Increasing awareness of avian ecological function

doi:10.1016/j.tree.2006.05.007

Trends in Ecology & Evolution

Volume 21, Issue 8, August 2006, Pages 464-471

https://doi.org/10.1016/j.tree.2006.05.007 Get rights and content

Birds are one of the most diverse groups of ecosystem service providers, whose ecological functions range from creating soil to shaping primate behavior, Nevertheless, the impression that birds have little influence on ecological processes has been hard to change. Given the ongoing declines in avian functional groups, there is a pressing need to compare avian ecological functions to those of other taxa, to understand how these functions translate to ecosystem services and to estimate the ecological implications of bird declines. Here, I review the ecological functions of birds, link them to ecosystem services and outline research priorities for understanding avian contributions to ecosystem functioning.

Section snippets

Birds as ecological actors

Birds are the best-studied class of organism and various investigations have established their significance as important mobile links (see Glossary) in the dynamics of natural and human-dominated ecosystems (Box 1; Figure 1) 1, 2, 3, 4, 5, 6. Birds also benefit humans by providing important ecosystem services [7], such as: provisioning services via game meat for food, down for garments and guano for fertilizer; regulating services by scavenging carcasses and waste, by controlling populations of

Genetic linkers

A hornbill (Figure 1a) swallowing fruits and defecating viable seeds away from the parent tree and a hummingbird (Figure 2b) pollinating flowers while foraging are important ‘genetic information linkers’ [1] because they transport plant genetic material via seed dispersal and pollination, respectively. These functions also result in ecosystem services for humans. Birds pollinate dozens of crop species [26] and avian seed dispersal is particularly important for big-seeded tropical tree species

Resource linkers

By transporting minerals and nutrients in their guano, birds can be vital resource linkers [1], particularly between marine and terrestrial [6], and between terrestrial and wetland [11] ecosystems. This ecological function provides the ecosystem service of crop fertilization, which can occur thousands of kilometers away from the original source of the nutrients.

Trophic process linkers

Birds that are trophic-process linkers connect habitats by serving as primary (Figure 1, Figure 2) or secondary (Figure 1, Figure 2) consumers across habitats [1]. The ecological function of predation is considered an ecosystem service if avian predators reduce agricultural pests and increase yields [5] or if they limit pest activity through fear [23]. Scavengers provide sanitary services, such as carcass disposal, waste recycling, indirect population control of scavenging mammalian disease

Non-trophic process linkers

Birds that are non-trophic process linkers (Figure 1, Figure 2) supply or facilitate an essential process that influences ‘the physicochemical environment rather than the trophic web’ [1] and are analogous to allogenic ecosystem engineers [83]. Such birds can indirectly generate ecosystem services, for example by providing frugivorous and predaceous birds with nesting cavities and nectarivorous birds with food resources [16].

Conclusions

Birds are important but ecologically little-known actors in many ecosystems. Avian seed dispersal might be the ecological function that affects the greatest number of species, especially considering its importance for late successional tropical trees with large seeds. Consequently, studies of the botanical implications of large avian frugivore extinctions are sorely needed. Compared with seed dispersal, bird pollination is an order of magnitude less common, but still important in regions such

Acknowledgements

Christensen, Koret, Moore Family and Winslow Foundations, National Geographic and Wildlife Conservation Societies, and Walter Loewenstern funded the research that inspired this paper. I am grateful to D. Wheye for creating such an excellent illustration. I thank K. Al-Khafaji, G.C. Daily, P.R. Ehrlich, W.F. Laurance, C. Peterson, R. Pringle, S. Renner and N.S. Sodhi for their valuable comments, and C. Kremen, K.A. Lythgoe, R. Nathan and an anonymous reviewer for their helpful reviews.

Glossary

Ecosystem engineers: organisms that directly or indirectly modulate the availability of resources to other species by causing physical state changes in biotic or abiotic materials [83].
Ecosystem services: the benefits that humans obtain from ecosystems [7]. If an avian ecological function, such as insect consumption, results in material benefits for humans, such as pest control, it is also considered an ecosystem service.
Functional group: the primary diet-based grouping that parallels the main

References (90)

V. Prakash
Catastrophic collapse of Indian white-backed Gyps bengalensis and long-billed Gyps indicus vulture populations
Biol. Conserv.
(2003)
G.D. Ruxton et al.
Obligate vertebrate scavengers must be large soaring fliers
J. Theor. Biol.
(2004)
R. Nathan et al.
Spatial patterns of seed dispersal, their determinants and consequences for recruitment
Trends Ecol. Evol.
(2000)
P. Fayt
Regulation of spruce bark beetles by woodpeckers – a literature review
Forest Ecol. Manage.
(2005)
A. Casas-Criville et al.
The European bee-eater (Merops apiaster) as an ecosystem engineer in arid environments
J. Arid Environ.
(2005)
J. Lundberg et al.
Mobile link organisms and ecosystem functioning: implications for ecosystem resilience and management
Ecosystems
(2003)
F.G. Stiles
On the role of birds in the dynamics of Neotropical forests
M. Proctor
The Natural History of Pollination
(1996)
D.J. Levey
Seed Dispersal and Frugivory: Ecology, Evolution and Conservation
(2002)
C.M.M. Mols et al.
Great tits can reduce caterpillar damage in apple orchards
J. Appl. Ecol.
(2002)

D.A. Croll

Introduced predators transform subarctic islands from grassland to tundra

Science

(2005)

Millennium Ecosystem Assessment

Ecosystems and Human Well-being: Synthesis

(2005)

A.W. Diamond et al.

The Value of Birds

(1987)

C.H. Sekercioglu

Impacts of birdwatching on human and avian communities

Environ. Conserv.

(2002)

D.M. Post

The role of migratory waterfowl as nutrient vectors in a managed wetland

Conserv. Biol.

(1998)

J.C. Heine et al.

Ornithogenic soils of the Cape Bird Adelie penguin rookeries, Antarctica

Polar Biol.

(1989)

K.M. Holbrook

Implications of long-distance movements of frugivorous rain forest hornbills

Ecography

(2002)

C.J. Clark

The role of arboreal seed dispersal groups on the seed rain of a lowland tropical forest

Biotropica

(2001)

J. Gradwohl et al.

The effect of a single species of avian predator on the arthropods of aerial leaf litter

Ecology

(1982)

G.C. Daily

Double keystone bird in a keystone species complex

Proc. Natl. Acad. Sci. U. S. A.

(1993)

J.C. Mitani

Predatory behavior of Crowned Hawk-eagles (Stephanoaetus coronatus) in Kibale National Park, Uganda

Behav. Ecol. Sociobiol.

(2001)

F. Sanchez-Pinero et al.

Bottom-up dynamics of allochthonous input: direct and indirect effects of seabirds on islands

Ecology

(2000)

S.A. Van Bael

Birds defend trees from herbivores in a Neotropical forest canopy

Proc. Natl. Acad. Sci. U. S. A.

(2003)

I. Perfecto

Greater predation in shaded coffee farms: the role of resident Neotropical birds

Ecology

(2004)

E.L. Preisser

Scared to death? The effects of intimidation and consumption in predator–prey interactions

Ecology

(2005)

C. Kremen

Managing ecosystem services: what do we need to know about their ecology?

Ecol. Lett.

(2005)

C.H. Sekercioglu

Ecosystem consequences of bird declines

Proc. Natl. Acad. Sci. U. S. A.

(2004)

G.P. Nabhan et al.

Services provided by pollinators

S.A. Foster et al.

The relationship between seed size and establishment conditions in tropical woody plants

Ecology

(1985)

C.R. Darwin

On the Origin of Species by Means of Natural Selection

(1859)

D.H. Janzen

Herbivores and the number of tree species in tropical forests

Am. Nat.

(1970)

J.H. Connell

On the role of natural enemies in preventing competitive exclusion in some marine animals and in forest trees

A. Packer et al.

Soil pathogens and spatial patterns of seedling mortality in a temperate tree

Nature

(2000)

H.F. Howe et al.

Ecology of seed dispersal

Annu. Rev. Ecol. Syst.

(1982)

M.A. Pizo

The seed dispersers and fruit syndromes of Myrtaceae in the Brazilian Atlantic forest

K.E. Harms

Pervasive density-dependent recruitment enhances seedling diversity in a tropical forest

Nature

(2000)

B.H. Tiffney et al.

Angiosperm growth habit, dispersal and diversification reconsidered

Evol. Ecol.

(1995)

N.J. Cordeiro et al.

Forest fragmentation severs mutualism between seed dispersers and an endemic African tree

Proc. Natl. Acad. Sci. U. S. A.

(2003)

D.G. Wenny

Advantages of seed dispersal: a re-evaluation of directed dispersal

Evol. Ecol. Res.

(2001)

C.F.E. Bacles

Genetic effects of chronic habitat fragmentation on tree species: the case of Sorbus aucuparia in a deforested Scottish landscape

Mol. Ecol.

(2004)

G.R. Robinson et al.

Forest restoration on a closed landfill: rapid addition of new species by bird dispersal

Conserv. Biol.

(1993)

B. Magnusson et al.

Vegetation on Surtsey, Iceland, during 1990–1998 under the influence of breeding gulls

Surtsey Res.

(2000)

D.J. Levey

Seed size and fruit-handling techniques of avian frugivores

Am. Nat.

(1987)

D.W. Snow

Tropical frugivorous birds and their food plants – a world survey

Biotropica

(1981)

A. Hamann et al.

Interactions among frugivores and fleshy fruit trees in a Philippine submontane rainforest

Conserv. Biol.

(1999)

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Trends in Ecology & Evolution

ReviewIncreasing awareness of avian ecological function

Section snippets

Birds as ecological actors

Genetic linkers

Resource linkers

Trophic process linkers

Non-trophic process linkers

Conclusions

Acknowledgements

Glossary

Biol. Conserv.

J. Theor. Biol.

Trends Ecol. Evol.

Forest Ecol. Manage.

J. Arid Environ.

Mobile link organisms and ecosystem functioning: implications for ecosystem resilience and management

Ecosystems

On the role of birds in the dynamics of Neotropical forests

The Natural History of Pollination

Seed Dispersal and Frugivory: Ecology, Evolution and Conservation

Great tits can reduce caterpillar damage in apple orchards

J. Appl. Ecol.

Introduced predators transform subarctic islands from grassland to tundra

Science

Ecosystems and Human Well-being: Synthesis

The Value of Birds

Impacts of birdwatching on human and avian communities

Environ. Conserv.

The role of migratory waterfowl as nutrient vectors in a managed wetland

Conserv. Biol.

Ornithogenic soils of the Cape Bird Adelie penguin rookeries, Antarctica

Polar Biol.

Implications of long-distance movements of frugivorous rain forest hornbills

Ecography

The role of arboreal seed dispersal groups on the seed rain of a lowland tropical forest

Biotropica

The effect of a single species of avian predator on the arthropods of aerial leaf litter

Ecology

Double keystone bird in a keystone species complex

Proc. Natl. Acad. Sci. U. S. A.

Predatory behavior of Crowned Hawk-eagles (Stephanoaetus coronatus) in Kibale National Park, Uganda

Behav. Ecol. Sociobiol.

Bottom-up dynamics of allochthonous input: direct and indirect effects of seabirds on islands

Ecology

Birds defend trees from herbivores in a Neotropical forest canopy

Proc. Natl. Acad. Sci. U. S. A.

Greater predation in shaded coffee farms: the role of resident Neotropical birds

Ecology

Scared to death? The effects of intimidation and consumption in predator–prey interactions

Ecology

Managing ecosystem services: what do we need to know about their ecology?

Ecol. Lett.

Ecosystem consequences of bird declines

Proc. Natl. Acad. Sci. U. S. A.

Services provided by pollinators

The relationship between seed size and establishment conditions in tropical woody plants

Ecology

On the Origin of Species by Means of Natural Selection

Herbivores and the number of tree species in tropical forests

Am. Nat.

On the role of natural enemies in preventing competitive exclusion in some marine animals and in forest trees

Soil pathogens and spatial patterns of seedling mortality in a temperate tree

Nature

Ecology of seed dispersal

Annu. Rev. Ecol. Syst.

The seed dispersers and fruit syndromes of Myrtaceae in the Brazilian Atlantic forest

Pervasive density-dependent recruitment enhances seedling diversity in a tropical forest

Nature

Angiosperm growth habit, dispersal and diversification reconsidered

Evol. Ecol.

Forest fragmentation severs mutualism between seed dispersers and an endemic African tree

Proc. Natl. Acad. Sci. U. S. A.

Advantages of seed dispersal: a re-evaluation of directed dispersal

Evol. Ecol. Res.

Genetic effects of chronic habitat fragmentation on tree species: the case of Sorbus aucuparia in a deforested Scottish landscape

Mol. Ecol.

Forest restoration on a closed landfill: rapid addition of new species by bird dispersal

Conserv. Biol.

Vegetation on Surtsey, Iceland, during 1990–1998 under the influence of breeding gulls

Review
Increasing awareness of avian ecological function