Assessing the population status for species requires accurate measures of local or regional numbers. For many species, standardized protocols exist for estimating local numbers through visual counts (e.g., Breeding Bird Survey routes, Christmas Bird Count circles, and point count protocols used by the US Forest Service). For many raptor species, monitoring populations at migratory bottlenecks such as the Goshute Mountains, NV, Hawk Mountain, PA, and Cape May, NJ, provide yearly indices of population health. Unfortunately, most monitoring protocols overlook a suite of small crepuscular or nocturnal species. Project Owlnet (www.projectowlnet.org) is a volunteer-based network of banding stations focusing on Northern Saw-whet Owl (Aegolius acadicus) migration in the eastern part of the United States and Canada. Information collected by Project Owlnet volunteer groups reveals that this small owl appears to be far more common than previously thought

Kim, Daniel H.

English

UNL | Libraries

University of Nebraska - Lincoln
DigitalCommons@University of Nebraska - Lincoln
Nebraska Bird Review Nebraska Ornithologists' Union
6-2005
Northern Saw-whet Owls: Rare or Overlooked?
An Example from the Central Platte Valley
Daniel H. Kim
Platte River Whooping Crane Maintenance Trust
Follow this and additional works at: http://digitalcommons.unl.edu/nebbirdrev
Part of the Ornithology Commons, Poultry or Avian Science Commons, and the Zoology
Commons
This Article is brought to you for free and open access by the Nebraska Ornithologists' Union at DigitalCommons@University of Nebraska - Lincoln. It
has been accepted for inclusion in Nebraska Bird Review by an authorized administrator of DigitalCommons@University of Nebraska - Lincoln.
Kim, Daniel H., "Northern Saw-whet Owls: Rare or Overlooked? An Example from the Central Platte Valley" (2005). Nebraska Bird
Review. 1114.
http://digitalcommons.unl.edu/nebbirdrev/1114
“Northern Saw-whet Owls: Rare or Overlooked? An Example from the Central Platte Valley” 
from Nebraska Bird Review (June 2005) 73(2). Copyright 2005 Nebraska Ornithologists’ 
Union. Used by permission.
Vol. 73 No. 2 The Nebraska Bird Review 
NORTHERN SAW-WHET OWLS: RARE OR OVERLOOKED? 
AN EXAMPLE FROM THE CENTRAL PLATTE VALLEY 
Daniel H. Kim 
Platte River Whooping Crane Maintenance Trust 
6611 W Whooping Crane Dr, Wood River, NE 68883 
dkim@whoopingcrane.org 
INTRODUCTION 
67 
Assessing the population status for species requires accurate measures of 
local or regional numbers. For many species, standardized protocols exist for 
estimating local numbers through visual counts (e.g., Breeding Bird Survey routes, 
Christmas Bird Count circles, and point count protocols used by the U.S. Forest 
Service). For many raptor species, monitoring populations at migratory bottlenecks 
such as the Goshute Mountains, NV, Hawk Mountain, PA, and Cape May, NJ, 
provide yearly indices of population health. Unfortunately, most monitoring 
protocols overlook a suite of small crepuscular or nocturnal species. Project Owlnet 
(www.projectowlnet.or") is a volunteer-based network of banding stations focusing 
on Northern Saw-whet Owl (Aego/ius acadicus) migration in the eastern part of the 
United States and Canada. Information collected by Project Owlnet volunteer 
groups reveals that this small owl appears to be far more common than previously 
thought. 
METHODS 
I set up a banding station at the Platte River Whooping Crane Maintenance 
Trust in Hall County. I placed three 12 x 3 m, 60mm mesh nets in a "T" formation 
68 The Nebraska Bird Review Vol. 73 No. 2 
in a small opening within a patch of gallery forest comprised of Eastern Cottonwood 
(Populus deltoides) and Eastern Redcedar (Juniperus virginiana). I used a Jimmy 
Stewart game caller with a continuous loop tape of a Northern Saw-whet Owl 
"advertisement call" played at approximately 90 dB (Cannings I 993 , Whalen and 
Watts 1999). Station operation started 8 October and continued sporadically through 
11 Dec 2004. Nets were open from dusk until 0200 - 0400 the following morning. 
Net checks occurred at least every 40 minutes, more often in cold temperatures. All 
owls were identified to species. Sex and age were assigned using unflattened wing 
chord, body mass, and molt pattern as described by Pyle (I 997) and Brinker 
(personal comm.). All owls were banded with a USGS leg band and released within 
25 minutes of capture. 
Northern Saw-whet Owls. Photo courtesy of Daniel Kim. 
RESULTS 
I operated the station a total of 14 nights for approximately 370 net hours. 
captured 16 owls: 14 Northern Saw-whet Owls and 2 Eastern Screech-Owls 
(Megascops asio). Of the 14 Northern Saw-whet Owls, IO were females and 4 were 
undetermined sex, while age composition was 4 hatch-year birds, 6 second-year 
birds, and 4 after-second-year birds (Table I). Peak captures occurred on 11- I 2 
November, when 9 birds were caught on two nights. 
DISCUSSION 
The capture bias towards female, after-hatch-year birds displayed in Nebraska is 
consistent with banding stations in the southeastern United States. Owl banding 
stations in the Northeast and mid-Atlantic regions display variable sex and age 
Vol. 73 No. 2 The Nebraska Bird Review 69 
capture rates (Brinker et. al. 1997). Capture rates are female-biased (69-96 %) at all 
stations in eastern and mid-Atlantic regions, with the sex-ratio bias increasing from 
north to south. The percent of after-hatch-year individuals increased from north to 
south, but was highly variable among years at all stations (Brinker et al. 1997). 
Northern Saw-whet Owls are considered uncommon regular winter residents 
throughout the eastern part of Nebraska (Sharpe et. al. 2001), yet only three 
Christmas Bird Count circles have ever recorded saw-whets (Lincoln, Omaha, and 
Lake Mcconaughy) during eight of 95 years with count circle data from Nebraska 
(National Audubon Society 2005). There are a couple of explanations for the dearth 
of CBC sightings. First, Northern Saw-whet Owls may not occur in Nebraska every 
year, as the number of migrating individuals relates to vole populations, resulting in 
"irruption" years when vole numbers crash in the northern forests, forcing northern 
owl species to move south in great numbers (Cheveau et al. 2004). Second, these 
small owls display little winter site fidelity and are not reliably found in the same 
areas over a series of winters (Marks and Doremus 2000). However, the most likely 
explanation is that these are small, secretive owls that remain undetected with 
passive survey methods. 
Table I. Capture data for 14 Northern Saw-whet Owls from Hall County, 
Nebraska. Date refers to date at time of sunset; therefore, captures occurring 
after 2359 hours correspond to the next calendar day. 
Date Time Sex Age Wing chord Weight 
(mm) (g) 
27 October 0230 Female Second-year 136 98 
6 November 2300 Female Hatch-year 141 96 
11 November 2220 Female Third-year 143 JOO 
11 November 2120 Female Second-year 139 90 
11 November 2220 Female Second-year 142 92 
11 November 1940 Female Hatch-year 142 102 
11 November 1940 Female Hatch-year 140 90 
11 November 1940 Female Hatch-year 134 96 
12 November 1920 Female After second-year 140 90 
20 November 0200 Female After second-year 142 86 
Average 139.9 94 
28 October 2130 Unknown Second-year 139 84 
6 November 0030 Unknown After second-year 135 86 
12 November 2120 Unknown Second-year 136 86 
12 November 2120 Unknown Second-year 136 86 
Average 136.5 85.5 
70 The Nebraska Bird Review Vol. 73 No. 2 
CONCLUSION 
Any comparisons made between one year of banding data from Nebraska and 
multiple studies from the East are tenuous at best. While all stations display 
female-biased capture rates, annual changes to percent of juvenile/adult captured in 
eastern populations preclude inferences from a single year of data from one banding 
station Nebraska. Banding stations throughout the Northeast are associated with 
local nature centers, and new stations in other regions like Nebraska could provide 
additional data on Northern Saw-whet Owl migratory patterns and winter 
distributions. In addition to a nature center staff member, locations near Lincoln and 
Omaha could draw upon a volunteer core of local birders and college students to run 
banding stations during weekends. Standardized protocols are available at the 
Project Owlnet website. 
LITERATURE CITED 
Brinker, D. F., K. E. Duffy, D. M. Whalen, B. D. Watts, and K. M. Dodge. 
"Autumn Migration of Northern Saw-whet Owls (Aegolius acadicus) in the 
Middle Atlantic and Northeastern United States: What Observations from 
1995 Suggest." Proceedings of the Second International Symposium on 
Biology and Conservation of Owls of the Northern Hemisphere, J. R. 
Duncan, D. H. Johnson and T. H. Nicholls, eds. 1997: 74-89. 
Cannings, R. J. "Northern Saw-whet Owl (Aegolius acadicus)." Birds of North 
America, No. 42 (A. Poole and F. Gill, eds). The Academy of Natural 
Sciences, Philadelphia, PA, and The American Ornithologists' Union, 
Washington D.C. 1993. 
Cheveau M., P. Drapeau, L. lmbeau, and Y. Bergeron. "Owl Winter Irruptions as 
an Indicator of Small Mammal Population Cycles in the Boreal Forest of 
Eastern North America." Oikos 107 (2004): 190-198. 
Elliot, L., D. Stokes, and L. Stokes. Stokes Field Guide to Bird Song: Eastern 
Region. Time Warner Audio Books. 1997. 
Marks J. S., and J. H. Doremus. "Are Northern Saw-Whet Owls Nomadic?" 
Journal of Raptor Research 34 (2000): 299-304 
National Audubon Society. The Christmas Bird Count Historical Results [Online]. 
Available at http://www.aµdubon.or~ird/cbc [21April2005] 
Pyle, P. The Identification Guide to North American Birds: Part I. Solinas, CA: . 
Slate Creek Press, 1997. 
Sharpe, R. S., W. R. Silcock, and J. G. Jorgensen. Birds of Nebraska Their 
Distribution and Temporal Occurrence. Lincoln, Nebraska: University of 
Nebraska Press, 2001. 
Whalen D. M. and B. D. Watts. "The Influence of Audio-lures on Capture Patterns 
of Migrant Northern Saw-whet Owls." Journal of Field Ornithology 
70 (1999): 163-168. 


Northern Saw-whet Owls: Rare or Overlooked? An Example from the Central Platte Valley

DigitalCommons@University of Nebraska

University of Nebraska - LincolnDigitalCommons@University of Nebraska - LincolnNebraska Bird Review Nebraska Ornithologists' Union6-2005Northern Saw-whet Owls: Rare or Overlooked?An Example from the Central Platte ValleyDaniel H. KimPlatte River Whooping Crane Maintenance TrustFollow this and additional works at: http://digitalcommons.unl.edu/nebbirdrevPart of the Ornithology Commons, Poultry or Avian Science Commons, and the ZoologyCommonsThis Article is brought to you for free and open access by the Nebraska Ornithologists' Union at DigitalCommons@University of Nebraska - Lincoln. Ithas been accepted for inclusion in Nebraska Bird Review by an authorized administrator of DigitalCommons@University of Nebraska - Lincoln.Kim, Daniel H., "Northern Saw-whet Owls: Rare or Overlooked? An Example from the Central Platte Valley" (2005). Nebraska BirdReview. 1114.http://digitalcommons.unl.edu/nebbirdrev/1114“Northern Saw-whet Owls: Rare or Overlooked? An Example from the Central Platte Valley” from Nebraska Bird Review (June 2005) 73(2). Copyright 2005 Nebraska Ornithologists’ Union. Used by permission.Vol. 73 No. 2 The Nebraska Bird Review NORTHERN SAW-WHET OWLS: RARE OR OVERLOOKED? AN EXAMPLE FROM THE CENTRAL PLATTE VALLEY Daniel H. Kim Platte River Whooping Crane Maintenance Trust 6611 W Whooping Crane Dr, Wood River, NE 68883 dkim@whoopingcrane.org INTRODUCTION 67 Assessing the population status for species requires accurate measures of local or regional numbers. For many species, standardized protocols exist for estimating local numbers through visual counts (e.g., Breeding Bird Survey routes, Christmas Bird Count circles, and point count protocols used by the U.S. Forest Service). For many raptor species, monitoring populations at migratory bottlenecks such as the Goshute Mountains, NV, Hawk Mountain, PA, and Cape May, NJ, provide yearly indices of population health. Unfortunately, most monitoring protocols overlook a suite of small crepuscular or nocturnal species. Project Owlnet (www.projectowlnet.or") is a volunteer-based network of banding stations focusing on Northern Saw-whet Owl (Aego/ius acadicus) migration in the eastern part of the United States and Canada. Information collected by Project Owlnet volunteer groups reveals that this small owl appears to be far more common than previously thought. METHODS I set up a banding station at the Platte River Whooping Crane Maintenance Trust in Hall County. I placed three 12 x 3 m, 60mm mesh nets in a "T" formation 68 The Nebraska Bird Review Vol. 73 No. 2 in a small opening within a patch of gallery forest comprised of Eastern Cottonwood (Populus deltoides) and Eastern Redcedar (Juniperus virginiana). I used a Jimmy Stewart game caller with a continuous loop tape of a Northern Saw-whet Owl "advertisement call" played at approximately 90 dB (Cannings I 993 , Whalen and Watts 1999). Station operation started 8 October and continued sporadically through 11 Dec 2004. Nets were open from dusk until 0200 - 0400 the following morning. Net checks occurred at least every 40 minutes, more often in cold temperatures. All owls were identified to species. Sex and age were assigned using unflattened wing chord, body mass, and molt pattern as described by Pyle (I 997) and Brinker (personal comm.). All owls were banded with a USGS leg band and released within 25 minutes of capture. Northern Saw-whet Owls. Photo courtesy of Daniel Kim. RESULTS I operated the station a total of 14 nights for approximately 370 net hours. captured 16 owls: 14 Northern Saw-whet Owls and 2 Eastern Screech-Owls (Megascops asio). Of the 14 Northern Saw-whet Owls, IO were females and 4 were undetermined sex, while age composition was 4 hatch-year birds, 6 second-year birds, and 4 after-second-year birds (Table I). Peak captures occurred on 11- I 2 November, when 9 birds were caught on two nights. DISCUSSION The capture bias towards female, after-hatch-year birds displayed in Nebraska is consistent with banding stations in the southeastern United States. Owl banding stations in the Northeast and mid-Atlantic regions display variable sex and age Vol. 73 No. 2 The Nebraska Bird Review 69 capture rates (Brinker et. al. 1997). Capture rates are female-biased (69-96 %) at all stations in eastern and mid-Atlantic regions, with the sex-ratio bias increasing from north to south. The percent of after-hatch-year individuals increased from north to south, but was highly variable among years at all stations (Brinker et al. 1997). Northern Saw-whet Owls are considered uncommon regular winter residents throughout the eastern part of Nebraska (Sharpe et. al. 2001), yet only three Christmas Bird Count circles have ever recorded saw-whets (Lincoln, Omaha, and Lake Mcconaughy) during eight of 95 years with count circle data from Nebraska (National Audubon Society 2005). There are a couple of explanations for the dearth of CBC sightings. First, Northern Saw-whet Owls may not occur in Nebraska every year, as the number of migrating individuals relates to vole populations, resulting in "irruption" years when vole numbers crash in the northern forests, forcing northern owl species to move south in great numbers (Cheveau et al. 2004). Second, these small owls display little winter site fidelity and are not reliably found in the same areas over a series of winters (Marks and Doremus 2000). However, the most likely explanation is that these are small, secretive owls that remain undetected with passive survey methods. Table I. Capture data for 14 Northern Saw-whet Owls from Hall County, Nebraska. Date refers to date at time of sunset; therefore, captures occurring after 2359 hours correspond to the next calendar day. Date Time Sex Age Wing chord Weight (mm) (g) 27 October 0230 Female Second-year 136 98 6 November 2300 Female Hatch-year 141 96 11 November 2220 Female Third-year 143 JOO 11 November 2120 Female Second-year 139 90 11 November 2220 Female Second-year 142 92 11 November 1940 Female Hatch-year 142 102 11 November 1940 Female Hatch-year 140 90 11 November 1940 Female Hatch-year 134 96 12 November 1920 Female After second-year 140 90 20 November 0200 Female After second-year 142 86 Average 139.9 94 28 October 2130 Unknown Second-year 139 84 6 November 0030 Unknown After second-year 135 86 12 November 2120 Unknown Second-year 136 86 12 November 2120 Unknown Second-year 136 86 Average 136.5 85.5 70 The Nebraska Bird Review Vol. 73 No. 2 CONCLUSION Any comparisons made between one year of banding data from Nebraska and multiple studies from the East are tenuous at best. While all stations display female-biased capture rates, annual changes to percent of juvenile/adult captured in eastern populations preclude inferences from a single year of data from one banding station Nebraska. Banding stations throughout the Northeast are associated with local nature centers, and new stations in other regions like Nebraska could provide additional data on Northern Saw-whet Owl migratory patterns and winter distributions. In addition to a nature center staff member, locations near Lincoln and Omaha could draw upon a volunteer core of local birders and college students to run banding stations during weekends. Standardized protocols are available at the Project Owlnet website. LITERATURE CITED Brinker, D. F., K. E. Duffy, D. M. Whalen, B. D. Watts, and K. M. Dodge. "Autumn Migration of Northern Saw-whet Owls (Aegolius acadicus) in the Middle Atlantic and Northeastern United States: What Observations from 1995 Suggest." Proceedings of the Second International Symposium on Biology and Conservation of Owls of the Northern Hemisphere, J. R. Duncan, D. H. Johnson and T. H. Nicholls, eds. 1997: 74-89. Cannings, R. J. "Northern Saw-whet Owl (Aegolius acadicus)." Birds of North America, No. 42 (A. Poole and F. Gill, eds). The Academy of Natural Sciences, Philadelphia, PA, and The American Ornithologists' Union, Washington D.C. 1993. Cheveau M., P. Drapeau, L. lmbeau, and Y. Bergeron. "Owl Winter Irruptions as an Indicator of Small Mammal Population Cycles in the Boreal Forest of Eastern North America." Oikos 107 (2004): 190-198. Elliot, L., D. Stokes, and L. Stokes. Stokes Field Guide to Bird Song: Eastern Region. Time Warner Audio Books. 1997. Marks J. S., and J. H. Doremus. "Are Northern Saw-Whet Owls Nomadic?" Journal of Raptor Research 34 (2000): 299-304 National Audubon Society. The Christmas Bird Count Historical Results [Online]. Available at http://www.aµdubon.or~ird/cbc [21April2005] Pyle, P. The Identification Guide to North American Birds: Part I. Solinas, CA: . Slate Creek Press, 1997. Sharpe, R. S., W. R. Silcock, and J. G. Jorgensen. Birds of Nebraska Their Distribution and Temporal Occurrence. Lincoln, Nebraska: University of Nebraska Press, 2001. Whalen D. M. and B. D. Watts. "The Influence of Audio-lures on Capture Patterns of Migrant Northern Saw-whet Owls." Journal of Field Ornithology 70 (1999): 163-168. 

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Northern Saw-whet Owls: Rare or Overlooked? An Example from the Central Platte Valley

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