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How does the northern hawk-owl see?

The northern hawk-owl (Surnia ulula) is a bird in the order Strigiformes. Its eyes belong to the vision type Owl and night bird.

Measured in this species: sharpness and night vision. Measured colour or sharpness: a measured receptor set or acuity in this species; other dials come from relatives or group defaults. Every value below carries its evidence level and sources; nothing is typed by hand.

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What stands out

The six dials

Evidence levels: how the tiers work. "Measured" means a value measured in this species; "Estimated" values come from a close relative or an eye-size formula.

Vision values for the northern hawk-owl (Surnia ulula), catalogue-v1
DialValueEvidenceSources
ColourColour receptors
3 receptor classes: 463 nm (SWS (blue)), 530 nm (MWS (green)), 555 nm (LWS (long))
receptor set of nearest measured relative Strix aluco (same family Strigidae)
Estimated[1][2]
SharpnessAcuity
19.2 cycles per degree
median of 1 anatomical-ganglion rows (method priority rule)
Measured[3]
Field of viewBinocular overlap
46°
median of 22 relatives in family Strigidae: Asio otus, Athene noctua, Bubo africanus, Bubo bengalensis, Bubo bubo, Bubo capensis
Estimated[4]
Total field of view
201°
median species-v1 total field of family Strigidae: Strix aluco
Estimated[5]
Sharp zones (foveas)Number of foveas
1
median of 48 relatives in class Aves: Branta canadensis, Cardinalis cardinalis, Passerina cyanea, Zenaida macroura, Cyanocitta cristata, Junco hyemalis
Group default[6][7][8]
Fovea type
single central fovea (displaced dorso-temporally from retinal centre)		Group default[6][7][8]
Night visionActivity pattern
nocturnal
mode of 6 rows (of 6 rows): cathemeral; nocturnal; scotopic
Measured (not re-verified)[9][10][11][12][13][14]
Rods vs cones
rod-dominated
nocturnal -> rod-dominated; crepuscular / cathemeral / mixed -> mixed; diurnal -> cone-dominated
Derived[9][10][11][12][13][14]
Motion (flicker fusion)Flicker fusion frequency
50 Hz
median of 3 relatives in family Strigidae: Bubo virginianus, Athene noctua, Asio flammeus
Estimated[15][16]

Related animals

More birds: all birds with measured vision data.

Sources

  1. Longcore T. 2023. A compendium of photopigment peak sensitivities and visual spectral response curves of terrestrial wildlife to guide design of outdoor nighttime lighting. Basic Appl Ecol 73:40-50. doi:10.1016/j.baae.2023.09.002. doi.org/10.5281/zenodo.8432720
  2. VPOD in-vivo (MSP / single-cell) lambda max compendium, file scp_cleaned.csv, VPOD GitHub (Frazer et al. 2025 bioRxiv 10.1101/2025.08.22.671864). github.com/VisualPhysiologyDB/visual-physiology-opsin-db/tree/main/scripts_n_notebooks/vpod_ML_workflows/mine_n_match/data_sources/lmax/vpod
  3. Caves EM, Fernandez-Juricic E, Kelley LA (2024) Ecological and morphological correlates of visual acuity in birds. J Exp Biol 227(2): jeb246063. Supplementary Table S1.. doi.org/10.1242/jeb.246063
  4. Potier S, Roulin A, Martin GR, Portugal SJ, Bonhomme V, Bouchet T, de Romans R, Meyrier E, Kelber A. 2023. Binocular field configuration in owls: the role of foraging ecology. Proc R Soc B 290: 20230664. Data figshare.. doi.org/10.1098/rspb.2023.0664
  5. species_v1:Martin 1984
  6. Moore BA, Tyrrell LP, Pita D, Bininda-Emonds ORP, Fernandez-Juricic E 2017. Does retinal configuration make the head and eyes of foveate birds move? Sci Rep 7: 38406. Appendix 1.. doi.org/10.1038/srep38406
  7. Potier S, Mitkus M, Bonadonna F, Duriez O, Isard P-F, Dulaurent T, Mentek M, Kelber A 2017. Eye size, fovea, and foraging ecology in accipitriform raptors. Brain Behav Evol 90: 232-242. Supplementary material (Tables S1, S2).. doi.org/10.1159/000479783
  8. Rodrigues T, Matter MM, Chiodini A, et al. 2026. Foveal vision in fast-flying birds hunting on the wing. bioRxiv 2026.06.05.730304. doi.org/10.64898/2026.06.05.730304
  9. Anderson SR, Wiens JJ. 2017. Out of the dark: 350 million years of conservatism and evolution in diel activity patterns in vertebrates. Evolution 71:1944-1959. Dryad doi:10.5061/dryad.fg700. doi.org/10.5061/dryad.fg700
  10. Light conditions and the evolution of the visual system in birds (figshare dataset, SupplementaryDataset1). doi.org/10.6084/m9.figshare.22116371.v3
  11. Choiniere JN, Neenan JM, Schmitz L, Ford DP, Chapelle KEJ, Balanoff AM, Sipla JS, Georgi JA, Walsh SA, Norell MA, Xu X, Clark JM, Benson RBJ. 2021. Evolution of vision and hearing modalities in theropod dinosaurs. Science 372:610-613. doi:10.1126/science.abe7941. Data: https://osf.io/teq73/. doi.org/10.1126/science.abe7941
  12. Wilman H, Belmaker J, Simpson J, de la Rosa C, Rivadeneira MM, Jetz W. 2014. EltonTraits 1.0: species-level foraging attributes of the world's birds and mammals. Ecology 95:2027. BirdFuncDat.txt. doi.org/10.6084/m9.figshare.3559887.v1
  13. Schmitz L, Motani R. 2011. Science 332:705-708, SOM. doi.org/10.1126/science.1200043
  14. Moura et al. 2024. A phylogeny-informed characterisation of global tetrapod traits addresses data gaps and biases. PLoS Biol 22:e3002658. TetrapodTraits v3.0.1.. doi.org/10.5281/zenodo.22536349
  15. Healy K, McNally L, Ruxton GD, Cooper N, Jackson AL. 2013. Metabolic rate and body size are linked with perception of temporal information. Animal Behaviour 86:685-696. Table 1. doi.org/10.1016/j.anbehav.2013.06.018
  16. Lafitte A, Sordello R, Legrand M, Nicolas V, Obein G, Reyjol Y. 2022. A flashing light may not be that flashy: A systematic review on critical fusion frequencies. PLoS ONE 17(12): e0279718. S10 File (CFF database). doi.org/10.1371/journal.pone.0279718
  17. Inger R, Bennie J, Davies TW, Gaston KJ. 2014. Potential biological and ecological effects of flickering artificial light. PLoS ONE 9(5): e98631. Table 3. doi.org/10.1371/journal.pone.0098631

Every value cites its sources (all sources). Data: catalogue-v1, built 2026-09-29. Accuracy notes: how accurate is this?