Avian Physiology

• Efficient respiratory & circulatory systems are necessary to support high basal metabolism, thermoregulation, and powered flight in birds Energy & Heat in Birds • Migration & fuel • Ruby-throated Hummingbird • Kinglets & Winter • Bergman’s Rule • Hidden Secrets of Nightjars • Cold feet?

Aerosteon riocoloradensis Theropod dinosaur with pneumatic bones. Pneumatic Features of Aerosteon Pneumatic Features of Aerosteon

Furcula, Ilium, and gastric ribs have pneumatic chambers consistent with “avian-like” air sac ventilation. If Dinosaurs had air sacs, then what else might one ask about dinosaur biology? Human Energy Efficiency New York City Marathon Champions

• 2600 kcalories per marathon (26.2 miles)

• 31,000 kcalories per gallon of gasoline

• 310 miles per gallon for a marathon runner—not bad!

Blackpoll Warbler Fall Migration

90-110 hour flight 25 mph 50% weight loss during flight

500 miles trans-gulf flight 20 -25 hours 5.5 grams pre-flight weight

Why are Eastern African Populations Great Marathon Runners? Weight Specific BMR for Amphibians, Lizards, Mammals, and Birds

6 Amphibians Lizards 5 Mammal 4 Birds

3

2

1Weight (mL O2 / g-hr) Rate Rate of Oxygen Consumption per 0 3 7 10 20 30 40 50 60 70 80 90 100 Body Weight (grams) Basal Metabolism and Ambient Temperature

Lower Critical Temperature

Upper Critical Temperature

(ml (ml / / g hr) Oxygen Consumption Oxygen ThermoNeutral Zone

Ambient Temperature (°C) How is body temperature managed?in the TNZ? • At TNZ – Insulation modulation – Restrict blood flow to feet – Peripheral blood flow adjustment

• Below LCT – Thermogenic mechanisms • Shivering – Non-shiver thermogenesis (mammals) Horned Lark – Other Ideas??? Body Temperature above UCT

• Hyperthermia • Gular Fluttering & Panting – Evaporative Cooling • Feather Insulation

Basal Metabolism and Ambient Temperature

(ml (ml / / g hr) Oxygen Consumption Oxygen

Ambient Temperature (°C) Ruby-throated Hummingbird Thermal Dynamics Size & Volume Relationship At 30 °C:

3 mg O2/g/hr x 5 cal/ml O2 x 3 g 14

12 = 45 cal / hr

10

8 = 360 cal / 8 hr at 30 °C

6

(ml (ml / / g hr) 4

2 Oxygen Consumption Oxygen

0

0 10 20 30 40 Ambient Temperature (°C) How much nectar is needed for 360 calories?

360 cal X 5 µl/cal = 450 µl Basal Metabolism versus Ambient Temperature in Hummingbirds At 15 °C:

8 mg O2/g/hr x 5 cal/ml O2 x 3 g 14

12 = 120 cal / hr

10

8 = 960 cal / 8 hr at 15 °C

6

(ml (ml / / g hr) 4

2 Oxygen Consumption Oxygen

0

0 10 20 30 40 Ambient Temperature (°C) How much nectar is needed for 960 calories?

960 cal X 5 µl/cal = 1200 µl How can a hummingbird survive overnight? Why does a hummingbird have great resting energetic demands? What are the options for over night survival?

14

12

10

8

6

(ml (ml / / g hr) 4

2 Oxygen Consumption Oxygen

0

0 10 20 30 40 Ambient Temperature (°C)

TORPOR—controlled reduction in basal metabolic rate; reduces energy requirements; lowers body temperature; slows heart rate, breathing, muscle tone works for some small birds and animals Why does a hummingbird have a high metabolic rate? • High surface area—low volume

• Advantage of small body size – Fast convective heat loss during hovering flight – Maneuverability • Disadvantage – Rapid heat loss during periods of inactivity – High food demand

Order Caprimulgiformes Why does torpor work for nightjars?

• Exploit unpredictable food resource – Temperature-dependent, aerial insects at dusk • Diurnal and seasonal torpor • Common Poorwill – Winter body temp to 4.3ºC – 2-3 months – 7 hour warm-up – Hopi People call the poor will Hölchoko—Sleeping One • Crypticity Seasonal Hibernation in Tawny Frogmouth Kinglets & Winter

• Golden-crowned kinglet is an obligate insectivore-winter in NE • Body Mass Comparison – Hummingbird-- 3 grams – Golden-crowned Kinglet—6 grams Ruby-crowned Kinglet – Black-capped Chickadee—12 grams • Shiver Thermogenesis—begins at lower critical temperature – Pectoralis major and leg muscles generate heat – Higher LCT for small birds • Microclimate selection • Huddling – Emperor Penguins – Dove Pyramids – Golden-crowned Kinglets

Cold Feet?

• Retractable landing gear protect feet in cold weather • Vasoconstriction in feet and legs • Countercurrent heat exchange • Blood shunt or bypass of feet--gulls Energy Savings in Huddling Emperor Penguins • Metabolic rates of – Isolated (I) – Loosely grouped (LG) – Free-Ranging (FR) • Measured by body mass changes • Shelter from wind • Reduction of Surface area • Microclimate adjustment

Gilbert et al., 2007 Energy Savings in Huddling Emperor Penguins

• Lower Critical Temperature at -10°C

• Large group, 39% lower BMR than individual – Wind protection – Microclimate – Surface area reduction

• Other adaptations??? Look and think about the Emperor Penguin body

Thermoregulation Solutions for Cold Survival • Torpor-hibernation – Diurnal – Seasonal • Bergman’s Rule – Bigger the better – Huddling • Feather Fluffing • Shiver Thermogenesis • Blood flow in feet/legs

Bergman’s Rule Downy Woodpecker

• Body size (wing length as a surrogate) increases with latitude.

• What is the advantage in cold dry climates?

• What is the advantage in warm moist climates?