BIOL 329 Lecture Notes - Lecture 17: Torpor, Monocular Vision, Color Vision
6 May 2018
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Lect 17
A chickadee (12 g) would use all of its fat reserves on an average BC winter night and would starve to
death by morning if it were to maintain constant body temp (40oC). Allow temp to drop 10oC overnight
which reduces standard metabolic rate by 30% (deep torpor). Still use up to 75% of the fat reserves –
needs to re-establish the fat reserves each day. Common Poorwill is the largest bird (60g) to enter deep
torpor – days, weeks or months. Hummingbirds enter varying states of torpor during day and night as a
function of ambient temperature, foraging success, predator risk. A 12% reduction in daily foraging time
results in 2 hours of torpor at night. 20% reduction = 3.5 hours of torpor. Increased torpor results in
increased mortality.
Vision:
Eyes immobile in most species. Have horizontal nictitating membrane that lubricates and protects. Field
of vision (Pigeon: wide monocular vision, narrow binocular vision. Owls: wide binoc, narrow monocular).
Birds use lateral vision for improved resolution. Forward (binoc) for depth/distance perception.
Vertebrate eye: Nocturnal: rod-dominated. Diurnal species have many more cones.
Vole: 1 cone pigment (peak ab 550 nm). The eye can only see white and black.
Wolf: 2 cones – color is a neural interpretation. They can see blues and greens but nothing in the
red/orange/yellow part of the spectrum.
Humans only have 1 photo pigment – we a’t see well at ight…?
Bird: 4 cone pigments (iodopsin) + rod pigment, rhodopsin, (503 nm) + 1-6 different colored oil droplets.
Also, sensitive to polarized light. Nocturnal birds have mainly rods w/ some cones. Retina divided into
two regions – a red field – on the dorsal quadrant and includes the binocular field of view.
The yellow field makes up the rest of the retinae. The cones have red, orange and yellow oil droplets at
the front of the cones and the relative proportion of these make up the red or yellow region. Oil
droplets give a sharper contrast between subtle differences in hue.
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Document Summary
A chickadee (12 g) would use all of its fat reserves on an average bc winter night and would starve to death by morning if it were to maintain constant body temp (40oc). Allow temp to drop 10oc overnight which reduces standard metabolic rate by 30% (deep torpor). Still use up to 75% of the fat reserves needs to re-establish the fat reserves each day. Common poorwill is the largest bird (60g) to enter deep torpor days, weeks or months. Hummingbirds enter varying states of torpor during day and night as a function of ambient temperature, foraging success, predator risk. A 12% reduction in daily foraging time results in 2 hours of torpor at night. Have horizontal nictitating membrane that lubricates and protects. Field of vision (pigeon: wide monocular vision, narrow binocular vision. Vole: 1 cone pigment (peak ab 550 nm). The eye can only see white and black. Wolf: 2 cones color is a neural interpretation.
