Pollution has direct and indirect impacts on bird populations

Pollution from a wide range of sources affects birds: agricultural and industrial effluents and urban wastewater can all have serious direct impacts on bird populations, through increased mortality, as well as less immediately obvious through reducing fertility (). Pollution can also have strong indirect effects on birds, by degrading habitats or reducing food supplies. More generally, birds can serve as invaluable indicators of the wider impacts of pollutants. They are often the most visible sign of the environmental problems caused by oil slicks
() and have highlighted the  broad environmental impacts of less well known persistent organic pollutants () and of acid-rain ().

• Pollution from agriculture, forestry and industry has significant impacts on birds
• Oil spills significantly reduce populations of seabirds and are costly to clean up
• Persistent organic pollutants stay in the environment, affecting humans and wildlife
• Acid rain continues to exceed critical loads in industrialised regions

Pesticides associated with farming continue to have a big impact 

Huge areas of farmland, rangeland, forest and wetland are treated with poisonous synthetic chemicals each year to control various plants, animals and disease-causing micro-organisms. Agriculture in the developing world in particular is becoming increasingly reliant on such biocides, many of which have been banned or restricted elsewhere. Unfortunately, their side-effects and longer-term impacts are often ignored or simply not known by those who use them and they have been identified as a contributory factor to the threatened status of many bird species (). Recently, a veterinary drug used to treat livestock has been linked to the collapse of vulture populations throughout South Asia ().

• Pesticides continue to poison birds on a large scale
• Vultures are under threat from the veterinary drug diclofenac

Rubbish and solid waste are an increasing problem

Rubbish and solid waste are also known to have serious impacts on many ecosystems and populations of wild species. For example, ‘junk’ dumped in the terrestrial environment is swallowed by scavenging raptors, resulting in low breeding success (). Such junk includes toxic lead shot, which is also a particular problem for waterfowl and gamebirds (). Likewise, floating plastic garbage dumped in the marine environment is commonly mistaken for prey by albatrosses and petrels, causing starvation and death ().

• Anthropogenic “junk” ingestion leads to high nestling mortality in vultures and condors
• Lead ammunition continues to build up in the environment, poisoning birds
• Seabirds suffer from eating "junk"