Nestlings and banding

We’re in the middle of the busiest part of the nesting season. Lots of nestlings are hatching, growing, and fledging right now, meaning we have to keep track of boxes to band and boxes to leave alone. Once chicks are big enough, we give them metal and/or color bands, and then wait a couple of weeks for them to leave the nest undisturbed. Even though there’s a lot to keep track of, this is my favorite part – seeing lots of baby birds growing up.

Bluebird nestling with new color bands
House wren nestling, ready for some jewelry

I also want to show how egg color can vary in bluebirds. We usually see bright blue eggs, but now and then the eggs are white! Earlier this month I found a nest with bluebird eggs that were almost completely white. They’ve since hatched into healthy chicks that I banded recently in Winters.

Have a nice Memorial Day weekend everyone, and stay safe!


Nesting Stages

Right now our nest boxes are showing a good range of the different stages of the nesting process. We’ve begun to see more boxes with little Western Bluebird and Tree Swallow chicks!

Tree Swallow nestlings; from their size, we think they just hatched earlier that day! We’ll leave them be while they grow nice and strong then check back in a couple weeks to band them before they fledge. Photo by Estefania Maravillas.
A Western Bluebird nest with nestlings and eggs off Old Davis Road. Photo by Michelle Mah.

The rest of the boxes vary from having just a few twigs as the parents begin building their nest, to having a couple eggs as the rest of the eggs are still being laid, to having the full clutch of warm incubating eggs. The majority are incubating now, so I’m excited for the nestlings that will be hatching soon.

A nice, hearty Tree Swallow clutch. On average they lay between 4-7 eggs. Picture by Michelle Mah.

In other exciting news, we have seen Ash-throated Flycatcher nests appearing in the boxes at Russell Ranch and in Winters, and some already have eggs.

Ash-throated Flycatcher nest in Winters. Photo by Monica Burnett.



Our nestboxes have a lot of eggs now, and many more nests! The Putah Creek nestbox trails from Winters to Davis all have active nests – tree swallows, western bluebirds, house wrens, and white-breasted nuthatches. The nestboxes in North Davis and up at Bird Haven are also very active. Within the next couple of weeks, a lot of eggs are expected to hatch, and soon after that we’re likely to begin the busiest wave of nestling banding this year.

Nests in Winters near Dry Creek. Top left: western bluebird nest. Top right: tree swallow nest with a lovely variety of feathers. Bottom: tree swallow nest with two eggs!

We don’t have any ash-throated flycatcher eggs yet, but we’ve observed adults around the creek, and I saw a pair together at one of our Winters sites. I hope they’ll have another good season.


Back in The Field

A lot has changed in the past month, but we’re checking nestboxes again! (If you’re reading this later, the COVID-19 shelter-in-place orders have recently halted or changed a lot of things in Davis and of course around the world.) We’re sadly not able to have groups of students out with us this season, and we really miss their help and their energy. However, our limited nestbox crew is doing a great job monitoring nests so far while keeping our equipment sanitized. We’re even beginning to band some nestlings.

WBNU nestling

White-breasted nuthatch nestling, one of our first nestlings this year. Photo by Estefania Maravillas

Our first banded nestlings this year were white-breasted nuthatches in Winters. They tend to nest earlier than our other usual species. Another nest of nuthatch eggs at Russell Ranch will hopefully hatch soon too. There are bluebird nestlings that will be banded soon in North Davis, which has a lot of other nests starting already, and Mace Boulevard has many bluebird and tree swallow eggs right now.


Male western bluebird in North Davis. Photo by Kelli O’Neill

WEBL nestlings

Baby bluebirds in Davis. Photo by Melanie Truan

It’s really nice to be outside again, and I hope we can bring a little of the fresh air into this blog for anyone stuck inside. If you’re able to go take a walk in this nice spring weather, keep an eye out for nests and migrating birds!


Walking path in Winters


Birds in pairs

The field crew and I have started checking nestboxes for any early nests. We’ve been seeing bluebirds and tree swallows in pairs hanging out near some of our nestboxes already, though the time for building up most nests has yet to come. We’ve been able to ID some previously banded birds by watching pairs that are starting to stay near boxes.


A nestbox in north Davis, waiting for the right tenants

It’s also a good time to clean out any boxes occupied by wasps or rats. Removing unwanted species from boxes is a somewhat unpleasant but important part of prepping for the songbird breeding season. Wasps are a pretty common issue for our boxes. We try to scrape them and their nests out early in the morning while it’s still cold and they’re not very active. Rats are less common, but usually dealt with pretty easily. Boxes with leaf nests (not built by birds) are emptied carefully, allowing hiding rats to jump out and run away. They seem to mostly stay out once we evict them early in the season. Sometimes wasps also hide in rat nests – those are my least favorite nests!

We’ve restocked all our field work supplies for the season too. Hopefully we have more than enough bands for the many new birds we expect to find.


Some of the color bands that will be put on birds’ legs this year


Tree Swallows

Last week, I saw about a dozen tree swallows flying together in Winters. I was replacing broken nestboxes, and a couple of them even inspected and sat near one new box for a bit! It’s still very early in the year, and I don’t expect them to start nesting until late March or early April. However, I’ve heard that some nestbox trail monitors in other states are also seeing early box visitors this year.


Tree swallows zooming through the air in Winters

We’ve recently received some lovely new nestboxes for the year from Ron and Sara Ringen. They have donated handmade nestboxes to our project for the past several years. Replacing and repairing old nestboxes makes our nestbox trails safer and more effective for the songbirds.


A fresh batch of nestboxes

Other animals like to hang around the nestboxes in winter. I recently found a couple of boxes full of walnuts, presumably stored by a squirrel. I’m not sure if it would have been able to remove the nuts again through the small box entrance. We’ve also had a lot of woodpecker damage. I caught a northern flicker in the middle of pecking a large hole in one nestbox last week. The drumming is really loud on a hollow nestbox!


Walnuts stored in a nestbox


A nestbox with an entrance hole that has been enlarged by a woodpecker

There aren’t many boxes left to replace or repair now. In about a month I’ll start checking for nests. Hoping for a great nesting season for our native songbirds!


Lush grass at our Mace Boulevard site


Preparing for Spring


Putah Creek near the city of Winters, January 2020

The 2020 breeding season has yet to begin for our cavity-nesting songbirds, but pretty soon it will be time to start repairing, re-hanging, replacing, and cleaning out the nestboxes. Most of the species that use these nestboxes tend to start scoping them out pretty early in the spring or late winter, so it’s important that we have everything in good condition and in the right locations at that point. However, if Putah Creek floods within the next couple of months, some boxes could still be swept away or become damaged. If only I knew how bad the rain and flooding are going to be this year.

Before we know it, spring will come and we’ll be spending hours each week checking nests and recording data. It leaves little time for catching up on other tasks, so now is the time to make all of our preparations.