Northern Hawk Owl

Surnia ulula

Order:
Strigiformes
Family:
Strigidae
Sections

Tables and Appendices

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Table 1

Characteristics of Northern Hawk Owl nest sites in North American (n = 58). Data from personal communications, references cited in text, and PAD, JRD.

VariableMeanMedianSEMinMaxn
Tree height (m)7.56.51.21.017.014
Nest height (m)7.46.00.70.221.041
Diameter at base (cm)50.940.010.225.0125.09
Diameter at nest (cm)27.326.83.320.435.14
Cavity depth (cm)16.414.62.82.640.012
Cavity diameter–min (cm)5.90.03.70.018.06
Cavity diameter–max (cm)4.00.04.00.020.05
Nest locationNumberNest tree genusNumberNest structureNumber
Alaska24Abies1Cavity19
Alberta9Acer1Snag top35
British Columbia6Betula9Stick nest4
Labrador3Fraxinus1
Manitoba3Larix3
Minnesota3Picea17
Montana1Pinus2
Newfoundland1Populus15
Ontario3Pseudotsuga3
Saskatchewan1Tsuga1
Vermont1
Wisconsin2
Yukon Territory1


Table 2

Linear measurements (mm) and mass (g) for Northern Hawk Owl in North America. Sample includes individuals from Alberta, Alaska, British Columbia, Labrador, Manitoba, Minnesota, Nova Scotia, Northwest Territories, Ontario, Quebec, Saskatchewan, and Yukon. Breeding status generally not known. Data from personal communications (see Acknowledgments), references cited in text, and PAD, JRD. Data given as mean ± SE (range, n).

  • (1)Wing-chord from carpal joint to tip of longest primary.
  • (2)From point between central pair of rectrices where they emerge from skin to tip of longest rectrix.
  • (3)From tip of bill to tip of longest rectrix.
  • (4)Chord from tip to anterior of nostril.
  • (5)By opening diagonal toes and measuring from tips of pads.

MaleFemalePooled sample
Wing (mm) (1)222.7 ± 1.5 (213–245, 24)228.3 ± 1.4 (210–242, 29)224.9 ± 0.4 (197–245, 321)
Tail (mm) (2)171.3 ± 2.2 (138–190, 28)173.8 ± 1.9 (156–191, 25)175.7 ± 0.6 (136–197, 257)
Total length (mm) (3)365.1 ± 8.4 (277–444, 17)374.7 ± 3.7 (310–398, 24)366.5 ± 4.7 (265–440, 47)
Bill (mm) (4)18.0 ± 0.3 (17.4–19.4, 6)19.5 ± 0.2 (18.6–20.0, 5)18.9 ± 0.3 (17.4–20.0, 5)
Foot (mm) (5)45.5 ± 0.1 (41–50, 168)
Ovaries (mm)9.3 ± 1.0 (5–12, 6)
Testes (mm)6.6 ± 1.0 (3.0–12.5, 12)
Mass (g)301.2 ± 4.8 (242–375, 42)339.8 ± 5.6 (250–454, 54)346.4 ± 2.5 (144.7–454.0, 339)


Appendix 1

Food of the Northern Hawk Owl from different regions of North America. Data represent number of prey. Data derived primarily from analysis of pellets.

RegionAlaska nestsAlaska nestsYukon nestsMinnesota winterMinnesota nestManitoba winterManitoba winterAlberta summerTotal% Total
SourceT. Osborne pers. comm.Kertell 1986Rohner et al. 1995Lane and Duncan 1987Lane and Duncan 1987JRD, PADNero 1995R. Gehlert pers. comm.
PREY:
Mammals
Clethrionomys5319191432635922.4
Microtus462373112944492483399762.3
Synaptomys27812472.9
Phenacomys333362.3
Peromyscus2130.2
Lemmus330.2
Lepus630362.3
Birds
1831221.4
Other
6824212976.1
Total prey/study
51651449325654253541,600100%
Prey/pellet
0.741.612.461.5Up to 41.35


Appendix 2

Summary of Northern Hawk Owl reproductive timing and success in different regions of Northern Hemisphere.

  • (1)Calculated for successful nests only.

LocationMedian laying dateLaying date rangeMean clutch sizeMean number of young fledged/nest (1)Source
Alaska and Arctic Canada4–17 May (“normal range”)30 Mar–26 Jun (n = 12)(3–7, freq. 7, rarely 9)Bent 1938b, Eckert 1974
Alaska9 Apr–2 May (n = 5)13 Apr–18 May (n = 2)5.38 (4–7, s = 0.92, n = 8)5.25 (3–7, s = 1.14, n = 12)Gabrielson and Lincoln 1959, Mindell 1983b, Kertell 1986, C. McIntyre pers. comm.
Sw. Yukon24 Apr (n = 9)19 Apr–11 May4 (2–5, n = 9)Rohner et al. 1995
British Columbia23 Apr–31 May2.42 (1–5, s = 1.16, n = 12)Campbell et al. 1990b
Alberta3–28 Apr (n = 19)1 Apr–4 Jun (n = 38)(3–7, freq. 7, rarely 9)Bent 1938b
6.67 (6–7, s = 0.58, n = 3)5.50 (2–7, s = 2.38, n = 4)Pinel et al. 1991, E. Pletz and R. Gehlert pers. comm.
Saskatchewan8 (n = 1)7 (n = 1)Hunter 1969, Hooper 1992a
Manitoba3 (n = 1)Lang et al. 1991
Minnesota22 Apr–15 Jun (n = 3)8 (n = 1)6.38 (6–7, s = 0.48, n = 4)Lane and Duncan 1987, Kehoe 1982, PAD, JRD
Wisconsin5 (n = 1)2 (n = 1)Bernard and Klugow 1963
Ontario19 Apr (n = 1)5 (n = 2)4 (n = 1)Peck and James 1983, E. Smith pers. comm.
Labrador and Newfoundland3 May–30 Jun (n = 6)(3–7, freq. 7, rarely 9)Bent 1938b, Eckert 1974
New Brunswick3.75 (3–5, s = 0.96, n = 4)A. MacCharles pers. comm., R. Walker pers. comm.
North America5.67 (51 eggs, 9 clutches)L. Kiff pers. comm.
Eurasia7 (3–13, n = ?)Cramp 1985a
Norway17 Apr–13 May (n = 2)4.5 (n = 2)Sonerud et al. 1987
FinlandLate Marlate Jun6.31 (3–13, n = 135)Mikkola 1983
Former USSRLate Mar–?Dement'ev and Gladkov 1966


Recommended Citation

Duncan, J. R. and P. A. Duncan (2014). Northern Hawk Owl (Surnia ulula), version 2.0. In The Birds of North America (A. F. Poole, Editor). Cornell Lab of Ornithology, Ithaca, NY, USA. https://doi.org/10.2173/bna.356