Did you ever wonder why some birds, such as Bluebirds and Robins, lay blue or bluish green eggs? And just as interesting why, in some cases, Bluebirds which generally lay blue eggs, a nest may comprise eggs that are almost white?
The earliest avian eggshells probably lacked color, or pigmentation. Over time, most likely to protect the eggs from predators, birds evolved a diverse range of colored shell markings from mottled brown, gray and beige to rainbow hues from pure white to pale pink, lavender, yellow, aqua, orange, blue, born and even black.
The molecules that cause pigmentation in bird eggs are biliverdin (the blue-green shades) and protoporphyrin (red and brown colors and speckles) but we can talk about blue eggs without getting too technical.
Basically, blue and blue-green strikes a balance between white and very dark colored eggs. Darker eggs are predicted in moderate light to shield the embryo from intense light, including harmful UV radiation. If when eggs are in an exposed nest and the shells are too dark, it can cause the interior to heat up, similar to a “dark car effect.” Simply stated, blue eggs regulate the effects of sunlight on the developing chick (embryo).
This doesn’t explain entirely why Eastern Bluebird eggs range from white to blue green. Many cavity nester’s eggs are white because the adults need to see the eggs in the dark. Wood Ducks are an example of cavity nesters with white eggs. American Robins generally nest in trees or a semi-exposed site and their eggs are blue, affording both protection from dangerous UV light and low risk from heating up. Eastern Bluebirds are cavity nesters but only about 4 to 5 percent of their eggs are white. Oftentimes when learning about a topic, myriad more questions come to mind!
In reading about blue eggs I thought readers would enjoy seeing the amazing speckled and pear-shaped brilliant blue egg of the Common Murre, from USFWS
Some birds with blue eggs that nest locally include Red-winged Blackbird, Gray Catbird, Snowy Egret, Great Blue Heron, Little Blue Heron, House Finch, Bluejay, Goldfinch, European Starling, Eastern Bluebird, and American Robin.
American Robin nest at a friend’s home
Both Bluebird nest egg photos courtesy Google image search
On a damp overcast day, a cloud of of Robins descended on our garden. The Dragon Lady hollies provided an abundance of food for the traveling flock. Their beautiful birdsongs filled the neighborhood as they went from tree to tree, devouring any remaining winter fruits.
Beautiful Robins in the garden this afternoon, filling their bellies with Winterberry, holly berries, and blueberries. I often get the sense that birds know when the weather is going to take a turn for the worse.
Their shadows in flight crisscrossing the light through my office window, I look up to see one feather-fluffed fellow sitting on a crabapple branch, gazing right back at me. I wonder, if I silently and cautiously open the window, will he fly in?
It is so very cold out doors. The flock seems more weary than in past years. One sits on the ground outside the window, barely moving aside when I walk down the garden path; another is half asleep in the holly limb overhead. There are fewer, too, perhaps only eight to ten when often we see several dozen. On this coldest of January days, it must be difficult to keep warm, especially as there are no little fish to catch along the frozen sea’s edge to warm their bellies.
This one was so worn out, he sat in the snow beneath the holly tree, eating what the other Robins dropped on the ground.
The winter Robins arrive to our garden every year in January, nearly to the day (today, January 21st). Our garden is a postage stamp but we have planted it richly for the songbirds. The pair of ‘Dragon Lady’ holly trees hold their berries for the Robins, the crabapples have yet to be sampled, the winterberry is still ripe with fruit, and the tiny rosehips of the climbing white rose are beckoning.
We’re fortunate that on Cape Ann many American Robins nest and migrate along our shores. Some Robins live here all the year round; some arrive in springtime, having spent the winter further south in parts warmer; and some–the ones I like to call winter Robins–arrive in January, from parts further north. We are like their Bermuda, and they are here to feed on wild fruits and berries, as well as small fish fry and fingerlings, and mollusks.
Robin Finds Christmas was a favorite book from childhood, given to me by my Grandmother. Funny how sweet little children’s stories stay with you forever. Robin Finds Christmas is about searching for the true meaning of Christmas and was written by the English writer and illustrator Molly Brett.
This beautiful Robin’s nest is located at the lovely home of the Del Vecchio family. Daughter Clara noticed that a sprig of lavender was used in nest building so they left out some colorful bits of yarn. The Robins built the nest atop a rolled up rug that was left standing beside their well-trafficked front door. Mama Robin doesn’t seem to mind a bit the constant comings and goings of the household. I’ve seen robins build nests in some crazy places, but this has to take the cake!
Thank you to Michele for allowing me to come and film what has to be the world’s most charming Robin’s nest!
Update on the Robin’s nest: Sadly, Michele reports that the nest was knocked over and the eggs have been scavenged. In our region, Robins typically have several broods and often use the same nest, so perhaps the nest can become reestablished.
Outside my office window is a pair of stately hollies, our “Dragon Ladies;” aptly named for their prickly foliage, and adjacent to the hollies is a sweet scented flowering crabapple. The autumn fruits of this particular crabapple are chunkier than most and, I simply assumed, must bear the worst tasting crabapples imaginable because year in and year out, the fruit is never, ever eaten by the birds. When flocks of robins arrive in our garden in late January, the winterberry and hollies are stripped bare of their fruits in a day, or two, at the most, after which the robins head to our neighbor’s sumac and then further down Plum Street to our other neighbor’s smaller and much better tasting crabapples.
Not this year! A pair of robins is setting up house along the garden path and they vigorously defend the crabapples from other robins. In late winter, robins typically switch over to worms, but with the ground still frozen solid, they are continuing to look for tree fruits. Unfortunately, much of it has been consumed.
Repeatedly, I noticed that our robin couple was struggling to eat the crabapples. They would snip off a stem and then drop it onto the brick path below and peck and peck and peck. A robin’s bill did not evolve to crack open grains and as it seems in this case, nor for penetrating our unusually hard crabapples. A great deal of energy was being spent to get a morsel of food, which is never a good thing because it can leave a creature weakened and at risk of freezing to death.
Robin on the wing
I picked a few berries and made a crabapple mash, placed it under the tree and, within hours, all the fruits were devoured! Now when feeding the pets and filling the bird feeders each morning I pluck a small handful of crabapples, mash, and place in the pie tin below the tree. I’ve experimented with adding blueberries and raspberries to the dish, but they prefer the crabapples.
If we move very slowly when walking down the path, they now allow us to come quite close—and what a treat to observe from this distance—beautiful, beautiful robins!
Do you think we will be rewarded with a nearby nest? I hope so!
The robins in our community have several different habits for surviving winter. There are year round resident robins that breed throughout Cape Ann during warmer months and also spend the winter here. A second group only breeds in our region, then migrates further south during the winter months. A third group, the robins that we see flocking to our shores beginning round about January 28th, are migrating from parts further north. They are very hungry and are looking for berries, fruit, and small fish.
In early spring, robins begin to disperse from flocks. The ground thaws and worms, insects, and snails once again become part of the robin’s diet. In early spring, too, is when we begin to hear the beautiful liquid notes of the male robin. He is singing to attract a mate. The robin’s song is one of the of most beloved and it is his music with which we associate the coming of spring.
With several edits and updates since I first wrote the following article, I think you’ll find the information helpful in knowing what to feed and to plant for the robins.
Flock of American Robins Eating Sumac, Halibut Point Rockport
Food for the American Robin
During the winter months Cape Ann often becomes home to large flocks of robins, and we have had the joy of hosting numerous numbers in our garden. I can’t help but notice their arrival. Their shadows descend, crisscrossing the window light, followed by a wild rumpus in the ‘Dragon Lady’ hollies. This pair of hollies is planted on opposing sides of the garden path, alongside my home office. I have learned to stealthily sneak up to a window, as any sudden activity inside startles birds that are investigating our garden, and they quickly disperse. Dining not only on berries of the ‘Dragon Ladies’, but also the ‘Blue Princess’ Meserve holly and winterberry bushes, I find dozens of noisy, hungry robins.
These winter nomads flock to trees and shrubs that hold their fruit through January and February, feasting on red cedar, American holly, Meserve hollies, chokecherries, crabapples, sumac, and juniper. Robins traveling along the shores of Cape Ann also comb the shoreline for mollusks, and go belly-deep for fish fry. Depleting their food supply, they move onto the next location. Gardens rife with fruiting shrubs and trees make an ideal destination for our migrating friends.
Year round resident robins will call your garden home when provided with trays of chopped fruit and raisins, supplemented with meal worms.
What to Plant for Robins
The garden designed to attract nesting pairs of summer resident robins, as well as flocks of winter travelers, would be comprised of trees and shrubs for nest building, plants that bear fruit and berries that are edible during the summer and fall, and plants that bear fruits that persist through the winter months. Suburban gardens and agricultural areas provide the ideal habitat, with open fields and lawns for foraging insects as well as trees and hedgerows in which to build their nests.
The following plants, suggested with robins in mind, will also attract legions of songbirds and Lepidoptera. The list is comprised primarily of indigenous species with a few non-native, but not invasive, plants included.
Trees for nesting ~ American Holly (Ilex opaca), Eastern Red Cedar (Juniperus virginiana), Red Maple (Acer rubrum), Sugar Maple (Acer saccharum), Flowering Dogwood (Cornus florida).
Summer and autumn fruit bearing trees, shrubs and vines for robins ~ Black Cherry (Prunus serotina), Blackberry (Rubus spp.), Flowering Dogwood (Cornus florida), Gray Dogwood (C. racemosa), Red-osier Dogwood (C. sericea), Silky Dogwood (C. amomum), Elderberry (Sambucus canadensis), Apple (Malus pumila), Virginia Rose (Rosa virginiana), Highbush Blueberry (Vaccinium corymbosum), Lowbush Blueberry (Vaccinium angustifolium), Wild Grape (Vitis spp.).
Trees and shrubs with fruits persisting through winter ~ Winterberry (Ilex verticillata), Mountain Ash (Sorbus americana), Crabapple (Malus spp.), Sargent’s Crabapple (Malus sargentii), American Holly (Ilex opaca), Meserve Hollies (Ilex x meserveae), Eastern Red Cedar (Juniperus virginiana), Common Juniper (Juniperus communis), Chokecherry (Prunus virginiana), Smooth Sumac (Rhus glabra), Staghorn Sumac (Rhus typhina).
Right on schedule, the robins have returned to our East Gloucester neighborhood! They were seen flocking to the holly berries, crabapples and sumac. This morning it was bleak and drizzly; I hope to see them back in our neighborhood on a sunnier day!
For more information about robins see previous posts here:
During this past summer while filming B-roll for the monarch film I shot some wonderful little scenes, the baby robins for example. Oftentimes I just happen upon some stunningly beautiful event unfolding and because too many beauty scenes got away from me in the past, I have gotten really smart about nearly always traveling with camera bag in tow.
The four baby robins were in a nest that had been constructed at slightly higher than waist height, in a tree that was for sale at Wolf Hill. My friends at both Wolf Hill and Goose Cove Gardens are always so kind to point out these exciting happenstances, whether robin nestlings or Black Swallowtail caterpillars and eggs, and they are always tremendously accommodating, never minding when I run back to the car to grab my cameras! I only needed approximately fifteen seconds of robin footage, and here you have it! Thank you so much Kate for steering me to the robins!
In my monarch film there is a sequence about the different types of migrations that happen through our region. American Robins are especially interesting as the species has evolved a multi-fold strategy for surviving winter; in the fall, some robins leave Cape Ann for regions further south, some stay throughout the winter, and some arrive in great flocks in January and February from parts further north; for the Canada to Gloucester winter robins, Cape Ann is like their Bermuda!