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American kestrel vision: the science and the numbers

Falco sparverius · order Falconiformes · Birds: all the numbers

Their sharpest vision resolves 30.85 cycles per degree, against 63.75 for people in this dataset.[6][7] Their eyes cover about 292° with 27.5° seen by both eyes.[10]

See it on your photoBack to How do kestrels see?
  • 30.85cycles per degree (sharpness)Measured
  • 292°field of viewEstimated

The American kestrel (Falco sparverius) is a bird in the order Falconiformes. Its eyes belong to the vision type Raptor telephoto: four cone types, two foveas and very high sharpness. Measured in this species: sharpness, field of view, foveas and night vision. Measured core: measured values on at least 3 of the 6 dials.

This is a simulation built from published eye measurements, not what the animal experiences.

Method: How we know what animals see (the See Like Animals vision engine) · Sources · Last updated . Every value below carries its evidence level and sources; nothing is typed by hand.

What kestrels see: colour receptors

American kestrel colour receptor peaks, 300 to 700 nmAmerican kestrel: 4 receptor peaks at 417.5, 452, 501, 570 nm; you: 3 at 421.5, 532, 558.4 nm. ultraviolet300400500600700
American kestrel: 417.5, 452, 501, 570 nmPeople: 421.5, 532, 558.4 nmWavelength in nanometres

What stands out

  • Its sharpest vision resolves 30.85 cycles per degree: the finest stripe pattern it can tell apart from grey.
  • Its eyes cover about 292° around the head, with 27.5° seen by both eyes at once.
  • Activity pattern: diurnal.

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. The last column gives the values for people from the same catalogue.

Vision values for the American kestrel (Falco sparverius), catalogue-v1
DialValueEvidenceSourcesPeople
ColourColour receptors
4 receptor classes: 417.5 nm (VS/SWS (violet)), 452 nm (SWS (blue)), 501 nm (MWS (green)), 570 nm (LWS (long))
receptor set of nearest measured relative Anas platyrhynchos (same class Aves)
Group default[1][2]Colour receptors: 3 receptor classes: 421.5 nm (VS/SWS (violet)), 532 nm (MWS (green)), 558.4 nm (LWS (long)) Measured (not re-verified)[2][3][4][5]
SharpnessAcuity
30.85 cycles per degree
median of 2 behavioural rows (method priority rule)
Measured[6][7]Acuity: 63.75 cycles per degree Measured[8][9]
Field of viewBinocular overlap
27.5°
median of 2 rows (eyes-at-rest rows preferred)
Measured[10][11]Binocular overlap: 122.5° Measured[12][13]
Total field of view: 200° Measured (not re-verified)[14]
Blind area behind the head: 160° Derived[14]
Eye placement: frontal Derived[12][13]
Total field of view
292°
rule: total = 360 - blind area
Derived[10]
Blind area behind the head
68°		Measured[10]
Eye placement
lateral
frontal if binocular overlap >= 60 deg, else lateral
Derived[10][11]
Binocular field, vertical extent
112.5°; elevation 90 deg (horizontal plane through the eyes); eyes at rest unless stated		Measured[15]
Sharp zones (foveas)Number of foveas
2
species-v1.csv text: 2 (central deep + temporal shallow)
Measured[16][17]Number of foveas: 1 Measured[18]
Fovea type: fovea Measured[18]
Fovea type
central fovea, temporal		Measured[16][17]
Night visionActivity pattern
diurnal
mode of 6 rows (of 6 rows): diurnal; not_nocturnal
Measured (not re-verified)[19][20][21][22][23][24]Activity pattern: diurnal Measured (not re-verified)[25][26][27][2][28][29][30][24]
Pupil shape: vertical Group default[31][32]
Reflective layer (tapetum): no Measured[33]
Rods vs cones: cone-dominated Derived[25][26][27][2][28][29][30][24]
Night sensitivity (optical, against people): S = 0.93 µm² sr, 1 times people (log10 ratio 0) Derived[34]
Rods vs cones
cone-dominated
nocturnal -> rod-dominated; crepuscular / cathemeral / mixed -> mixed; diurnal -> cone-dominated
Derived[19][20][21][22][23][24]
Motion (flicker fusion)Flicker fusion frequency
113.25 Hz
median of 2 relatives in genus Falco: Falco peregrinus, Falco cherrug
Estimated[35][36]Flicker fusion frequency: 60 Hz Measured[37][38]

All birds side by side: Birds: every measurement. Method: how we know what animals see.

Sources

  1. Lind et al. 2014
  2. Longcore 2023
  3. Kirwan
  4. Müller et al. 2009
  5. Thermal Activation and Photoactivation of Visual… 2004
  6. Caves et al. 2018
  7. Caves et al. 2024
  8. Kirk et al. 2004
  9. Veilleux et al. 2014
  10. Tyrrell et al. 2017
  11. Tyrrell et al. 2017
  12. Heesy 2004
  13. Heffner et al. 1992
  14. Campbell & Green 1965
  15. O'Rourke et al. 2010
  16. Rasys et al. 2024
  17. Potier et al. 2017
  18. Kopania et al. 2025
  19. Angielczyk et al. 2014
  20. Light conditions and the evolution of…
  21. Choiniere et al. 2021
  22. Wilman et al. 2014
  23. Schmitz et al. 2011
  24. Moura et al. 2024
  25. Anderson et al. 2017
  26. Borges et al. 2018
  27. Wilman et al. 2014
  28. Maor et al. 2017
  29. Jones et al. 2009
  30. Schmitz et al. 2011
  31. Banks et al. 2015
  32. Cervino et al. 2021
  33. Guareschi et al. 2025
  34. Brauburger et al. 2026
  35. Haarlem et al. 2026
  36. Lafitte et al. 2022
  37. Healy et al. 2013
  38. Inger et al. 2014

Every value cites its sources (all sources). Values were extracted from these works and converted (units, medians, derived values); changes are ours, and the listed sources do not endorse this site. Data: catalogue-v1, built 2026-09-29. Accuracy notes: how accurate is this? Method: how we know.