Birds: Diversity, Behaviour And Conservation: Mating

Front 1

Why are some birds monogamous?

Back 1

• High potential for parental care.
• More offspring if males are present.

Front 2

Give examples of how long some pair bonds last.

Back 2

• Grouse - only copulate together.
  
• Ducks - stay together during prolonged courtship period.
• Swans and geese - mate for life.

Front 3

Why mate for life?

Back 3

• Saves on investment in courtship time and energy.
  
• Guaranteed partner each year.

Front 4

What types of polygamous relationships are there?

Back 4

• Resource defence - males defend patches of resources, females choose males based on territory quality e.g. red-winged blackbirds.
  
• Female defence - rare, males fight to control clusters of breeding females, females build nests.
• Leks - small display sites, can be communal e.g. black grouse or solitary e.g. pheasant. Competition between males.

Front 5

Why lek?

Back 5

• 'Hot spot' males gather where they will find high densities of females.
  
• 'Hot shot' males gather around dominant experienced males in order to increases their chances of being noticed.
• Allows females to compare males.

Front 6

What is cooperative breeding (Kinship)?

Back 6

• Wild turkeys court as groups.
  
• Males in same lek tend to be more related to each other than males in other leks.
• Dominant male gets more offspring that subordinates.
• But better to be a subordinate male helping a sibling get lots of matings that they would have achieved on their own.

Front 7

What are cooperative courtship displays?

Back 7

• Males help dominate male gain matings.
  
• Why - Direct way to gain some matings, indirect benefit (inclusive fitness). Delayed direct benefit as one may inherit the patch.

Front 8

What are the costs of reproduction?

Back 8

High effort into breeding means lower survival rates as there is less time to forage and defend and effort has to be put into parental care.

Front 9

What affects timing of breeding?

Back 9

• Generally limited breeding season.
  
• Triggered by length of day.
• Affected by food availability.
• In tropical regions more likely to be triggered by food availability.

Front 10

How do nests vary?

Back 10

• Some birds have no nest e.g. guillemot.
• Platform nest e.g. wood-pigeon.
• Statant cup nest e.g. blackbird.
• Pensile cup nest e.g. goldcrest.
• Adherent cups e.g. swallows.
• Domed nests e.g. house martin.
• Globular nest e.g. magpie.

Front 11

What is the structure of bird eggs?

Back 11

• Large.
• Shell.
• Outer and inner membrane.
• Albumen (White).
• Yolk, surrounded by vitelline membrane.
• Chalazae - keep yolk in middle.
• Germinal spot - where embryo develops.

Front 12

What are types of egg are there?

Back 12

• Precocial - chick hatches and is able to defend itself and forage - takes longer to develop and the eggs are usually larger.
  
• Altricial - chick helpless, blind and naked - needs parental care, eggs usually smaller and quicker to develop.

Front 13

What shape are eggs?

Back 13

• Hole nesters - typically round eggs e.g. kingfisher.
• Cliff nesters - long pyriform (pear shaped) eggs e.g. guillemots.
• Shorebirds - 4 inward pointing eggs for compactness.

Front 14

Describe egg markings.

Back 14

• Very diverse.
• Pigment is aquired when eggs are rotated in the oviduct.
• Larger and generally more pigments as the eggs travels down the oviduct.
• Hole nesters - usually have unpigmented eggs.
• Open cup nesters have heavy pigmentation to act as camouflage.

Front 15

How do clutch size and egg laying vary in number and time?

Back 15

• Usually laid in the morning.
  
• Time between eggs determined by secreting various layers.
• Smaller birds such as ducks, 24 hours apart, penguins 3-6 days, kiwis 14-30 days.
• The key factor in clutch size is food.

Front 16

How did clutch size evolve?

Back 16

• Clutch size is the product of natural selection.
• Variation in clutch size is heritable.
• Optimal clutch size is not always the largest possible due to costs of breeding.

Front 17

How does fledgling success vary?

Back 17

• Influenced by food, parasites, predators and weather.
  
• Food abundance low = smaller siblings get killed.
• Brood reduction by adults - preferentially feed larger, more vocal offspring.

Front 18

What are the differences in characteristics of altrical and precocial young?

Back 18

• Altricial - closed eyes when hatched, absent or sparce down, immobile, heavily dependent on parents, eggs 4-10% of female weight.
• Precocial - eyes open when hatched, covered in down, able to walk and swim, vary in parental needs, eggs 9-25% female weight.