Friday, April 21, 2017


Western Screech Owl inside a nest box
Can you see the the owl in the box?  You are looking at the head and back of a Western Screech Owl inside nest box # 15. We believe she is incubating eggs due to her flattened posture and absolute stillness when we peeked the camera into the box. If she is incubating and all goes well, we can expect to see 2-7 nestlings within the next month.

So how did we see her? This winter Ken and crew installed nest boxes to determine potential use of the BCCER as breeding site for Northern Saw-whet owls, a cavity nesting species. To check the nests Ken attached a flexible cable with tiny camera and LED light to a bamboo pole, plugged in to his tablet. He can feed the camera quietly into the cavity entrance, see what is inside on his screen and then take a photo. We have conducted two box checks,

Ken's nest-cam set up. The camera is at the end of the pole
inside box #4. He is viewing the inside of the box on his tablet.

one on March 11 and one on April 19. In March, we found bird feces in two two boxes but no birds were present. We guessed the boxes were used by Northern Flickers roosting in the boxes at night. In April, we found identifying flicker feathers in the same boxes, and then we found the screech owl in a third box, What a fun surprise! Learn more about Western Screech Owls here.

Monday, March 6, 2017

SPRING MIGRATION, what do we know?

As with many of our questions, the answer is.....more study is needed! According to Project Owlnet, spring migration is poorly studied. And so, Ken and the owl monitoring team are making winter/spring efforts more standardized to identify migration timing on the Reserve. So far this year we have seen some new activity near the end of February with 10 new owls so far! Here's what it looks like:
February 25, 2 new owls
February 27, 5 new owls and 1 recap
February 28, 1 recap
March 2, 3 new owls
March 3, 0 owls
Bander Erika Iacona with one of the February 27 owls.
Is this a sign of spring migration? Possible, BUT, this year has been unusual, relative to the past 5 drought years. We have had record rainfalls and snow levels in the Sierra, which may hinder birds from moving to their breeding sites too early.So, we will continue our spring efforts to  enlighten our migration question this year. WAIT FOR IT!

Thursday, February 16, 2017


We know based on aural and/or visual detections that we have at least five species of owls on the Reserve; great horned owl, Northern pygmy owl, Northern saw-whet owl (NSWO, fall through spring?), California spotted owl (winter only), and Western screech owl (WESO). The screech owls are year-round residents and will sometimes come to investigate our NSWO caller, so they get caught in the nets. We have banded 25 WESO over 12 years of monitoring NSWO. Sometimes we are lucky to see them roosting in a cavity during the day, or perching at night. Banders Erika and Ken saw this owl perching in the barn, likely
Western screech owl in the barn at the Reserve
Possibly foraging on bats? He/she appears a little
perturbed at the disruption!
taking advantage of barn mammals. It may have been foraging on the bats that roost there! There happens to be a colony of wintering free-tailed bats, and potentially other bat species, living in the barn. I have seen great horned owls, peregrines, merlins, kestrels and red-tailed hawks capturing bats as they exit their roosts. It was quite an exciting flight dynamic as the predator bursts in a cloud of bats.  The success rate on capturing bats seemed pretty low. What we need to determine if this WESO has a palate for bats, is to find some pellets to identify prey remains.

Wednesday, February 15, 2017

A Winter Owl's Meal

Ken and team have continued monitoring owls through the winter and have found that three individuals have remained on site since fall. Three others were newly banded this winter and recaptured. It appears the wintering population of saw-whets on the Reserve is pretty good-which indicates that the prey base it sound. And proof is in the owl mass- all have increased since their first banding. Below is an example of this female's weight history, captured and weighed three times.
one wintering NSWO captured and weighed 3 times
01Jan2017 =  90.5 gr
02Feb2017 =  95.6 gr
11Feb2017 = 101.7 gr

NSWO are primarily rodent predators, but are also opportunistic, taking advantage of what's available (birds, insects, etc).From previous pellet analysis conducted by Julie Shaw (see earlier posts in 2010-2013) and visual observations we know Reserve owls eat field mice, deer mice and California voles. One owl even ate rain beetles! Saw-whets will often make two meals out of one prey item and roost with it or cache it for the next meal.

A great web photo of a NSWO with deer mouse prey

Friday, January 27, 2017


In a fun competition, Ken Sobon and I bet on which banding site would band the most saw-whet owls for the 2017 Snow Goose Festival (SGF) field trips. The festival is a great opportunity to see if owls are wintering on site. SO, Ken and crew Julie Newman, Wyatt Hersey and Maureen Morales, and Reserve research director Jon Aull, took SGF participants up to the BCCER (our typical fall monitoring site). Banders Julie Woodruff, Erika Iacona  and I, set up nets at Butte Creek Ecological Preserve (BCEP), an alternate winter banding site. AND the winner was........
Ken Sobon bands a wintering  saw-whet owl at the BCCER 
Red light helps the owl adjust to the night sky where it will be released

SGF participant releases a saw-whet owl
BCCER-with 2 saw-whet owls! We had no saw-whet owls at BCEP- but Butte Creek was flowing high and very loud which may have had a impact on owls hearing our broadcast. Our night was enhanced by loads of stars and Ryan's (Reserve staff) fire. Guests were offered an opportunity to band owls this fall. At the end of the night when all was quiet, a western screech owl flew into our site and called for a half hour.

Friday, January 20, 2017

ATTENTION SAW-WHET OWLS - Nest Boxes Available!

Ken Sobon and team have installed over 15 nest boxes on the Big Chico Creek Ecological Reserve (BCCER). He is hoping that the boxes will attract saw-whets, perhaps those wintering on the Reserve or moving through in spring, will stay and nest. If a pair does-it would be the first documented saw-whets breeding on site! We haven't done any summer surveys so we can't say they don't breed here. Generally I think the Reserve is too low in elevation (and hot) for Sierra Nevada breeding habitat, but these owls are shown to be nomadic, meaning they will breed where conditions are right (good prey, micro-climate) and don't often return to the same breeding area.
Locations of seven nest boxes on the Reserve. Also see our two banding sites, OWL2 and OWL3. The structures include barn workshop, office and old ranch house.The forests provide cover and good roosting habitat for owls and the meadows are great habitat for foraging for rodents.
You can see the boxes are distributed around, mostly under good canopy cover and near meadows for foraging and all boxes face NE (cooler). Some are on different tree species, some near small drainages, some with a different slope aspect.  It will be really exciting to check these boxes. Other cavity nesters that might find the boxes homey are western screech owl, ash-throated flycatcher, northern flying squirrel, wood rats and???  Monitoring begins in early March. Stay tuned!
This box #8 will be under a fairly dense cavity when the oaks leaf out.
You can see the canopy closure in the aerial google earth photo above
taken in late May.

Wednesday, January 18, 2017

Let's Get it Started! Nest Box Program for the 2017 NSWO Breeding Season

New project co-director Ken Sobon is moving forward into the breeding season for owls. We don't know if NSWO breed on site, but we have captured them as late as 4 April, likely during spring migration. We have made limited attempts during the late spring, early summer to identify nesting birds, with negative results. BUT this species is opportunistic and considered to be nomadic, nesting where the prey base and other conditions are right, and not necessarily returning to the same nesting area. Habitats on the Reserve could be good for saw-owl breeding in some years.

Ken's nest box building team, hoping to entice saw-whet owls!

Drilling the "cavity" entrance
Ken and his team may be monitoring for years before
actually finding a breeding owl, or it could happen this spring. If he does find a saw-whet it will be the first documented nesting on site. He might also find other cavity nesters using the boxes including Western screech owl, American kestrel, ash-throated flycatcher, northern flying squirrels and ??? Check back to our blog!

Ken installing nest box #5