Contributed by Ornithologist Laura Erickson

Includes:

• color
• incubation
• hatching
• care of
• potential dangers/predators
• abandoned eggs

Q. What color are robin eggs?

A. Blue. People have actually named a color "robin's egg blue" for the precise shade.

Q. What compound in the eggshell makes the eggs blue? Does this compound require a special nutrient in the robin's diet?

A. The eggshell color comes from pigments in the mother robin's blood! Hemoglobin from ruptured blood cells is transformed into "bile pigments," which are carried by the robin's blood to where the eggshell forms. So she doesn't need anything special in her diet to have properly colored eggs.

Q. Does only the female incubate the eggs?

A. Yes. The male doesn't have a brood patch and doesn't know how to brood eggs.

Q. How long does it take for robin eggs to hatch?

A. Incubation lasts for 12-14 days from the time the last egg is laid.

Q. For how much of the day does a robin incubate the eggs?

A. Females spend about 50 minutes of every hour incubating.

Q. Will the male robin take over the nest if the mother cannot?

A cat killed one of my nesting robins and she was sitting on four eggs.

A. How very sad. If the female was killed, the eggs are doomed. The male doesn't have a brood patch and doesn't know how to brood eggs.

Q. How long does the mother robin wait before she starts laying eggs?

A. The robin has to have a completed nest before she has a place to lay her eggs. Usually she'll start within a day or two, but the timing can be affected by a few things: Both Mom and Dad Robin have to have good nutrition before they'll be ready to lay eggs. If the weather has been bad and she has to spend a lot of time looking for food, she may not have the energy. If it's been cold, she may be delaying because she won't be able to produce the heat necessary to incubate. The female has to ovulate before egg formation starts, and in a very late spring, she may not be ready even though the nest is built.

Q. How many eggs do robins normally lay?

A. Most robin clutches during their first nesting of a season have 3 or 4 eggs. Very rarely there are 5, but this most often happens when a robin lays an egg in another robin's nest. Second and third nestings of a season sometimes have only 2 eggs.

Q. Why do robins lay their eggs later in the day than most songbirds?

A. Robins get a lot of their calories from food from the worms they eat. They find their worms by sight, so there needs to be a little light for them to hunt, but the worms hide soon after sunrise. So robins eat first thing in the morning, and THEN lay their eggs.

Q. Will a blue jay steal eggs from a robin's nest?

We have been watching two nests in our yard. Yesterday I found an egg on the ground away from the nest in a different part of the yard. I checked one of the nests and all four eggs were gone. I'm thinking blue jays may have robbed the robin's nest.

A. Sadly, if the female was killed, the eggs are doomed. The male doesn't have a brood patch and doesn't know how to brood eggs. If it was the male who died, the female might continue to incubate, but may just give the nest up for lost because the chances of bringing off more than one or two nestlings is very slight with just her to feed them. Also, the female starts focusing on a new batch of eggs after the young fledge, so the father is quite essential for the 'finishing school' lessons on surviving. Outdoor cats are a serious ecological problem, but also cause such heartbreaking individual losses. I'm very sorry. That said, please do write to let us know if one of the parents attends the nest, and what happens, as this is best way for scientists to keep on learning about robins and their individual differences.

The main predators of robin eggs are blue jays, crows, snakes, squirrels. Deer eat a lot of bird eggs and nestlings, too, but only from ground nests. Snakes swallow eggs on the spot, and since you found one egg in the yard, a snake most certainly wasn't the culprit. Squirrels usually stay up in branches, and seldom drop their eggs, so I'm betting it wasn't a squirrel, either. Jays and crows are both egg and nestling eaters, and so it's hard to be sure which species raided your nest. Robins actually appreciate having jays around as long as they stay away from their nests, because jays are good at warning about other dangers. But it's heartbreaking to lose the eggs or nestlings of any nest to predators. And the worst problem with crows and jays is that both species are highly intelligent. If you are studying the nests in your yard, be sure that there are no crows or jays watching you. If they figure out that you're watching nests, they may start watching for you to lead them to their next supper.

Q. What can we do with the robin egg we found in our yard?

A. The best thing to do with an egg that you find is to simply leave it be. I know you're concerned about the little baby growing in it, but there is a strong chance that there may not even be a baby in there. This may be an egg that wasn't fertilized, or didn't develop properly. After the other babies are a day or two old, the parents get rid of unhatched eggs just in case one of the growing babies accidentally crushes it. Rotten eggs are no fun!

There is also a chance that there really was a healthy baby inside the egg. One likely case: a predator may have carried off the egg, and dropped it in a panic as the angry parents dive-bombed it. Although the egg looks fine on the outside, the baby inside may have been badly shaken during the flight and especially when it was dropped. If so, the baby inside may already be dead or may soon die, and if it does survive to hatch, there is a strong possibility that it will be badly deformed, making its short life unendurably painful.

Even if the egg were perfectly healthy, the chance of a human successfully incubating the egg and then successfully raising the baby from a hatchling is VERY remote. Robin eggs require high humidity, gentle daily turning, and level heat. You'd need a high-quality incubator to do it properly. Then once the babies hatch, parent robins feed them regurgitated worms and insects for the first three or four days--something humans just can't do!. Newly hatched robins are weak and helpless, and their parents are designed precisely and have the exact right instincts for taking care of them. Our human hands are clumsy, and we have too many other concerns in our daily lives to devote every waking moment to a baby robin, as its real parents would do naturally.

People tend to both under- AND over-estimate the amount of food baby robins need, giving them too much in single feedings and not enough over an entire day. The real parents spend literally every waking hour searching for food for them, returning to the nest every few minutes all day long, from sunrise to sunset. Can you do this consistently for several weeks? It's also very difficult to make a baby bird diet exactly balanced. Robins feed their young worms, insects, spiders, and some fruits. Outdoors, the nest is shaded enough to protect from sun but gets a few rays of sun each day, which the baby requires for manufacturing Vitamin D-3. Indoors, you need to provide this vitamin, but it's very difficult to make the precise balance of calories and vitamins and minerals that natural robin parents provide.

There are very good reasons why it is against state and federal laws in the US to raise wild baby birds. Death at the hands of well-meaning people who aren't feeding a robin nestling the proper diet can be painful for the baby. Far, far better to just allow the egg to cool. If a baby is still alive in there, it will simply stop developing within the egg, before it develops any awareness of pain.

Q. Should we try to raise abandoned eggs ourselves?

A robin nest on our eaves has seven eggs in it, and suddenly the robins are gone! We haven't seen the mother in 4 days!

A. First, it is against state and federal laws to keep any wild bird — whether an egg, chick or adult. Robins only abandon their eggs when something happens that tells the robins they will have a poor chance of success. It seems unlikely that humans will have greater success. I know how sad it is to see these beautiful eggs and how very tempting it is to want to save the tiny babies inside. But it's just as heartbreaking to watch the babies start out healthy, with their egg sac to provide some nutrition for a couple of days, and then wither and die at our hands.

As for the seven eggs, that is too many for one robin to have laid. There must have been another bird laying her eggs in there besides the pair. That may be why it was abandoned. Ornithologists call robins determinate layers. After a female robin lays four or five eggs, her body simply stops producing more until she's incubated and raised these.

Q. Did I harm the eggs by watering a hanging plant in which a robin is nesting?

Before I knew the eggs were there (the plant is higher than I can see inside) I watered it with warm water, surely pouring water directly over at least one of the eggs. The mother is still sitting on the nest. What's the chance that I've already harmed the eggs?

A. Anything that is outdoors has to be at least a little waterproof. If the eggs weren’t sitting in water for longer than a few minutes, the ones that got wet should be fine.

Q. Should I just quit watering the plant and let it die?

The nest is in the middle of the plant, so I could water around the edges. I'm afraid I will harm the eggs and baby birds when they hatch.

A. It should be fine to water around the edge of the plant, but give the mother time to fly off each time, and don’t water after the babies’ feathers are growing thick and they get close to fledging.

Q. How do we know if the bird inside a robin egg is thriving?

My daughter found an intact Robin egg in the grass. There was no nest anywhere. We took it home wondering if the bird was still alive in its egg. We are currently trying to keep it by putting it in an abandoned nest under warm light.

A. If a robin egg is on the ground, it was either infertile and dumped by the parents, and won't hatch—or it was carried off by a jay or crow, and the robin parents chased them and forced the thief to drop the egg. The shaking and dropping could have badly damaged the embryo, and if the egg did hatch, the baby would not be likely to survive long.

Even if the egg were healthy, most of us just don't see all the work that goes into incubation. The right temperature is important, but so is humidity, and so is frequent turning to ensure that no part of the growing chick gets dried out or stuck to the shell. Then, if it did survive to hatch, keeping a tiny chick alive is very, very difficult to do successfully, even by a trained wildlife rehabilitator. These are some of the reasons it is against state and federal laws to keep any wild bird egg or chick.