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Questions and Answers
What is the primary function of the ovum in birds after fertilization?
What is the primary function of the ovum in birds after fertilization?
In which part of the female bird's anatomy does sperm from multiple males compete to fertilize the ovum?
In which part of the female bird's anatomy does sperm from multiple males compete to fertilize the ovum?
How do bird testes respond during the breeding season?
How do bird testes respond during the breeding season?
What is the primary method of copulation in most birds without a penis?
What is the primary method of copulation in most birds without a penis?
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What distinguishes the composition of yolk in bird eggs?
What distinguishes the composition of yolk in bird eggs?
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What role does the cloaca play in birds?
What role does the cloaca play in birds?
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What is a unique feature of certain waterfowl in relation to their reproductive anatomy?
What is a unique feature of certain waterfowl in relation to their reproductive anatomy?
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What predominantly influences the timing of sperm formation in birds?
What predominantly influences the timing of sperm formation in birds?
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What is the primary purpose of bowers created by bowerbirds?
What is the primary purpose of bowers created by bowerbirds?
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In the Hotshot Model of lek evolution, which males do younger males tend to cluster around?
In the Hotshot Model of lek evolution, which males do younger males tend to cluster around?
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Which statement correctly defines monogamy in bird species?
Which statement correctly defines monogamy in bird species?
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What is a significant benefit of cooperative breeding for helper birds?
What is a significant benefit of cooperative breeding for helper birds?
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Which breeding system is characterized by the female defending resources to attract multiple males?
Which breeding system is characterized by the female defending resources to attract multiple males?
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What behavioral trait does brood parasitism typically exemplify?
What behavioral trait does brood parasitism typically exemplify?
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In the context of lek behavior, what is the Female Preference Model?
In the context of lek behavior, what is the Female Preference Model?
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Which type of bower is characterized by sticks built around a central pole?
Which type of bower is characterized by sticks built around a central pole?
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What is a common characteristic of obligate brood parasites?
What is a common characteristic of obligate brood parasites?
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What role do older male Purple Martins typically play in extra-pair copulations?
What role do older male Purple Martins typically play in extra-pair copulations?
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What is one of the ecological factors that might promote cooperative breeding?
What is one of the ecological factors that might promote cooperative breeding?
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How does kin selection explain altruistic behavior in cooperative breeding?
How does kin selection explain altruistic behavior in cooperative breeding?
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What percentage of offspring in some species, like Tree Swallows, is commonly fathered by males outside the mated pair?
What percentage of offspring in some species, like Tree Swallows, is commonly fathered by males outside the mated pair?
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Which evolutionary model explains males gathering based on where they are likely to encounter females?
Which evolutionary model explains males gathering based on where they are likely to encounter females?
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What role does albumen play in avian eggs?
What role does albumen play in avian eggs?
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Which of the following best describes the relationship between egg yolk percentages and chick maturity at hatching?
Which of the following best describes the relationship between egg yolk percentages and chick maturity at hatching?
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What is the primary purpose of the eggshell in avian biology?
What is the primary purpose of the eggshell in avian biology?
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What does 'lek' refer to in avian mating behavior?
What does 'lek' refer to in avian mating behavior?
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Which evolutionary hypothesis suggests that elaborate sexual traits provide material benefits to females?
Which evolutionary hypothesis suggests that elaborate sexual traits provide material benefits to females?
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How do elevated male displays contribute to reproductive success?
How do elevated male displays contribute to reproductive success?
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What mechanism allows embryos to perform gas exchange within the egg?
What mechanism allows embryos to perform gas exchange within the egg?
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Which bird species is known for exhibiting the longest tail among males that increases mating success?
Which bird species is known for exhibiting the longest tail among males that increases mating success?
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What is the main evolutionary advantage of sexual dimorphism in birds?
What is the main evolutionary advantage of sexual dimorphism in birds?
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Which structure surrounds the developing embryo and provides a protective environment?
Which structure surrounds the developing embryo and provides a protective environment?
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In terms of reproductive success, what can be inferred from the male Bokolink's display time being reduced?
In terms of reproductive success, what can be inferred from the male Bokolink's display time being reduced?
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Why might males of cliff-nesting species develop more pointed eggs?
Why might males of cliff-nesting species develop more pointed eggs?
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What is indicated by brighter males in House Finch populations?
What is indicated by brighter males in House Finch populations?
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In avian development, where does fertilization typically occur during the egg assembly process?
In avian development, where does fertilization typically occur during the egg assembly process?
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What is the structure that encases the yolk in a bird's egg?
What is the structure that encases the yolk in a bird's egg?
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How do bird testes differ from those of most mammals?
How do bird testes differ from those of most mammals?
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What is the primary method birds use during copulation when lacking a penis?
What is the primary method birds use during copulation when lacking a penis?
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What is the primary function of the seminal vesicles in male birds?
What is the primary function of the seminal vesicles in male birds?
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Which two bird clades are known to possess a penis?
Which two bird clades are known to possess a penis?
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What is unique about the yolk composition in a bird's egg?
What is unique about the yolk composition in a bird's egg?
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What is the role of the central latebra in the yolk?
What is the role of the central latebra in the yolk?
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What is the primary reason that the size of bird testes can increase during the breeding season?
What is the primary reason that the size of bird testes can increase during the breeding season?
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Which statement about the development of a mature ovum is correct?
Which statement about the development of a mature ovum is correct?
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What is the main purpose of the albumen in bird eggs?
What is the main purpose of the albumen in bird eggs?
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Which factor primarily impacts the structural integrity of avian eggshells?
Which factor primarily impacts the structural integrity of avian eggshells?
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In what way do eggs differ across species in relation to chick maturity at hatching?
In what way do eggs differ across species in relation to chick maturity at hatching?
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What is the significance of sexual selection in avian species?
What is the significance of sexual selection in avian species?
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What role does mate choice play in sexual selection among birds?
What role does mate choice play in sexual selection among birds?
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What is a characteristic feature of leks in avian mating behavior?
What is a characteristic feature of leks in avian mating behavior?
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What do elaborate sexual ornaments in males often indicate according to the honest advertising concept?
What do elaborate sexual ornaments in males often indicate according to the honest advertising concept?
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Which hypothesis regarding sexual selection suggests that females prefer males with exaggerated traits even when it confers no direct survival benefit?
Which hypothesis regarding sexual selection suggests that females prefer males with exaggerated traits even when it confers no direct survival benefit?
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Which of these is NOT a function of the extraembryonic membranes in avian embryos?
Which of these is NOT a function of the extraembryonic membranes in avian embryos?
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How does the size and shape of eggs relate to nesting behaviors among cliff-nesting species?
How does the size and shape of eggs relate to nesting behaviors among cliff-nesting species?
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What characteristic is associated with the Hotshot Model of lek evolution?
What characteristic is associated with the Hotshot Model of lek evolution?
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Which of the following best describes the purpose of bower complexity in bowerbirds?
Which of the following best describes the purpose of bower complexity in bowerbirds?
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What does cooperative breeding primarily rely on?
What does cooperative breeding primarily rely on?
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Which statement about extra-pair copulations (EPC) is true?
Which statement about extra-pair copulations (EPC) is true?
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What is a key reason younger males delay dispersal and choose to help in cooperative breeding?
What is a key reason younger males delay dispersal and choose to help in cooperative breeding?
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Which characteristic is most common among obligate brood parasites?
Which characteristic is most common among obligate brood parasites?
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What is the main benefit of the Female Preference Model in lekking behavior?
What is the main benefit of the Female Preference Model in lekking behavior?
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What evolutionary benefit might older male Purple Martins gain from extra-pair copulations?
What evolutionary benefit might older male Purple Martins gain from extra-pair copulations?
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What advantage does kin selection provide in the context of cooperative breeding?
What advantage does kin selection provide in the context of cooperative breeding?
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What is a significant characteristic of the yolk in bird eggs?
What is a significant characteristic of the yolk in bird eggs?
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How does sperm storage in female birds benefit reproduction?
How does sperm storage in female birds benefit reproduction?
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What is true regarding the testes of birds compared to mammals?
What is true regarding the testes of birds compared to mammals?
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What adaptation allows certain waterfowl to have elongated reproductive organs?
What adaptation allows certain waterfowl to have elongated reproductive organs?
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In most birds, how is copulation typically accomplished?
In most birds, how is copulation typically accomplished?
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Which feature distinguishes erectile mechanisms in the reproductive system of birds?
Which feature distinguishes erectile mechanisms in the reproductive system of birds?
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Which bird species is an exception by having two functional ovaries?
Which bird species is an exception by having two functional ovaries?
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What role does the central latebra play in bird yolk structure?
What role does the central latebra play in bird yolk structure?
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What mechanism allows most birds, lacking a penis, to mate?
What mechanism allows most birds, lacking a penis, to mate?
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How do female birds influence sperm competition?
How do female birds influence sperm competition?
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What is the primary evolutionary purpose of the bowers created by bowerbirds?
What is the primary evolutionary purpose of the bowers created by bowerbirds?
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In the context of breeding systems, which statement correctly describes polygyny in birds?
In the context of breeding systems, which statement correctly describes polygyny in birds?
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Which of the following models illustrates how females are attracted to clusters of males in leks?
Which of the following models illustrates how females are attracted to clusters of males in leks?
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What percentage of offspring in Tree Swallows can commonly be fathered by males outside of the mated pair through extra-pair copulations?
What percentage of offspring in Tree Swallows can commonly be fathered by males outside of the mated pair through extra-pair copulations?
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How do helpers in cooperative breeding improve the chances of fledgling success?
How do helpers in cooperative breeding improve the chances of fledgling success?
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What characteristic is associated with obligate brood parasites?
What characteristic is associated with obligate brood parasites?
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Which of the following describes a key aspect of the Hotshot Model in lek evolution?
Which of the following describes a key aspect of the Hotshot Model in lek evolution?
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In what environment is cooperative breeding more likely to be favored?
In what environment is cooperative breeding more likely to be favored?
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What mechanism underlies the concept of reciprocal altruism in cooperative breeding?
What mechanism underlies the concept of reciprocal altruism in cooperative breeding?
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What is the function of cooperative displays in species like the Long-tailed Manakins?
What is the function of cooperative displays in species like the Long-tailed Manakins?
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What differentiates why some bird species, like cliff-nesting birds, have evolved more pointed eggs?
What differentiates why some bird species, like cliff-nesting birds, have evolved more pointed eggs?
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Which factor is crucial for eggshells to effectively protect the developing embryo?
Which factor is crucial for eggshells to effectively protect the developing embryo?
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What does the term 'good genes' hypothesis in sexual selection suggest?
What does the term 'good genes' hypothesis in sexual selection suggest?
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What is the purpose of the albumen in avian eggs?
What is the purpose of the albumen in avian eggs?
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What role does sexual dimorphism play in avian species according to the content?
What role does sexual dimorphism play in avian species according to the content?
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Which process best describes the formation of an egg from ovulation to shell formation?
Which process best describes the formation of an egg from ovulation to shell formation?
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What evolutionary advantage is suggested by the existence of leks in certain bird species?
What evolutionary advantage is suggested by the existence of leks in certain bird species?
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What does intersexual selection primarily involve in the context of mate choice?
What does intersexual selection primarily involve in the context of mate choice?
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What are the three extraembryonic membranes that the embryo in an avian egg possesses?
What are the three extraembryonic membranes that the embryo in an avian egg possesses?
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What does the term 'runaway selection' refer to in sexual selection theory?
What does the term 'runaway selection' refer to in sexual selection theory?
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Study Notes
Avian Reproductive Biology
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Ovaries and Ovum:
- Most birds have one functional ovary (left). Kiwis, raptors, some pigeons, gulls, and a few passerines have two.
- Ovum (egg) is a mature reproductive cell.
- Ovum development involves yolk layer formation and germ cell differentiation.
- Yolk is composed of large (yellow) and small (white) globules.
- A fluid center (vitellin) is encased in a membrane and separated from the albumen (egg white).
- Albumen makes up ~50-70% of egg weight.
Testes and Sperm
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Testes:
- Located in the body cavity at body temperature.
- Most mammals have external testes to reduce heat that damages sperm.
- Attached to the dorsal wall of the kidney.
- Sperm production primarily happens at night (reduced heat).
- Testis size can increase greatly during breeding season.
- Sperm forms in seminiferous tubules, stored in seminal vesicles.
- Sperm structure is similar to other vertebrates (head, midsection, tail).
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Sperm Storage:
- Female birds can store sperm in storage tubules to facilitate sperm competition.
- Sperm of multiple males compete to fertilize the ovum.
Genitalia
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Penis:
- Most birds lack a penis, unlike some reptiles and mammals.
- Found only in Ratites (Paleognathae) and Landfowl/Waterfowl (Galloanseridae).
- Modification of the cloaca wall is homologous to the mammalian/reptilian penis. Lost many times in evolution.
- Cloaca: cavity for excretory and genital products.
- Cloacal contact is the primary mating method.
- Waterfowl have elaborate, spiral, lymph-powered penises.
Copulation
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Copulation Process:
- Male typically mounts female.
- Cloacas are brought into contact.
- Some birds perform this mid-air (swifts).
- Copulation is brief and frequent in most species (seconds). Some species (Goshawks) have frequent copulation.
- Some birds have enlarged cloacal protuberances serving as male copulatory organs (esp. colonial nesting species - sperm competition).
Eggs
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Structure:
- Avian eggs are cleidoic (closed).
- Evolved from naked amniotic eggs, freeing reptiles from aquatic reproduction.
- The shell calcifies (protecting) but prevents water absorption.
- Albumen is essential for water packaging.
- Yolk provides energy (lipids, proteins, water). Yolk percentage varies greatly across species. Yolk percentage correlates with chick helplessness (altricial) or mobility (precocial) at hatching.
- Eggshells provide structural support and protection. Pores allow gas exchange.
- Eggs vary incredibly in size and color (hummingbirds to elephant birds). Egg size correlates positively with body mass.
- Eggs are typically oval but vary in shape; more pointed shapes are common in cliff nesters to prevent rolling.
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Egg Development and Embryo:
- Eggs are assembled as they pass through the oviduct (1 day - 1 week).
- Fertilization occurs high in the oviduct.
- Albumen, shell membranes, and shell form sequentially.
- Egg provides a secure environment for embryonic development (passive gas exchange, uric acid excretion).
- The embryo has three extraembryonic membranes (amnion, chorion, allantoic sac).
Sexual Selection
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Sexual Dimorphism:
- Differences in male and female traits challenge natural selection's principles as best traits would be favored, regardless of sex.
- Ecological or reproductive roles may lead to sexual differences.
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Sexual Selection:
- Differential reproductive success due to variation in mating success.
- Heritable traits affecting mating ability are favored; more successful traits are passed down.
Mate Choice
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Processes:
- Primarily driven by male-male competition (intrasexual) and female choice (intersexual).
- Elaborate displays (morphological, behavioral) often evolve in males (costly, not survival-promoting, but reproductive benefits are gained).
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Hypotheses:
- Good genes: Genetic/physiological superiority.
- Direct benefits: Material resources/protection.
- Runaway selection: Arbitrary female preference.
- Females assess mate quality to gain survival or reproductive benefits.
- Ornaments/behaviors indicate male quality/resourcefulness.
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Honest Advertising:
- Traits reliably reflecting male fitness (e.g., brightness in house finches, longer displays in Bobolinks, larger fleshy combs in red junglefowl).
Leks and Display Grounds
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Leks: Communal display grounds where males gather.
- No other resources than mating opportunities offered.
- Single males may dominate copulation (promiscuous species).
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Models of Lek Evolution:
- Hot Spot: Males congregate where females are likely.
- Hotshot: Males gather around experienced, attractive males.
- Female Preference: Females prefer large clusters of males.
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Examples: Black grouse, Great Argus, Andean Cock-of-the-Rock.
Bowers
- Bowerbirds Create elaborate display courts (bowers) out of sticks/grass.
- Current evidence suggests that bowers show male quality.
- Bower size and traits indicate good health and status (parasite load, body size).
Breeding Systems
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Diversity: Diverse breeding systems across bird species.
- Trade-offs in current vs. future reproduction.
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Monogamy: Predominant system; often socially monogamous (extra-pair copulations).
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Polygyny: Males mate with multiple females (rare).
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Polyandry: Females mate with multiple males (rare).
Extra-Pair Mating
- EPCs: Common across many socially monogamous species.
- Potentially significant source of genetic contribution from males outside the pair bond.
- Examples: Tree Swallows, Purple Martins.
Cooperative Breeding
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Helpers: Offspring provide care for parents' nest.
- Sacrifice own reproduction (altruism).
- Kin selection: helpers gain indirect fitness (via relatives).
- Reciprocal altruism: trade help for future benefits.
- Environmental constraints (low rainfall, high temp variance) may favor cooperative breeding.
- Examples: Green Wood Hoopoes, Siberian Jays, White-fronted Bee-eaters.
Brood Parasitism
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Definition: Laying eggs in other birds' nests.
- Facultative: Occasional; intraspecific or interspecific.
- Obligate: Never raise their own young (cuckoos, cowbirds, honeyguides).
- Co-evolutionary strategies have developed.
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Description
Explore the fascinating aspects of avian reproductive biology in this quiz. Learn about the unique aspects of bird ovaries, ovum development, testes, and sperm production. Test your knowledge on how these processes differ from other vertebrates.
