Geese flying over a rural texas property

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This videnda depicts flightpaths of migrating geese as grouped colored lines over a rural North Texas location on a day in early March 2019.  The light-colored field within the dark border represents a circle of 320 meters (350 yards) diameter.  The flightpaths overlay an aerial view of the location and a compass rose.  

More details

The number of lines in a flightpath represents the number of geese in the skein (skein = flock of geese).  The small arrows at the front of lines represent the geese themselves and show their direction of flight, as does the characteristic V-shape pointing in their direction of flight.  For curvilinear flightpaths, direction was defined as a chord between the two points of flightpath-circle intersection.  The goose-in-arrow points the direction of the net mathematical flightpath vector.  

Color of the flightpath signifies the exact time of day it occurred (violet end of spectrum = AM; red = PM; details in Specifications below).  Geese migrate primarily overnight, which means they take off late in the day and land in the morning.  This explains the complete lack of mid-spectral (orange, yellow, green) flightpath color.  However, the orange color of the goose indicates the weighted average of morning and evening fly-by times.  

All fly-bys were at treetop level.  You usually hear geese honking in the distance before seeing them.  Geese flying into the outer ring of this circular work are often heard but not yet seen.  Once within the inner circle, they become increasingly audible and then visible.  A large roosting area just east of the location explains the eastern concentration of activity and seemingly random directions of flight.  

https://www.jstor.org/stable/4161751?seq=1

Factors Influencing the Timing, Distance, and Path of Migrations of Canada Geese.  ML Wege, DG Raveling. The Wilson Bulletin 95(2): 209-221, 1983.  

https://www.csu.edu/cerc/researchreports/documents/MigrationofBirdsCircular.pdf

Migration of Birds, Circular 16. 3rd Ed., U.S. Department of the Interior, U.S. Fish and Wildlife Service, 1998.  

https://link.springer.com/article/10.1007/s10336-006-0054-8

Ecology of spring-migrating Anatidae: a review.  C Arzel, J Elmberg, M Guillemain. Journal of Ornithology 147(2): 167-184, 2006. 

 

Specifications:

  • Two-dimensional circular vector graphic artwork; size according to display surface preference.  

  • Center of circle represents:  32.6669 latitude, -97.5820 longitude on Earth’s surface (a residence near Aledo, Texas, USA).  

  • “Auditory-only” radius (to inner edge of black border):  160 meters.  

  • “Visual” radius (inner concentric circle):  120 meters.  

  • Observations made and data collected in early March 2019.  

  • Total number of geese:  86.  

  • Number of skeins:  9.

  • Range of skein size:  2 – 28.  

  • Net flight path vector:  216°.  

  • Time was converted to color as follows:  the “day” was taken as 30 minutes before sunrise to 30 minutes after sunset, which was 622 – 1901.  Time across this span was converted to hundredths of hours and equaled 1279 h / 100.  The visual spectrum was taken as 380 – 780 nm (violet – red; range = 400 nm).  The light wavelength increment per unit time therefore equaled 400 / 1279, or 0.3127 nm / (h / 100).  Violet was assigned to morning, and red to evening, such that
    light wavelength for a given time = 380 + ((time – 622) X 0.3127).  

  • First and last fly-by times and corresponding light wavelengths: 
    815 🡪 443 nm, or RGB 001bff; 1840 🡪 769 nm, or RGB 7a0000.

  • Weighted average fly-by time and corresponding light wavelength:  1422 🡪 634 nm.