The services birds provide to our environment and to people are hugely significant. From dispersing seeds and predating insects, to cycling nutrients and air purification, birds play environmental roles as predators, pollinators, scavengers, seed dispersers, seed predators, and ecosystem engineers. Scientists group the services into four categories: supporting, regulating, provisioning and cultural.
Examples of supporting services include nutrient cycling and the formation of soil. This category is the foundation without which other ecosystem services could not be produced. Because they often span many different habitats, birds are well-suited to moving nutrients from one place to another. One study on the islands in the Gulf of California looked at the differences in soil quality between islands with and without seabirds (and therefore their guano): it showed that islands with seabirds had plants that grew both taller and faster than those on islands without birds.(1)
This example also illustrates the intricate ways habitats are connected and can impact each other. The productivity of the ocean regulates the number of fish it can support, which impacts the number of birds that feed on the fish, which impacts how many birds will roost on the island and leave guano deposits, which affects the productivity of the ocean.
Regulating services includes the benefits gained from the regulation of ecosystem processes, including seed dispersal, carbon sequestration, waste decomposition and air purification. When birds pick a seed or fruit from a plant, they transport the seed to another place where it can germinate. This not only allows a new plant to grow, it also increases the genetic diversity of plants in a particular area, strengthening the health of the ecosystem. Forest growth sequesters more carbon, preventing it from going into the atmosphere where it would contribute to climate change.
Seed dispersal is often considered to be the most important ecological service birds provide. In some forests, birds disperse up to 92% of all tree and woody species, including 85% of timber species, 182 edible plants, 153 medicinal plants, 146 ornamental plants, and 84 others with economic or cultural uses.(2)
Another interesting study looked at corvids – a family of birds that includes ravens, jays, crows and magpies – as ecosystem engineers. Corvids store seeds in caches spread around the landscape, a practice known as ‘scatter-hoarding.’ The birds store more seeds than they eat, so some sprout. Many trees, including oaks and pines, have specific adaptations to encourage seed dispersal, producing large, nutritious seeds with protective chemicals that keep them from rotting, making the seeds more suitable for scatter-hoarding.(3)
Scavenging birds – including corvids and vultures – provide waste decomposition services. They eat organic litter and road kill, transforming it into nutrient-rich waste.
Provisioning services involve products we harvest from ecosystems and includes many examples of how birds impact the raising of crops and livestock. One example is the Yellow Warbler, a bird that migrates to Canada in the summer. Daniel Karp, a US ecologist, has discovered that insect-eating birds devour the worst pest of Costa Rican coffee plantations, reducing damage to ripening coffee berries. He used sophisticated DNA tests to prove that Yellow Warblers and four other bird species gorge on coffee berry borer beetles, the most damaging insect to the world’s $90 billion/year coffee industry. When birds were excluded from the tested farms, the borer-infestation rate doubled. Karp calculated that the service provided by the birds increases income to growers by $310 / hectare / year. (4)
Another example is the great tits useful contribution to apple orchards. Construction and maintenance of nest boxes for great tits, which forage on caterpillars that cause damage to crops, result in a significant improvement in crop yields.(5)
One study estimated the economic value of the bird predation of western spruce budworms, an insect which defoliates valuable forest trees. The voracious evening grosbeak was compared to spraying with insecticides, and found that this small birds’ services would cost at least $1,820 US per square km over a 100 year rotation! (6)
Another study examined the role of songbirds in maintaining the health and productivity of forest trees. Scientists netted white oak trees, leaving gaps large enough for insects, but not birds. They found that the trees that were caged to keep out birds suffered twice as many insects, and had twice as much of their foliage eaten compared to the uncaged trees. As a result, scientists are predicting that the widespread decline of song birds will threaten the productivity of forests in Canada and the United States as well as in the birds’ wintering grounds in the tropical forests of Central and South America.(7)
The last category, cultural services, is very different from the others, and includes less tangible benefits. Services within this category include spiritual enrichment, cultivating an appreciation of nature, and sacred practices.
One service in this category is relatively quantifiable, and that is the bird-watching industry. Canadian estimates are hard to find, but bird-watching is one of the most popular outdoor activities in Canada, and contributes billions of dollars to the Canadian economy. According to the US Fish and Wildlife Service, more than $100 billion dollars a year is spent on birdwatching equipment and travel in the US. The industry employs some 666,000 people, and some 46 million Americans enjoy watching and feeding birds. (8)
Not only is there enormous economic value in bird-watching, there is also enormous – and inestimable – value in connecting with nature. A study in the UK demonstrated that bird-watching is beneficial to mental health.(9) Birding is also an excellent way to introduce both children and adults to the joys of spending time in the natural world and foster an appreciation for nature.
Perhaps that’s why birds factor into religions across the globe. Eagles are considered sacred messengers that carry prayers to the spirit world in many indigenous North American religions. (10) In Ancient Greece, the goddess Athena was represented by an owl, and in India, the peacock represents Mother Earth. In Christianity, the dove is a symbol of the Holy Spirit (as well as peace), and the eagle is a symbol of the resurrection of Christ.(11) In the Qur’an (Qur’an 16: 79), birds’ ability to fly is cited as proof of God’s existence. (12) The Ashkenazic Jewish practice of Shabbot Shirah involves feeding birds, and Numbers 11 tells how God – via a strong wind – provided quails for the hungry Israelites at one point during their long journey to the Promised Land. (13)
These are just a few examples of the services birds provide: there are many more. But bird populations are declining across North and South America. A full 37% of bird species are of high conservation concern, according to the State of North American Birds Report (2016), meaning they require immediate attention or risk extinction. We need to act to conserve our bird populations before their populations have declined to such an extent that ecosystems are devastated. Learn more about what you can do to help birds at Save Bird Lives.
(1) “Nutrient fluxes from water to land: seabirds affect plant nutrient status on Gulf of California islands”, by Wendy B. Anderson and Gary A. Polis, Oecologia, March 1999, Volume 118, Issue 3, pp 324–332
(3) “Scatter-hoarding corvids as seed dispersers for oaks and pines: A review of a widely distributed mutualism and its utility to habitat restoration,” by Mario B. Pensedorfer, T. Scott Sillette, Walter D. Koenig, and Scott A. Morrison, The Condor 118(2):215-237, 2016
(4) “Forest bolsters bird abundance, pest control and coffee yield” by Daniel S. Karp, Chase D. Mendenhall, Randi Figueroa Sandi, Nicolas Chaumont, Paul R. Ehrlich, Elizabeth A. Hadly and Gretchen C. Daily, Ecology Letters, Volume 16, Issue 11, November 2013.