Feeding birds in our towns and cities: a global research

opportunity

Author
Jones, DN, James Reynolds, S

Published
2008

Journal Title
Journal of Avian Biology

DOI
https://doi.org/10.1111/j.0908-8857.2008.04271.x

Copyright Statement
© The Author(s) 2008. For information about this journal please refer to the journal's website.

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https://onlinelibrary.wiley.com/doi/full/10.1111/j.0908-8857.2008.04271.x

Griffith Research Online

https://research-repository.griffith.edu.au
Feeding birds in our towns and cities: A global research opportunity

Darryl N. Jones and S. James Reynolds

D. N. Jones (correspondence), Centre for Innovative Conservation Strategies, Griffith

University, Nathan, Qld 4111, Australia. E-mail: D.Jones@griffith.edu.au - S. J. Reynolds,
Centre for Ornithology, School of Biosciences, University of Birmingham, Edgbaston,
Birmingham, B15 2TT, UK

Date: 20 November 2007

Correspondence:

Darryl N Jones
Centre for Innovative Conservation Strategies, Griffith University, Nathan, Qld 4111,
Australia.
Email: D.Jones@griffith.edu.au

Running Head: Wild bird feeding

 Wild bird feeding is one of the most common forms of human-wildlife interactions in
the Western world. Originally a practice providing nutritional assistance to over-
wintering birds, especially in more northern latitudes, birds throughout the cities of the
world are now provided with considerable amounts and a variety of foods year-round.
Despite the global nature of the practice, remarkably little is known about the
outcomes and implications of what may be seen as a supplementary feeding
experiment on a massive scale. Although many claims are made about the benefits of
feeding, there are growing concerns about the spread of disease, poor nutrition, risk of
dependency and many other important issues. Constructive debate among increasingly
vigorous proponents and opponents is currently constrained by a lack of reliable
information. Here we argue that bird feeding provides an important, if challenging,
opportunity for fundamental research in urban ecology.

Every day, throughout the Western world, householders place seeds, sugar mixtures, food
scraps and meats on trays and in hanging feeders, as supplementary food sources for wild
birds. Whether to ameliorate poor foraging conditions, to monitor species richness and
abundance, or simply to enjoy the presence of otherwise free-living wildlife, many people are
passionate participants in the supplementary feeding of wild birds (Dunn and Tessaglia-
Hymes 1990, Cannon 2000, Howard and Jones 2004). Participation rates are consistently high
across the Western world: percentages of households providing food for birds at some time
have been estimated at 43-50% for the United States (Deis 1988, Geis and Pomerey 1993,
U.S. Dept. Interior and U.S. Dept Commerce 1997, Rogers 2002), 34-75% for the United
Kingdom (Cowie and Hinsley 1988) and 38-57% for Australia (Rollinson et al. 2003, Howard
and Jones 2004), with up to half of these doing so daily (Rollinson et al. 2003, Chamberlain et
al. 2005).
By a range of measures, it is an activity operating on a large scale. In the US alone,
recent estimates indicate that over 82 million people are involved, purchasing over 450
million kg of seed at a cost of about US$3.5 billion each year; a further US$730 million was
spent on feeders and related hardware (U.S. Dept. Interior, Fish and Wildlife Service 1998,
2002). Comparable figures for elsewhere are not readily available but it is estimated that
US$440 million and US$220 million are spent annually on supplementary food in the UK and
in mainland Europe, respectively (CJ Wildlife pers. comm.). While providing small amounts
of food to attract wild animals has probably been a feature of human settlements for millennia
(Kellert 1997), it is only during the last few decades that the feeding of birds has become
widespread with a concordant growth of allied industries (seed, feeders, guidebooks etc.)
(Peterson 2000, Chinery 2004).

2
 Feeding has traditionally been a winter activity, which probably started as humane
assistance for malnourished birds during harsh Northern Hemisphere seasons (Dunn and
Tessaglia-Hymes 1990, Brittingham 1991, Kress 1998). This probably remains the
predominant practice in many parts of the US and UK, but it is now also commonly practiced
year-round, with many feeders replenished daily throughout the year (Cannon at al. 2005).
Indeed, considerable effort is n
ow b
einge
xpe
nde
dtoc
onv
inc
ethemor
etr
adi
ti
ona
l‘wi
nte
r-
o
nly
’pa
rti
cip
ant
sth
aty
ear
-round feeding is both appropriate and beneficial to wild bird
populations, aiding survival and enhancing reproduction (Anon. 2004).
The role of food quality and availability in the ecology of animals is a well-
researched field (see review by Boutin 1990) and the provision of supplementary foods is
established as an experimental method for the study of the influence of food on the behaviour
and condition of a broad range of taxa (The Wildlife Society 2007). Supplementary feeding
has also been used as a wildlife management technique to enhance the survival and
reproductive success of species (e.g., Castro et al. 2003, Gonzalez et al. 2006, Houston et al.
2007), to concentrate animals for observation and hunting (Dunkley and Cattet 2003), to
assist in monitoring disease, and to reduce predation on target species by provisioning
predators (The Wildlife Society 2007).
Many supplementary feeding experiments have shown that even moderate amounts of
additional foods can profoundly influence reproductive outcomes of the target species (e.g.,
see reviews by Boutin 1990, Christians 2002). The majority of these studies show that
increasing the available food resource advances the onset of reproduction, prolongs the
breeding period and increases the number of young produced per year (Boutin 1990). In some
bird species, more food also results in more offspring per breeding attempt (e.g., Schoech
1996). More recently, researchers have started to investigate the influence of specific aspects
of the nutritional components of diets, including the importance of protein and lipids in the
control of breeding and on a range of hormonal and behavioural outcomes (e.g., Pravosudov
et al. 2001, Schoech and Bowman 2003, Schoech et al. 2004). The findings of such studies
have important implications for a wide range of management practices as well as
understanding the complex nature of diet in the lives of animals (e.g., Arizmedi et al. 2007).
It is appropriate, therefore, to view the practice of wild bird feeding as a large-scale
supplementary feeding experiment. Such experiments, however, are designed to test
predictions about the role of food in the reproductive biology of focal species. For the
i
millonso
fda
ilyf
eedi
ng‘
expe
rime
nts
’be
ingc
onduc
tedwor
ld-wide, however, the aims
appear to be primarily concerned with promoting observation and survival of birds.
Furthermore, it is away from the feeders that the results of these experiments will be
manifested, in the survival and breeding performance of supplemented birds. For almost all of
the species using supplementary food sources, however, the long-term implications for

3
individuals, populations and communities are almost entirely unknown. Indeed, despite the
ubiquity of garden bird feeding, remarkably little is known about the influences of
supplementation on the population ecology of the birds involved. We contend that
supplementary feeding of wild birds provides a wealth of research opportunities addressing
how anthropogenic augmentation of food availability might influence birds. Here, we
describe some important issues concerning the supplementary feeding of birds that remain
poorly understood and suggest that it is time to explore them in more detail.

Why do we feed wild birds?

The obvious popularity of wild bird feeding would appear to be related to the pleasure it
brings the participants, through intimate contact with wild animals, the exercise of humane
concern, and the experiential knowledge gained from these encounters (Rohde and Kendle
1994, Miller 2005). These dimensions of bird feeding, although universally and intuitively
asserted (Cannon 2000, Marshall 2004), nonetheless remain as assumptions until assessed
more widely. For example, Howard and Jones (2004) conducted a study in Brisbane,
Australia, where people engaged in feeding wild birds were asked to express their reasons for
doing so. While a clear majority stated that the practice gave them pleasure, confirming what
is intuitively apparent, a significant proportion of the participants also expressed their
mot
iva
tioni
nte
rmst
hatt
her
ese
arc
her
ste
rme
d‘e
nvi
ronme
nta
lat
one
ment
’:t
hes
epe
opl
e
stated that they fed wild birds from a desire to redress human environmental impacts. For
mpl
exa e,r
esponde
ntss
tat
ed“
Iwa
ntt
otr
yandun
dos
omeoft
hede
str
uct
ionc
aus
edby
h
uma
ns”a
nd“
Weh
avede
str
oye
dthe
irha
bit
ats
,Iwa
ntt
ogi
ves
ome
thi
ngba
ck”(
Howa
rda
nd
Jones 2004). These are strong sentiments and suggest a far more complex array of
environmental and philosophical perceptions than may be expected from such a seemingly
simple activity (Miller 2005).
Certainly participants in wildlife feeding feel strongly towards it and many endorse
the frequently expressed opinion that wildlife feeding is of definite benefit to the animals
involved (Howard and Jones 2004); the suggestion that feeding may be primarily for human
enjoyment tends to be vigorously countered (Erickson 2003, Fitzpatrick 2003). Contemporary
advocates of feeding typically highlight the broader conservation importance of the practice
(Cannon 1999, Toms 2003, Marshall 2004, Cannon et al. 2005). In the UK, especially,
domestic gardens are now the primary habitat supporting high proportions of national
populations of numerous songbird species, including some that are declining such as the song
thrush Turdus philomelos, with garden feeders almost certainly being a crucial resource
(Cannon et al. 2005, Chamberlain et al. 2005). It is now commonplace to find the provision of
supplementary foods by householders stated clearly as a fundamental means for facilitating
wild bird survival in urban areas, in both popular articles (e.g., British Trust for Ornithology

4
2003, Toms 2003, Marshall 2004) and scientific research papers (e.g., Chamberlain et al.
2005, Schoech et al. In press).
While there are numerous concerns about the possible impacts of wild bird feeding
(see below), many of which are openly acknowledged and discussed, there is also a growing
debate over whether potential benefits adequately outweigh the likely impacts (Green and
Higginbottom 2000). That feeding is regarded as a positive activity by many significant
stakeholders and commentators within the feeding community is evidenced by the significant
support forthcoming when the practice is questioned. The reaction from a large number of
North American participants and organizations to a negative front-page story in The Wall
Street Journal (Sterba 2002) and related articles (e.g., Rogers 2002) was marked and provided
a valuable insight into the perceptions of both proponents and opponents (see Erickson 2003,
Fitzgerald 2003). Nonetheless, despite the profuse and often detailed refutations of the many
claims made in such reports, the reality is that extremely little factual information is currently
available on which to establish constructive debate. This provides an obvious opportunity for
productive collaborations between ornithologists and social scientists, and other specialists.

Concerns about the impacts of feeding

While feeding is likely to benefit the survival of individuals of certain species, it is also clear
that the overwhelming majority of species fed in urban environments are abundant and
widespread (Chace and Walsh 2006). Indeed, in the US and Australia, there are concerns that
feeding may enhance populations of some introduced species, such as common starlings
Sturnus vulgaris and house sparrows Passer domesticus, as well as certain larger and more
behaviourally dominant species at the expense of native species (Chace and Walsh 2006,
Parsons et al. 2006). In the UK, for example, recent increases in the number and distribution
of feral rose-ringed parakeets Psittacula krameri, which out-compete most other garden bird
species at feeders, is of concern (Cannon 2000). This is also a key concern in Australia, where
the predominance of large and aggressive species such as pied currawongs Strepera graculina
at feeding stations has been implicated in the local decline of numerous smaller and more
subordinate species (Parsons et al. 2006). Corvids are a particular concern in the UK where
apparent increases in urban-dwelling Eurasian magpies Pica pica, for example, have caused
alarm among the feeding public (Cannon 1999). The presence of corvids in urban areas is
often assumed to increase nest predation, although there is relatively little direct evidence of
this (Marzluff and Neatherlin 2006). Nonetheless, in such cases, feeding may be indirectly
responsible for declines in local avian biodiversity (Parsons et al. 2006).
Understanding the influence that wild bird feeding may be having on local
biodiversity is only one of a number of reasons why investigating the implications of feeding
is important. Additional concerns include the: possibility that fed birds may become

5
dependent on human-provided foods; spread of diseases; impact of inappropriate or
nutritionally inferior foods on avian health and survival; loss of foraging skills; changes in
movements and migration patterns; increases in interspecific and human-directed aggression.
Although such concerns are widely discussed (Orams 2002, The Wildlife Society 2007),
developing a sound basis for the promotion of best practice guidelines requires reference to a
sound base of studies conducted on a broad diversity of species over a large spatial
distribution.
The issue of dependence – the possibility that animals may become
significantly reliant upon anthropogenic foods –is probably the most often cited concern
regarding supplementation (Brittingham and Temple 1988, Sterba 2002). Until recently, the
sole study to investigate this issue specifically found no evidence of dependency among
winter-fed black-capped chickadees Poecile atricapillus, in Wisconsin, USA (Brittingham
and Temple 1992). Interestingly, almost 80% of the diet of the fed birds was natural food
items, despite easy-access to feeders. In studies of chick provisioning among blue tits
Cyanistes caeruleus in the UK (Cowie and Hinsley 1988) and Florida scrub-jays Aphelocoma
coerulescens in the US (Fleisher et al. 2003), only about 30% of the food brought to nestlings
was not natural in origin.
In Australia, the diet of suburban Australian magpies Gymnorhina tibicen - the most
common bird species using feeders throughout the country (Jones 2002) - was dominated by
naturally-sourced soil and ground invertebrates obtained through natural foraging behaviours
(
O’Le
arya
ndJ
one
s2006
).Mor
eov
er,mos
toft
hef
ood
s(86
%ofa
lli
tems
)br
oug
htt
o
nestlings by breeding magpies were ground invertebrates, even though numerous feeding
stations were readily available. This was an unexpected finding, especially late in the
breeding cycle when pairs were often raising several chicks; despite the seemingly obvious
energetic saving represented by diced sausage and ground beef, these magpies persisted with
t
hei
rde
mandi
ng‘
no-junk-f
ood’po
lic
yinc
hic
kpr
ovi
si
oni
ng(
O’Le
arya
ndJ
one
s2006)
.
While Australian magpies were clearly not dependent or even reliant on
supplementary food, urban-dwelling Florida scrub-jays have been shown to consume
significantly more human-provided foods than non-urban conspecifics (Sauter et al. 2006).
Nonetheless, to date, there appear to have been no studies demonstrating dependency in any
free-ranging species. There are, however, instances in which specific animals have become
reliant on supplementary foods, although these were all in situations involving feeding
wildlife for tourist benefits (Orams 2002) or to facilitate breeding in endangered species
(Powesland and Lloyd 1994).
When freely-available supplementary foods are exploited by urban-dwelling species,
there are several readily predictable outcomes, among the most consistent being a significant
advance of breeding dates (Martin 1987, Boal and Mannan 1999). Studies of Florida scrub-

6
 r
jays (Fleisher et al. 2003), ceta
inl
yth
ebe
sts
tudi
ed‘
urba
n’s
pec
iesf
rom t
hep
ers
pec
tiv
eof
the influence of feeding, and Australian magpies (Rollinson and Jones 2002), have both
shown that in some years populations with access to supplementary food can start breeding up
to 17 and 13 days earlier, respectively, than unsupplemented conspecifics. Comparisons
between urban and non-urban populations also reveal increases in the number of breeding
attempts, greatly improved survival and often, but not always, improved reproductive output
per year (Boal and Mannan 1999, Bowman and Woolfenden 2001, Rollinson and Jones
2002). In almost all such studies, the influence of bird feeders was strongly implicated.
While there is no doubt that the quality of many commercial seed mixes has steadily
improved over recent years, many now providing nutritionally complete diets, concerns about
the impact of unbalanced, inappropriate or inadequate food supplements remain prominent
(Schoech et al. 2004). For example, numerous studies of feeding practice have shown that
bread is one of the most common supplements provided world-wide (Orams 2002, Rollinson
et al. 2003, Chace and Walsh 2006); whether the influence of this highly refined and
processed food type on birds is useful, harmful or insignificant remains unknown despite its
ubiquity.
There has been, however, an increase in interest in more specific nutritional aspects
of wild bird feeding, although such studies are few in number (Pravosudov et al. 2001,
Schoech and Bowman 2003, Schoech et al. 2004). For example, there is some evidence that
Australian magpies that consume regular amounts of processed, high-lipid foods (e.g. meats -
Rollinson et al. 2003) have elevated plasma cholesterol levels, although the long-term
implications of this are not yet known (Ishigame et al. 2006). Certainly, some species appear
to adjust their activity schedules in response to the nutritional nature of the food types
available to them: Florida scrub-jays, for example, with access to a high fat-high protein
supplement spent 12% less time foraging than wildland (unsupplemented) birds (Schoech et
al. 2004). Nonetheless, surprisingly little is known about the nutritional and bio-physiological
influences of the food types that are provided for wild birds, even though almost all such
f
oodsf
orm no pa
rto
fmos
tsp
eci
es’n
atu
raldi
ets
.We
ll-publicised concern (e.g. see
www.birdfeeding.com) over the apparent over-reliance - and possible resultant health issues -
of some species on certain food types is an example of apparent self-regulation within the
bird seed industry although dependable data on the extent of the use of these food types are,
again, hard to obtain.
Feeders have been implicated in the spread of several important avian diseases
(Bradley and Altizer 2006). Accessibility to a concentrated food source at a feeder inevitably
results in an aggregation of birds where contact with infected individuals is much more likely
(Brittingham and Temple 1988). In Australia, outbreaks of Psittacine Beak and Feather
Disease and the spread of the bacterium Clostridia (which is associated with necrotising

7
enteritis) among lorikeets Trichoglosus spp. has been attributed to their frequent use of
feeders (New South Wales NPWS 2003), although the link has yet to be established. In the
UK, Garden BirdWatch (see http://www.bto.org/gbw/index.htm for details) participants are
currently monitoring the incidence of Trichomoniasis following an outbreak of this disease
among European greenfinches Carduelis chloris (Toms 2006). Similarly, data from large
numbers of Project FeederWatch (see http://www.birds.cornell.edu/pfw/ for details)
volunteers in North America (Dhondt et al. 2001) have provided the basis for a detailed
understanding of the disease dynamics of the current epidemic of Mycoplasmal conjunctivis
among house finches Carpodacus mexicanus (Dhondt et al. 2005).
The potential role of feeders in increasing disease risk is well recognised: almost all
the material promoting and explaining feeding of wild birds includes prominent attention to
hygiene (e.g., RSPB 2007); advice to Project FeederWatch participants, for example, has
been especially explicit on this issue (Cornell Laboratory for Ornithology 2007). That the
practice of feeding per se could be responsible for disease spread is, however, vigorously
denied by supporters, who often cite a lack of direct evidence as support (Erickson 2003). In
some cases, however, circumstantial evidence has been sufficient for the instigation of anti-
feeding directives. For example, in an unusual reaction to disease outbreak, the Department of
Fish and Game in California recently requested that feeders be temporarily removed from
northern areas of the state in an attempt to limit the spread of a parasitic Trichomoniasis
among band-tailed pigeons Patagioenas fasciata and mourning doves Zenaida macroura
(Department of Fish and Game, California 2005). Whether such advice was followed remains
unknown.

Promoting and opposing feeding

For some wildlife agencies and individuals, the apparent risks associated with the feeding of
birds have led to well publicised attempts to control or ban the practice entirely. This is
certainly the case in Australia where several state wildlife and conservation agencies
strongly discourage all forms of wildlife feeding (Seipen and Stanley 1996, Tasmanian Parks
and Wildlife Service 2002, Petrie et al. 2003). While these recent official reactions relate
mainly to activities in reserves (Orams 2002), there are clear signs that some agencies would
like to impose significant controls on wildlife feeding even in suburban and urban areas
(Howard and Jones 2004). Despite the popularity of the practice in Australia (Rollinson et al.
2003), most agency publications that address the topic are invariably negative, typically
listing the numerous concerns mentioned above, and suggesting strongly that feeding is
harmful (Hunter 2001, Petrie et al. 2003).
In contrast, prominent Northern Hemisphere organizations such as the British Trust
for Ornithology, Royal Society for the Protection of Birds, Cornell Laboratory of Ornithology

8
and many others actively promote wildlife feeding as an activity promoting conservation.
Nonetheless, while these groups implicitly assume that feeding is beneficial to the birds as
well as enjoyable to the human participants, there is also acknowledgement of many of the
issues of concern. One prominent assertion is that feeding leads to closer contact with nature,
which in turn enhances a‘
cons
erv
ati
one
thi
c’;p
eop
lewhof
eedbi
rdsa
remor
eli
kel
ytoc
are
more about conservation (Green and Higginbottom 2000). Interestingly, studies of support for
conservation among bird watchers has yielded mixed results with some finding strong
conservation interest and motivation while for others this was less certain (McFarlane 1994,
Hvenegaard 2002).
It is evident that virtually all of the concerns and claims made by both proponents and
opponents of the practice of providing supplementary food supplies - whether it is
dependency, disease or dietary deficiency, or any of the numerous other important associated
issues - research-based findings remain relatively rare. What is known with high levels of
certainty, due to the amount of effort invested by the wild bird food industry itself, relates
mainly to the preferences of the main target species: seed types, feeder design and, location,
time of the day and season, food colour, taste and nutritional composition favoured or avoided
(Dunn and Tessaglia-Hymes 1990, Kress 1998). These are crucial factors required to
maximise bird visitation and consumption rates, and are constantly being assessed and
monitored by a large and competitive global industry. However, with the focus on sustained
study of such minutiae, the broader ecological and behavioural implications for species have
been neglected to date.

Conclusion
What is certain, due to decades of careful supplementary feeding experiments conducted on a
wide variety of taxa, is that alterations in the availability and quality of food resources can
influence breeding activity. Whether these changes are important and positive or detrimental,
however, cannot currently be discussed with clarity and certainty. Despite this, there can be
little doubt that the feeding of wild birds is of profound importance to urban populations of
birds. Moreover, it is an almost universal practice that is likely to increase in popularity;
steadily urbanising Westerners, more and more divorced from contact with nature, appear to
be searching for simple and meaningful ways of interacting with wildlife (Miller 2005).
Feeding wild birds appears to be an obvious and effective means of doing so. Many people
who enjoy feeding birds, and many of those who oppose the practice, are deeply concerned
about its impacts.
Undertaking research in this context is not without significant logistical, ethical and
methodological challenges. Almost unavoidably, studies of bird feeding in suburban
landscapes have to cope with and account for the levels of community attention and

9
involvement often unfamiliar to many researchers. But carefully managed alliances between
residents and researchers may provide opportunities normally unavailable for most of the
l
att
er.Thet
rul
yphe
nome
nalc
ove
rag
eofs
uch‘
cit
iz
ens
cie
nce
’pr
ogr
amme
ssuc
hasProject
FeederWatch in the US (Dhondt et al. 2001), Garden BirdWatch in the UK (Cannon et al.
2005) and the recently launched Birds in Backyards program in Australia, provide
unprecedented details of the birds visiting suburban gardens. However, the success of such
programs requires careful and critical attention to a range of methodological concerns.
Smaller-scale intensive studies, focussing on specific issues, are also essential,
although it is likely that these will also require the cultivation of productive relationships with
residents. Among the main priorities for investigation are issues of dependency, over-reliance
on inappropriate supplements (including high oil-content seeds and protein-rich meats), and
the implications for survival and reproduction of the individuals involved. Moreover, it is
critical that we determine the percentage of overall diet constituted by supplementary foods
for a range of species and during different seasons. Underlying this research aim is the
requirement for research examining dietary shifts (and concomitant changes in foraging
behaviour) between breeding and non-breeding stages of the annual cycle of focal taxa.
Technological advances, such as stable isotope analysis and PIT tags, allow us to quantify the
assimilation of food supplements (e.g., Davis et al. 2005) and visitation rates to feeders and
broods (e.g., Freitag et al. 2001), respectively, providing invaluable insight into how food
supplementation influences the nutritional ecology, breeding biology, health and, ultimately,
the life history of birds feeding in urban environments.
We strongly encourage researchers, especially those already working in urban
environments, to consider explicitly the role and influence of wild bird feeding on the avian
populations that share our towns and cities.

Acknowledgments
This paper was started while DNJ was a sabbatical guest of the Department of Biological
Sciences at Victoria University of Wellington, New Zealand. He is especially grateful to
Wayne Linklater and Ralph Powlesland for their hospitality and ideas. The concepts sketched
out here have developed over several years and we are deeply grateful for the stimulations
and discussions with many students/friends/colleagues, especially Jon Easton, Tim Harrison,
Pe
terHowa
rd,Tom Ne
als
on,Re
bec
caO’
Lea
ry,Gr
aha
m Ma
rti
n,Mi
che
ll
eOos
t,Mi
che
ll
e
Plant, Dan Rollinson, Jen Smith and Leoni Thomas. We thank Peter Deans and Chris
Whittles at CJ Wildlife for estimates of supplementary food purchase in the UK and Europe.
Finally, we are grateful to several anonymous referees and Barbara Helm for many helpful
comments and suggestions

10
References
Anon. 2004. How summer feeding is boosting wild bird sales. Pet Product Marketing, Aug.
2003: 13.
Arizmedi, M. C., Monterrubio-Solis, C., Lourdes J., Flores-Moreno I. and Lopez-Saut, E.
2007. Effect of the presence of nectar feeders on the breeding success of Salvia
mexicana and Salvia fulgens in a suburban park near Mexico City. - Biol. Conserv.
136: 155-158.
Boa l,C. W.a ndMa nna n,R.W.1 999 .Compa ra t
iveb reedi
nge co l
og yofCoope r’sha wk sin
urban and exurban areas of southeastern Arizona. - J. Wildl. Manage. 63: 77-84.
Boutin, S. 1990. Food supplementation experiments with terrestrial vertebrates: Patterns,
problems, and the future. - Can. J. Zool. 68: 203-220.
Bradley, C. A. and Altizer, S. 2006. Urbanization and the ecology of wildlife diseases. -
Trends Ecol. Evol. 22: 95-122.
British Trust for Ornithology. 2003. Garden Birdwatch: Feeding Garden Birds. –
http://www.bto/org
Brittingham, M. C. 1991. Effect of winter feeding on wild birds. –In: Adams, L. W. and
Leedy, D. L. (eds). Wildlife Conservation in Metropolitan Environments. National
Institute for Urban Wildlife, Columbia, pp. 185-190.
Brittingham, M. C. and Temple, S. A. 1988. Avian disease and winter feeding. - Passenger
Pigeon 50: 195-203.
Brittingham, M. C. and Temple, S. A. 1992. Does winter feeding promote dependency? - J.
Field Ornith. 63: 190-194.
Cannon, A. 1999. The significance of private gardens for bird conservation. - Bird. Conserv.
Int. 9: 287-297.
Cannon, A. 2000. The Garden Birdwatch Handbook. British Trust for Ornithology, Thetford.
Cannon, A. R., Chamberlain, D. E., Toms M. P., Hatchwell, B. J. and Gaston, K.J. 2005.
Trends in the use of private gardens by wild birds in Great Britain 1995-2002. - J.
Appl. Ecol. 42: 659-671.
Castro, I., Brunton, D. H., Mason, K. M., Ebert, B. and Griffiths, R. 2003. Life history traits
and food supplementation affect productivity in a translocated population of hihi
(Stitchbird, Notiomystis cincta). - Biol. Conserv. 114: 271-280.
Chace, J. F. and Walsh, J. J. 2006. Urban effects on native avifauna: a review. - Landscape
Urban Plan. 74: 46-69.
Chamberlain, D. E., Vickery, J. A., Glue, D. E., Robinson, R. A., Conway, G. J., Woodburn,
R. J. W. and Cannon A. R. 2005. Annual and seasonal trends in the use of garden
feeders by birds in winter. - Ibis 147: 563-575.
Chinery, M. 2004. Attracting Wildlife to your Garden. Collins, London.
Christians, J. K. 2002. Avian egg size: variation within species and inflexibility within
individuals. - Biol. Rev. Camb. Philos. Soc. 77: 1-26.
Cornell Laboratory of Ornithology. 2007. Project FeederWatch.
http://www.birds.cornell.edu.edu/pfw/AboutBirdsandFeeding?FAQsBirdFeeding.htm
Cowie, R. J. and Hinsley, S. A. 1988. Feeding ecology of great tits (Parus major) and blue
tits (Parus caeruleus) breeding in suburban gardens. - J. Anim. Ecol. 57: 611-626.
Davis,S. E., Nager, R. G. and Furness, R. W. 2005. Food availability affects adult survival as
well as breeding success of parasitic jaegers. - Ecology 86: 1047-1056.
Deis, R. 1986. Is bird feeding a no-no? - Defenders 54: 17-18.
Department of Fish and Game, California. 2006. DFG asks Northern Californians to remove
bird feeders to slow avian disease. http://dfga.ca.gov/news/news06/06041.html
Dhondt, A. A., Hochachka, W. M., Altizer, S. M. and Hartup, B. K. 2001. The house finch
not zone: citizen science on the trail of an epidemic. - Living Bird 20: 24-30.
Dhondt, A. A., Altizer, S., Cooch, E. G., Davis, A. K., Dobson, A., Driscoll, M. J., Hartup, B.
K., Hawley, D. M., Hochachka, W. M., Hosseini, P. R., Jennelle, C. S., Kollias, G.
V., Ley, D. H., Swarthout, E. C. and Sydenstricker, K. V. 2005. Dynamics of a novel

11
 pathogen in an avian host: Mycoplasmal conjunctivitis in house finches. - Acta
Tropica 94: 77-93.
Dunkley, L. and Cattet, M. R. L. 2003. A comprehensive review of the ecological and human
social effects of artificial feeding and baiting of wildlife. Parks Canada Agency and
Saskatchewan Environment.
Dunn, E. H. and Tessaglia-Hymes, D. L. 1990. Birds at Your Feeder. W. W. Norton, New
York.
Erickson, L. 2003. Wall Street Journal bird feeding article distorts truth. -
http://www.lauraerickson.com/Birds/Conservation/WSJDistortions1.html.
Fitzgerald, J. W. 2003. In defense of bird feeding. - Birdscope, Spring 2003.
http://www.cornell.edu/publications/birdscope/Spring2003/In_Defense.html
Fleischer, A. L., Bowman, R. and Woolfenden, G. E. 2003. Variation in foraging behaviour,
diet, and time of breeding in Florida scrub-jays in suburban and wildland habitats. -
Condor 105: 515-527.
Freitag, A., Martinoli, A. and Urzelai, J. 2001. Monitoring the feeding activity of nesting
birds with an autonomous system: case study of the endangered wryneck Jynx
torquilla. - Bird Study 48: 102-109.
Geis, A. D. and Pomeroy, L. N. 1993. Reaction of wild bird populations to a supplementary
food source. –Trans. North Am. Wildl. Nat. Res. Conf. 44-61.
González, L. M., Margalida, A. Sänchez, R. and Oria, J. 2006. Supplementary feeding as an
effective tool for improving breeding success in the Spanish imperial eagle (Aquila
adalberti). –Biol. Conserv. 129: 477-486.
Green, R. J. and Higginbottom, K. 2000. The effects of non-consumptive wildlife tourism on
free-ranging wildlife: a review. - Pacific Conserv. Biol. 6: 183-197.
Houston, D., McInnes, K., Elliot, G. Eason, D. Moorhouse, R. and Cockrem, J. 2007. The use
of a nutritional supplement to improve egg production in the endangered kakapo. -
Biol. Conserv. 138: 248-255.
Howard, P. and Jones, D. N. 2004. A qualitative study of wildlife feeding in south-east
Queensland. In: Burger, S. K. and Lunney, D. eds). Urban Wildlife: More than Meets
the Eye. Royal Zoological Society of New South Wales, Sydney, pp. 55-62.
Hunter, J. 2001. Urban antics: To feed or not to feed? - Landscope 17: 54.
Hvenegaard, G. T. 2002. Birder specialization differences in conservation involvement,
demographics and motivations. Human Dimens. Wildl. &: 21-36.
Ishigame, G., Baxter, G. S. and Lisle, A. T. 2006. Effects of artificial foods on the blood
chemistry of the Australian magpie. –Austral. Ecol. 31: 199-207.
Jones, D. N. 2002. Magpie Alert: Learning to Live with a Wild Neighbour. NSW University
Press, Sydney.
Kellert, S. R. 1997. Kinship to Mastery: Biophilia in Human Evolution and Development.
Island Press, Washington.
Kress, S. W. 1998. Bird Gardens: Welcoming Wild Birds to your Yard. Brooklyn Botanic
Gardens, Brooklyn.
Marshall, R. 2004. Urban wildlife: Feeding wild birds. -
http://www.birdhealth.com.au/Urban/main.htm
McFarlane, B. L. 1994. Specialization and motivations of birdwatchers. –Wildl. Soc. Bull.
22: 361-370.
Martin, T. E. 1987. Food as a limit on breeding birds: a life-history perspective. - Ann. Rev.
Ecol. Syst. 18: 453-487.
Marzluff, J. M. and Neatherlin, E. 2006. Corvid response to human settlements and
campgrounds: Causes, consequences, and challenges for conservation. - Biol.
Conserv. 130: 301-314.
Miller, J. R. 2005. Biodiversity conservation and the extinction of experience. - Trends Ecol.
Evol. 20: 430-434.
O’ Lear y,R.a ndJ ones ,D. N.2006. Theu seofs uppl eme ntaryf oodsbyAus tral
ianma gpies
Gymnorhina tibicen: Implications for wildlife feeding in suburban environments. –
Austral. Ecol. 31: 208-216.

12
Orams, M. B. 2002. Feeding wildlife as a tourism attraction: a review of issues and impacts. -
Tourism Manag. 23: 281-293.
Parsons, H., Major, R. E. and French, K. 2006. Species interactions and habitat associations
of birds inhabiting urban areas of Sydney, Australia. –Austral. Ecol. 31: 217-227.
Peterson, R. T. 2000. Feeder Birds- Eastern North America. Houghton Mifflin, Boston.
Petrie, M., Walsh, D. and Hotchkins, D. 2003. Encountering wildlife without feeding. - Land
For Wildlife Extension Note 20, Queensland Parks and Wildlife Service, Brisbane.
Powlesland, R. G. and Lloyd, B. D. 1994. Use of supplementary feeding to induce breeding in
free-living kakapo Strigops habroptilus in New Zealand. Biol. Cons. 69: 97-106.
Pravosudov, V. V., Kitaysky, A. S., Wingfield, J. C. and Clayton, N. S. 2001. Long-term
unpredictable foraging conditions and physiological stress response in mountain
chickadees. - Gen. Comp. Endocrinol. 123: 324-331.
Rohde, C. L. E. and Kendle, A. D. 1994. Human well-bring, natural landscapes and wildlife
in urban areas: A review. English Nature Science, English Nature, London.
Rogers, J. 2002. Birdfeeding: Another viewpoint. Alberta Naturalist 31: 1-11.
Rol l
ins on ,D. ,O’ Le ary,R.a ndJ ones,D.N.20 03. Thep racti
ceo fwi ldlifefeed ingi n
suburban Brisbane. - Corella 27: 52-58.
Rollinson, D. J. and Jones, D. N. 2002. Variation in breeding parameters of the Australian
magpie Gymnorhina tibicen in suburban and rural environments. Urb. Ecosystems. 6:
257-269.
Royal Society for the Protection of Birds. 2007. Helping birds.
http://www.rspb.org.uk/advice/helpingbirds/feeding/whatfoods/index.asp
Sauter, A., Bowman, R. J., Schoech, S. J. and Pasinelli, G. 2006. Does optimal foraging
theory explain why suburban Florida scrub-jays (Aphelocoma coerulescens) feed
their young human-provided food? - Behav. Ecol. Sociobiol. 60: 465-474.
Schoech, S. J. 1996. The effects of supplementary food on body condition and the timing of
reproduction in a cooperative breeder, the Florida scrub-jay. - Condor 98: 234-244.
Schoech, S. J. and Bowman, R. 2003. Does differential access tp protein influence differences
in timing of breeding of Florida scrub-jays (Aphelocoma coerulsecans) in suburban
and wildland habitats. - Auk 120: 1127-2003.
Schoech, S. J., Bowman, R. and Reynolds, S. J. 2004. Food supplementation and possible
mechanisms underlying early breeding in the Florida scrub-jay (Aphelocoma
coerulsecans). –Hormone. Behav. 46: 565-573.
Schoech, S. J., Bridge, E. S., Boughton, R. K., Reynolds, S. J., Atwell, J. W. and Bowman, R.
In press. Food supplementation: A tool to increase reproductive output? A case study
in the threatened Florida scrub-jay. - Biol. Conserv.
Seipe n ,G.a ndSt an l
e y,J.1996.“ Pleas e,don ’tfeedt hea nimals.
”Ra ng er35:22-24.
Sterba, J. P. 2002. American backyard feeders may do harm to wild birds: Feeding wild birds
lures pest, predators, causing illness and distorting populations. - Wall Street Journal
27 December 2002.
Tasmania Parks and Wildlife Service. 2002. Keeping Wildlife Wild. - Tasmania Parks and
Wildlife Service, Hobart.
The Wildlife Society. 2007. Baiting and Supplementary Feeding of Game Wildlife Species.
http://www.wildlife.org
Toms, M. P. 2003. The BTO/CJ Garden Birdwatch Book. British Trust for Ornithology,
Thetford.
Toms, M. P. 2006. Garden bird health initiative. Bird Table Magazine 48: 10-11.
United States Department of the Interior, Fish and Wildlife Service. 1988. 1985 National
Survey of Fishing, Hunting and Wildlife-Associated Recreation. U.S. Gov. Print.
Office, Washington, D. C. Pp. 167.
United States Department of the Interior, Fish and Wildlife Service. 2002. 2001 National
Survey of Fishing, Hunting and Wildlife-Associated Recreation.
http://www.census.gov/prod/2002pubs/FHWO1.pdf

13
United States Department of the Interior and United States Department of Commerce. 1997.
1996 National Survey of Fishing, Hunting and Wildlife-Associated Recreation. U.S.
Gov. Print. Office, Washington, D. C. Pp. 188.

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