Ornithology Lecture 15

Overview of Bird Reproductive Behaviors

  • This section discusses the mating systems and parental care in birds, highlighting their significance in the ecological and evolutionary framework.

Key Upcoming Events

  • Test Next Tuesday: Material covered today will not be included.

  • Lab at Hardberger Park: Tomorrow starting at 8 AM. Bring binoculars.

  • Carpooling: Email instructor if you need assistance with transportation.

Meeting Location for Lab

  • Urban Ecology Center Parking Lot:

    • Entrance: Military Highway next to Wardsburg HEB.

    • Identify meeting spot: A walking path near a large parking lot.

  • Purpose: Explore grassland restoration areas, practice identifying grassland and raptor birds.

Mating Systems in Birds

Overview of Mating Systems

  • Monogamy:

    • Definition: One male mates with one female.

    • Prevalence: About 91% of bird species are monogamous.

    • Concept of social monogamy: Bonds established, but may involve extra-pair copulations (EPCs).

    • EPC occurs when one or both partners mate outside their established bond, affecting genetic diversity.

  • Polygamy:

    • Definition: One individual of one sex mates with multiple individuals of the opposite sex.

    • Types:

    • Polygyny: One male mates with several females (2% of species, e.g., red-winged blackbirds).

    • Polyandry: One female mates with multiple males, less common (e.g., Wilson's Phalarope).

    • Polygynandry: Males and females have multiple partners, seen less frequently (e.g., ostriches, often confused with promiscuity).

Factors Influencing Mating Choices

  • Parental Investment: Decides roles in mating systems and affects offspring survival rates.

  • Sexual Selection: Drives differences in reproductive strategies between males and females (e.g., males compete for mates, females choose mates).

  • Resource Availability: Affects decisions to stay or leave, impacting whether males or females provide care.

Parental Care

  • Most bird species exhibit biparental care due to the need for offspring survival.

    • Examples: Housing (nests) and feeding are crucial duties often performed by males.

  • Role of Environment: Changes in habitat and resource availability can shift mating systems from monogamy to polygamy.

  • Altricial vs. Precocial:

    • Altricial: Offspring require high parental care (e.g., songbirds).

    • Precocial: Offspring are relatively independent quickly (e.g., grouse).

Game Theory in Parental Investment

  • Modeling Decisions:

    • Use probability models to understand male and female decisions on parental care and the relative success of offspring in various scenarios.

    • Males often have the first opportunity to leave due to the costly nature of internal fertilization for females.

Evolutionary Considerations

  • Sexual Conflict: Adaptive strategies arise to maximize reproductive success but may contradict each other between sexes.

  • Natural vs Sexual Selection: Emphasis on the evolutionary pressure that shapes bird behaviors across species.

Case Studies of Bird Behaviors

  • Examination of specific birds like the Harris's hawk exhibiting cooperative breeding strategies, and adaptations among species based on available resources and environmental conditions.

  • The notion of kin selection and the benefits siblings gain from helping allied reproductive efforts.

  • Examples of cooperative leks and display behaviors where males attract females through group dynamics.

Environmental Shifts and Mating Strategies

  • Impacts of climate change on breeding patterns and survival strategies, requiring adaptability of mating systems.

  • Observations of behavior shifts in species like the red knots due to decoupling of migration timing and food availability.

Conclusion

  • Understanding mating systems and parental investments highlights the dynamic interplay between ecological factors and reproductive strategies in birds. This knowledge is essential for future studies on avian behavior and conservation efforts.