Major Threats to Birds In Canada

The threat that has impacted the most species in recent decades is habitat loss.  This trend is set to continue.  The primary drivers in Canada are land use changes, such as agricultural activity, urban development, natural resource extraction, and infrastructure development.  Loss of bird habitat affects both terrestrial and aquatic environments, including marine areas. 

When we talk about habitat loss, we include both degradation and fragmentation.  Habitat degradation renders places unavailable to some species; human disturbance is a major contributor, for example off-road vehicle use on Piping Plover breeding habitat.  Habitat fragmentation is the break-up of large patches of habitat into smaller pieces that are unsuitable for some species, which is a key issue with grassland birds, for example.  

Chemical pesticides and contaminants affect birds mainly by degrading bird habitats, and reducing the food available to birds.  This occurs in terrestrial and aquatic habitats impacted by large-scale agriculture, forestry, industrial, and transport activities that release man-made, toxic chemicals into the environment. 

This issue was first brought to the public’s attention nearly sixty years ago in Rachel Carson’s Silent Spring.  Her work led to the use of the agricultural poison, DDT, being made illegal in some countries.  That precipitated one of conservation’s success stories: the recovery of raptor populations, some from near-extinction.  However, fifty years on from the DDT ban, many toxic chemicals remain in widespread use across Canada and most other nations.

Industrial-scale use of chemical pesticides in agriculture and forestry pose a major contemporary threat to a large number of bird species in Canada. These poisons kill insects that birds feed on, and plants that birds, or their insect prey, feed and live on.  Birds that feed on insects, especially aerial insectivores, birds that feed almost exclusively on insects while on the wing, show some of the steepest declines of any bird group.

Invasive species are non-native animals or plants introduced to a new environment, either intentionally (for example for fur production) or unintentionally (e.g., seed dispersal, stowaway rats), which cause a detrimental impact to one or more native species or habitats.  The feral cat is technically an invasive species, and we treat domestic cats that spend time outdoors in this same category.

Predation by domestic and feral cats causes the single largest number of bird deaths (mainly to common and widespread species) of any of these five major threats.  Of major conservation concern to birds in Canada are rats and raccoons, which predate major seabird breeding colonies on islands off the west coast.  Invasive plants threaten habitats in many Important Bird Areas, for example Spartina anglica (common cordgrass) that could change bird-rich mudflats in the Fraser Estuary into unproductive grassland, and Phragmites australis (common reed) that is choking Long Point Biosphere Reserve wetlands rendering habitats unsuitable for several bird and other species at risk.

Birds colliding with man-made structures, and unintentional vehicle collisions with bird nests, are a major cause of mortality. The largest cause of individual bird deaths in this category is believed to be collisions with windows in buildings. This occurs both by day, when birds fly into glass reflecting habitat or landscape behind them, and at night during migration, when birds are attracted to unnaturally bright light and become disoriented and collide with the light and nearby structures. This latter effect occurs in cities, at industrial facilities on land, on offshore platforms with flares, and on cruise ships.  These and other “incidental mortality” factors, including marine fisheries, vehicle, wind turbine and power line collisions, and mechanical destruction of bird nests by industrial forest harvest and agricultural activities, are quantified in detail in this dedicated issue of Birds Canada and the Society of Canadian Ornithologists’ prestigious journal Avian Conservation and Ecology.

The rapidly changing climate is the threat that creates the most uncertainty about the future of bird populations in Canada.  Some predictions state that two-thirds of North America’s birds will be seriously affected, with Canadian Arctic and Boreal birds being the most vulnerable.

The climate crisis affects birds in different ways. Changing temperatures and rainfall patterns drive changes in the habitats to which birds are adapted. As the habitats “move”, most birds must move with them. One of the starkest examples is the alpine bird community, which quite literally has nowhere else to go.

For the many migratory birds that rely on the early summer pulse of insects to feed their young, warmer temperatures promote earlier emergence of insects, creating “mis-matches” with their migration timing. The consequences may be that fewer young birds are raised into the population.