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« Blue Ice » Phenomenon and Migratory Birds

In the last several years, people living near wooded areas in Châteauguay, Mercier and the West Island of Montréal have noticed strange purplish stains on their homes, cars and lawn furniture. Some have thought that the stains might stem from airplanes dumping toilet waste as they approach the Pierre-Elliott-Trudeau airport.

Transport Canada takes all allegations about objects or waste falling from airplanes in flight very seriously. It is important to mention that airplanes are equipped with watertight reservoirs that are designed to be emptied using specialized equipment at airports. Furthermore, the Canadian Aviation Regulations prohibit airplanes from emptying their toilet waste in mid-flight. Nevertheless, we thoroughly investigated the matter.

Migratory Birds and Wild Berries

According to the biologists, ornithologists and bird specialists Transport Canada consulted, these mysterious purplish stains are actually bird droppings of birds having ingested wild berries.

Samples were collected at the citizens' homes and analyzed at an independent laboratory for Transport Canada. The results proved that the liquid was in fact bird droppings. The same results were also confirmed by several specialists called upon by the region's media to conduct their own analysis.

Why does this phenomenon occur mainly in the fall?

Before migrating, birds eat the blue fruit of the Virginia creeper as well as chokecherries and pin cherries growing on the outskirts of Montréal, in areas that still have abundant vegetation. 

The droppings are purplish due to the colour of these wild berries, very common in the fall, which the birds eat in large number to prepare for their long trip south.

 

Since the birds (robins, sparrows, waxwings and mockingbirds) travel in flocks of several hundred, this explains the profusion of purplish stains they leave behind. Other bird species that are not long-distance migrants (starlings, common grackles or blackbirds, brown-headed cowbirds and red-winged blackbirds) also eat these berries and can leave stains.

 

Birds digest very quickly, beginning to relieve themselves almost immediately upon finishing their feast. This is why complaints were mostly filed from suburbs where there is still a lot of vegetation at that time of year.

 

 

 Formation of “Real” Blue Ice

The blue ice phenomenon does occur, but it is increasingly rare. Quebec's last reported case dates back several years. Airplanes with washrooms must be equipped with waterproof reservoirs that are designed to be emptied with specialized equipment at airports. They are not made to be emptied in flight, either voluntarily or accidentally.

It is possible that a malfunctioning valve could cause the contents of the reservoir to leak. This generally happens when an airplane is flying at high altitudes. The liquid escaping from the faulty valve freezes and sticks to the airplane's outer surface. Upon preparing for landing, when the airplane approaches the ground and the temperature rises, the ice formed by the escaping liquid begins to melt and detaches.

In the last several years, however, aircraft have begun using a new toilet system that uses compressed air and hardly any water, making the phenomenon even less likely to occur.

Transport Canada's Role

The Canadian Aviation Regulations prohibit airplanes in flight from dropping anything that could create a hazard to persons or property on the ground. That is why Transport Canada takes questions and complaints from citizens very seriously and the Department looks into all reported events of this type. In fact, one of our inspectors will visit citizens who request it in order to look into the situation.

In response to certain complaints, special inspections were carried out at the airport to ensure that none of the airplanes had a leak in their toilet reservoir. These visits helped collect data and establish facts that, after analysis and consultation by specialists, confirmed that there was no link between the airplanes and purplish stains found on the citizens' properties.

Transport Canada intends to continue these inspections in order to prevent a potential blue ice situation from occurring and thus protecting citizens and the environment.

History of the Phenomenon

In the fall of 2005, a resident of a western suburb of Montréal complained that an airplane flying over the area on its way to the Pierre-Elliott-Trudeau airport dumped sanitary liquid on his home. The Ministère de l'Environment du Québec quickly sent investigators to the site. An analysis of samples taken from the home concluded that the liquid was bird droppings.

 American Robin
©_Marcel Gauthier

 

In the fall of 2006, another citizen complained to a Montréal daily newspaper that his home and property were splashed with purplish liquid. A specialist responded in the same newspaper, explaining that the liquid was bird droppings from birds eating the blue fruit of Virginia creepers (parthenocissus) growing on the outskirts of Montréal.

In October 2007, in the week following the broadcast of a televised report about blue ice, Transport Canada received 11 telephone calls from people reporting that their home was sprayed with liquid from airplane toilets. A Transport Canada inspector visited the sites. Samples were taken and analyzed at an independent laboratory.

The laboratory results concluded that the substance could not be the liquid used in airplane toilets and that it is very likely that the stains were left by birds that had eaten purple-coloured fruit.

Finally, purplish stains were recently analyzed for certain television programs. The results also proved that the stains were bird droppings.

If you have any other questions about this phenomenon, do not hesitate to send them to us via our Civil Aviation Issues Reporting System. In last resort, you can also directly call Civil Aviation System Safety at 514 633-3249.

Date modified:

2012-03-12

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