Thursday, February 16, 2017

BAT-EATING WESTERN SCREECH OWL?

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

2017 SNOW GOOSE FESTIVAL RESULTS!

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




Tuesday, January 10, 2017

New Project Directors Ken Sobon and Julie Newman 2017

Welcome Ken and Julie as the Northern saw-whet owl fall monitoring project's new directors. What a great journey it has been and a privilege to pass the project along to these two dedicated volunteers. Ken is the VP for Altacal Audubon Society (our project sponsor) and Julie is a professional environmental scientist. Both have banded and participated with the project for several years.
Ken Sobon, NSWO project Co-director
Julie Newman, NSWO project Co-director

Long-term monitoring of a species is essential to understand population trends and local natural history. Thank you for continuing this important work. Great team! 

Tuesday, November 22, 2016

57 OWLS MAKE UP SEASON 2016!

We had another great season with 57 new NSWO and 8 same season recaptures. The  owls arrived steadily and we only dipped one night, so 17 out of 18 nights of effort, we banded owls. There were two peak migration nights on November 1 (8 owls and 1 recapture) and November 16 (8 new owls!).
A trio of owls could indicate family members flying together.
On these peak nights we typically capture multiple owls in one run and there is current DNA research to determine if these may be siblings or family members migrating together. The eight same season recaps is our record for recaptures in one season. They stayed on the property between 6 days and 26 days and may continue to winter on the Reserve. Their overlapping and continued presence and good body weight indicates a healthy prey base (rodents) for so many owls.This year we had several chunky owls with a good amount of fat and weights over 100 grams! Fat, which can be seen as a yellow layer under the skin, is an important fuel for migration and cold winter nights.
This individual has 3-4 generations of feathers, noted by the different colors in the
blocks of feathers; she is over 3 years old
We have also noted that the older birds tend to migrate later (we capture them later in the season), probably because the young of the year disperse early from their natal area. On our last banding night we banded this older female with several generations of feathers. These birds can be challenging to age, but it is great to see that some owls survive seasons of migration and breeding.

Thank you volunteers Julie Woodruff, Ken Sobon, Julie Newman, Wyatt Hersey, Erika Iacona, Maureen Morales and Kim Armstrong, for another great season of owl monitoring, season 12!!!!