Birds & Ecosystem Services | EnvironmentalScience.org The Value of Birds Birds are present throughout almost every habitat across the globe. No matter where you go, there is always evidence of birds even if you don't see the animals themselves. Things like holes pecked in tree bark by woodpeckers or the remnants of a nest are indicative of the presence of birds. While such marks left behind by these animals may seem insignificant, in many cases the activities of birds can have large consequences for the ecosystems they inhabit, making them incredibly important in the overall functioning of various ecosystems. By contributing in such an important way to ecosystem health, birds can provide a number of direct benefits to humans. The Millennium Ecosystem Assessment, a study initiated by the United Nations, coined the term “ecosystem services” to describe these kinds of services.  According to this panel, ecosystem services fall into four broadly defined categories and as we survey the diversity of birds across the globe, we find many ways in which the activities of birds provide services in each one of these. Supporting Services 1 http://www.environmentalscience.org/birds-ecosystem-services#_ENREF_1 Actions within this category are those that are required for all other ecosystem services to be produced, such as nutrient cycling and the formation of soil.  This category can be thought of as a foundation of processes without which other ecosystem services could not be produced. Birds can help in these services by nutrient cycling, which has been documented in many habitats. By spreading activities through different habitats, birds can move nutrients from one place to another, which is particularly relevant in places where plant growth is limited by nutrient availability. A study on the islands in the Gulf of California showed that when birds roosted on them, the guano deposits they left behind provided nutrients to plants on the island  . As a result, islands with seabirds had plants that grew taller and faster and were much more productive than those on islands without birds. Because the quality of these plants impacts the number of consumers and the structure of the food web, these birds exerted a bottom­up effect on the food web by regulating primary productivity. This example is also interesting from an ecological standpoint because it exemplifies the intricate ways in which seemingly disparate habitats are connected and can impact one another. The primary productivity in the ocean regulates the number of fish it can support, which then impacts the number of birds that can feed on these fish, which then influences how many birds will roost on the island and leave guano deposits, ultimately dictating the primary productivity and food web structure on the island. Barry Commoner, one of the founders of the environmental movement, laid out four laws of ecology in his 1971 book The Closing Circle. One of these is “Everything is connected t ...

1. Birds & Ecosystem Services | EnvironmentalScience.org
The Value of Birds
Birds are present throughout almost every habitat across the glo
be. No matter where you go, there is
always evidence of birds even if you don't see the animals them
selves. Things like holes pecked in tree
bark by woodpeckers or the remnants of a nest are indicative of
the presence of birds. While such marks
left behind by these animals may seem insignificant, in many ca
ses the activities of birds can have large
consequences for the ecosystems they inhabit, making them incr
edibly important in the overall
functioning of various ecosystems.
By contributing in such an important way to ecosystem health, b
irds can provide a number of direct
benefits to humans. The Millennium Ecosystem Assessment, a st
udy initiated by the United Nations,
coined the term “ecosystem services” to describe these kinds of
services. According to this panel,
ecosystem services fall into four broadly defined categories and
as we survey the diversity of birds
across the globe, we find many ways in which the activities of b
irds provide services in each one of
these.
Supporting Services
1

2. http://www.environmentalscience.org/birds-ecosystem-
services#_ENREF_1
Actions within this category are those that are required for all o
ther ecosystem services to be produced,
such as nutrient cycling and the formation of soil.
This category can be thought of as a foundation of
processes without which other ecosystem services could not be
produced.
Birds can help in these services by nutrient cycling, which has b
een documented in many habitats. By
spreading activities through different habitats, birds can move n
utrients from one place to another, which
is particularly relevant in places where plant growth is limited b
y nutrient availability. A study on the
islands in the Gulf of California showed that when birds roosted
on them, the guano deposits they left
behind provided nutrients to plants on the island
. As a result, islands with seabirds had plants that grew
taller and faster and were much more productive than those on i
slands without birds. Because the
quality of these plants impacts the number of consumers and the
structure of the food web, these birds
exerted a bottom-up effect on the food web by regulating primar
y productivity.
This example is also interesting from an ecological standpoint b
ecause it exemplifies the intricate ways
in which seemingly disparate habitats are connected and can im
pact one another. The primary
productivity in the ocean regulates the number of fish it can sup
port, which then impacts the number of
birds that can feed on these fish, which then influences how ma
ny birds will roost on the island and leave

3. guano deposits, ultimately dictating the primary productivity an
d food web structure on the island. Barry
Commoner, one of the founders of the environmental movement,
laid out four laws of ecology in his
1971 book The Closing Circle. One of these is “Everything is co
nnected to everything else,” a premise
we see clearly demonstrated in this example as birds serve as a
vector for nutrients between aquatic
and terrestrial habitats.
Birds are also capable of stimulating primary productivity in oth
er ways, which supports the functioning of
ecosystems, an example exhibited by birds in salt marshes. In A
laska, lesser snow geese and Canada
snow geese stopover in salt marshes during spring migrations.
While they are foraging in these
marshes, they trample the ground, which tears up leaf litter and
incorporates it into the soil. The smaller
particle size and increased contact with the soil promotes greate
r decomposition, freeing nitrogen from
the leaf litter and allowing it to cycle through the ecosystem.
In the southeastern United States, cordgrass is the dominant pla
nt in salt marshes. The salt marsh
periwinkle is a major predator of cordgrass and in the absence o
f predation, these snails can overgraze
the grasses and completely convert a productive marsh into mud
flats. Predation of snails controls their
numbers, which regulates primary productivity of salt marshes.
Several species of birds such as
oystercatchers, curlews, and plovers are predators of these snail
s and exert top-down population
controls, which prevents overgrazing. In terms of the dollar valu
e of services provided to humans,
wetlands are considered one of the most valuable habitats, provi
ding an array of important services like

4. shoreline stabilization and water filtration.
The presence of birds in these habitats ensures ecosystem
functioning, allowing humans to gain the maximum benefit from
these valuable ecosystems.
1
2
3
4
5
http://www.environmentalscience.org/birds-ecosystem-
services#_ENREF_1
http://www.environmentalscience.org/birds-ecosystem-
services#_ENREF_2
http://www.environmentalscience.org/birds-ecosystem-
services#_ENREF_3
http://www.environmentalscience.org/birds-ecosystem-
services#_ENREF_4
http://www.environmentalscience.org/birds-ecosystem-
services#_ENREF_5
Provisioning Services
Many of the support services mentioned above can also be classi
fied as provisioning services, our next
category. Provisioning services encompasses products that we h
arvest from ecosystems and we can
find many examples of activities in this category by examining
how birds can positively impact the raising
of crops and livestock.

5. A common traditional practice in the farming of rice straw in Ca
lifornia was to burn the fields after
harvest. However, this technique was banned in recent years to
prevent air pollution and a widely used
alternative is to flood fields instead. These flooded fields create
habitat that is used for foraging by
waterfowl. As these birds dive down to where the layer of straw
rests on the ground, they tear, shred,
and churn up the pieces of straw looking for grain and invertebr
ates. Such activities allow for greater
contact of the soil with straw, increasing microbial decompositi
on. An experimental study in which
waterfowl were permitted into areas of a flooded field and exclu
ded from others showed that when the
birds were present, there was a smaller biomass of straw, as wel
l as lower nutrient concentrations. This
study indicated the waterfowl presence successfully led to incre
ased decomposition of straw in the field,
which could prevent the need for autumn tillage, saving growers
a substantial amount of money.
In agricultural systems, birds can also be beneficial through the
regulation of pests. In Guatemalan
coffee plantations with higher abundances of insectivorous birds
, there were fewer insects which
resulted in less herbivorous damage to the leaves of crops.
Experiments in Jamaica showed that the
presence of birds led to a decrease in insect pests and increased
the amount of saleable crops, leading
to an increase in farm profits of up to $310 per hectare per year.
Similarly, the construction of nest
boxes for great tits in apple orchards has been shown to lead to
greater numbers of birds in the area,
which forage on caterpillars that can cause damage to crops, res
ulting in significantly higher crop

6. yields.
If installed and maintained properly, the construction of bird ne
st boxes can eliminate the need
for pesticides, saving farmers money and preventing potentially
dangerous chemicals from being
applied. Similarly, the use of artificial perches for raptors aroun
d agricultural fields may increase the
number of raptors that prey on rodents that can cause damage to
crops.
Mutualistic relationships between birds and livestock can also b
e beneficial to humans. Many birds perch
on livestock like cattle and forage on insects that live on them.
Cattle egrets are particularly well known
for making a living this way, and although they are native to Af
rica, their range has expanded
dramatically concurrent with increases in the clearing of land fo
r farming. While the birds benefit from a
readily available food source, the animals on which they forage
benefit from the removal of harmful
parasites. In many parts of the world, people rely on cows for fo
od and for milk. When infested with ticks,
cows can become anemic and milk production flags. In Pakistan
, birds are capable of effectively preying
on these parasites, leading to healthier and more productive cow
s. This predation by birds is even
more effective than pesticides in some cases. Through these inte
ractions, humans gain a benefit by not
spending money on expensive pesticides and by having more pr
oductive and healthier livestock.
6
7
8

7. 9
10
11
12
http://www.environmentalscience.org/birds-ecosystem-
services#_ENREF_6
http://www.environmentalscience.org/birds-ecosystem-
services#_ENREF_7
http://www.environmentalscience.org/birds-ecosystem-
services#_ENREF_8
http://www.environmentalscience.org/birds-ecosystem-
services#_ENREF_9
http://www.environmentalscience.org/birds-ecosystem-
services#_ENREF_10
http://www.environmentalscience.org/birds-ecosystem-
services#_ENREF_11
http://www.environmentalscience.org/birds-ecosystem-
services#_ENREF_12
Regulating Services
In this category, we group the benefits that are gained from the
regulation of ecosystem processes. This
includes services such as carbon sequestration, waste decomposi
tion, and air purification. As with the
other categories, there is no shortage of bird contributions to ser
vices in this arena.
Birds are important scavengers in many ecosystems, removing t
he carcasses of dead animals. While

8. vultures are probably the best known for this, many types of bir
ds opportunistically scavenge on this
food source when it is available. In the Serengeti of Africa, vult
ures are capable of consuming hundreds
of pounds of dead meat per kilometer annually and in Yemen, v
ultures can remove up to 25% of the
organic waste produced in towns by humans.
Scavenging by birds is an important mechanism of
waste disposal in many areas and prevents the outbreak of disea
ses than can occur through the
accumulation of animal carcasses. In India, declines in vultures
led to increases in feral dogs as there
was less competition for carrion as a food source. The explosion
of the dog population led to increases
in rabies outbreaks and human injuries from dog attacks. The tot
al estimated health cost of vulture
declines between 1993 and 2006 is a whopping $34 billion.
It is obvious in this case that the value of
birds to humans can be quite high and underscores the direct im
portance of healthy birds populations to
humans.
Another way that birds can provide regulating services is throug
h promoting forest growth. This is
important to humans because forests can sequester carbon and p
revent it from going into the
atmosphere where it would contribute to climate change. Birds a
re able to perform this role through
dispersing plant seeds during foraging. When they pick a seed o
r fruit from a plant and fly off with it, they
end up transporting the seed to another place where it can germi
nate. This behavior is a major
mechanism for seed dispersal in many plants and can increase th
e genetic diversity of plants in a
particular area by spreading seeds. In some cases, animals can c
arry seeds more than 40 meters away

9. from the source tree.
By germinating the seeds of trees, birds can contribute to the ref
oresting of deforested lands,
diminishing the costs of restoration.
In oak forests in Sweden, the cost of replacing the seed dispers
al
services of Eurasian jays in oak regeneration is an estimated $9,
400 per hectare. Birds provide a
valuable service in the expansion of forests, which sequester car
bon and perform a number of other
services that stand to benefit humans.
Cultural Services
The last category is cultural services and is a bit different from
the others because it more abstract and
includes less material benefits. As opposed to more tangible thi
ngs like crop yields or water purification,
services within the cultural category include things such as spiri
tual enrichment and the appreciation of
nature.
13, 14
15
16
17
18
http://www.environmentalscience.org/birds-ecosystem-
services#_ENREF_13
http://www.environmentalscience.org/birds-ecosystem-

10. services#_ENREF_14
http://www.environmentalscience.org/birds-ecosystem-
services#_ENREF_15
http://www.environmentalscience.org/birds-ecosystem-
services#_ENREF_16
http://www.environmentalscience.org/birds-ecosystem-
services#_ENREF_17
http://www.environmentalscience.org/birds-ecosystem-
services#_ENREF_18
An example of a service in this category is bird watching, which
can be used as to foster ecotourism as a
source of income. Many nature centers and nonprofit environme
ntal organizations create revenue
through taking visitors on bird watching tours. These kinds of a
ctivities can also be used to introduce
students and children to the outdoors in order to foster an appre
ciation for nature. Similarly, zoos often
acquire rare birds and then use them as a heavily marketed featu
re attraction to increase traffic and
visitor revenue.
Birds also serve a number of cultural roles and factor heavily in
to religions across the globe. For
example, eagles are considered sacred messengers that carry pra
yers to the spiritual world in many
Native American religions. Eagle feathers are believed to have
holy powers and capturing eagles to
remove the feathers is part of a sacred ritual.
In many religions, vultures are considered deities that
play a large part in their mythology and traditions.
While it is difficult to place a dollar value on services
within the cultural category, they are just as important because t
he spiritual enrichment and appreciation
of nature that birds provide is an essential part of the human ex

11. perience.
Summary
In this review, we have taken an ecological approach by focusin
g on ways that birds provide services to
humans through their interactions with the environment. Howev
er, it should also be noted that the direct
take of birds and their products also provides economic benefit i
n many cases. Cultures across the world
hunt birds and eggs for subsistence and to make a living. In Mal
aysia, the nests of swiftlets are
harvested for their use in cooking. They are considered a delica
cy and are an extremely valuable
commodity, with a single nest of good quality having a value of
more than $700 in some cases. Many
cultures also harvest birds for uses in traditional medicine. In th
e cultural category, many people gain
recreational benefit by hunting birds. In cases where this huntin
g is regulated, the sale of permits raises
money that is used to fund governmental agencies and services.
Because birds are so common in most habitats, we often overloo
k their ecological significance.
However, their ecological roles are incredibly important and hu
mans can benefit monetarily through the
many actions of birds. The examples described above are just a
few of the many ways that birds provide
19
20
21
http://www.environmentalscience.org/birds-ecosystem-
services#_ENREF_19

12. http://www.environmentalscience.org/birds-ecosystem-
services#_ENREF_20
http://www.environmentalscience.org/birds-ecosystem-
services#_ENREF_21
ecosystem services. Quantifying the monetary benefit from bird
s around the world is nearly impossible,
but likely numbers in the billions of dollars annually. The value
we gain from birds warrants a serious
investigation into causes of declines and provides additional rati
onale for the continued study and
conservation of these animals.
Sources
1. Millennium Ecosystem Assessment Findings. 2005: Millenniu
m Ecosystem Assessment.
2. Anderson, W.B. and G.A. Polis, Nutrient fluxes from water to
land: seabirds affect plant nutrient status
on Gulf of California islands. Oecologia, 1999. 118(3): p. 324-3
32.
3. Zacheis, A., R.W. Ruess, and J.W. Hupp, Nitrogen dynamics
in an Alaskan salt marsh following spring
use by geese. Oecologia, 2002. 130(4): p. 600-608.
4. Silliman, B.R. and M.D. Bertness, A trophic cascade regulate
s salt marsh primary production.
Proceedings of the national Academy of Sciences, 2002. 99(16):
p. 10500-10505.
5. Costanza, R., et al., The value of New Jersey's ecosystem ser
vices and natural capital. 2006.
6. Bird, J., G. Pettygrove, and J. Eadie, The impact of waterfowl
foraging on the decomposition of rice
straw: mutual benefits for rice growers and waterfowl. Journal o

13. f Applied Ecology, 2000. 37(5): p.
728-741.
7. Greenberg, R., et al., The impact of avian insectivory on arthr
opods and leaf damage in some
Guatemalan coffee plantations. Ecology, 2000. 81(6): p. 1750-1
755.
8. Johnson, M., J. Kellermann, and A. Stercho, Pest reduction se
rvices by birds in shade and sun coffee
in Jamaica. Animal Conservation, 2010. 13(2): p. 140-147.
9. Mols, C.M. and M.E. Visser, Great tits can reduce caterpillar
damage in apple orchards. Journal of
Applied Ecology, 2002. 39(6): p. 888-899.
10. Kay, B., et al., The use of artifical perches to increase preda
tion on house mice (Mus domesticus) by
raptors. Wildlife Research. 21(1): p. 95-105.
11. Burnie, D., Bird: The Definitive Visual Guide. 2007, Great
Britain: Doring Kindersley Limited.
12. Perveen, F., et al., Ixodid ticks infestation in livestock and t
heir traditional control in N-WFP, Pakistan.
Pakistan Journal of Entomology Karachi, 2010. 25(1): p. 43.
13. Prakash, V., et al., Catastrophic collapse of Indian white-ba
cked (Gyps bengalensis) and long-billed
(Gyps indicus) vulture populations. Biological conservation, 20
03. 109(3): p. 381-390.
14. Gangoso, L., et al., Reinventing mutualism between humans
and wild fauna: insights from vultures as
ecosystem services providers. Conservation Letters, 2013. 6(3):
p. 172-179.

14. 15. Markandya, A., et al., Counting the cost of vulture decline-
An appraisal of the human health and other
benefits of vultures in India. Ecological Economics, 2008. 67(2)
: p. 194-204.
16. Godoy, J.A. and P. Jordano, Seed dispersal by animals: exac
t identification of source trees with
endocarp DNA microsatellites. Molecular Ecology, 2001. 10(9):
p. 2275-2283.
17. Wunderle Jr, J.M., The role of animal seed dispersal in acce
lerating native forest regeneration on
degraded tropical lands. Forest Ecology and Management, 1997.
99(1-2): p. 223-235.
18. Hougner, C., J. Colding, and T. Söderqvist, Economic valuat
ion of a seed dispersal service in the
Stockholm National Urban Park, Sweden. Ecological Economics
, 2006. 59(3): p. 364-374.
19. De Meo, A.M., Access to eagles and eagle parts: Environme
ntal protection v. native American free
exercise of religion. Hastings Const. LQ, 1994. 22: p. 771.
20. Benson, E.P., The Vulture: The Sky and the Earth. Palenque
Round Tables, 1996. 10: p. 309-319.
21. Whelan, C.J., D.G. Wenny, and R.J. Marquis, Ecosystem ser
vices provided by birds. Annals of the
New York Academy of Sciences, 2008. 1134(1): p. 25-60.