Barred Owls

 

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Dispersal
Nest Box Plan
Orphans
Adult Territories

The Ecology of Barred Owls in the North Carolina Piedmont 

 A Radio-telemetry Study

Barred Owls in the News

On Jan. 6th, WJZY aired a Charlotte Now program wherein I talked about our on-going studies of Barred Owls in Charlotte. Link here to watch the show (it's about 30 minutes).

The Lehrer News Hour recently broadcast a segment on Spotted Owls. Barred Owls play a role in the seemingly never-ending plight of the endangered Northern Spotted Owl. Link here to watch the segment. Be forewarned that if you have blood pressure issues you may want to take some valium before watching a Bush-appointee refusing to answer a question from a U.S. Representative about their plans for the owl, which, as is par for the course, ignore all the science that has been published on the issue. 

Contents of these pages:

Introduction
Natural History (Barred Owl basics)

Nest Location - A map of the nests in the south Charlotte suburbs
Radio tracking
      Movement of young leaving their nest areas, "Dispersal" - See where the young tagged this year (and last) went after leaving their nest areas. We will update these maps about once a week through the summer. 
Nest boxes
      See
maps of the south Charlotte nests in 2004 and 2007.
Orphans -Radio tracking orphans released by Carolina Raptor Center
You can help - with contributions to support our research or helping in the field with nest location, tracking, and banding.

Introduction

    My graduate students and I, in collaboration with Carolina Raptor Center, have been studying Barred Owls in the central Piedmont of North Carolina since 2001. The project's goals include increasing our knowledge of the ecology of the Barred Owl, particularly in suburban habitats, using the owls as environmental monitors, student training, and increasing community sensitivity and involvement in the environment in their own backyards.

     The first phase of the research was a study by UNC-Charlotte graduate student, Eric Harrold, comparing the home range, prey habits, and habitat characteristics of Barred Owls living in suburban environments with birds living in forested habitats less modified by humans. This research has been funded by the Impact Fund of the Foundation for the Carolinas, UNC-Charlotte's Biology Department, and the Carolina Bird Club. Eric defended his thesis in April 2003. Read his thesis abstract.

     Our third field season (2004) saw our total breeding pairs under study go up to 45--the largest ever single-year study of Barred Owl breeding ecology. Two more students picked up the ball from Eric and are studying our local owls. We radio tagged 11 young (two at rural nests and nine in the suburbs) as part of Jim Mason's thesis comparing the survivorship of our city birds to the pairs we are following in the country. Jim defended his M.Sc. thesis in November of 2004 (read the abstract). Patti Kelly followed our marked suburban birds in the non-breeding season. Her data will be used in future publications on differences in territory size across seasons and years. 

     2005 was a terrible year for Barred Owls. During the early part of the nesting season, when the adults had eggs or small young, Charlotte experienced rains of monsoonal proportions. Quite a few of our nests are in  "branch scars," where a branch has broken off a tree and a bit of rot creates a bowl-like depression. Many of these don't drain well, so the nest bowls flooded, drowning eggs or young.

     The weather was much more cooperative in 2006 and reproductive success was back to normal. This was our first year to install video cameras in nest boxes. Cori Cauble will be comparing the diets of suburban and rural owls using this technology for her M.Sc. thesis at UNC-Charlotte.

     2007 was our (humans and owls) best year ever. We had fewer pairs (35) under observation, but got more data from those birds. 22 of the 25 nests (88%) where we knew the outcome were successful. At least 36 young were fledged, and we banded 26 of these. We have radios on four young--two in the city and two in the country. As of 15 October all four birds are doing well. The city birds have settled down, both about 1.5 miles from their nest, while the country birds just started moving.

     We had video cams in 5 nests and are getting very interesting data on feeding habits.

    We're always looking for volunteers to help with all aspects of the project--finding nests and tracking birds. Please e-mail if you're interested.

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Nest Boxes

 Part of this long-term research effort entails establishing a population of owls in nest boxes that are easily accessible to our researchers. We have already placed about 50 boxes in suitable habitat. In 2004, 11 boxes were in use.

(This box is larger than our current version, which has a 19" x 19" floor plan.)

    We hope to continue to expand the number of boxes in our study area. If you have a box already on your property or would like to build, or buy one, please contact us via email (rbierreg@email.uncc.edu - just click to send a message).

   Barred Owls will use nest boxes, but putting one up is no guarantee that it will be used, as we've discovered. Boxes should be up by mid September. If they're put up much later, the birds may have already made their housing decision for the upcoming breeding season. They should be 15-20' off the ground. Click the link below to see the design we've come up with after several years of experimenting. We will provide and install a box in return for a $100 contribution to the Barred Owl project. If you'd like to build the box yourself, click the link below for plans. If you build and install a box yourself, we'd appreciate knowing where the box is and monitoring it if owls use it.

  Click here to see the "Definitive" Barred Owl Nest Box plan.

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Nest Location (see maps)

    Barred owls usually nest in a hole in a big tree. The holes can be of all sorts. Often the nest will be in a broken hollow trunk, which we call chimney nests. (And they will use real chimneys, which just look like brick trees to an owl.) More often in the city, where we don't let hollow, dead trees stand around very long, the nests will be in a hollow tree with the birds entering through a hole in the side of the tree. Often they will find a cavity where a branch has broken off the side of a tree, leaving an uncovered cavity. Quite rarely, they will use an abandoned hawk or crow nest. (Great-horned Owls do this much more commonly.)
    Through determined field work, the help of radio telemetry, and a little bit of good luck, we have located nests in rural areas (Latta Plantation and Reedy Creek Nature Preserves, and rural Harrisburg), and  in trees, chimneys, and nest boxes in suburban Charlotte.
    In 2004, we followed 45 nesting pairs. 11 of these were in rural forests and parks, with the rest mostly in the south Charlotte suburbs. Click here to see a map of the nests in the south Charlotte suburbs.
    If you know of a nest anywhere in the Charlotte area, we would like to include it in our study. This means we would take some measurements of the nest tree and, if possible, count eggs and band young in the spring. [Send an email if you know of a nest that doesn't appear to be on our map.]

The picture below are of typical rural nest trees, which are very often dead. Suburban nests are almost always in live trees.
    

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Radio Tracking

    Most of our work is based on capturing adult or young owls and outfitting them with small radio transmitters. The transmitters are attached like a little backpack with the antenna extending down the birds back, as can be seen in the picture above).

Radio Telemetry-Orphans

     Way back in 2000, we performed a pilot radio-telemetry study tracking owls that made it through our rehabilitation process. This project was undertaken in part to learn about following owls with telemetry, but also to begin to collect some data on the fate of birds that pass through a raptor rehabilitation program.
     In 2001 we followed three orphans after their release from Carolina Raptor Center. The first bird was killed by a Great-horned Owl about a week after it was released. We collected that bird's transmitter from a pile of feathers and redeployed it on our next release.
     The other two birds we followed were also graduates of "Mouse School" at CRC. This means that they were young birds brought into CRC in the spring because, for one reason or another, we could not reunite them with their parents. Once they were full grown they spent a week or so in a large flight pen catching live mice. Having demonstrated their proficiency at this all important task, they were ready for release into the wild

   The first bird, nicknamed "Natalia," (although we later learned it was a male) fell out of its nest at the Nature Museum in Freedom Park in the spring of 2001. It was released on 25 July, after a broken wing healed. ( In this picture, you can see the radio antenna coming off the bird's back.)

We followed as it wandered through south Charlotte and finally settled in to a neighborhood east of South Blvd, near the Arrowood intersection. In February, it had a run-in with a car and spent a few more days at CRC's rehab center before being released into the wild (again!).

     The other bird was killed by a car a couple of months after being released. 

     In 2004, we radio tagged 5 orphans released in rural habitats around Carolina Raptor Center (3 birds) and Davidson College (2 birds).

See more details on the orphan tracking project.

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Radio Telemetry-Adult Home Ranges & Dispersing Young

   We have trapped and outfitted over 30 adult Barred Owls with small (10 g) radio transmitters, mounted back-pack style with smooth teflon ribbon. A couple of birds decided they didn't want to be part of the study and somehow got the radios off, while the majority seem to not even notice their high-tech accoutrement. We are now following these birds to learn how big a territory they need and what sorts of habitat they prefer to hunt in.
    We have analyzed and mapped 40-50 locations for nine adult Barred Owls in the south Charlotte suburbs in 2001-2002. Click here to see a map of adult territories. These studies continue as we look at how territories change over different breeding seasons and see how similar territories will be when one of a pair dies and is replaced. 

 

YOUNG

    One of the important questions we hope to answer with this research is whether owls in the city/suburban habitat are as successful as their country cousins. To do this, we need to follow young and see how long they survive after leaving their nest areas.

   In the spring of 2002, we placed radios on two young, one from the Princeton pair near Freedom Park, and one from the Colville pair in Eastover. In 2003 we tagged eight young, and we are currently (2004) following 11 birds as they wander around Charlotte looking for a place to settle down.
      See details of this research.

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How you can help

     If you know of a pair of nesting Barred Owls in Charlotte or the surrounding rural areas, please email (click on the link to send a message) or call Rob Bierregaard (704 516-4615) and let us know where "your" birds are.

    You can also contribute financially by donating ear-marked funds to Carolina Raptor Center. A $200 gift will pay for a new radio transmitter for the study, and a $100 donation will pay for refurbishing one of the radios on a bird we are currently monitoring. Please contact Rob Bierregaard for details. A $150 donation will get you a nest box if you're in the appropriate habitat.

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