Lecture 19 - Birds

Question 1

Birds: when did they appear, what new characteristics did they bring, where do they mainly reside in, and what are the other interesting features?

Answer 1

150mYa as a further developed dinosaurs

Feathers used for powered flight

Everywhere

• Flight (involves many complex anatomical/
  physiological adaptations)
• Parental behaviour, nests (can also be burrows, or
  scrapes) (very rare in modern reptiles)
• Sexual selection for structures and behaviours,
  mainly on males
• Remarkable intelligence in some lineages

Question 2

The eight stages of feather development

Answer 2

1. Single filament
2. Multiple filaments joined at their base
3. Multiple filaments joined at their base to a central filament
4. Multiple filaments along the length of a central
   filament
5. Multiple filaments arising from the edge of a
   membranous structure
6. Pennaceous feather with a vane of barbs and barbules and central rachis
7. Pennaceous feather with an asymmetrical rachis
8. Undifferentiated vane with central rachis

Question 3

The first stage of feather development: what is it, what was it likely used for, and what animals have/had this stage?

Answer 3

1. Single filament

Thermoregulation, communication, etc

Early dinosaurs (sauropods, theropods)

Question 4

The second stage of feather development: what is it, what was it likely used for, and what animals have/had this stage?

Answer 4

2. Multiple filaments joined at their base

Thermoregulation, communication, etc

Early dinosaurs (sauropods, theropods)

Question 5

The third stage of feather development: what is it, what was it likely used for, and what animals have/had this stage?

Answer 5

3. Multiple filaments joined at their base to a central filament

Thermoregulation, communication, etc

Early dinosaurs (sauropods, theropods)

Question 6

The fourth stage of feather development: what is it, what was it likely used for, and what animals have/had this stage?

Answer 6

4. Multiple filaments along the length of a central
   filament

Thermoregulation, communication, etc

Early dinosaurs (sauropods, theropods)

Question 7

The fifth stage of feather development: what is it, what was it likely used for, and what animals have/had this stage?

Answer 7

5. Multiple filaments arising from the edge of a
   membranous structure

Thermoregulation, communication, etc

Early dinosaurs (sauropods, theropods)

Question 8

The sixth stage of feather development: what is it, what was it likely used for, and what animals have/had this stage?

Answer 8

6. Pennaceous feather with a vane of barbs and barbules and central rachis

Thermoregulation, communication, early flight etc

Maniraptora

Question 9

The seventh stage of feather development: what is it, what was it likely used for, and what animals have/had this stage?

Answer 9

7. Pennaceous feather with an asymmetrical rachis

Thermoregulation, communication, flight etc

Maniraptora, Paraves, modern day birds

Question 10

The eighth stage of feather development: what is it, what was it likely used for, and what animals have/had this stage?

Answer 10

8. Undifferentiated vane with central rachis

Thermoregulation, communication, flight etc

Maniraptora, Paraves, modern day birds

Question 11

How did flight evolve?

Answer 11

Not sure - four main hypotheses put forward:

• Cursorial (running, clasping insects leads to wingstroke)
• Arboreal (tree-climbing) model (flying squirrel)
• Pouncing predation, refined control leads to flight
• Wing-assisted incline running (WAIR) (eg escaping

Question 12

What are the ecological benefits that birds have?

Answer 12

There is a huge range of living niches available, from mountain tops to seas (a larger geographic range which can be used for migration purposes too), a large range of eating niches available Predators, scavengers, herbivores, insectivores,
granivores, etc

Growing flightless and large is also possible

Question 13

Parental care: what is it, why is it used, and when is it used?

Answer 13

Behaviour that increases the fitness of offspring by caring for the offspring in their early life

Parental investment - this behaviour increases offspring fitness at the cost of a parent’s ability to reproduce in the future

Superprecocial - precocial - altricial - superaltricial
The more precocial the offspring is, the more mature and mobile it is

Question 14

Female infanticide in birds

Answer 14

Wattled jacanas – males care and polyandrous females defend territories

If a female is removed, a new female arrives, kills
male’s young, the male mates with new female and rears her young

Question 15

Nests

Answer 15

Altricial species build structures to protect their young

Nests can be scrapes, platforms, or cups.
Form generally species-specific, even in closely related species.

Question 16

To what extent do female birds that prefer longer tails actually prefer longer tails?

Answer 16

Malte Andersson (1982,1992) experimentally manipulated tail length to examine if females preferred males with longer tails

He found that, even when the tail length was longer than ideal and ended up being too costly, it was still preferred

Question 17

How do birds sing?

Answer 17

Elaborate learned songs evolved at least three times in separate lineages