Tree Swallow survivors

One box at Dry Creek Confluence is particularly special, because on the day I went to band the chicks about 2 weeks ago the box was found on the ground because the branch had broken from the wind. The Tree Swallow nestlings in the box were barely alive, very weak, and very stunted in their growth for their age, it seemed that they may have been on the ground and under the fallen branch for at least a full day (it was also the highest box of all the nestbox trails, so it was a big fall). After banding them quickly we put the box the box back up, close to the original location, hoping that the nearby Tree Swallows flying around were their parents. I checked the box a couple days later when I was back at the site to band another box, and I saw both parents actively feeding them. Now the chicks are almost ready to fledge!


Tree Swallow almost-fledgling waiting for food

Here are a couple recent banding photos:


Banded Western Bluebird nestlings


Tree Swallow nestling

And just a small update on the Lake Berryessa glory hole – it is no longer spilling!


Lake Berryessa glory hole 5/27/17

-Evelien de Greef

Stages of Tree Swallow

All the pictures in the post were taken this morning, from several different clutches. It’s interesting to see the differences in appearances throughout the growth stages.

Here are some Tree Swallow chicks just about 1-2 days old. Their eyes are not open yet, their skin is very pink.


Tree Swallow chicks ~1-2 days old

The chicks below are about 4 days old. Their eyes are still not open. You can start to see the feather tracts forming on their skin.


Tree Swallow chicks ~4 days old

Here we have some chicks that are just a little older than a week. Their pin feathers (developing feathers) are present and eyes are open.


Tree Swallow chicks ~9 days old

This cup of Tree Swallows (below) are about 2 weeks of age, and just banded this morning.


Tree Swallow chicks ~14 days old

After we band them, we do not disturb the nestbox for about 2 weeks in order to give them the appropriate amount of time to fledge. In the picture below, you can see some older Tree Swallow nestlings hanging out at the nest hole waiting for their parents to come back with food. These nestlings were banded last week, so we just passed by this box today. Next week we’ll check the box to see that they all have left.


Tree Swallow chicks more than 20 days old

Here’s a video of one of the parents feeding the nestling waiting at the nest hole:

Tree Swallow feeding

After they have successfully fledged the nest, they may still rely on the parents to feed them for a little longer. Sometimes you can observe young birds begging for food when they vibrate their wings when the parents is near with food. We hope to see them again in the future, as a breeding mother or father rearing the next generation.


Tree Swallow mom ready to feed the nestlings

-Evelien de Greef

Birds in hot weather

This month is going by very fast. I can hardly believe there’s only 9 days left of this month.

Lately it’s been getting really hot. Today in Davis it’s going to be in the upper 90’s. I’ve observed a strange behavior in some birds, where they sit in the sun on a very hot day, poof up, tilt their head, and pant. I’ve noticed this in multiple species of songbirds. I wondered why they don’t just move to the shade. I thought it was very bizarre, because to me it looked like they were voluntarily giving themselves heat stress.  Apparently this sunning behavior may be a way for the birds to get rid of parasites (mites, lice…). By being in the heat, the parasites are forced to move off their back and onto their sides, and then the birds can just preen them off. It’s also just very hot so even when they’re not sunning, they are panting and holding their wings out a bit away from their body to lower body temperature.


Tree Swallow pair in the sun

Birds are quite amazing in how they survive this hot weather while continuing to take care of their eggs and chicks. The Killdeer mother on her nest at Dry Creek Confluence is still sitting in the hot gravel in direct sunlight keeping her nest at the right temperature (incubation is also used to keep eggs cool in hot weather). It’s been quite a few weeks seeing the Killdeer, I thought that her eggs would have hatched by now. Hopefully they didn’t get cooked.


Killdeer on her nest

With less rain and more hot weather, the creek water levels have returned to normal now. Previously flooded trails are reopened and all our boxes are accessible. Some boxes are gone (had been swept away), but otherwise the rest held up pretty well.


Putah Creek- Picnic Grounds 5/21/2017

Here are some recent photos:


Tree Swallow

At our nestbox site at Dry Creek Confluence, there are 2 boxes on poles someone had set up a while back. One of them is now being occupied by Tree Swallows (photo below). Last year we had a House Sparrow attempt in this box. We haven’t had any House Sparrows this season at all, not even one nesting attempt.


Pair of Tree Swallows

Here are some photos of Western Bluebirds with some food, ready to feed the hungry chicks:


Western Bluebird. Photo: Bob McLandress


Western Bluebird


recently hatched Western Bluebirds

Here are a few pictures of some of our interns doing nestbox work:


Jessica Kwok, Hanika Cook, and Lynette Williams checking a nestbox. Photo: Bob McLandress


David Eng, Jan Ng, and Christina Torres holding banded House Wren chicks


Lydia Kim, Matt Godoy, and Christina Scott holding banded Tree Swallow chicks


Tree Swallow chick being banded

It’s halfway through the nestbox season, time is going by fast!

-Evelien de Greef

Nestlings on top of nestlings

Lots of banding going on right now. The 2nd half of May is the busiest time of the nestbox season. Here are some photos of nestlings this past week:


We have a few nests of Ash-throated Flycatcher eggs, however, none of them have hatched yet.

In the theme of bird babies and spring, here’s a nest of Red-tailed Hawk nestlings I saw yesterday morning when I did a bird survey by Old Davis Rd. I think songbirds are cuter.


Red-tailed Hawk nest with 3 chicks

-Evelien de Greef

Sexing birds

Can you tell which Tree Swallow is a male and which is a female? Males tend to look more blue than green. But sometimes older females can look like that as well. The Tree Swallow on the right (above) fooled us by letting us think she was a male until we caught her and saw a brood patch.

Tree Swallows can be hard to sex based on plumage alone, which is why we check for brood patches in females and cloacal protuberances in males when we have them in hand. A brood patch is a bare patch of skin on the underside that the female uses to incubate her eggs and young. Breeding males will have a cloacal protuberance, which is a swollen cloaca, instead of a brood patch.

Sometimes you can tell differences in coloration. Here, the female is the greener one on the left, and the male is the bluer one on the right. It’s certainly easier to tell when they’re side by side.


Tree Swallow adult female (left) and male (right)

Regarding nestlings, Western Bluebirds nestlings are the only ones that we can sex. All the other nestlings (TRES, ATFL, and HOWR) all have the same plumage at that age so we can’t tell. Notice the shade of blue in these two nestlings. The darker shade of blue is a male (on the left) and the lighter shade of blue is a female (on the right)


Western Bluebird nestlings male (left) and female (right)

-Evelien de Greef

Bluebirds at the Arboretum, and first Ash-throated Flycatcher eggs

The Arboretum is getting filled with Western Bluebird nests. A few of them now have young chicks. Here is Rachel holding young bluebird chicks:


Rachel Alsheikh holding young Western Bluebird chicks

Wednesday morning at the Arboretum we were able to catch a few females on the nests, using proper timing (important to avoid catching adults in certain time periods of nesting!) and handling. Two of them were already banded – I love catching banded ones. The two recaptures were birds that nested here in the Arboretum last year. Since they raised successful clutches last year at the Arboretum, they’re back again this year.


Asiya Bhaisaheb holding female Western Bluebird


Rachel measuring the tarsus on a female Western Bluebird

The yellow lips you see on the chicks are used to help guide the parents to feed them. When the chicks open their mouths, the yellow lips make a circle shape, called a gape, basically signaling parents to “insert food here.”


young Western Bluebird chicks

At Russell Ranch, we found our first nest of Ash-throated Flycatcher eggs. This species likes to use mammal fur to make their nest, creating a really soft (and stinky) cup.


Ash-throated Flycatcher nest with 3 eggs


Ash-throated Flycatcher egg

Water level on the creek has gone down quite a bit. We are able to check some more boxes for the first time this season. I went to check out the glory hole this evening one last time before it stops spilling. It’s so close to not spilling!!


Lake Berryessa Glory Hole almost not spilling

Although not really related to Putah Creek, here’s an image looking over Solano County from my drive back from visiting the glory hole. I thought it was super cool to see this view, you can see Sacramento city in the distance.


Solano County

-Evelien de Greef


Chicks and chicks!

Here are pictures of some of our field crew holding chickies (and a couple with adult Tree Swallows).


House Wren parent with some grub

Here is our first banded Tree Swallow nestling of the season!


Tree Swallow nestling

Here are some young chicks. Tree Swallows on the left, Western Bluebirds on the right. Notice the difference in skin colors! Western Bluebirds chick are much more yellow.

-Evelien de Greef