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

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