A Cassin’s Vireo Nest

Zero to Eighteen in Two Weeks

Two years ago, a pair of Cassin’s vireos nested above a light under the eave of our garage in North Idaho.

After the chicks fledged, Rob removed the nest. Our research suggested that songbirds prefer not to use the same nest, so Rob thought he was helping by giving them a clear platform to rebuild.

Last year, they nested in the capped stovepipe over the same garage. This year, they found their old nest from two years ago, which I had used to adorn my grapevine wreath hanging on the side of the garage.

Surprise!

One June day, I walked past the wreath, just a foot or two away, and found myself eye-to-eye with a Cassin’s vireo! From that day forward, I gave them a wide berth so they wouldn’t abandon their nest.

They made some repairs and shored up the nest. As with years past, four eggs were laid. Birds typically lay one egg per day and don’t begin sitting on them until they are all laid. Both parents will share incubation duties, which last 12-14 days.

Vireos are small, spectacled songbirds who feed primarily on insects. Cassin’s vireos (vireo cassinii) were named for nineteenth-century ornithologist John Cassin. They are common in the northern Rockies and Pacific states. As neotropical migrants, they winter in Mexico.

The Hatchlings

I returned from a trip on July 4th to find three naked, bug-eyed chicks and one egg. The next day, there were four chicks and no remnants of the shell.

For the first two to three days, the chicks live off the nutrients from their yolk sac. After that, the parents feed them constantly. I would keep an eye on the nest as I went about my day, and when the parents were gone, I’d surreptitiously sneak in for a quick iPhone picture.

Temperatures climbed into the upper 90s for a week. The sun hits the nest for an hour or so late in the day; one of the parents would perch at the edge of the nest to shade the chicks during these hours.

The Nestlings

They grow so fast. Look at the difference in size and feathering in two days (July 5 – July 7)! By July 11th, at one week old, they are starting to look like birds. The nestling’s eyes are open, and they are beginning to sprout feathers.

The parents are spending more and more time feeding the chicks. It takes both of them to keep up.

It’s been a banner year for yellow jackets, and I’m pleased to say that the vireos fed these to their brood as well. With both parents feeding, they still somehow keep track of whose turn it is to eat. None of the nestlings grew faster than the others or seemed to dominate the nest.

I would sit on my deck and work while keeping an eye on the nest. With the long lens on my camera, I could get pictures of the feeding without interfering.

It’s getting more crowded by the day. It’s easy to attribute emotions to these charismatic little birds.

Observations

I always learn something about the wildlife around me when I can take the time to sit and watch deliberately. Today, I learned how songbirds keep a crowded nest of birds, who, like all babies, are primarily eating, pooping, and sleeping clean.

The parents would often perch with an insect in their mouth before approaching the nest. Maybe they were scanning to be sure it was safe to approach? Perhaps they just need to resituate before presenting the insect to one of the kids? Sometimes, when the meal was really big, they’d place it in the open mouth of a chick and then have to poke it down into their crop!

The Fledging

The nestling period lasts thirteen to fourteen days. Once the birds leave the nest, they are still dependent on their parents for a few days for food and protection as they cannot yet fly. On the surface, it seems like a ridiculous adaptation. But evolution tells us that the risk of a noisy nest full of birds attracting predators is greater.

The first three chicks left early on the fourteenth day. In the evening, there was still one in the nest, maybe enjoying all of that space! By the following morning, July 21st, the nest was empty. I never saw them around being fed by their parents, which is a testament to their survival skills in being so stealthy feeding flightless birds. As fast as I watched them grow in the nest, it’s no surprise that it only takes a few days as a fledgling before they fly off to fend for themselves.

I wonder where they’ll nest next year. I will leave this nest alone for them in case my vireos want to use it again!

If you’re interested in purchasing or licensing any images you see here, please email me at SNewenham at exploringnaturephotos.com, and I’ll make it happen.

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