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Lesser scaup vision: the science and the numbers

Aythya affinis · order Anseriformes · Birds: all the numbers

Its sharpest vision resolves 11.2 cycles per degree, against 63.75 for people in this dataset.[6] Both eyes see the same 35.3° in front of it.[9]

See it on your photoBack to How does the lesser scaup see?
  • 11.2cycles per degree (sharpness)Measured
  • 35.3°seen by both eyesMeasured

The lesser scaup (Aythya affinis) is a bird in the order Anseriformes. Its eyes belong to the vision type Panoramic grain-eater and wader: four cone types, low to moderate sharpness and an almost all-round field of view. Measured in this species: sharpness, field of view 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 the lesser scaup sees: colour receptors

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

What stands out

  • Its sharpest vision resolves 11.2 cycles per degree: the finest stripe pattern it can tell apart from grey.
  • Both eyes see the same 35.3° in front of it (binocular overlap), where depth is judged best.
  • 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 lesser scaup (Aythya affinis), 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 family Anatidae)
Estimated[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
11.2 cycles per degree
median of 1 anatomical-ganglion rows (method priority rule)
Measured[6]Acuity: 63.75 cycles per degree Measured[7][8]
Field of viewBinocular overlap
35.3°
median of 1 rows (eyes-at-rest rows preferred)
Measured[9]Binocular overlap: 122.5° Measured[10][11]
Total field of view: 200° Measured (not re-verified)[12]
Blind area behind the head: 160° Derived[12]
Eye placement: frontal Derived[10][11]
Total field of view
306°
median total field (measured, or 360 - blind area) of relatives in family Anatidae: Mergus merganser
Estimated[13]
Blind area behind the head
54°		Estimated[13]
Eye placement
lateral
frontal if binocular overlap >= 60 deg, else lateral
Derived[9]
Sharp zones (foveas)Number of foveas
1
median of 1 relatives in family Anatidae: Branta canadensis
Estimated[14]Number of foveas: 1 Measured[15]
Fovea type: fovea Measured[15]
Fovea type
single central fovea (displaced dorso-temporally from retinal centre)		Estimated[14]
Night visionActivity pattern
diurnal
mode of 5 rows (of 5 rows): cathemeral; diurnal; not_nocturnal; photopic
Measured (not re-verified)[16][17][18][19][20]Activity pattern: diurnal Measured (not re-verified)[16][21][22][2][23][24][19][20]
Pupil shape: vertical Group default[25][26]
Reflective layer (tapetum): no Measured[27]
Rods vs cones: cone-dominated Derived[16][21][22][2][23][24][19][20]
Rods vs cones
cone-dominated
nocturnal -> rod-dominated; crepuscular / cathemeral / mixed -> mixed; diurnal -> cone-dominated
Derived[16][17][18][19][20]
Motion (flicker fusion)Flicker fusion frequency
88.5 Hz
median of 17 relatives in class Aves: Bubo virginianus, Melopsittacus undulatus, Passer domesticus, Taeniopygia guttata, Columba livia, Calypte anna
Group default[28][29][30][31][32]Flicker fusion frequency: 60 Hz Measured[30][31]

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. Kirk et al. 2004
  8. Veilleux et al. 2014
  9. Cantlay et al. 2023
  10. Heesy 2004
  11. Heffner et al. 1992
  12. Campbell & Green 1965
  13. Pecsics et al. 2023
  14. Moore et al. 2017
  15. Kopania et al. 2025
  16. Anderson et al. 2017
  17. Light conditions and the evolution of…
  18. Wilman et al. 2014
  19. Schmitz et al. 2011
  20. Moura et al. 2024
  21. Borges et al. 2018
  22. Wilman et al. 2014
  23. Maor et al. 2017
  24. Jones et al. 2009
  25. Banks et al. 2015
  26. Cervino et al. 2021
  27. Guareschi et al. 2025
  28. Boström et al. 2016
  29. Haarlem et al. 2026
  30. Healy et al. 2013
  31. Inger et al. 2014
  32. Lafitte et al. 2022

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.