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Raptor Surveys


Raptors

The word "raptor" comes from the Latin word "rapere," which means to seize or plunder. Today, the word is used to describe a group of birds also known as "birds of prey." All birds share some common traits such as feathers, wings, laying eggs, and being warm-blooded; however, there are certain characteristics that set raptors apart from other birds. Raptors have

Value of Raptors

The presence of raptors in the wild serves as a barometer of ecological health. Birds of prey are predators at the top of the food chain; because threats like pesticides, habitat loss, and climate change have the most dramatic impact on top predators, we refer to them as indicator species. Researching the population trends of raptors provides a cost-effective and efficient means to detecting environmental change, allowing us to take conservation action that is driven by the latest scientific data. Raptors also play an important ecological role by controlling populations of rodents and other small mammals.



Golden Eagle

Raptors on the INL Site

There are around 450 species of ratpros worldwide. In North America, there are about 34 common diurnal species (active during the day) and 20 common nocturnal species (active at night). On the INL Site, there are 22 documented raptors:

Diurnal

  • Turkey Vulture (Cathartes aura)
  • Osprey (Pandion haliaetus)
  • Bald Eagle (Haliaeetus leucocephalus)
  • Northern Harrier (Circus cyaneus)
  • Sharp-shinned Hawk (Accipiter striatus)
  • Cooper's Hawk (Accipiter cooperii)
  • Northern Goshawk (Accipiter gentilis)
  • Swainson's Hawk (Buteo swainsoni)
  • Red-tailed Hawk (Buteo jamaicensis)
  • Ferruginous Hawk (Buteo regalis)
  • Rough-legged Hawk (Buteo lagopus)
  • Golden Eagle (Aquila chrysaetos)
  • American Kestral(Falco sparverius)
  • Merlin (Falco columbarius)
  • Peregrine Falcon (Falco peregrinus)
  • Gyrfalcon (Falco rusticolus)
  • Prairie Falcon (Falco mexicanus)
  • Burrowing Owl (Athene cunicularia)

Nocturnal

  • Great Horned Owl (Bubo virginianus)
  • Long-eared Owl (Asio otus)
  • Short-eared Owl (Asio flammeus)
  • Northern Sawwhet Owl (Aegolius acadicus)

Midwinter Bald Eagle Count

Each January, hundreds of volunteers and wildlife professionals throughout the United States count eagles along standardized, non-overlapping survey routes as part of the Midwinter Bald Eagle Survey. These annual surveys commenced in 1979 and today are managed by the U.S. Geological Survey (USGS). The Midwinter Bald Eagle Surveys were originally established to develop a population index of wintering bald eagles in the lower 48 states, determine bald eagle distribution, and identify previously unrecognized areas of important winter habitat.

Midwinter Bald Eagle Count on the INL Site

On the INL Site, Midwinter Bald Eagle Surveys have taken place since 1983. In early January of each year, two teams drive along established routes across the north and south of the INL Site and record the number and locations of all bald and golden eagles that they see. Observers also record the same information for other raptors, common ravens, shrikes (Lanius spp.), and black-billed magpies they observe along each route. Data are submitted to the regional coordinator of the USGS Biological Resource Division to be added to the nationwide database.

Cumulative data from past surveys (2000-2020)

Species  2000  2001  2002  2003  2004   2005 2006  2007  2008   2009  2010 2011  2012  2013   2014  2015  2016  2017  2018 2019   2020
 Bald Eagle   2 6  1  2  2    6  1  7 4 4  5  2  1        2  1 2  
Golden Eagle  8  5  8  7  7  6  16  5  11  12  12 12  7  5  7  1  14  29  6  14  6
 Unidentified Eagle              2                            
Prairie Falcon   1    1      2  1        2                1  4  
Peregrine Falcon                                           
Gyrfalcon                                           
 Merlin                1                          
 American Kestral  5      4  1    3  1      2 1  2      1  4   4  2  
Rough-legged Hawk   80  43  12  301  28  61  288  36  24  75  217  144  22  17  15  21  128  64  82  148  3
 Red-tailed Hawk        2    2  1  4  1  2      2  1      6    2  1  
Ferruginous Hawk          1      1          2           1    1  
Swainson's Hawk                 1    1    1    1        1      
Unknown Hawk                     8    1  1  1  1  3  35  6  5  4  
Northern Harrier   1  3    1    1    3              1        1  3  
 Great-horned Owl   1        2    2                            
 Short-eared Owl                1                      1    
Raven*   19  78  49  140  46 21  142  28  72  143  96  139  62  154  73 67  167  107  53  164  107
 Northern Shrike** 2    2    1  2  1    1  1    4  2      1    2  1    
Loggerhead Shrike***                             1  1            
Magpie***               18  2    7  16    2  8  10  4  15  8  6  33  30
*Added to the Raptor Count in 1992 because ravens function ecologically as raptors.
** Added to the Raptor Count in 1992 because of concerns about declining shrike populations.
***Added to Raptor Count in 2013
****Added to Raptor Count in 2006

©2020 ESER Program.