often than usual to try to make worms more available, especially since the weather was warm and dry, which causes worms to go deeper into the soil. I also bought a cup of meal worms and placed some near the nest in the mornings. Later in the nesting period I saw her feeding them the fruit of English laurel (an invasive species), the product of an untrimmed neighboring hedge, as well as blueberries from our yard. Robins are important seed dispersers and large seeds are regurgitated.


We can’t talk about feedings without mentioning what comes afterwards. Nestlings of passerines (and some other kinds of birds) bag up their poop into a neat little receptacle called a fecal sac, which is essentially a white mucous membrane filled with poop. Parents either carry them away or eat them to keep the nest clean and tidy. Some accounts say that robins will eat the sacs when the nestling are young, as they contain much undigested food, and then carry them away toward the end of the nesting period when the birds (and sacs) are much bigger. Not so with Camille—she ate them until the very end, even when the globs became quite large.

On Day 3 I could clearly hear tiny vocalizations from the babies when Mom approached or perched on the nest. Also, dark pterylae (feather tracks from which their contour feathers arise) were now visible.

Day 3

And then there were two
Day 4 was uneventful, and except for some hot afternoon sun on the nest causing heat stress, everything seemed fine. One of them was a little bigger and stronger looking than the other two; no doubt the first to hatch. At the end of Day 4, Rick saw all three gaping as usual when Camille landed on the nest. The next morning, after watching the nest for some time, I realized that I could only see two babies. After Camille left to forage I opened the window and took photos to see if I could detect the third chick in an enlargement. After downloading, I was devastated: One of the babies must have died during the night and apparently was carried off by Camille (no one was found beneath the nest on the ground).

Day 5

Nestling mortality is usually either due to predation or starvation, but I have doubts about a predator attack, for several reasons: More than one nestling would likely be missing; being a light sleeper I would have heard something outside the window; no predators were ever seen near the nest, and there would probably be some damage to the nest (in the case of a large predator like a raccoon). It’s impossible to know for sure, but most likely the cause was starvation of the youngest who may have been nearly a day younger than the first to hatch. Although they all looked close in size, with a smaller body mass compared to siblings, he might not have been able to compete for food, and the afternoon heat may have weakened him further. One study showed that most starvation occurred late in the season due to reduced availability of earthworms. If only I had known it was that dire, I would have put out more meal worms! Reportedly, only about 25 percent of nests are “successful,” defined as producing just one baby robin, so they’ve got it rough. No wonder they have more than one brood.

Brother and sister?
Their rate of growth was incredibly rapid and daily changes were obvious, especially when comparing photographs. After the fifth day we could see their individuality. One was larger and appeared about a day ahead of the other. His eyes opened a day sooner (on Day 5), his feathers grew in sooner, and he basically just looked stronger. The other was a bit scrawny-looking and we wondered about gender differences, even at this young age.

Day 6_

Day 6

 

Day 9

Day 9

 

As they matured, I began to think the larger one might be male, especially when feathers on his head appeared darker. I named him “Big Boy” and the smaller one “Lilla” (Swedish for little). Cornell Lab of Ornithology mentions that male juveniles “may have fewer pale shafts on the crown, larger and blacker spots on the breast, and upperparts may average darker than in females.” Later it appeared that perhaps my guess was correct.

The only worry now was the heat: During their first week, temperatures were in the mid-80s and on Day 2 they were showing heat stress by doing an avian version of panting called gular fluttering, in which birds rapidly flap membranes in their throats to increase evaporation. The second week, temperatures soared into the low 100s and I read that young birds are more likely to die from excessive heat that cold. Rick and I to put our heads together and created a shade barrier that we hoped would help during the hottest part of the afternoon. Up went part of an old bedsheet that we managed to hook on nearby branches as high as we could. While it didn’t create a lot of shade, it did supply some after 5 PM. I hate to think what would have happened had the heat come during incubation (eggs rarely hatch at air temperatures over 104ºF).

Gular fluttering on Day 11.

Gular fluttering on Day 11.

 

Day 12

A hot Day 12.


The empty nest
Young robins typically leave the nest (fledge) 14 to 16 days after hatching. On August 4 (Day 13), Big Boy ventured to the edge of the nest and sat there, no doubt knowing the this would be one of the most dangerous times of his life. I saw him perch twice and go back to his sister, who wasn’t too keen on taking on the world just yet. The next day, in the middle of the afternoon following a fruity snack provided by Mom, Big Boy again sat on the nest’s edge. Then, all of a sudden, he bravely took to his wings for the first time. It was a short, shaky downward flight that took him into our neighbor’s yard where I could no longer see him.

Big Boy, an hour before he left the nest.

I knew Camille would go after him to ensure his safety and to reassure him during this terrifying time, and I assumed she’d return to Lilla in a fairly short time. I was curious how long she would spend with Big Boy out on his own, so we took turns watching the nest. When three hours rolled by and Lilla was calling out for her mother, I began to worry. Fledglings need their parents to teach them all about dangers and how to stay out of harm’s way, and to feed them for the first few days and then teach them how to forage for themselves.

Finally, after a long three and a half hours, Lilla returned to the nest to feed Lilla. What a relief to me, but also to Lilla who had never been separated from Camille for so long! We wondered how long she would stay in the nest by herself.

Lilla, alone in the nest

A heat-stressed Lilla, alone in the nest.

Early the next morning, Day 15, I was lying in bed pinned down by a sleepy cat. I heard robin voices outside the window and wondered what all the commotion was about, but didn’t want to mess with the sleeping beauty. Then, silence. When I finally managed to get to the window, she was gone. Little Lilla was now a fledgling, and the nest was silent and empty.

Though Camille was probably relieved to have her offspring finally fledge, I was a mess. Watching these selfless little birds had filled me with a sense of calm and made me temporarily forget the troubles of the world. The bond I built with them, though totally one-sided, was real and deep (and we didn’t even get to say goodbye!). Viewing the nest now was just an excuse to tear up, and it didn’t help that they were now out of sight, in the neighbor”s “pesticide marinaded yard,” as Rick describes it. But two mornings later, when I saw Big Boy perched inside our leafy fig tree, wisely trying to remain unseen, pragmatism reminded me that fledglings have to turn into successful adult birds—they need to hone their foraging techniques, learn their species’ song, form social relationships, and recognize good breeding habitat when they see it—so that they too can reproduce. To help out, plates of wormy compost went into the back yard in the hopes of luring them away from pesticides.

Big Boy, Day 16

Big Boy, Day 16

 

Lilla on Day 19

Lilla, Day 19

 

Camille collects blueberry treats (Day 20).

Camille collects berry treats (Day 20).

 

The fledging period is complex and fascinating and I wish I could have witnessed more of it, but I caught glimpses of both Lilla and Big Boy a few more times as Camille fed them berries or worms. The last time I saw them with Camille was exactly three weeks after leaving the nest and they appeared to be well on their way to adulthood.

It’s now been 4.5 weeks and there are no signs of the juveniles, who are likely nearby but no longer dependent on their parents. They will wear their freckled juvenile plumage until autumn. Small groups of adults frequent our leaf litter now and then to forage together, so evidently breeding territories are now obsolete. This morning I photographed a robin who had the exact same eye ring as Camille, looking for blueberries.

Researchers say that only a quarter of young robins make it through their first year. I hope Big Boy and Lilla beat the odds.

So now you know.

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Want to help American robins?

♦ Avoid using pesticides.
♦ Provide open ground-foraging habitat that can accumulate leaf litter beneath trees.
♦ Grow fruit-bearing native trees and shrubs, such as madrone, serviceberry, and thimbleberry (in the Northwest), which are especially important for inexperienced juveniles.
♦ Allow muddy areas to remain for mud collecting and snails for females needing calcium.
♦ Install a bird bath in a quiet spot where it can easily be maintained and observed.
♦ Avoid pruning trees and shrubs in the spring and early summer when robins are building nests.
♦ Keep kitty indoors and discourage others from visiting your property.
♦ Prevent robins from being injured or killed by window collisions.

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© 2017 Eileen M. Stark

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