BEST YEAR EVER 2017, 162 NEW OWLS!

Fall 2017 migration season kept the BCCER owl banders very busy, and very happy! We had 175 total captures including 162 new owls and 13 same season recaptures. The owls consisted of 121 females, 11 males and 30 of unknown sex. We had a whopping 120 hatch year owls (owls hatched in summer 2017) and 40 owls were two years and older (17 were three+ years!). See the previous post for more details: http://birdbling.blogspot.com/2017/11/one-hundred-and-twenty-nine-owls.html

ONE HUNDRED AND TWENTY NINE OWLS!!!

Yep, that's how many owls we have banded since our first night of owls on October 12, with an opening night of 13 owls! Now on November 3rd, we still have a couple of weeks of migration (October 15-November 15, with sampling on either end). It is our highest number of migrating owls since we have run the station annually in 2005. VERY exciting! The majority >80% have been Hatch Year (HY) owls, hatched sometime this summer in 2017. All these youngsters are easy to age. Here's how. We look at the dorsal side of their wings to see what their molt pattern looks like. And we use descriptions like chocolate to describe the color differences between new and old feathers. We look at the remiges; the primaries (10) and secondaries (13).

Hatch Year, all feathers one age (uniform molt pattern)

Second Year, outer primaries and inner (closest to body) secondaries have been replaced,the new feathers are darker(dark chocolate) and of higher quality then the old,
retained (milk chocolate) feathers. 

After Second Year, (over 2 years old) has three generations of feathers
fresh (dark chocolate), old (milk chocolate) and very old (old milk chocolate!)

And then, there is the magic trick to confirm our age determination. We look at the ventral wing and turn on a black light and like a black light poster, the feathers glow! It's actually a pigment called porphyrin. If you like chemistry, go here to learn more about porphyrins.

Notice the difference in porphyrin glow? As the feather ages, the pigment ages too;
the older feathers don't glow as brightly as the fresh feathers. How old is this bird?

OH, AND THAT SPIDER....

The wolf spider! Volunteer Mary Muchowski found this lady on our way down to check the nets. Guest Dan Roskopf was with us to meet a NSWO, and took the spider's photo. She's a protective mother, carrying tens of babies on her back. Apparently this is rare spider behavior, only wolf spiders do it, so I feel very excited that we got to see her! Watch this video to see a live version of active young wolf spiders: 

Wolf spider mother and hitch-hiking babies, Dan's photo

there is always something interesting in the night.... Come join us and see for yourself!

Dan and Mary with NSWO, Dan's first!

OWLS, BATS AND SPIDERS, OH MY!

Owl season was off and running on October 13, 2017 when program directors Ken and Julie and volunteer Mary, banded a whopping 13 owls!! Since then, we have been out six more nights and have banded 5, 5, 2, 7 and 6 owls, = 38 owls, averaging 6 owls a night. A great surprise, we had one recapture from our Snow Goose Festival event from January 2017, showing migration site fidelity. Recapture information is always valuable.

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  NSWO profile. They are amazing tiny predators, and captivate all that meet them!

Lucky guests, meet and release a NSWO

Volunteer Carol Anderson with saw-whet owl.
Volunteers help drive our program, thank you!

All our other owls are new owls without bands and most are hatch year birds, meaning owls were hatched in summer 2017, and it was a great summer for saw-whet owl breeding! We have also captured and released 3 pallid bats, a flying squirrel and a katydid!

OWLETS In a Box and Another Occupant

Ken was able to check the owlet box this week; the chicks look healthy and mom is still roosting in the box with them. Both owlets are losing their down feathers and looking more and more like adults as their contour feathers grow. They were more curious about the camera then mom, who has the adult wisdom to avoid predators, lie flat and be still.

This owlet in the box is still pretty downy.

This owlet is slightly older, showing more contour feathers

The nestling phase is about 35 days so they should fledge between the 3rd week and end of June. We were hoping to put up some cameras around the nest box to watch the parents deliver food and the chicks fledge, but the supporting trees were too far away. We'll have to come up with other ideas.

Meanwhile, last week we found another occupant in nest box #2. We have deduced, based on the list of cavity nesting birds in the area, that it was an ash-throated flycatcher egg. Since there was only one egg and it had ants on it, we determined it was abandoned. This weeks' box check confirmed it, no new eggs, more ants.  Here's how Cornell Lab of Ornithology describes the egg, "creamy white with reddish brown streaks and elongated blotches." Click this link for more information about the ash-throated flycatcher. 

Western Screech OWLET UPDATE and Photo Essay!

#1! Lots of down but some contour feathers appearing

#2 of the two owlets

It was time to band the owlets after peeking into the box last week, I determined they were old enough, ~ 3 weeks to 1 month old and getting ready to "fledge." Typically owls leave the nest cavity and are called "branchers", because that's what they do, sometimes falling clumsily to the ground, climb up a tree, and perch on a branch. Their growing flight feathers are heavy with blood and they beg for food and begin to persistently follow their parents around before they are capable of even moderate flight. I wondered about this being a successful strategy because it seems safer remaining in a protected cavity. But after seeing and smelling the remains of this nest box, I think I figured out why it's best to get out of there (see below!)

At least 3 prey remains in this nestbox

Here is more evidence of the male being a good provider with three different prey remains that might be a deer mouse, vole or gopher and the tiny remains of a pocket mouse or other tiny rodent.

Ken climbs the ladder and hands me the mom for
weighing and checking the band we put on last week.
You can see the plug in the nest hole.

We begin with Ken removing the female from the box (the nest hole is plugged to ensure she doesn't flush out of the nest) and handing her to me. She is held in a bag until the nestlings are banded. As typical for screech owls, she is very calm through this process.The female has a lot invested with two owlets, so would unlikely abandon a nest at this stage. Both owlets were plump at 135-145 grams (the same weight as some adult males).  We banded and weighed them separately, so owlet #1 remained in the bag quietly waiting for the sibling.The mom was also well-fed, weighing in at 190 grams!

One owlet banded and held in a cloth bag until the second owlet is processed

The owlets are returned to the nest box, then mom is returned. We wait about five minutes to remove the plug before leaving the owls safely in their box. I have no doubt the male is roosting somewhere nearby, but we were unable to find him.

OWLS and OWLETS!

Today Ken and I checked the boxes on the Reserve. We were particularly interested in Nest Box #15 (sort of like an address) where we discovered a nesting Western Screech Owl, 37 days ago in April. Today May 27, we saw a mom owl with her two owlets and a nice meal for the chicks, a deer mouse (peromyscus sp.)

A view from above: 3 screech owls and breakfast. Note the larger owlet on the left.
Owl eggs hatch asynchronously, so one will be a little older than the next.

Ken removed the female and lowered her down to me for banding. She remained still and calm through the process.We returned her to the box after taking some measurements and examining her condition.

Here I am taking the wing chord measurement of the owl.
Note the band on her right leg.

Then I looked at her brood patch. Hormones help release breast feathers providing direct heat exchange for incubating eggs and brooding young,until owlets can thermoregulate on their own. This female's brood patch is already getting pin feathers (two dark lines under her bare skin), because the owlet's feathers now keep them warm. By fall her breast will be feathered, which will help keep her warm for the winter months.

The brood patch, well past its use for warming chicks. Because the
chicks now have feathers they no longer need warming by the adult.

Leftover prey shows the male is a good provider. He was likely roosting in a cavity nearby, and maybe observing us. Stay tuned for the rest of the story!

A view with the mom removed. The owlets are about the size
of an adult deer mouse (right corner), and too small to band.

The Cornell Lab of ornithology is a great resource for bird natural history including screech owls. Also click here for a nice overview of owl courtship and reproductive behavior.