Spotted Owls

Since the star of my blog- the saw-whet owl, is out of our project area for the summer, I will introduce you to another species- the Spotted Owl (Strix occidentalis). I was fortunate to have my first wildlife job in 1988 when I worked with the US Forest Service gathering baseline data on the Northern Spotted Owl (Strix occidentalis caurina- N. SPOW). Since, then the N. SPOW has been listed as threatened under the Endangered Species Act (1990) in Washington, Oregon and California, primarily due to loss of habitat (late successional forests), and in the last decade and second major threat - competition with the Barred Owl (Strix varia). The Barred Owl expanded its range from the east of the Rockies and is a larger, more aggressive and more opportunistic owl (in habitat and prey preferences) then the Spotted Owl. More on the Barred Owl later.

Working in Washington for a consulting firm for five years, I had the opportunity to help conduct a demographic study, where we located, captured, color-banded, and followed families of spotted owls and their young as seen in the photo above. These owls are amazingly tame and have incredible dark eyes. They are considered a large owl and primarily eat flying squirrels and wood rats.

The California Spotted Owl (Strix occidentalis occidentalis - CA SPOW) is found in our neck of the woods (the southern-most Cascade Range, Coast and Sierra Nevada Ranges) and is not currently listed (it is a CA species of special concern) although the Barred Owl populations are increasing here and becoming a threat to Spotted populations. I have worked with the CA SPOW for a several years for a consulting firm and currently for the US Forest Service. We are also monitoring their populaitons in the Sierra Nevada and documenting their reproductive success. To me, the subspecies are very similar in looks and behavior. The plumage of the CA SPOW is somewhat lighter than the N. SPOW which might you see in the picture below, a handsome male spotted owl - photo by my colleague Mary Muchowski. I do love my work!

Steve's Owl Recorder- the technical side of monitoring

Steve King is one of the owl project's dedicated volunteers and brings his technical expertise to our program. Steve set up a remote broadcasting and recording device on the Big Chico Creek Ecological Reserve (BCCER) that he can monitor from his computer at home. Here is how he explains it.

The owl recorder is a device that can play a bird or owl call (in this case a N. Saw-whet Owl) and then record for a period of time after. The recorder can run completely unattended or can be commanded to play specific calls and record from anyplace with Internet service. The idea was to help us better understand when the Northern Saw-whet owl arrives and/or passes through the BCCER during migration. It was designed using a small low power computer. A USB audio input and output device was connected and a audio amplifier was also added that was capable of driving outdoor speakers. The picture above shows the recorder (and Steve) with the antenna on top, computer in the white box and the speakers down below. The battery is on the ground and the solar panel is behind the camera in a sunny location.

The call is played for 15 to 30 seconds and the recording is started right after the call ends. The time of the recording can vary. Once the recording is completed, it is sent to another computer over a wireless connection. The second computer is a little more powerful and it converts the audio wave file recording to a MP3 file and also creates a spectrogram of the audio recording. The spectrogram and recording are uploaded to a web page where we check for sounds. We can look at the spectrogram to determine if any sounds are on the recording. Below is a spectrogram after playing a Saw-whet Owl call, which shows a Saw-whet responding in a series of toots. The spectrogram and recording below was made in April of 2011.

Follow this link if you would like to hear the audio for the spectrogram. This was the latest detection for a Northern Saw-whet owl on the reserve for this season. There was a little wind that night, which shows up on the right of the spectrogram. There is also a highway in the area.

Pretty cool stuff! (comment by D Garcia)

Spring Migration- what do the years tell?

Just recently we completed our NSWO spring sampling and ended up with a California Bat and no owls.

Most every year we - the owl team - make some efforts to determine when the N. Saw-whet Owl spring migration occurs in our area. We have nailed down the fall migration which occurs between Oct 1 and Nov 30, and peaks at the end of Oct, beginning of November. We also know that birds winter at the Reserves based on recaptures in winter months and telemetry locations in 2011. I would consider any February birds that we captured as wintering birds, with some possible movement at the end of February.

Over the years it appears that the birds move between the first and last week of March. 2009 was odd as we had a March 4 capture (could have been wintering) and an April 4th capture (our latest season capture). Using Steve's technology (a remote broadcaster and recorder) we have documented our latest detection on April 21, 2011!

Here are the data. Please note all of the 0 detection/capture nights and think about how dedicated my volunteers are to continue through the years.

2006

1/6/2006 (3 [2 and 1 recap] at BCCER)

2/7/2006 (3 [1 and 2 recaps] at BCCER)

2/22/2006 (0 at forest ranch)

3/7/2006 (2 at BCCER)

3/20/2006 (detections but no captures)

4/21/2006 (0 at BCCER)

4/28/2006 (0 detections/captures at BCCER)

4/30/2006 (0 detections at BCCER)

5/7/2006 (0 detections Magalia @2600')

5/12/2006 (0 detections forest ranch @3000')

5/16/2006 (0 detections at BCCER)

5/17/2006 (0 detections at Magalia)

2007

1/21/2007 (2 [1 recap at BCCER)

3/1/2007 (0 at BCCER)

3/10/2007 (4 at BCEP)

3/16/2007 (0 at BCEP)

2008

2/19/2008 (1 at BCEP)

2009

1/22/2009 (1 at BCEP)

2/28/2009 (0 BCCER)

3/6/2009 (1 at BCEP)

3/20/2009 (o captures but NSWO detection at BCCER)

3/23/2009 (3 at BCCER)

3/25/2009 (3 at BCCER)

2010

1/8/2010 (2 at BCEP)

1/8/2010 (3 [2 new plus 1 recap] at BCCER)

1/31/2010 (0 at BCCER)

2/18/2010 (0 at BCCER)

2/25/2010 (0 at BCCER)

3/4/2010 (1 at BCCER)

3/11/2010 (0 at BCCER)

3/13/2010 (0 at BCCER)

3/25/2010 (0 at BCCER)

4/4/2010 (1 at BCCER)

4/7/2010 (0 at BCCER)

4/21/2010 (0 at BCCER)

4/30/2010 (0 captures/detections)

2011

2/10/ 2011 (2 [1 new and 1 recap at BCEP)

3/7/ 2011 (3 [1 new and 2 recaps at BCCER)

3/29/2011 (no detections or captures at BCEP)

3/30/2011 (no detections or captures at BCCER)

4/12/2011 (bird tooting-heard on Steve's remote recorder)

recordings in between April 12 and April 21 accidentally deleted by me

4/21/2011 (bird wailing- heard on Steve's remote recorder)

Winter Sampling at BCCER - March 7, 2011

On this winter night we set up our station at OWL3 at the BCCER. Past years have suggested that spring migration to the summering grounds occurs in early March when we have captured several owls in one setting. On this night serenaded by a great horned owl and numerous flocks of snow geese flying overhead, we captured three owls, but only one of these was unbanded. The other two owls had been captured three times previously, making this their fourth capture, an uncommon event. Our recapture rate is low and this is attributed to the birds being "net savvy;" once a bird is captured they rarely go back to the same site during the same season. These two owls seem to be "net happy," due to the high number of times they have been captured in the same season. It tells me that the audiolure is extremely attractive to some owls!

Here is their story.

Both birds were banded on October 15, 2010 during fall migration at the OWL3 site at BCCER. They are identified as band number 1014-14523 and 1014-14524, and although their band numbers are sequential, they were banded at different times that night. Each was captured on different nights two more times until March 7, 2011, when they were captured together again- this time during the same net run time. The number of days between capture is 149 days -close to 5 months, which is great evidence that the BCCER provides fine wintering habitat for these owls. Other research has suggested that siblings may travel together during migration, and although we can't say for sure, these birds could be siblings, based on the their capture patterns, see below.

Capture Date / Mass in grams / Sex (based on wing chord length and mass)

1014-14523

10/15/2010 84.3 unknown

11/1/2010 98.9 female

1/27/2011 84.9 unknown

3/07/ 2011 86.9 unknown

1014-14524

10/15/2010 95.4 female

10/16/2010 90.4 female

11/3/2010 97.2 female

3/07/ 201 93 female

Winter Sampling at Butte Creek Feb 10, 2011

Several of us met at the Butte Creek Ecological Reserve (BCEP) to conduct a second sampling of wintering saw-whets in this area. In January 2011 we banded 6 NSWO, a record for this location in winter. Under a 1/2 moon and a starry night sky we sat listening to flocks of snow geese and tundra swans, canada and white-fronted geese, and a saw the dark silhouette of a great horned owl over our heads. We heard only a few saw-whet owl vocalizations and recaptured a bird of unknown sex (wing/mass measurements in the M/F overlap range) banded in January 2011, and one new Second Year female, her cuteness captured (above) by Steve King.

The following images/photo shows an aerial view/on the ground habitat of where we set up our nets at BCEP. Click on the image for a closer view of our net array.

Saying Farewell to HB - removing the radio harness

Here you can see the location of HB's radio- somewhat obscured by her feathers- placed properly on her back. She has preened her antenna which is why it is kinked (Glenn photo).

Julie Shaw, CSU Chico grad student researching winter roosts sites of the saw-whet, called me and said "HB is low in a toyon, do you want to take her harness off?" HB is our remaining BCCER owl that still had a radio, for 91 days. Because the radios or so small (see earlier post "tracking the saw-whet"), they last only about 90 days-so we knew the battery would die soon. HB has been alternating in high (85') to low (3-6') perches and this day she was low. Although the radio harness or backpack is designed to bio-degrade, hers was still intact and I wanted to remove the backpack to set her free of any impediments caused by us. HB presented us with a perfect opportunity! Julie's trackers Glenn and Shannon took some of following photos-thanks!

Removing the harness

Step 1: find the bird. There she was about 6 feet high in a toyon shrub (Julie Shaw photo)

Step 2; Capture. There are many ways to capture a roosting saw-whet. I chose to use a capture technique where, with an extension pole, I place a coated loop around her head and wing. This immobilizes her temporarily while Julie then can hand catch her, as the second picture shows (Shannon photos).

Preparing to capture

HB is safely captured

And happily, Julie has safely secured HB (Shannon photo)

Step 3: Remove the harness. Next we find the harness material and clip it with scissors, and remove the backpack and radio. HB, in the second pic in this cell, is now free of her harness (Shannon photos).

removing the harness

harness-free

Step 4: check body condition. We want to check her body condition to see make sure the harness did not cause problems. Her keel (breastbone), felt fleshy on each side- indicating she was flying and eating well. We knew this though because Julie had found many pellets (regurgitated bones and fur/indigestible prey parts), and we alway saw urates below her roost, also indicating she was eating, thus hunting well. We checked her skin for potential abrasions from the material/radio- and fortunately there were none (Shannon photos).

checking the keel

checking the skin

We also weighed her and found that she was 97 grams, up 3 grams from her original mass of 94 grams! HB, a darling owl, who gave of lots of information about the wintering habits of saw-whet owls (Glenn photo).

Step 5: release. We released HB with high hopes that she would continue her success through the breeding season, likely somewhere in the Sierra Nevada Range, and thanking her for enlightening us to what habitats and prey (Julie collected almost 45 pellets that she will analyze for species composition) some saw-whet owls will take advantage of during the winter. These insights are invaluable for saw-whet owl conservation (Julie photo).

And as with any happy ending, we had a fantastic sunset as we exited the BCCER (Dawn photo)!

Those nestlings have BRANCHED

Have you ever seen anything cuter? These sweet branchers ( an owl nestling who leaves the nest cavity and "branches" to nearby trees but is very dependent on parents) are the 2 kids that were mucking it up in front of the camera from their nest cavity (see them on video under the COOL LINKS tab). I received this photo from Tess McGurie who happened to be in our Snow Goose Festival "Owl night Out" event. She told me about this pic by Albert Boosman who photographed the branchers on May 21, 2010. Keep your eyes peeled for the petite fluffballs when hiking in the forests in summer!