It started with half of a sky-blue American robin’s egg.

I imagined Mother Nature smiling down on me as she placed the cracked piece of manna a few feet from my front door earlier this spring. My first bird egg. What a gift.

Craning my neck, I searched the two 9-foot-tall shrubs and huge box elder standing sentinel next to me, hoping to spot a hidden nest where tiny, naked robin nestlings huddled under their mama. No luck.

So I gave a silent thank you and added the delicate shell to a windowsill collection of other detritus I’ve been gifted from Mama N, like small animal skulls and bird feathers, and went on with my day.

And then, I was blessed again, a couple of weeks later, with bird egg No. 2, though I didn’t realize what it was at first.

As I went to fill my bird feeders, something odd lay in one of the trays — a pearly, whitish, light blue orb. What the heck? It hadn’t been there before. It looked like a marble.

So I plucked it out to give it a good lookover. And then I decided to give it a tiny squeeze. Bad idea. It was an egg. The albumen and yolk splattered all over me, and I might have let fly a few choice words at the messy surprise.

I felt bereft. It had to be a bird egg of some sort, but who left it there? Mama bird? Papa? A predator? A lazy squirrel?

I didn’t think I’d killed anything, as the explosion had no makings of a tiny bird. And it wouldn’t have lived long anyway, there in the tray, with no mom or dad incubating it. So I said OK, thank you? to Mama N for her second, slimier and more melancholy gift.

Suzy Hiskey, an environmental educator and Denver Audubon volunteer, wasn’t sure what it was either, but she had some ideas. She’s been monitoring nests, eggs and hatchings since 2013 and contributing those observations to the Cornell Lab of Ornithology’s NestWatch program.

She’s had numerous wrens make a home in her yard, and recently found a few of the eggs from their first clutch outside of the nest, in the back part of the yard, which prompted her to check the nest.

Eggs can be moved in a variety of ways, she says.

“It’s possible for a predator to pick it up, and if they get startled, they might drop it,” Hiskey said. “Squirrels do eat eggs. It’s possible a bigger bird could have moved it from the nest, like blue jays, crows and starlings. There are a lot of birds that also prey upon the eggs of other species.”

It could also be one of the parent birds removing it from the nest if it hasn’t hatched, and they sense it’s either not fertilized or damaged from heat or getting knocked into the side of the nest.

Development of the embryo happens during incubation, when the eggs must be kept at body temperature for a length of time that differs among species. Most songbirds and woodpeckers incubate for around two weeks. They care for the eggs, rotating them, keeping them warm, and protecting them. Some birds don’t leave the nest, Hiskey says. Either the male feeds the female during that time, or in some species, both the male and female take turns incubating. Waterfowl, raptors and owls have different lengths of incubation.

Perhaps the egg I found was unfertilized, because it was only one frying pan and some olive oil away from turning into a sunny-side up meal. The question I neglected to ask Hiskey was: Can you eat a bird egg?

Is that a dumb question? We eat chicken eggs all the time. Somehow, though, it makes me a little nauseous to think about eating a robin’s egg. I’ll pass.

As I ponder this, a juvenile robin, easily identified by its speckled breast, bathes in my bird bath, splashing around, gurgling the water, and drinking it. If only he had a rubber ducky. Perhaps this is the same bird that burst out of the shell that now rests on my windowsill. Congratulations on your successful fledging, Roberto the Robin.

Hiskey first got entranced by bird nests when a pair of robins built a home on her front porch that was easily visible from inside. She joined the NestWatch network and began keeping tabs every day.

Anyone can join NestWatch, a community science program where people can self-educate themselves about nests and nesting birds, then take a short quiz to get certified to safely monitor nests. It’s important to monitor with a minimum of disturbance so it doesn’t affect the success of the nest. There’s a protocol to safely observing our tiny dinosaur relatives. Find it online at nestwatch.org.

You can learn what kind of nest boxes are preferred by different species, the best placement of the box, how to mitigate squirrels and other predators, and what to look for in a store-bought nest box. If you’re feeling handy, there are designs to build your own. And if you’re not, bird stores are better places to buy from than hardware stores, Hiskey says.

“The size needs to be right for the bird you want to attract,” she said. “The inside needs to be rough or have a climbing device or ladder for young birds to get out. Ideally, it can be opened so it can be cleaned in the fall or winter.”

We’re now heading toward the end of nesting season. Some birds start as early as March or April, especially if they’re non-migratory birds and the weather cooperates, as it did this year. However, that can lead to an unsuccessful nest, as it did for Hiskey, when an early house finch nest failed, perhaps due to the warm temperatures, followed by a couple of cold snaps. There were also a larger number of birds competing for nesting sites in her yard this year. She noticed multiple species checking out the hot spots.

That uptick in her backyard birds reflects the bird population at large, which had been in decline since a big die-off in 2019, she says. Scientists are working to decipher why bird populations now seem to be growing. Hiskey theorizes their decline was due to an inability to reproduce and replace their numbers, which has since changed for some reason.

“I’m hoping what we’re seeing is that birds have been able to get populations up again, and that they’ve reproduced successfully for a few years,” she said. “Song birds in our yards — a lot of them have sight fidelity. They return to the same location year after year. And their young will often return to the same general vicinity where they were raised. This year, I lost a couple of nests for the first time, but it was because of a lot of competition.”