Threats to Birds

Threats to Birds
Destruction of the tropical humid montane forests to give way to a coffee plantation.

Threats to Birds

Birds are the most representative and ubiquitous group of animals. Any natural area is reasonably the habitat for one or many bird species.

Precisely because birds occupy almost all habitats on earth, any human activity that involves the extraction or transformation of natural areas is likely to come into conflict with some bird or community of birds. Widespread conflicts with human activities make birds a great indicator or barometer of environmental health.

Most threats to birds or conservation problems involving birds are related to human actions.

The leading threats to bird survival include:

Habitat Loss

The greatest threat to birds and the common denominator of biodiversity loss is the destruction and degradation of habitats. Habitat loss includes fragmentation, destruction, and alteration of the natural areas that birds need to complete their annual or seasonal cycle.

The most common human activities that cause bird conservation problems are mining, excessive extraction of natural resources, the transformation of natural habitats for agricultural purposes, pollution resulting from industrial activities, and urban sprawl.

In addition to the direct effect of extractive activities and habitat transformation, an indirect effect is the fragmentation of continuous habitats. Open spaces without vegetation cover or areas with agricultural plantations constitute barriers to many bird species’ dispersal.

Species with small or fragmented habitats have difficulty completing life cycles, leading to population decline followed by local extinction.

starling_threats to birds
The European Starling (Sturnus vulgaris) was introduced in North America, where it competes with native species for nesting cavities.

Introduced species

An introduced or exotic species is one that has established a breeding population in regions outside its region of origin. Man, generally transports introduced species. There is a list of more than 200 species of introduced birds with established populations around the world.

The problem with introduced species is that they can compete with native species for food and shelter. Some introduced species are aggressive and displace native species from naturally limited nesting cavities.

One problem with introduced species is the loss of the genetic integrity of native species through hybridization or crossing.

Another problem is the introduction of diseases and other pathogens to which native species are not adapted.

The introduction of birds to new regions usually occurs in two ways:

  • Intentional Introduction: A deliberate introduction occurs when individuals of a species are released with the specific objective of establishing a population in the new location. The liberation of individuals goes through a period of adaptation. If the introduction is not successful quickly, more individuals are introduced to help the initial population establish and begin reproducing without dietary supplements or additional individuals’ release. Intentionally introduced birds are primarily species used for sport hunting.
  • An accidental Introduction is the most common type of introduction of birds. An unintentional introduction occurs when birds imported into a country or region as pets escape and establish new populations. The number of species on the market for ornamental birds and pets is large, and perhaps most, at some point, will escape. However, very few species can establish populations where they escape.
  • The species that establish populations generally come from places where climatic conditions and habitat types are similar to the introduction site.
  • The groups of birds that most often establish introduced populations include parrots, sparrows, pigeons, and ornamental ducks.

hunting_threats to birds
The illegal hunting of birds has reduced the number of certain species to critical population levels.

Illegal Hunting

Some birds are overhunted for commercial and subsistence purposes, for food, or their feathers.

Historically, the overhunting of certain species has been the leading cause of extinction. Subsistence hunting at the local level rarely results in species extinction. Commercial hunting is more likely to lead to the demise of a species.

The Passenger pigeon (Ectopistes migratorius) is the best-known example of human-induced bird extinction. This geographically widespread North American pigeon was the most abundant bird in the world. When hunting became a commercial activity, the species became extinct in just a few decades.


Hybridization occurs when individuals of an introduced species interbreed with individuals of a native species producing intermediate individuals with both parents’ characteristics.

Ornamental bird breeders often hybridize in captivity to obtain new varieties and colors of ornamental birds.

The problem occurs when ornamental birds escape or are released into regions where closely related species are naturally found. When the escapee species establishes itself in the new area, it reproduces freely with the native species, producing offspring with characteristics of neither the native nor the introduced species.

The biggest problem occurs when the introduced species is dispersed throughout the geographic range of the native species, genetically contaminating the entire population and eventually causing the native species to disappear as such but to be made up of hybrid individuals.

pelagic waters
Fishing with long lines is responsible for the death of thousands of albatrosses.

Other threats

  • Use of Pesticides: DDT (dichloro-diphenyl-trichloroethane) is a synthetic organic compound used as an insecticide. Raptor consumed prey contaminated with DDT became contaminated themselves. DDT caused the egg shells very thin to the point that the eggs broke by incubating females’ gentle pressure.

As a result, no new individuals were produced to replace the adults that died naturally, and populations were reduced, in some cases, to critical numbers. DDT was banned in 1972, and many raptor species began their dramatic population recovery.

  • Fuel spills: Oil and other fuel spills have devastating effects on birds, particularly seabirds. The oil adheres to the birds’ feathers, causing the feather to lose its waterproofing properties and exposes the bird’s sensitive skin to extreme temperatures. This can lead to hypothermia. Also, instinctively, the bird tries to remove the oil from its feathers by preening, which causes the bird to ingest the oil, causing severe damage to its internal organs.

Long-line Fishing:

mortality resulting from incidental longline fishing poses a serious threat to many species of pelagic birds, particularly albatrosses.

Fishing vessels are important sources of food for many populations of seabirds. Birds congregate around vessels, searching for discards after processing the fish on board.

Seabirds try to eat the bait from hooks along a fishing line, getting hook-trapped and drowning.

Most species of albatrosses are now included in some category of threat or danger of extinction. It is estimated that the number of birds killed by accidental capture from longline fishing reaches more than 300,000 birds per year.

Overall, the number of albatrosses caught by longline fisheries is high. However, the total number of albatrosses killed by individual boats is usually quite low. Such a low number per boat is why this sector of the fishing industry has resisted the idea that their industry is causing bird populations to decline.


  • Brothers NP. 1991. “Albatross mortality and associated bait loss in the Japanese longline fishery in the southern ocean.” Biological Conservation 55: 255-268.
  • Gill, F. (1995). Ornithology. W.H Freeman and Company, New York.
  • Moore, R., Robinson, W., Lovette, I., & Robinson, T. (2008). Experimental evidence for extreme dispersal limitation in tropical forest birds. Ecology Letters, 11(9):960-968.


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