Prof. C. Hemelrijk - Spreeuwen, hoe zwermen ze?
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This document discusses starling flock behavior through computer modeling and empirical data. It summarizes that starling flock movements arise from self-organization based on local interactions between individuals. Models show that flock shapes vary due to aspects of flying behavior like banking during turns. Asynchrony in behavior, such as during turns, and a low number of interaction partners between individuals leads to more complex and variable flock shapes. Agitation waves that appear to confuse predators may result from an orientation wave caused by individuals repeatedly zigzagging escape maneuvers, rather than from density changes. Understanding flock behavior is achieved through building computational models based on hypothesized local interaction rules between individuals.
Prof. C. Hemelrijk - Spreeuwen, hoe zwermen ze?
- 1. 12/1/2014 1 Spreeuwen, hoe zwermen ze? Prof. Dr. Charlotte K. Hemelrijk Behavioral Ecology and Self-organization Centre for Ecological and Evolutionary Studies University of Groningen The Netherlands Beautiful movements Youtube Hoograven Dancing above the sleeping site
- 2. 12/1/2014 2 Advantages of complex movements Protection against predation: Confusion effect How do individuals move collectively? Agitation wave Complex flocking behaviour Telepathy (Selous, 1931) Selforganisation Interactions of starlings are local, 7 neighbours (Ballerini et al 2008) Models of self-organised moving groups schools of fish (Couzin et al, 2002;Hensor et al 2005; Hemelrijk et al 2011) Starling flocks by self-organisation?
- 3. 12/1/2014 3 Understanding by building Rules of local interaction Complex patterns of the group Self-organization Pfeifer and Scheier 1999 Hypotheses for empirical studies Model of fish school Shape is oblong, but bird flocks have all kinds of shapes Individuals move and interact with neighbours: attraction alignment avoidance: through slowing down Hemelrijk & Hildenbrandt, 2008, Ethology (Katz et al 2011; Herbert-Read et al 2011)
- 4. 12/1/2014 4 Starling flocks slaapplaats - coordination (attraction, alignment, avoidance) - with 7 closest neighbours - staying above sleeping site Hildenbrandt Model with Hildenbrandt, Carere, Hemelrijk, 2010, Behav Eco Wrong, not like starlings What is missing?
- 5. 12/1/2014 5 Flying behaviour! Spreeuwen Lift (before rolling) Lift (after rolling) Gravity Centripetal force Centrifugal force Flying:10 m/s = 36 km/h Banking while turning Hildenbrandt, Carere, Hemelrijk, 2010, Behav Eco Model StarDisplay with banking Resembles empirical data in shape, orientation, internal structure Hildenbrandt, Carere, Hemelrijk, 2010, Behav Eco
- 6. 12/1/2014 6 Variation of shape Turning behavior Fixed speed Asynchrony Large flock size Low number of interaction partners Hemelrijk, Hildenbrandt, 2011, PLOS ONE Model StarDisplay wide oblong Rock doves oblong wide Turning causes changes of shape Flying: Low variation of speed Hemelrijk, Hildenbrandt, 2011, PLOS ONE
- 7. 12/1/2014 7 Asynchrony during turning Causes shape changes due to temporary compression Resembles Rock doves (Pomeroy and Heppner,1992) N = 2000 NND Volume (m3) Volume 0 10 20 30 40 50 60 -> Time turn turn Large flock size, 20.000 individuals Complex flock shape Hemelrijk, Hildenbrandt, 2011, 2012, PLOS ONE, InterfaceFocus
- 8. 12/1/2014 8 Low number of interaction partners -> flock members are less aligned and further apart -> shape is complex and variable High number of neighbours (50) -> more synchronous Low (6 or 7) -> asynchronous Variation of flock shapes in birds Due to Biophysics of flying behaviour: Low variability of speed (-> change of shape) Banking in turn (-> loss of altitude) Asynchrony of behaviour within flock: Turning, Low number of interaction partners, High number of flock members Hemelrijk, Hildenbrandt, 2011, PLOS ONE
- 9. 12/1/2014 9 Agitation wave in starling flock Waves reduce capture succes Procaccini at el 2011, Animal Behaviour What behaviour underlies it? Flocks are too far away to observe this. Density wave or orientation wave ? Change in visible wing surface Maximal Minimal projected area Zig-manoeuvre Orientation wave? Hemelrijk, van Zuidam, Hildenbrandt, under review
- 10. 12/1/2014 10 Agitation waves ≒Wave of orientation In dunlins (Potts 1984), white belly, brown back In anchovies (Radakov 1973; Gerlotto et al. 2006a) silvery belly, dark back ≒Density wave in herring (Axelsen et al. 2001) What escape manoeuvre is used by starlings? Study in model Extensions to Stardisplay: Location of predator attack: escape manoeuvre Escape manoeuvre (R端debeck 1950, 1951) Repeated by close neighbours Two manoevres Speeding-up-forward into the flock (-> density wave) A Zigzag like movement (-> orientation wave) Hemelrijk, van Zuidam, Hildenbrandt, under review Zigzag escape
- 11. 12/1/2014 11 Repeated speeding up manoeuvre No visible agitation wave Insufficient contrast in density or density-changes too slow? Repeated Zig (Rolling) Observable agitation wave Wave speed as in empirical data Agitation wave is an orientation wave rather than density wave Hemelrijk, van Zuidam, Hildenbrandt, under review
- 12. 12/1/2014 12 Understanding by building Rules of local interaction Complex patterns of the group Self-organization Pfeifer and Scheier 1999 Hypotheses for empirical studies Thanks Collaborators Hanno Hildenbrandt (scientific programmer) Claudio Carere (empirical data) Lars van Zuidam (master student) Grants EU grant StarFlag Pilot grant NWO