Artificial light as a pollutant
Willy Wagtail case study
Artificial light
urbanisation has changed environment drastically and quickly
light pollution
Includes: Streetlights, building lights, security lights
the most widely spread form of pollution
2% annual increase
30 x brighter than the moon
80% of the population lives in light polluted areas
Sky glow (light pollution) visible 60km away from melbourne
natural light
Used as a cue
By: mammals, birds, reptiles, fish and invertebrates
for: foraging, migration, breeding, communication, vigilance, sleep
eg. sea turtles hatchlings confuse street lights for the moon and head away from sea
lunar cycle
100 fold change in brightness at night over the lunar cycle
impacts behaviour
by acting as a timing cue (eg. mass coral spawning)
changes predator and prey relationship (due to changes in visibility)
difficult to study animal behaviour at night
bird song
territory defence
mate attraction
~70% of female birds also sing
folkstory: willie wagtails sing more during a full moon
Aim: to test if willie wagtails sing more with increasing moonlight brightness
Methods: 8 willie wagtails, Bioacoustics recorder (BAR), Frontier labs, >600 hours night time recording
Locations: Rural/low light pollution areas
who sings at night?
1,550 detections, 97% matched males
accuracy of automatic song detection: 95% of all wagtail songs and 99% accuracy of sp.
song rate (centred by site) increased with lunar illumination
Aim: to test for a relationship between nocturnal song and artificial light at night
Method: 25 locations, rural hub adn various sites in and around CBD (Lux range 0.05-0.40) amd 1,875 night time hours)
Increasing nocturnal brightness suppresses nocturnal song behaviour
Artificial light interacts with moonlight to cause different effects ℗ob of singing with high sky glow for greatest lunar illumination is lowest)
all research so far used correlation data (isn't always causation)
willie wagtails sang significantly less after lights were turned on
solutions
warm coloured lights
only use lights were necessary (light sensors in parks)
shield outdoor lights
change in culture
summary
changes in moonlight affect animal behaviour
light pollution is the most widespread form of pollution
artifical light at night changes song behaviour in willie wagtails
simple changes can reduce light pollution