1. Temperature Regulation
Gaviiformes
Loons
(“Divers” in the UK)
5 species
Holarctic distribution

2. Loon’s legs and feet are designed for propelling them through the water. They stand and walk on land with great difficulty.
Descendents of an ancient assemblage of seabirds that evolved in the early Tertiary.
Loons eat mostly fish and are among the best diving birds. They can reach depths of 75 meters and stay underwater for up to 8 minutes.

3. “Loons nest in masses of water vegetation, which they pile on small islands or close to the edge of open water.” Gill 2007

5. Common Loon

7. Loons use loud yodeling calls on their breeding territories

9. Pacific Loon

10. Pacific Loon

11. Red-throated Loon

12. Red-throated Loon

14. Body temperature

15. Examine behavioral & physiological responses to heat and cold
Lecture’s goals
Survey avian Tb
Examine behavioral & physiological responses to heat and cold

16. Body Temperature Humans are very precise Tb regulators
Normal human Tb is 37ºC
Daily 1ºC rhythm, w/ 36ºC late in sleep cycle
Human lethal 41ºC (105.8ºF)

17. Avian Temperature Avian Tb allowed to vary, sometimes widely
Measured during rest phase, Tb of most bird species is 40 ± 1.5ºC
1-3ºC higher during active phase
Lethal Tb 46-47ºC (116ºF v 106ºF)

18. Exceptions Penguins 37.0-38.9ºC Ratites 37.8-39.2ºC
Procellariiformes ºC

19. Avian Circadian Rhythm 1-3ºC
Brown Towhee

20. Basic principle
Large animals have high thermal inertia, it takes the input or loss of a large quantity of heat to change their body temperature

21. White-crowned Sparrow

22. Summary Bird Tb higher than human Tb, except for “primative birds”
Bird Tb more variable than human Tb
Lethal Tb 10°C higher in birds than humans

23. Regulating body temperature

24. Birds and mammals are endotherms
Cyclodus = Australian Northern Blue-tongue Lizard, Bettongia = Australian rat-kangaroo

25. Endotherms regulate their Tb by balancing heat gain and heat loss through physiology and behavior Heat gain = Heat loss

27. Thermal Neutral Zone Within the TNZ, birds change their insulation
Postural adjustments fluff up feathers, tuck head and beak, sit on feet
Alter blood flow to periphery

28. Responses to Cold Below Tlc insulation is maximal
Linear inc. in heat production
Shivering

29. Responses to heat Above Tlc insulation is minimal
panting
Above Tlc insulation is minimal
Pump out heat via evaporative cooling

30. Behavioral responses to cold
Reduce surface area
Seek warmer microclimate

32. Physiological responses to cold
Shivering
Hypothermia
Torpor

33. Shivering Below Tlc, all birds shiver
Shivering more effective in winter
Amer. Goldfinches survive -70ºC for 8 hours in winter, only 1 hr in summer
Insulation greater in winter
American Goldfinch

35. Lower Critical Temperature
Large birds have relatively less surface area and are thus better insulated
Tlc varies with size
Emperor Penguin -10ºC
Small finch 30ºC

36. Hypothermia
Decreases Tb – Ta gradient and hence need for increased heat production
Roadrunner & Turkey Vulture dec Tb to 34ºC at night
Boreal Chickadees, at -60ºC, can fly with Tb as low as 30ºC
Hypothermia is a fall in Tb below normal temperature.

37. Roadrunner sunning
In morning Roadrunners turn back to sun, raise back feathers exposing the black skin to the sun’s warming rays. Thus they use solar heat to increase their Tb rather than relying on metabolic heat productions. This saves energy.

38. Ditto Turkey Vultures

39. Peripheral Hypothermia

41. Counter Current Heat Exchange

43. Torpor Profound hypothermia
Heart, respiration, and metabolic rates greatly reduced
Nightjars, swifts and hummingbirds
Torpid Anna’s Hummingbird

45. Hibernation

46. Responses to Heat
Behavioral Select favorable microclimate Minimize surface area Droop wings
Physiological Hyperthermia Inc evaporative water loss (no sweat
glands)

47. Gular Flutter
Nonpasserines only
All birds pant