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NEW Audubon has supported research on the nesting ecology of red-shouldered hawks for a number of years. It is a threatened species in Wisconsin, depending on large stands of mature hardwoods, wetland woods or mixed hardwoods and conifers. Its population is much reduced in the northern part of its range though it was once one of the most common hawks in eastern United States.

redshouldered hawk

An adult Red-shouldered hawk, photo taken by Dan Helgeson.

John and Eugene Jacobs have been the principal investigators for this study, and have included university students and others for the field work. We have summaries of several of their annual reports on this page.


Red-shouldered Hawk Nesting Biology

hawk nest

Annual Report of Reproduction for Red-shouldered Hawks for Central and Northeast Wisconsin 2009

By John Jacobs and Eugene Jacobs
Acknowledgements: Red-shouldered Hawk research for 2007 was sponsored by the US Dept. of Agriculture—Forest Service: Chequamegon-Nicolet National Forest, Wisconsin’s Land Fund, and the Northeastern Wisconsin Audubon Society Inc.  Scott Anderson, Mark Steinbach, Joe Barns helped with field work.  Bob Rosenfield and Tom Erdman reported nest locations.
Only nest sites in the southern one half of the Nicolet National Forest (NNF) were searched for active nests. The southern area of Nicolet typically has higher Red-shouldered Hawk densities than the northern districts. The northern portion was not searched due to time constraints.
This year Red-shoulder reproduction was again low but not as low as in some years (2005 and 2007), and as in most years, Central Wisconsin’s reproduction was higher than NNF or NE Wisconsin. It is hard to believe a hawk population can maintain itself with only one in three nesting attempts producing young to the fledging stage.  Red-shoulders remain in a somewhat precarious situation due to the low reproduction and should remain on the state threatened species list.

2009 table of nesting success

* One nest was not included because the birds fledged before final nest check.

Annual Report of Reproduction for Red-shouldered Hawk in Northeast Wisconsin, 2007

By John Jacobs
Acknowledgements: Red-shouldered Hawk research for 2007 was sponsored by the US Dept. of Agriculture—Forest Service: Chequamegon-Nicolet National Forest, Audubon’s Land Fund for Wisconsin, and the Northeastern Wisconsin Audubon Society Inc.  Scott Anderson, Mark and Adam Steinbach, Dorothy and Beth Summers, and Ed Smith helped with field work.
This year’s statistics only cover Northeast Wisconsin.  Central Wisconsin will be reported separately.

2007 table of nesting success

Annual Report of Reproduction of Red-shouldered Hawks for Northeastern and Central Wisconsin 2003


By John Jacobs and Eugene Jacobs
Acknowledgements: Red-shouldered Hawk research for 2003 was sponsored by the US Dept. of Agriculture—Forest Service: Chequamegon-Nicolet National Forest and by the Weather Friend Land Fund of Northeastern Wisconsin Audubon Society, Inc.  Elaine and Debbie Friedrick, Ed Smith, Jacob Glatt, Greg and Mary Jacobs Joan Berkopec, Ron Eichhorn, Mary Schmaus, Scott Anderson and Ed Houston helped with field work.
A very wide range of nesting success was again found this year, emphasizing the value of a long term study, large sample size and several geographic areas. Reproduction in central Wisconsin was at a high level. Reproduction on Nicolet National Forest was low, the rest of northeastern Wisconsin was much better than last year but still relatively low. The late tree leaf out due to a cold spring might have been the reason for predation of young and adults. Overall, the number of active nests and the reproductive success were slightly lower this year
than last year.
NNF: Nicolet National Forest, S & E of NNF: northeastern Wisconsin east and south of Nicolet National Forest, CEN WI: Central Wisconsin, Portage and Wood counties.

2003 table of nesting success

Annual Report of Reproduction for Red-shouldered Hawks for Northeastern and Central Wisconsin 2002

By John Jacobs and Eugene Jacobs
Acknowledgements: Red-shouldered Hawk research for 2002 was sponsored by the US Forest Service and the Northeastern Wisconsin Audubon Society.
A very wide range of nesting success was found this year emphasizing the value of a large sample size and monitoring several geographic areas. Reproduction in central Wisconsin was at a 30-yr. high level. Reproduction on Nicolet National Forest was good while the rest of northeastern Wisconsin was at a 30-yr. low. The late tree leaf out due to a cold spring might have been the reason for increased predation of young and adults in the S. & E. of NNF areas. Overall, the number of active nests found and reproductive success are lower this year than last year.
NNF: Nicolet National Forest, S & E of NNF: northeastern Wisconsin east and south of Nicolet National Forest, CEN WI: Central Wisconsin, Portage and Wood counties

2002 table of nesting success

Annual Report of Reproduction for Red-shouldered Hawks for Northeastern and Central Wisconsin 2000

This year’s written report is included in a 20 year summary of the research, available here.

2000 table of nesting success

Progress Report for Wisconsin Red-shouldered Hawk Nesting Ecology 1997

from: John Jacobs and Eugene Jacobs
Active Territories are sites in which red-shouldered Hawks (RS) were seen or heard or had a nest fixed up. Active Nests are nests which had eggs laid in them. Successful nests produced young to the fledgling stage. Only 57 active nests out of 150 sites is extremely low.  As we searched sites we located 126 old or previously used nests that were not active this year.  At some sites we found as many as 5 old nests without finding an active nest. Possibly no active nest was in some of these territories. Our field experience has shown that most active RS nests are within 200 yards of last year's nest, so we feel we were looking in the most likely places.  A late tree leafout gave us a longer season to search for nests.
1997 was the most successful nesting season we have monitored during the past 27 years.  Percent successful nests was outstanding.  YG/active nest and YG/successful nest were both very high. The main reason for this unusually high reproduction this year appears to be high small mammal populations. Beech mast and evergeen cone crop for 1996 must have been very good
because we observed many more small mammals  this year than last year and more than most other years. (Small mammals constitute 40% of RS diet during the nesting season.) Chipmunk, red-squirrel, vole, star-nosed mole, and short-tailed shrew numbers were most notable. Grouse and snowshoe hare were also much more numerous than during the past six years. Although we have not found hare or grouse as prey of RS, other predators such as great horned owls, fisher and raccoons feed on them and when there is an abundance of food items not only is there more food for the RS but fewer RS end up as food for these other predators.
Prime RS nesting habitat needs protection if RS are going to recover, especially on county forests which do not protect nest sites or mature forests as the Nicolet National Forest does.  Numbers of fisher, raccoons, and great horned owls remain high. All are predators on RS.
The Red-shouldered project this year was supported by grants from: The Wisconsin Department of Natural Resources—Bureau of Endangered Resources, Brown County Conservation Alliance (Sportsman of Brown County), U.S. Forest Service-Nicolet National Forest, Northeastern Wisconsin Audubon Society, and The Wisconsin Society for Ornithology. Sumner Matteson, Wisconsin Department of Natural Resources-Bureau of Endangered Resources, assisted with funding sources.

Progress Report for Wisconsin Red-shouldered Hawk Nesting Ecology 1996

by John Jacobs and Eugene Jacobs
Total Areas Searched is the forested habitat where Red-shouldered Hawks (RS) were probably/possibly nesting, RS had nested previously at 127 of these sites. This year we searched the most sites ever covered in a single season.  Twenty-two New Sites were searched this year, RS were found at 7 of these and 4 new active nests located. As we searched sites we located 133 old or previously used nests that were not active this year. At some sites we found as many as 4 old nests without finding an active nest. Possibly no active nest was in some of these territories.  Our field experience has shown that most active RS nests are within 200 yards of last years nest, so we feel we were looking in the most likely places. A very late tree leafout gave us a longer season to search for nests.  Active Territories are sites in which RS were seen or heard or had a nest fixed up.
Active Nests are nests which had eggs laid in them. Successful nests produced young to the fledgling stage. Yg/active nest is the number of young divided by the number of active nests.  Yg/successful nest is the number of young divided by the number of nests that were successful, this tells the average brood size.
Only 55 active nests out of 149 sites is extremely low. The cold spring is probably the main cause for the relative few number of nests found and the very low reproductive rate (yg/active nest) of 0.64.  Late leafout made the RS nests vulnerable to predators for a longer period of time.
Acknowledgements: This project was supported by grants from The Society of Tympanuchus Cupido Pinnatus, The U.S. Forest Service-Nicolet National Forest, Northeastern Wisconsin Audubon Society, and The Wisconsin Society for Ornithology. Sumner Matteson, Wisconsin Department of Natural Resources-Bureau of Endangered Resources, assisted with funding sources.

1996 table of nesting success

Recent Publications on Red-shouldered Hawks

Besides annual reports to the Forest Service and Wisconsin Department of Natural Resources-Bureau of Endangered Resources, research sponsored in part by Audubon's Land Fund for Wisconsin (Weather Friend Land Fund Grant) has been used by John Jacobs to write three documents which encourage preservation of wild natural habitats in Wisconsin.

l. The Red-shouldered Hawk account for the Atlas of the breeding birds of Wisconsin. Noel J. Cutright, Bettie R. Harriman, and Robert W. Howe editors. 2006. WI Society for Ornithology.
2. Jacobs, J. P., and E. A. Jacobs. 2002. Conservation assessment for red-shouldered hawk (Buteo lineatus): National Forests of north central states. U.S. Department of Agriculture, Forest Service, Eastern Region, Milwaukee, Wisconsin, USA. This publication is available on the US Forest Service Website
3. Red-shouldered Hawk account for Wisconsin Bird Conservation Initiative and the Comprehensive Wildlife Conservation Plan. Available here. The Red-shouldered hawk has been designated a Species of Greatest Conservation Need by these committees.
4. Jacobs, J. P., and E. A. Jacobs. 2000 Summary of Red-shouldered Hawk Reproduction in Northeastern and Central Wisconsin. unpublished report for the WI DNR is available here.

King, J, J.Woodford, and S.DuBay. 2007. Developing a Statewide Red-shouldered Hawk Survey: A Regional Evaluation of Citizen Volunteers. available at
WI Aquatic and Terrestrial Resources Inventory

Woodford, J. E., C.A. Eloranta, and A. Rinaldi. 2008. Nest Density, Productivity, and Habitat Selection of Red-Shouldered Hawks in a Contiguous Forest. Journal of Raptor Research 42(2):79-86. Reports on a study in Menominee County.

redshouldered hawk

photo by Jacobs

 

 

 

 

 

 

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