Evelien’s final nestboxing

This is my final post here, as my position at the museum as the nestbox project coordinator is coming to an end. The project will continue, but this is the last few days of my experience with the Putah Creek Nestbox Highway. I was thinking about waiting until my last day to post this, but time is running short and I did not want to forget.

The field season is not over just yet, but I’ll be leaving California in less than two weeks. I’ll start with some updates and notes about this season and then end the post on a personal note.

All of our remaining active boxes are Western Bluebirds. I think because of their varied diet, they are able to nest successfully so late in the season. So far this season has produced 860 fledglings total and there are still a few more to come. Although it is not the final fledgling count, this is already the most number of fledglings this nestbox program has produced in a single year.


Western Bluebird nestlings

Kristen and I were surprised to find a new clutch of bluebird eggs recently, in a box that was otherwise inactive for the whole season. What we thought were the last two bluebird broods will be banded next weekend, but it seems like I’ll miss the new final clutch of bluebirds.


Kristen Z. and Evelien D. with western bluebird nestlings

Recaptures and re-sights are my favorite part of the nestbox experience. It tells us part of the birds’ stories and teaches us about their movements along the creek.


Western Bluebird male

Catching adult birds is challenging with the pole lifter device, but it is so rewarding. When we catch a banded adult, the first thing I do is look up the band information. Sometimes I don’t even wait until I’m back in my office and I’ll end up squinting at my phone to look at a tiny screen of spreadsheets with all the band numbers, trying to see where and when the bird was originally banded.

One of the highlights of this season was finding multiple 7-year old Tree Swallows. One was banded as a nestling in an orchard in 2011, and she raised a brood this year at Russell Ranch. Another was banded as a second-year bird in 2012 and has been seen nesting at Picnic Grounds multiple times (2012, 2016, & 2018). I think it’s amazing what these birds are capable of and how long some can live. The other extraordinary recurring bird is the bluebird, Tufty (I posted in April), who has nested at the same box every year since 2014. His nest of eggs was depredated in April this year and he has not been seen nesting again since. Although his nesting efforts ended on a sad note, he has been very faithful to his overall very successful box. He has a special place in my heart because every year I’ve been a part of this project he has not failed to show up for me.

Each year the breeding season zips by and it’s sometimes hard for me to believe I’ve been a part of the nestbox program for 5 seasons now. I feel like we just got our first eggs yesterday. I will miss Davis tremendously, which has been my longest home of 7 years, and I will miss the museum family that has been so wonderful to me. I’m going to start graduate school in Manitoba, Canada, in September. I’m extremely excited for this new adventure because I’ll be studying Purple Martins and their migration!

This photo I took in 2014 (below) is still my favorite of all of my nestbox photos. Like the nestlings getting ready to leave the nest, it is time for me to fledge from Davis and start the next chapter in my life.


Goodbye everyone, and thank you for following this blog. As the Putah Creek nestbox project continues, so will this blog but it will be lead by someone else. I’ve enjoyed sharing updates about the nesting birds and the creek, and I hope you have all enjoyed reading it as well.

-Evelien de Greef



Final nesting


Western Bluebird

The nestbox season is winding down. The last box of House Wrens were banded yesterday and the last Tree Swallow and Ash-throated Flycatcher chicks are coming up soon.


Bluebird eggs

There are a good amount of Western Bluebirds still active, in fact we even got new bluebird eggs this week! The photo to the left is a new clutch found at Picnic Grounds this morning. Yesterday a new clutch was found at Old Davis Rd. We’ll continue to look our for any more new ones, but those two may be the last nests.

This isn’t the final count, but so far 700 nestlings have fledged. There are still a handful more boxes left to band next week, and just a few more that have yet to hatch.

Also an update on the bluebird swallow mixed nest mentioned in the previous post- the tree swallow egg disappeared (possibly depredated, or thrown out by the bluebird), and there are now just bluebird chicks in that nest.

The breeding season is coming close to the end, and so is my stay in Davis. Time is going by so fast I can hardly believe it’s already middle of July.

-Evelien de Greef

Bluebird and swallow combined nest

Here’s an interesting case where a Western Bluebird took over a Tree Swallow nest. Last week this nest had 1 swallow egg, and today a bluebird has taken over with 5 more eggs and is now incubating all of them. This behavior of taking over a nest with eggs is seen more often in Ash-throated Flycatchers, but any bird has the ability to do it. Perhaps the Tree Swallow egg was abandoned and the bluebirds thought it was time for their turn, or perhaps the bluebird did decide to take over an occupied nest.


Western Bluebird nest (5 eggs) with +1 Tree Swallow egg

Nest take-overs are very common in the nest building stage (seen by the layers of different nesting material) but not as common when there are already eggs present. This is the first time I’ve seen a bluebird nest incubating an additional swallow egg. I do not expect the Tree Swallow egg to hatch, but we will see what happens in a couple weeks!

We have banded our 2nd clutch of Ash-throated Flycatchers, and we just got a couple more new flycatcher nests!


Ash-throated Flycatcher nestlings

We are still getting more and more hatches every week. Here is a Western Bluebird chick just about 7 days old.


Western Bluebird chick ~ 1 week old

It’s always great to see very attentive parents. This House Wren went right back to her chicks after I checked her nest.


House Wren

And here’s a Western Bluebird mother keeping watch.


Western Bluebird on nest box

So far 560 nestlings have fledged. Lots of boxes are starting on their second round!

-Evelien de Greef

Transitioning to Summer

Spring quarter is ending and we are now heading into the summer portion of the field season. We are so grateful for our field team! A big thank you to DeLayni Millar, Kristen Zumdahl, and our undergraduate interns Andra George, Annia Maliguine, Calvin Proctor, Danielle Fradet, Danielle Myers, David Eng, Elisa Fernandes-Mcdade, Emily Aguilar, Emir Gokce, Estefania Maravillas, Faith Yang, Genevieve Murphy-Skilling, Harnawaz Boparai, Josephing Rodgers, Juanita Stoltz, Kevin Ha, Kimberly Cabrera, Konatsu Ono, Lisa Pacumio, Lynette Williams, Mario Froelich, Megan Duncanson, Melissa Alpizar, Rayven Hernandez, & Yenifer Guzman.

Some of the interns will be continuing with us this summer for the 2nd wave of nestbox activity. 🙂

Here’s a tree swallow with a mouthful of mayflies on the left, and another swallow with a mouthful of damselfly “spaghetti” on the right.

And here’s a Western Bluebird nestling on the left, and some Tree Swallow nestlings on the right.

A lot of broods are currently in the process of fledgling. Below is photo of an almost-fledgling Tree Swallow waiting for his parents to come back with food. We do not disturb the box when they’re this old to avoid inducing them to prematurely fledge. After we give them enough time to fledge on their own, we’ll check the box to see if they have made it out successfully (indicated by an empty poo-filled nest). So far this season over 300 bird babies have successfully fledged. This number will likely double in the next few weeks!


Tree Swallow almost ready to fledge

The temperatures are going up as we are entering the summer heat. We’ll now start to check boxes only in the mornings.

-Evelien de Greef

First Ash-throated Flycatcher nestlings

Yesterday we banded our first clutch of Ash-throated Flycatcher nestlings. Ash-throated Flycatchers breed later than the other nestbox species because of their delayed arrival. Right now there a couple more active flycatcher nests, hopefully we’ll get continue to get some more soon.


Ash-throated Flycatcher nestling


Ash-throated Flycatcher nestlings

So far this season there have been over 600 chicks on the nestbox highway. Out of those, almost 100 have already fledged. Some boxes are already on its way for a 2nd clutch!


Tree Swallow nest with eggs

A note-worthy brood at Dry Creek Confluence is this group of 8 nestlings (photo below). This is the largest brood size I’ve seen in Tree Swallows. All of them are doing very well and have lots of fat. Their parents are doing a fantastic job.


Tree Swallow nestlings

Here are some more photos of our weekly field teams: 🙂


Annie M., Danielle M., & Faith Y. with Tree Swallow nestlings


Lisa P., David E., & Kimberly C. with Western Bluebird nestlings


Josie R., Konatsu O., & Rayven H. with Tree Swallow chicks


DeLayni M., Melissa A., Lynette W., & Estefania M. with Western Bluebird nestlings


Tree Swallow nestling

-Evelien de Greef


Female vs Male Tree Swallows

For Tree Swallow adults, males generally have the bluer plumage than the females. In the photo below you can see them side by side and notice the plumage difference. However, it is still good to confirm with them in hand because some females can look very blue. When we catch them, we can confirm females with the presence of a brood patch, which is a bare patch of skin on their underside that is used to transfer heat directly to their eggs and chicks. Males will have a cloacal protuberance (a swollen cloaca), an indication of breeding condition.


Tree Swallow pair (female left, male right)

The season continues to be super busy! Some broods have already fledged (meaning the nestlings have made it out into the open), and there could be some second clutches starting soon. Here are some recent photos of some of our interns with adult Tree Swallows.



Tree Swallow

Happy Spring!

-Evelien de Greef

Mother birds

Happy Mother’s Day to all mothers including the birds! It’s a lot of work for the birds to raise their chicks, having to incubate eggs for a couple weeks and then after hatching there is non-stop feeding from sunrise to sunset! There are lots of baby birds right now, and we’ve banded many nestlings the past week, and much more to come. P1200036.jpg

Here are some photos of our hard-working field teams!

DeLayni M., Juanita S., Harnawaz B., and Emily A. with House Wren nestlings

Elisa F., Calvin P., and Andra G. with Western Bluebird nestlings


Maria F., Yenifer G., and Kevin H. with Tree Swallow nestlings


Lisa P., Sam Y., and Megan D. with Western Bluebird nestlings

After banding the nestlings, we leave them undisturbed for about 1.5-2 weeks to give them enough time to fledge. When passing by nests that are almost ready to fledge, we sometimes see the young birds stick their head out of the hole while they wait for their parents to come back with food.


Tree Swallow fledglings at box

-Evelien de Greef