Monday, December 10, 2012

Determining the Sex of a Saw-whet Owl

Our 116 owl captures during our 2012 banding efforts resulted in a typical skewed sex ratio with high numbers of females. This is common across saw-whet owl banding stations and it is assumed that territorial males might not migrate or are not as attracted to the audiolure as are females, thus capturing fewer males.  

Our BCCER population looked like this: 77 females (66%), 13 (11%) males, and 26 (22%)of unknown sex.  So how do we determine an owl's gender anyway?  A method used by all Project Owlnet banders is to measure the wing chord and the mass (weight) of the bird. Together the results of two variables can help determine the sex. 
Measuring the wing chord distance; the distance from the wrist
to the longest  primary feather using the natural curve of the wing.

weighing the saw-whet owl in a tube to contain the bird
Of course there can be some overlap between the size of the male and female owl, and that becomes the "unknown" zone.  Below is a the discriminant analysis function using the wing chord and weight of known gender birds, to help banders determine sex. The red points are females, the blue  points are males. If an individual's measures fall in an area of overlap, we have to identify its gender as unknown.

a discriminant analysis function using wing chord and 
weight to predict the gender of a  saw-whet owl

To learn more about this function, or sexing and ageing saw-whets, go to the direct source, project owlnet!

Thursday, November 29, 2012

Flying for OWLS! In search of Gizmo, Belle and Cupcake

As a biologist you get to meet some cool people and do some cool stuff!  I met pilot Bruce King at an Altacal Audubon Society meeting. Knowing I was installing radio transmitters on wintering saw-whet owls with grad student Julie Shaw, he offered to take us up in the air if the owls flew our of the study area- the Big Chico Creek Ecological Reserve (BCCER).  Bruce is a pilot, farmer and photographer, taking pics of our beautiful region.  See his website: BruceKingPhotography for some amazing photos. 

Bruce King and his tail-dragger plane-seats 2!
Julie and I installed 3 transmitters on Saw-whets we named Gizmo, Belle and Cupcake. They stayed on the Reserve for only a few days each and we lost their signal.

Here's Belle before release, note her radio antenna
emerging from her backpack (under feathers)

Call in the Owl Detection Support Team: Bruce, we need to fly! I was the lucky passenger. Bruce's plane is a Super Cub model, light in weight for lift and maneuverability it provided a rather cozy ride!

Pilots seat and controls-I'm right behind this seat!

Ready to fly-sitting in the back seat with all my gear
including a receiver  to detect  owls.
We started at the Ranchaero Airport in Chico and flew just south of downtown then up highway 32 to where we released the owls at the BCCER. You can see it was a lovely view with the fall colors in peak and clear skies toward Lassen.
Flying up the Big Chico Creek Canyon 

We flew right over the Reserve. You can see the barn, maintenance facilities and ranch house.  The barn is where we install the transmitters and our OWL3 banding station is just west (left) of the meadow in the mixed forest.

Having no signal we headed north along the foothills to Red Bluff. I recreated the flight path here, although it is not completely accurate, we covered about 150 miles, flying south along the Sacramento River.  We passed over many of the wildlife refuges which looked so beautiful in fall color.

Bruce showed me several eagle nests including one with a bald eagle sitting in it, I suppose a good winter roosting site.  We flew over the Butte Sink and saw many large flocks of white-fronted geese, tundra swans, sandhill cranes, smaller flocks of snow geese and many groupings of decoys staged by hunters. And although we never detected an owl it was well worth this exciting adventure. Thanks Bruce for your expertise and generous donation!

Saturday, November 10, 2012

"Making and Keeping Memories - Ending Alzheimer's" Silent Auction Winners Meet the Owls!

Our crew met with the silent auction winners for an owl night out, at the "Making and Keeping Memories" Alzheimer's Association Fundraiser hosted by Becky, April and the Book Family Farm in June 2012.  This was a successful and tasty event, with wine and beer/food pairings and music by the Railflowers.

Friday's guests were an interesting group of 6 well-traveled and adventurous ladies (2 having just zip-lined over the forests of Costa Rica!) and they fared well during the coldest night of the banding season so far  -  38*F.  Fortunately we were able to treat our guests with a heater and hot drinks. At sunset we heard a N. Pygmy Owl trilling. In the early night we heard Sandhill Cranes and later Tundra Swans overhead.

Ladies from the Alzheimer's Fundraiser with me and a Saw-whet Owl
Although the night seemed perfect, a cold night following a storm with no moon, the first 3 net runs were empty, other than a rain beetle that we released from the nets. Then came the owls, 4 in total, including this photogenic After Second Year (ASY) male. Our 4th owl broke the season total at 100 owls! We think our guests definitely made, and will keep, the fun memory of meeting the saw-whet owls. Us too! 
ASY Male - photo by Steve King

Monday, November 5, 2012


We are having a fabulous season for owls!  Last year at this time we were at 77 owls at this date and we are currently at 84. Click here to see 2011/2012 comparisons. Our hatch year to adult ratio is higher this year, indicating a decent reproductive rate in the 2012 season. Here are the latest stats:
10/27 7 NSWO, 2HY/5AHY
10/29 1 NSWO, AHY
11/1   6 NSWO, 2 HY, 4 AHY
11/2   8 NSWO 4 HY, 4 AHY
11/3 10 NSWO 5 HY, 5 AHY

A first year male NSWO. Like other raptors, males
are smaller than females. Photo by Steve King


Our project is pretty well known in the community after 8 years, and we encourage and make room every season to have people attend field trips and other events to come see the adorable saw-whet.  Scheduling can be tricky with training new volunteers our owl protocol, inclement weather cancellations and banding only 5 nights/week for 5 weeks! This season alone we've great nights with the following groups and events plus several other guests not included in the following:
Donations Events
Candles in the Canyon winners
Snow Goose Festival winners
Alzheimer's Fundraiser
Field Trips
Sacramento Audubon
BCCER (2 groups)

The amazement on people's faces is obvious when a saw-whet is extracted gently from the nets or a bag for processing. The saw-whets make good candidates for showing the public due to their mostly mellow nature and tolerance for handling. Often they seem as curious about us as we are them. Check out some of our happy guests!

Sacramento Audubon Group
Guest of
Candles in the Canyon winner

BCCER outing - the owls can be calmed
when gently stroking their forehead
BCCER outing happy guest!
Lucky Owloween Group - Altacal Audubon Society and volunteers 
Early to bed Owloween boys, still got to see
an owl - and adopted her through our Adopt-an-Owl program!

TRACKING GIZMO!" - adventures of raffle winner

On our "Owloween" field trip we had our guests select 4 tickets for our raffle fundraiser winners. The prizes were a choice between a nighttime banding adventure or a daytime tracking excursion.  Winner Rachel Libby  (congratulations Rachel!) chose to trek the Big Chico Creek Ecological Reserve with MS student Julie Shaw. Together they waded across Big Chico Creek (barefoot!) and climbed steep slopes while scrambling through the brush in search of "GIZMO," our first radioed owl of the season. Julie and I installed a transmitter on Gizmo, a two-year old female, on November 1, 2012. By the next day she had flown across the creek and for days was tucked away in places impossible to get a visual on her.

"Gizmo", tracked to her daytime roost, a Toyon. Photo by Julie Shaw
On Nov 5, Gizmo was found across the creek from green gate, looking great, with her radio and harness in place. You can see her radio antennae in this picture. Click here to see her travel map. Nice work tracking the elusive Saw-whet owl Julie and Rachel!

Saturday, October 27, 2012


Tonight, October 27th,  we will draw 4 lucky winners to meet the Saw-whet, by day or night.  This is a unique adventure and will make a great gift too! See the details about our outings at the September 2012 Post (this blog).  Tickets are 1 for $3.00 or 2 for $5.00 and can be purchased by emailing with the number of tickets you want.  Then, send your check to: Altacal Audubon Society PO Box 3671 Chico, California 95927-3671, and put OWL RAFFLE in the memo line.  Below is an example of whoooooo you might see, by day- or night!

POM (egranate), one of our radio-marked owls,
 tracked to her daytime roost.  She was very interested in our activities!
J. Shaw Photo
We have added a bunch of new owl photos for adoption, including this cutie below.  Adoption certificates make great gifts and help support our program.  Thank you for your support!
Northern Saw-whet Owl, by night, you could see one!

Sunday, October 21, 2012

KIDS and OWLS (and banding results Oct 15-19)

We love having parents and their kids come to meet the owls. It's our opportunity to excite them about the night and owls, and science and conservation.  On Friday, we had two very engaging children, one a budding writer and the other on his way to becoming an investigative reporter. We had a great time answering all kinds of questions and laughing-and so did they! 
Happy owlers and their very first saw-whet owl (photo by Shari Brogden)
Our captures have been interesting; a boom and then a decline.  Here are the results from our last 4 banding nights:
Oct 15 - 12 NSWO 8 HY/4 AHY
Oct 17 - 10 NSWO 7 HY/3 AHY
Oct 18 - 4 NSWO  1 HY/3 AHY
Oct 19 - 2 NSWO  2 HY
We have a nice ratio of hatch year birds (61%) to adults (39%), indicating good reproductive success (or very net savvy adults!)

Wednesday, October 17, 2012

12 Owls and 2 Oddities

Our owl numbers are increasing nicely, it is proving to be a great start to our year.  Here are the last two nights of banding results:
October 13: 3 NSWO 1 HY, 2 AHY (2 hours)
October 15: 12 NSWO!!! 8 HY, 4 AHY (4.5 hours)

Catching owls, particularly in the numbers we do, results in those with some abnormalities. Here are two: a crossed bill which could be very detrimental to hunting, and one white talon, which is likely non-threatening in any way, just different. Steve King took this picture, from the left of the owl. You can see the long mandible.
from the right you see the crossed maxilla. The good news is this bird is at least 2 years old, so has learned to live with the challenge of an abnormal beak. Unfortunately beak abnormalities have increased since the 1990's and based on information found on the web about deformities: "in birds can be caused by many different factors, including environmental contaminants, nutritional deficiencies, and bacterial, viral, fungal or parasitic infections"(" Other than our foreign recap from Montana, we have no idea where this bird came from.
Banders  Mike and Raina photographed this bird with one white talon, which is likely non-threatening in any way, just different. Although it does appear to be longer than the black talons.
The more birds we capture, the more we are likely to see some oddities. We always discover something new!

Saturday, October 13, 2012


Our saw-whet season officially starts October 15 with our standardized 5 days/week monitoring. But we always like to do a little random sampling to see when the first birds show up.  And we are glad we did!

Trio of Saw-whets! Photo by Steve King
Starting on September 29th, we had a zero owl night, with no owls (of any species) heard. On October 6th banders Mike Fisher, Raina and Steve King and Julie Shaw gave a special outing to Big Chico Creek Ecological Reserve guests. Everyone was incredibly pleased with TWO saw-whet owls and a Myotis bat, hooting Great horned owls and a trilling screech owl.

Since then:
October 8: 2 NSWO, 1 Hatch year (HY), 1 After Hatch Year (AHY)
October 11: 6 NSWO, 3 HY and 3 AHY!

It is bound to be a good season for owls!
You can join us too - check out the post below for our awesome owl outing raffle.

Sunday, September 16, 2012


OWL Fans Unite! 
Fundraiser to Support Altacal's  Northern Saw-whet Owl Project!
Northern Saw-whet Owl nestling, photo by Marcel Holyoak
Two Unique Adventures at the Big Chico Creek Ecological Reserve 
**for 4 Lucky Winners and 4 lucky guests!**

1)     Northern Saw-whet Owl Mist Netting and Banding - a nocturnal excursion!
Saw-whet Owl release, photo by Steve King
Tune in to the forest night life under the Milky Way, listening to owls; hooting Great Horned, trilling Western Screech, and tooting Saw-whets, and the sounds of other nocturnal critters. You will learn about the migratory ecology of the Northern Saw-whet Owl (Aegolius acadicus) in the Sierra Nevada foothills with avian ecologist Dawn Garcia and her banding crew. Mist-netting and banding will be conducted at the Reserve where Dawn is researching owl migration, now in its 8th season.  Guests will observe owl banding and data collection, and may have the rare opportunity to release one of the petite owls!  It is an easy walk from the banding station to the nets. A specific date between October 30 and November 30, 2012 will be arranged with the raffle winners as the season approaches. 
2) Tracking the Northern Saw-whet Owl - a diurnal excursion!
Enjoy beautiful fall foliage and avian species such as red-tailed hawks, California quail, wild turkey, sparrows, hermit and varied thrushes, American dippers, and possible western screech/northern pygmy owls while tracking radio-marked saw-whet owls. Bobcats, mule deer, and bears are often seen on the Reserve as well.  Tracking may include crossing Big Chico Creek and hiking up steep slopes. The terrain can be strenuous depending on where the owls are.  Be prepared for an adventure! A specific date between November through December 2012 will be arranged with raffle winners as the season approaches.

"Luna" Saw-whet Owl roosting, photo by Julie Shaw
How to Purchase Tickets!
Raffle tickets will sell for $3.00/ticket or 2 for $5.00 at our September 17 and October 15 programs at the Chico Creek Nature Center and events: The Oroville Salmon Festival  on September 22, 2012 and Sacramento Wildlife Refuge’s Birthday Bash on October 13, 2012. You can also email me at  We will draw names for four winners on October 27, 2012.  ** each winner can invite 1 guest for the excursion of their choice.**

Sunday, July 22, 2012

Flammulated Owl Night at Lake Davis

Mid-July I took fellow owl researcher Julie Shaw to check out a Flammulated Owl (Otus flammeolus) project that is occurring on the Plumas National Forest. I work on the Plumas, conducting Northern Goshawk and Spotted Owl surveys (and other species surveys), but not near Lake Davis. David Arsenault, founder of American Valley Environmental and Plumas Audubon Society (PAS) President, received funding from the US Forest Service (Beckworth) to conduct Flammulated Owl (FLOW) nesting surveys around Lake Davis where FLOW numbers are known to be high. He will examine FLOW populations in different FS management areas including fuel reduced and harvested stands. For more about this exciting and necessary project go here. David invited us to join him and his crew for an evening of FLOW banding. We were targeting the adults in one known nest. They found a nesting pair in a small woodpecker cavity (probably a white-headed woodpecker) in the large snag in the middle of this pic. This is what nesting FLOW habitat looks like.
Flammulated Owl habitat and nest cavity
You can also see the cavity here. David's crew is setting up mist nets proximate to the nest. They had watched the pair's flight path and knew that there were 3 eggs the cavity (2-4 is average).  They knew the birds would fly back and forth with moths, beetles and other insects - to feed the nestlings.
Setting nets in front of the nest snag
And we were successful!  Although the female bounced off the net and was too wise that night to be captured (she was captured and banded later). The male was captured 2x. See Julie taking out the male FLOW from the net.

Julie extracting male Flammulated Owl
Once extracted,  we weighed the male - a whopping 51 grams.  Our small male Saw-whets weigh 73 grams.  The one N. Pygmy Owl that I banded weighed 61 grams. These Flammulateds are tiny predators!  
Colin weighing FLOW - 51 grams, David taking data
Male FLOW - note the rusty/rufous color on the owl, giving the
species its ' name: flame or of a reddish color.
And I got to release my first-in-the-hand, Flammulated Owl!  We took down the nets and left the owls to their nocturnal foraging. Thanks David and crew, we look forward to hearing more of your study results.
Happy me!

Friday, February 10, 2012

Snow Goose Festival Outing 2012 - Owl Success!

Every season for the Snow Goose Festival we offer our Northern Saw-whet Owl banding and survey. It is always a sell out and this year was no different. The late January date (26) also allows us to see if we continue to have wintering saw-whets on the Reserve. We always start off with an owl prowl to survey the other species in the area. This year we had the resident pair of Great Horned Owls, putting on a nice vocal show of dueting.
As in most raptors the female is bigger than the male, but in the owls, the female has a higher pitched voice, making a nice auditory duet of high (female) and low (male) responses. I love this picture from the web showing the size difference, although these birds are much lighter in color than the Reserve pair. We also had a Western Screech Owl calling in the fog, very close over our heads with only nearby trees visible - very dramatic! Saw-whets were calling vocalizations that we describe as banshee wails, chitters and squirrel chirps. It was a very active night for our participants ears!
Our most exciting moment though was on the very last net run of the night - when two Saw-whet owls (seen in this pic held by me and Raina) flew into the nets, one right in front of our guests. We were all very awed as usual by the beauty of the little predators, and ended the night knowing that indeed, two new owls (previously unbanded) were wintering on the Reserve. Of course it is unknown to us if these owls have been here since fall migration and avoided the nets, or came in later, after our migration station had closed for the season. Another mystery!

Thank you Steve and Raina King and Nancy Nelson for helping with another successful owl adventure!