Why are bafflers so bright?

May has been a big month for the South East Trawl Fishery with 95% of the otter board trawl vessels installing bird bafflers.  Bird bafflers use brightly coloured droppers that hang off the metal boom arms and backbone of rope. The droppers are typically made from orange or red pipe hose or sometimes even rope.   There has been some speculation within the fleet as to whether seabirds, such as albatross,  can actually see these bright colours.

In 1979 (when some of the Albatrosses we are avoiding today were alive), Peter Harper observed that albatrosses and giant petrels were attracted to orange and red coloured bits of rubbish that were thrown overboard from a research vessel.  Harper saw that the birds went straight for the orange peel first and upon discovering it wasn’t edible moved on to other orange and red items of rubbish – including red cigarette packets.  To test whether the birds were reacting to the brightness or the colour of the various rubbish items, he offered the birds paper balls in 10 different colours with equivalent light reflecting qualities.  He observed that some birds showed preference for the orange and red coloured paper balls, followed by pink, yellow, blue, white and green respectively.

WHY – Harper reasoned that the birds were attracted to the orange and red coloured paper balls because they resembled a familiar food source of a similar colour. His theory was that Albatrosses and petrels eat invertebrates such as krill and mysids (shrimp-like crustaceans) that are orange and red in colour due to their carotenoid content (a type of pigment produced by plants).  So it seems that when it comes to fishing vessels, birds are attracted by smell but then use visual cues such as bright colour to locate food and touch to determine whether or not it can be eaten.

Research in this area has come a long way since the 70’s as have marine pollution regulations. vA study by Stoddard and Prum in 2011 found that birds can actually see colours that are invisible to humans because they have additional colour cones in their retina that are sensitive to ultraviolet range.

Given this information, when it comes to seabird mitigation devices such as bafflers, it makes sense to use brightly coloured materials that the birds can see clearly and avoid colliding with.