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Urban Birds. Connor Dolighan and Sky Freeman. The fitness benefit of association with humans: elevated success of birds breeding indoors. By: Anders Pape Moller. Big Picture Questions. Wanted to investigate the fitness of animal – human associations

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urban birds

Urban Birds

Connor Dolighan and Sky Freeman

the fitness benefit of association with humans elevated success of birds breeding indoors

The fitness benefit of association with humans:elevated success of birds breeding indoors

By: Anders PapeMoller

big picture questions
Big Picture Questions
  • Wanted to investigate the fitness of animal – human associations
  • Study this association in breeding birds in regards to general nest predation rate due to human proximity
  • If substantial fitness benefit exists, species having been adapting to urban environments longer should have larger fraction of overall population.
major findings
Major Findings
  • Birds nesting indoors (in a barn, shed or other building) had less nest predation than outdoor nests.
  • Difference in nest predation rate was directly related to time of urbanization
  • Recently urbanized species benefit most of human proximity as nest protection, this then decreases with time.
slide7

Barn swallows :

    • 1.59yr generation time
    • Known to have breed in association with humans for at least 4000yrs
    • About 2500 generations, plenty of time for adaptation
    • 99% of current population found to nest indoors
slide8

Blackbirds

    • 2.27yrs generation time
    • Know to haven been associated around humans only about 100 yrs
    • 44 generations, not a lot of time for adaptation to have taken place
    • 15% of current population know to nest indoors
future studies
Future Studies
  • Interspecific association between corticosterone levels in exposure to humans
  • Reduction in fear reactions
    • Frequency of alarm calls
    • Distance required to cause retreat of bird
    • Distance bird retreats for human
introduction
Introduction
  • Populations subject to changes likely to experience rapid changes in traits.
  • Phenotypic plasticity vs. genetic evolution.
  • Examined changes in boldness and endocrine stress response between two dark-eyed junco populations (urban and wildland).
terminology
Terminology
  • Boldness – Tendency to explore and take risks (quantified using EEB and FID).
  • Early exploratory behaviour (EEB) – Time taken for an individual to explore a new environment.
  • Flight initiation distance (FID) – Distance at which a bird begins to fly between observer and bird.
  • Endocrine stress response (CORT levels) – associated with boldness behaviour.
supporting papers
Supporting Papers
  • EEB found to be repeatable in individuals, heritable, and responsive to artificial selection (Verbeek et al. 1994, Dingemanse et al. 2002, Drent et al. 2003).
  • Studies indicate boldness behaviours should diverge among populations occupying environments that favour shy or bold individuals.
questions
Questions
  • Do boldness and CORT levels differ between the two populations?
  • Phenotypic plasticity or genetic evolution?  Common garden study.
  • Do boldness and CORT levels covary within and among populations?
  • Drift or natural selection?
methods
Methods

A = Approximate location of urban population (University of California – San Diego)

B = Approximate location of ancestral range population (near Mt. Laguna, CA)

methods1
Methods
  • Juncos from both populations were banded.
  • FID recorded (foraging birds and incubating females).
  • Blood samples collected to measure CORT
  • Juveniles caught from both populations for common garden study.
common garden study methods
Common Garden Study Methods
  • Juveniles raised in captivity.
  • EEB measured (i.e. how extensively individuals explored a novel aviary room).
results
Results

Flight initiation distances – field study

results1
Results

CORT Response

results2
Results

Exploratory behaviour – common garden study

results3
Results

Covariation between CORT and exploratory behaviour – common garden study

discussion
Discussion
  • Results suggest selective forces of urban environment have led to hormonal and behavioural adaptations.
  • Common garden study, along with other previous studies, suggest differences are not due to plasticity.
  • Future work:
  • Revealing how traits are correlated and understanding how phenotypes respond to new, changing environments.
  • Genetic studies.
references
References

Atwell JW, Cardoso GC, Whittaker DJ, Campbell-Nelson S, Robertson KW, and Ketterson ED. 2012. Boldness behavior and stress physiology in a novel urban environment suggest rapid correlated evolutionary adaptation. Behavioral Ecology. 5: 960-969.

Moller AP. 2010. The fitness benefit of association with humans: elevated success of birds breeding indoors. Behavioral Ecology. 21: 913-918.

discussion questions
Discussion Questions
  • What are some potential flaws in these two studies and how could future research methods be improved?
  • In the paper by Atwell et al., do you think there are any alternative conclusions that could be drawn? That is, are the researchers’ findings and explanations justified or could there be more to the junco story?