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Colour preferences of UK garden birds at supplementary seed feeders


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Supplementary feeding of garden birds generally has benefits for both bird populations and human wellbeing. Birds have excellent colour vision, and show preferences for food items of particular colours, but research into colour preferences associated with artificial feeders is limited to hummingbirds. Here, we investigated the colour preferences of common UK garden birds foraging at seed-dispensing artificial feeders containing identical food. We presented birds simultaneously with an array of eight differently coloured feeders, and recorded the number of visits made to each colour over 370 30-minute observation periods in the winter of 2014/15. In addition, we surveyed visitors to a garden centre and science festival to determine the colour preferences of likely purchasers of seed feeders. Our results suggest that silver and green feeders were visited by higher numbers of individuals of several common garden bird species, while red and yellow feeders received fewer visits. In contrast, people preferred red, yellow, blue and green feeders. We suggest that green feeders may be simultaneously marketable and attractive to foraging birds.
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Colour preferences of UK garden birds at
supplementary seed feeders
Luke Rothery, Graham W. Scott, Lesley J. Morrell*
School of Environmental Sciences, University of Hull, Kingston-upon-Hull, United Kingdom
Supplementary feeding of garden birds generally has benefits for both bird populations and
human wellbeing. Birds have excellent colour vision, and show preferences for food items of
particular colours, but research into colour preferences associated with artificial feeders is
limited to hummingbirds. Here, we investigated the colour preferences of common UK gar-
den birds foraging at seed-dispensing artificial feeders containing identical food. We pre-
sented birds simultaneously with an array of eight differently coloured feeders, and recorded
the number of visits made to each colour over 370 30-minute observation periods in the win-
ter of 2014/15. In addition, we surveyed visitors to a garden centre and science festival to
determine the colour preferences of likely purchasers of seed feeders. Our results suggest
that silver and green feeders were visited by higher numbers of individuals of several com-
mon garden bird species, while red and yellow feeders received fewer visits. In contrast,
people preferred red, yellow, blue and green feeders. We suggest that green feeders may
be simultaneously marketable and attractive to foraging birds.
It has been estimated that 20–40% of people in the UK, North America, Australia and New
Zealand regularly provide wild birds with additional food (supplementary feeding) at some
point in the year (typically during the winter months) [1,2]. In the UK, approximately 60% of
households with gardens provide food for birds [3], estimated at 12.6 million households [1],
7.4 million of which use bird feeders [4]. As a result the UK wild bird feeding industry was esti-
mated as being worth £210m per annum [5], and the wild bird care market rose 15% in value
between 2014 and 2015 [6]. Levels of bird feeding vary enormously across society [7], but the
importance of the connection between people and nature to human well-being in urban envi-
ronments is well established [8,9]. People feed birds because it gives them a sense of personal
wellbeing, although the underpinning emotions, experiences and personal perceptions of the
people feeding birds are certainly more complex than such a simplistic statement might sug-
gest [10]. Some people (those involved in avian monitoring or research) feed birds in order to
attract them for capture, measurement and subsequent release.
During the northern hemisphere winter natural food resources are at their lowest level of
availability [11] and a bird’s thermodynamic costs are at their highest [12]. Over winter
PLOS ONE | DOI:10.1371/journal.pone.0172422 February 17, 2017 1 / 14
Citation: Rothery L, Scott GW, Morrell LJ (2017)
Colour preferences of UK garden birds at
supplementary seed feeders. PLoS ONE 12(2):
e0172422. doi:10.1371/journal.pone.0172422
Editor: Adrian G. Dyer, Monash University,
Received: October 19, 2016
Accepted: February 4, 2017
Published: February 17, 2017
Copyright: ©2017 Rothery et al. This is an open
access article distributed under the terms of the
Creative Commons Attribution License, which
permits unrestricted use, distribution, and
reproduction in any medium, provided the original
author and source are credited.
Data Availability Statement: All relevant data are
held within the paper and its Supporting
Information Files.
Funding: Funding was provided by Westland
Horticulture and the former School of Biological,
Biomedical & Environmental Sciences at the
University of Hull. Westland Horticulture played a
role in the conceptualisation of the research
question, but no role in data collection and
analysis, decision to publish or preparation of the
Competing interests: I have read the journal’s
policy and the authors of this manuscript have the
survival is thus highly dependent upon the characteristics and availability of food supply [11].
Gaining enough energy each day to ensure overnight survival is particularly important for
small passerines: individuals in the tit family (Paridae) can lose up to 10% of their body weight
overnight in winter [13]. Supplementary feeding may off-set the effects of winter resource
depletion [14] and in many cases a winter feeding station may be the most abundant and
dependable food source in a particular area [15]. Supplementary feeding has been recorded as
having a number of other benefits to birds, including larger clutch sizes (house sparrows Passer
domesticus [16]), better body condition and more rapid recovery from injury (Carolina chicka-
dee Parus carolinensis, tufted titmice Parus bicolor and white-breasted nuthatch Sitta carolinen-
sis [17]). Supplementary feeding increases both the range of species and number of individuals
visiting gardens [1,18] and increases abundance at a landscape scale [1]. In the UK, for exam-
ple, supplementary feeding has been implicated in population increases of both house sparrow
and starling (Sturnus vulgaris [19]) and may be important in the evolution of ‘new’ migration
strategies amongst over-wintering blackcap (Sylvia atricapilla [20]), and a reduction in neo-
phobia in urban birds relative to rural ones [21].
In order that the benefits of supplementary feeding to both birds and the people who feed
them are realised it is essential that food be provided in a way that makes it accessible to birds.
In the case of the seed based foods provided to passerines supplementary feeding most often
involves the use of commercially available tubular seed dispensers [9]. These feeders com-
monly consist of a transparent plastic tube through which seeds are visible to birds and col-
oured metal or plastic lids, bases, perches and feeder ports. Here, we report an investigation
into whether the colour of these metal or plastic parts affected the number of birds choosing to
feed at a particular feeder. For a feeder to attract larger numbers of birds, something likely to
be seen as preferable by those that purchase feeders, the colour should be attractive or neutral
to either a particular target species, or seed feeding birds more generally [22]. A feeder the col-
our of which birds avoid would not be an effective feeder.
Birds have excellent colour vision and exhibit the ability to distinguish and choose between
different colours and shades [2325]. Here, we focus on colour preferences in relation to forag-
ing. Multiple studies report preferences of birds for food items of a particular colour. Great tits
(Parus major) blue tits (Cyanistes caeruleus) and Eurasian nuthatches (Sitta europaea) all pre-
ferred uncoloured (natural) peanuts over those that had been dyed white [26]. Willson et al.
[27] reviewed a number of studies demonstrating that frugivorous birds prefer black or red
grapes or cherries over other colours such as green and yellow, but point out that preference
for colour here is confounded by preference for other factors associated with colour, such as
ripeness, size and nutritional value [27]. Other studies have used artificial or novel foods dyed
different colours and found colour-based preferences [2729]. Willson et al [27] reported a
preference for red, and avoidance of yellow in three species of frugivorous bird, while North
Island robins (Petroica longipes) preferred yellow and avoid blue and brown [29] for example.
Preferences for colour associated with supplementary feeders, rather than food, have exclu-
sively focused on the preferences of hummingbirds (Trochillidae) at feeders designed to pro-
vide sugar syrup. While hummingbird-pollinated flowers tend to be red [30,31], and birds
tend to prefer red-pigmented flowers over those lacking red pigments (e.g. [3234], reviewed
in [31]), experimental studies on feeders do not show a consistent preference for any particular
colour (e.g. [3537], reviewed in [31]). Instead, factors such as location [38,39], previous expe-
rience [4042] and nectar quality [38,42] appear to be more important in determining choice.
We have been unable to find any peer-reviewed studies of the impact of seed dispensing feeder
colour on bird feeding behaviour. One anecdotal report [43] suggested that work carried out
by the British Trust for Ornithology demonstrated colour-based preferences for birds visiting
seed and peanut feeders, namely that blue seed feeders are preferred during the summer, while
Colour preferences of UK garden birds at supplementary seed feeders
PLOS ONE | DOI:10.1371/journal.pone.0172422 February 17, 2017 2 / 14
following competing interests: Consumables/travel
funding was received from Westland Horticulture
to carry out the research. The funders specified the
initial research question but played no role in study
design, data collection and analysis, decision to
publish or preparation of the manuscript.
silver feeders are preferred in winter (although goldfinches preferred green), and red peanut
feeders are preferred over other colours. The primary aim of our research was to investigate
the effect of feeder colour on the feeding preferences of wild birds. As an additional aim we
investigated the level to which birds and the humans who feed them agreed on their preferred
feeder colour, an important consideration for those who make and sell feeders and those who
use them.
Bird colour preference
To explore the effect of colour on the number of visits by birds, we recorded bird visit rates to
8 different coloured feeders at three sites on 78 sampling days during the winter/spring of
2014/15 (November 2014 to May 2015).
Data were collected at Tophill Low Nature Reserve (Driffield, East Yorkshire TA 075,492),
The University of Hull Botanic Garden (Cottingham, East Yorkshire TA 050,329) and a subur-
ban garden in Otley (West Yorkshire SE 195,472). These sites were chosen due to accessibility
and the presence of existing artificial feeders with regular avian visitors. The feeders used
(Natures Feast Royal Seed Feeders, Westland Horticulture) were of transparent tubular design
with metal lids, two metal ports and two straight metal perches. The metal parts of each feeder
were painted a single colour using Hammerite Metal Paint. The proprietary colours used were
Smooth Black,Smooth Blue,Smooth Dark Green,Smooth Red,Smooth White,Smooth Yellow,
Hammered Silver and Purple (achieved by mixing Smooth Blue,Smooth Red and Smooth White
at a ratio of 3:2:1). Analysis of the feeder colours can be found in the section below. Through-
out the experiment the feeders were filled with “Nature’s Feast High energy No Mess 12 Seed
Blend” (Westland Horticulture, UK).
At each site the feeders were suspended in a line from a metal cross-bar, 30 cm apart from
one another and 1.5m above the ground. At any time, one feeder of each of the 8 colours used
was available (see S1 Fig). The order of the feeders along the cross-bar was changed after every
30 minute observation period according to a pre-determined random pattern to control for
any preferences based on feeder position rather than colour. Feeders were filled at the begin-
ning of each observation period and cleaned thoroughly every 14 days. During each data col-
lection session the numbers of feeding visits by birds to each of the feeders in the array were
recorded over 30 minutes. A feeding visit was defined as a bird landing on the perch and tak-
ing food from the feeder port. Birds were identified to species level, but as it was not possible
to distinguish between individuals of the same species, each visit to the feeders was counted as
an independent data point. All observations periods were video recorded (Sony Handycam
HDR-CX240E) mounted on a tripod approximately 10m from the feeders. Identification and
counting of birds either took place in real-time in the field or later using the video recordings
(where the number of visits was too high to allow for accurate real-time recording).
Data were collected across a total of 370 observation periods (Otley: 208; Tophill; 26 Botanic
Gardens: 136), and a total of 7535 visits to the feeders were recorded (Table 1).
Human colour preference
To assess the preferences of likely purchasers of bird feeders, we collected data in a garden cen-
tre (Hornsea Garden Centre, Sigglesthorne, Hornsea, UK) where similar feeders were sold (3
days, 8 2-hour sample periods) and at the University of Hull Science Festival (1 day as a single
sample period). At each venue we explained to adult volunteers that we were investigating the
choices made by birds and people but we did not provide any information on actual bird pref-
erences (S2 Fig). People were shown the coloured feeders used in the study and asked simply
Colour preferences of UK garden birds at supplementary seed feeders
PLOS ONE | DOI:10.1371/journal.pone.0172422 February 17, 2017 3 / 14
to indicate (by placing a token in an appropriately coloured container) which they would be
most likely to buy for their own garden. Containers were emptied and tokens counted at the
end of each sample period. In total, 587 ‘votes’ were cast during the poll.
Data analysis
All analysis was carried out using R v3.2.3 [44]. The total number of visits (across all species, to
give a measure of the overall preference for particular colours) to the feeders were analysed
using a generalised linear mixed effects model with a Poisson error distribution (as appropriate
for count data). Observation period and site were added as random effects to account for non-
independence of visits to feeders displayed at the same time, and overall differences in bird
populations at a given site. An observation-level random effect was included to account for
overdispersion in the data [45]. Re-leveling the data within the model allowed for all pairwise
comparisons between colours to be made, and p-values were corrected for multiple testing
across pairwise comparisons using the false discovery rate control method [46]. The same anal-
ysis was used for the number of visits for each species with more than 100 total visits to the
feeders (see S1 to S5 Tables), to evaluate whether different species had different colour prefer-
ences. Preferences expressed by visitors to the garden centre and science festival were also ana-
lysed using the same methodology.
Feeder colour analysis
To objectively describe the colour of the feeders, photographs of the feeder lids were taken
in RAW format using a Canon Powershot G12 camera. Lids were placed into a light tent
(EZCube, Ventura, CA, USA) under daylight spectrum illumination with a white reflectance
standard (Ocean Optics, Dunedin, FL, USA).
Images were processed using the Image Calibration and Analysis Toolbox [47] plugin for
ImageJ 1.50i [45]. After using the toolbox to linearise and standardise the image against the
white standard, a patch on each feeder that was approximately the same distance and orienta-
tion as the reflectance standard and free from specular reflections, was selected, and the mean
camera-specific RGB values of the patch were recorded (16-bit colour depth).
To summarise the luminance independent colour measures, RG and BY ratios were calcu-
lated (RG = (R-G)/(R+G); BY = B–((R+G)/2)/ B+((R+G)/2); Fig 1A). These ratios describe
the redness versus greenness (RG), and blueness versus yellowness (BY) of a stimulus and
Table 1. Summary of data, showing the total number of visits by each species at each site, and the number of sample periods in which that species
was observed at least once.
Species Thwaite Gardens Tophill Low Otley Total Sample periods
Blue tit Cyanistes caeruleus 810 1824 629 3263 108
Great tit Parus major 833 1564 13 2410 38
House sparrow Passer domesticus --701 701 58
Coal tit Periparus ater 311 116 109 536 48
Robin Erithacus rubecula 171 12 105 288 75
Starling Sturnus vulgaris - - 172 172 13
Greenfinch Chloris chloris - 1 135 136 21
Marsh tit Poecile palustris - 16 - 16 3
Long tailed tit Aegithalos caudatus 2 3 - 5 2
Bullfinch Pyrrhula pyrrhula 5 - - 5 3
Goldfinch Carduelis carduelis - 3 - 3 1
Total 2132 3539 1864 7535 370
Colour preferences of UK garden birds at supplementary seed feeders
PLOS ONE | DOI:10.1371/journal.pone.0172422 February 17, 2017 4 / 14
approximate human and potential avian opponent colour channels [48]. Additionally, lumi-
nance ((R+G+B)/3) is shown in Fig 1B. As the camera was not UV sensitive and had not been
characterised (i.e. the spectral sensitivity of each sensor measured), it was not possible to mea-
sure reflectance in the UV range or transform the RGB values into avian colour space [47].
Ethical statement
Experiments were approved by the University of Hull’s School of Biological, Biomedical and
Environmental Sciences and Faculty of Science and Engineering ethical review committees
before commencement. All avian work was observational, and carried out at locations where
supplementary feeding of birds already occurred and would continue after data collection was
completed. Permission to carry out fieldwork was granted by the University of Hull (Thwaite
Gardens), Richard Hampshire (Tophill Low Reserve Warden) and Mark Rothery (Otley site
owner). The field studies did not involve endangered or protected species. All participation in
the human colour preference was entirely voluntary and the purpose of the experiment was
explained to the participants either verbally or via an A4 poster displayed near the stand (S2
Fig). Written consent was not obtained to ensure participation was simple and to maximise
the number of participants, and approved by the institutional review boards above. No data on
the participants (other than their choice of colour) was collected.
Bird colour preference
There was a significant effect of feeder colour on the number of visits to the feeders (F
7, 875
6.120, p <0.001; Fig 2A). Birds made significantly more visits to the silver feeder and signifi-
cantly fewer visits to the red and yellow feeders than any other colour (all p<0.05; Table 2).
Green was visited significantly more often than any other colour except silver, but there was
no difference in the number of visits to blue, purple, white and black.
For blue tits (Fig 2B,S1 Table), there was a significant effect of colour on number of visits
7, 749.73
= 4.3575, P <0.001). Yellow and red were the least visited colours, and were visited
with similar regularity (S1 Table, p >0.05). Yellow was visited significantly less than all other
Fig 1. Analysis of feeder colour. (A) RG and BY ratios, and (B) luminance for the 8 different feeder colours.
Colour preferences of UK garden birds at supplementary seed feeders
PLOS ONE | DOI:10.1371/journal.pone.0172422 February 17, 2017 5 / 14
Fig 2. Bird colour preferences. Mean numbers of visits per observation period to feeders of each colour, for (A) all species combined, (B) Blue tit
Cyanistes caeruleus (C) Great tit Parus major (D) Coal tit Periparus ater (E) House sparrow Passer domesticus and (F) Robin Erithacus rubecula.
Error bars represent +/- 1 S.E.
Colour preferences of UK garden birds at supplementary seed feeders
PLOS ONE | DOI:10.1371/journal.pone.0172422 February 17, 2017 6 / 14
colours except white (p >0.050), while visits to red were not different from white or green
(p >0.05). There were no differences in the number of visits between the other colours
(p >0.05; S1 Table).
For great tits (Fig 2C,S2 Table), there was a significant effect of colour on number of visits
= 2.671, p = 0.011). There were significantly fewer visits to yellow than to all other col-
ours except red (p <0.05 in all cases), while red was visited significantly less often than green
(p = 0.017). There were no other significant pairwise differences (S2 Table).
Table 2. Pairwise comparisons of visits to feeders.
Red Yellow Green Blue Purple White Silver Black
Red - z = -2.042 z = -10.765 z = -7.383 z = -7.129 z = 5.793 z = 12.751 z = -7.614
p = 0.052 p<0.001 p <0.001 p <0.001 p <0.001 p <0.001 p <0.001
Yellow -0.114±0.056 - z = -12.650 z = -9.440 z = -9.093 z = -7.779 z = -14.586 z = -9.569
p<0.001 p <0.001 p <0.001 p <0.001 p <0.001 p <0.001
Green -0.519±0.048 -0.633±0.050 - z = 3.413 z = -3.774 z = -5.128 z = 2.115 z = 3.278
p = 0.001 p <0.001 p <0.001 p = 0.046 p = 0.001
Blue -0.372±0.050 -0.485±0.051 0.148±0.043 - z = -0.363 z = -1.728 z = 5.512 z = -0.135
p = 0.743 p = 0.098 p<0.001 p = 0. 892
Purple -0.355±0.050 -0.469±0.052 -0.164±0.043 -0.016±0.045 - z = -1.365 z = 5.870 z = -0.499
p = 0.193 p<0.001 p = 0.666
White 0.292±0.050 -0.406±0.052 -0.277±0.044 -0.079±0.046 -0.063±0.046 - z = -7.212 z = -1.863
p<0.001 p = 0.076
Silver 0.606±0.047 -0.719±0.049 0.086±0.041 0.234±0.042 0.250±0.043 -0.313±0.043 - z = 5.378
Black -0.378±0.005 -0.491±0.051 0.142±0.043 -0.006±0.045 -0.022±0.045 -0.085±0.046 0.228±0.042 -
The cells above the diagonal show the z- and p-values, while the estimate ±standard error is below the diagonal. Significant p-values are highlighted in
Fig 3. Human colour preferences. (A) Mean number of tokens placed into the container corresponding to each coloured feeder by potential
purchasers of bird feeders. (B) The combined preferences of potential purchasers (x axis) and visits by all birds (y axis) for each colour feeder. Error
bars represent +/- 1 S.E.
Colour preferences of UK garden birds at supplementary seed feeders
PLOS ONE | DOI:10.1371/journal.pone.0172422 February 17, 2017 7 / 14
For coal tits, there was a significant overall effect of colour on visits (F
= 3.796, p <0.001),
but no significant pairwise comparisons were found after correction for multiple testing (Fig 2D;
S3 Table).
For house sparrows, there was a significant effect of colour on visits (F
= 11.139,
P<0.001). The yellow feeder was visited significantly less often than all other colours (Fig 2E,
S4 Table, p <0.05 in all cases), and red was visited less often than blue, green, silver and black
(p <0.05). White and purple were visited less often than blue, green and black (p <0.05)
which were the colours visited most (although not significantly more than silver; S4 Table)
For robins, there was a significant effect of colour on visits (F
7, 518
= 3.1033, p = 0.003; Fig 2F).
Black, the most visited colour, was visited significantly more often than purple and white (p <0.05,
S5 Table), the least visited colours, but no other pairwise comparisons were significant.
There was no significant effect of colour on visits for greenfinch (F
= 1.3.383, p = 0.217)
or starling (F
= 1.232, P = 0.294), and no other species was recorded more than 100 times
during the sample period, so their preferences have not been analysed.
Human colour preference
There was a significant effect of colour on the preferences observed in our survey (F
= 10.485,
P = <0.001; Fig 3A). Pairwise comparisons revealed that red, yellow, green and blue were pre-
ferred over purple, white, silver and black (Table 3). Fig 3B shows the mean number of visits by
birds plotted against the mean number of votes from visitors, and suggests that human and bird
preferences do not necessarily align. Colours in the top right of Fig 3B are those that received
high visit rates from birds and high numbers of votes from visitors, and we suggest those colours
(green and to a lesser extent, blue) may be simultaneously marketable and well-visited by birds.
While red and yellow received high numbers of votes from visitors, these are the colours that
received the lowest numbers of visits from birds.
Overall, birds preferentially visited the silver feeders, followed by green, and made fewer visits
to the red and yellow feeders when all feeders were displayed simultaneously. These patterns
Table 3. Pairwise comparisons of votes by visitors to the garden centre and science festival.
Red Yellow Green Blue Purple White Silver Black
Red - z = -0.474 z = 0.620 z = -0.182 z = 3.285 z = -4.014 z = -4.234 z = 3.759
p = 0.810 p = 0.715 p = 0.887 p = 0.003 p <0.001 p <0.001 p = 0.001
Yellow -0.722±1.522 - z = 0.146 z = -0.657 z = 2.810 z = 3.540 z = 3.759 z = 3.285
p = 0.884 p = 0.718 p = 0.011 p = 0.002 p = 0.001 p = 0.003
Green 0.944±1.522 0.222±1.522 - z = -0.803 z = -2.664 z = -3.394 z = -3.613 z = 3.139
p = 0.659 p = 0.015 p = 0.002 p = 0.001 p = 0.004
Blue -0.278±1.522 -1.000±1.522 -1.222±1.522 - z = -3.467 z = -4.197 z = -4.416 z = 3.942
p = 0.002 p <0.001 p <0.001 p <0.001
Purple 5.000±1.522 4.278±1.522 -4.056±1.522 -5.278±1.522 - z = -0.730 z = -0.949 z = 0.474
p = 0.688 p = 0.568 p = 0.810
White -6.111±1.522 5.389±1.522 -5.167±1.522 -6.389±1.522 -1.111±1.522 - z = 0.219 z = -0.255
p = 0.891 p = 0.895
Silver -6.444±1.522 5.722±1.522 -5.500±1.522 -6.722±1.522 1.444±1.522 0.333±1.522 - z = -0.474
p = 0.810
Black 5.722±1.522 5.000±1.522 4.778±1.522 6.000±1.522 0.722±1.522 -0.389±1.522 -0.722±1.522 -
The cells above the diagonal show the t- and p-values, while the estimate ±standard error is below the diagonal. Significant p-values are highlighted in bold.
Colour preferences of UK garden birds at supplementary seed feeders
PLOS ONE | DOI:10.1371/journal.pone.0172422 February 17, 2017 8 / 14
are likely driven by the preferences of the most abundant species at the feeders (blue tits and
great tits), which showed similar preferences to the overall patterns. These patterns contrast
with the preferences expressed by the potential purchasers of feeders, who preferred red, yel-
low, green and blue, but rarely voted for silver. In terms of feeder design, this suggests that
green (and to a lesser extent, blue) may be simultaneously marketable and well visited by birds.
Our findings also suggest that different species of birds may have different colour preferences,
although the total number of visits by some species was too low to evaluate this.
Silver and green feeders may be preferred over red and yellow for a variety of reasons. Green
and silver are common colours for birdfeeders, and familiarity with particular colours may have
played a role in determining preferences. Urban birds show lower neophobia in the presence of
a novel object at supplementary feeding stations relative to rural birds [21] suggesting that famil-
iarity with feeder colour may not be essential in attracting birds to urban gardens. In humming-
birds, previous experience of particular colours plays a role in colour choice. Anna’s (Calypte
anna) and rufous (Salasphorus rufus) hummingbirds preferentially choose red feeders if captured
from red-flowered Ribes speciousm plants, but prefer yellow if captured near yellow-flowered
Nicostiana glauca [41]. Hummingbirds can also be trained to prefer particular colours when that
colour is associated with higher quality rewards [34,38,42]. As the seed quality in our feeders was
identical, the preferences exhibited by the birds could have been due to our choice of locations
where birds were regularly fed, and thus familiar with commonly coloured feeders.
In contrast, red and yellow are uncommon colours for seed dispensing bird feeders. Neopho-
bia in relation to food colour has been well documented in both birds (e.g. [4953]) and other
species [54,55]. Red and yellow are also associated with warning colouration and aposematism,
and may be avoided by foraging birds [56,57]. Red and yellow feeders may also be more con-
spicuous against the background (while green and silver are more cryptic), which may increase
perceived predation risk [58]. However, these colours may also make the resource more con-
spicuous from a distance [59] and thus brightly coloured feeders may be effective in attracting
birds to new foraging sites more rapidly: some evidence from Anna’s hummingbirds suggests
that red feeders placed in novel locations initially attract more birds than other colours [39], but
red is a common colour of the nectar resource for this species, and so may not be applicable to
seed-feeding birds. Our experiment does not allow us to speculate on whether particular colours
would be more or less attractive to birds if put out alone.
The colours we presented to the birds were based on the availability of coloured metal
paints and human vision, rather than avian colour space [47]. In contrast to humans, birds are
tetrachromatic and able to see in UV [25], and thus would have perceived the feeders differ-
ently to humans. To fully understand feeder choice from an avian perspective, colours should
be interpreted and manipulated in avian, rather than human, colour space [2325] However,
feeder colour choice is ultimately driven by the purchasers of feeders rather than the birds
themselves, and thus human perception of the colours is an important consideration.
During data collection, we observed (but did not record) multiple events where a competitor
displaced feeding individuals from one feeder to another. This may mask feeding preferences as
individuals are then recorded at less preferred feeder colours, a limitation of presenting all col-
ours together. The ways in which different options are presented often affects the choices that
animals make. Hummingbirds offered a choice between red and yellow-flowered Mimulus aur-
antiacus prefer to feed at the red morph [60], but in a hybrid population where orange morphs
occur, visit orange flowers more often than expected by chance, given their prevalence in the
population [31]. Preferences between two option may also be affected by the addition of a third
option (e.g. if A is preferred over B, and B over C, then A is not necessarily preferred over C),
violating the principle that choices are ‘rational’ and preferences are transitive [61,62]. Evidence
suggests that the principle of rational choice is violated by a range of species, including humans
Colour preferences of UK garden birds at supplementary seed feeders
PLOS ONE | DOI:10.1371/journal.pone.0172422 February 17, 2017 9 / 14
(e.g. [6365]), honeybees (Apis mellifera [66]), rufous hummingbirds [61,67], starlings [68] and
grey jays (Perisoreus canadensis [66]). By presenting all colours together (and covering a wide
range of colour options) we were able to overcome some of these issues associated with animal
Further work is needed to explore interspecific differences in colour preference: for the bird
feeder industry, it may be desirable to design and market feeders for particular target species or
groups of species—those that are seen as desirable by the people that feed birds. Further questions
include whether feeder colour is important for attracting birds to a new feeding site, increasing
avian visitor numbers at existing feeding sites, and whether different types of feeders, such as
those designed to dispense seeds, peanuts or nyjer seeds, would attract more birds if they were
different colours. Finally, other factors, such as distance to cover, or the type and quality of food
provided [69] may be more important in determining the ‘success’ of a particular feeder than the
colour, as in hummingbirds (e.g. [3842]) or these factors, and others, may trade off with colour
in determining the number of visits by birds, as they forage optimally [70].
Supporting information
S1 Fig. Birdfeeders in the field. An example array of filled birdfeeders ready for observations
in the field. The colour order (from left to right) is: red, yellow, blue, silver, green, purple,
white, black. Colour order was randomised between trials.
S2 Fig. Poster explaining the project. A copy of the poster explaining the project, as displayed
at the Science Festival and in the garden centre.
S1 Table. Pairwise comparisons of visits to feeders by blue tits. The cells above the diagonal
show the z- and p-values, while the estimate ±standard error is below the diagonal. Significant
p-values are highlighted in bold.
S2 Table. Pairwise comparisons of visits to feeders by great tits. The cells above the diagonal
show the z- and p-values, while the estimate ±standard error is below the diagonal. Significant
p-values are highlighted in bold.
S3 Table. Pairwise comparisons of visits to feeders by coal tits. The cells above the diagonal
show the z- and p-values, while the estimate ±standard error is below the diagonal. Significant
p-values are highlighted in bold.
S4 Table. Pairwise comparisons of visits to feeders by house sparrows. The cells above the
diagonal show the z- and p-values, while the estimate ±standard error is below the diagonal.
Significant p-values are highlighted in bold.
S5 Table. Pairwise comparisons of visits to feeders by robins. The cells above the diagonal
show the z- and p-values, while the estimate ±standard error is below the diagonal. Significant
p-values are highlighted in bold.
S1 Data. Avian preference data.
Colour preferences of UK garden birds at supplementary seed feeders
PLOS ONE | DOI:10.1371/journal.pone.0172422 February 17, 2017 10 / 14
S2 Data. Human preference data.
We thank Rose Bull and Adam Lea for assistance with data collection, William Allen for assis-
tance with the feeder colour analysis, Martin McDaid and Lorron Bright for useful discussions,
and Hornsea Garden Centre for allowing us to collect data on human choices. Adrian Dyer,
Piotr Tryjanowski, Roland Ennos, Sue Hull, Katherine Jones and an anonymous referee pro-
vided useful feedback on earlier versions of this manuscript.
Author Contributions
Conceptualization: LJM GWS.
Data curation: LJM LR.
Formal analysis: LJM LR.
Funding acquisition: LJM GWS.
Investigation: LR.
Methodology: LJM GWS LR.
Project administration: LJM GWS.
Supervision: LJM GWS.
Visualization: LJM.
Writing – original draft: LR LJM GWS.
Writing – review & editing: LJM GWS LR.
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... To summarize the luminance independent (chromatic) color measures, the RG and BY ratios were calculated from camera-specific RGB component values (Table A2 in Appendix), as follows: RG = (R − G)/ (R + G); BY = (B − (R + G)/2)/(B + (R + G)/2) (Rothery, Scott, & Morrell, 2017). These ratios describe the redness versus greenness (RG) and blueness versus yellowness (BY) of each color. ...
... These ratios describe the redness versus greenness (RG) and blueness versus yellowness (BY) of each color. We also calculated the luminance (achromatic measure) of each color as (R + G + B)/3 (Rothery et al., 2017) and expressed it as a percentage of the maximum component value, i.e., of 255 ( Figure 4). We expected multiple predator species to attack our models; consequently, we did not attempt to transform the RGB values into an avian or other animal color space. ...
... Yellow coloration, along with other long-wavelength colors, is an effective warning signal, in particular because yellow is highly conspicuous when viewed against green foliage across a variety of habitats (Stevens & Ruxton, 2012). Birds are usually not attracted by yellow fruits (Sinnott-Armstrong et al., 2018) and avoid yellow bird feeders (Rothery et al., 2017). Interestingly, we found that yellow models were also attacked at low rates by arthropod predators in all climatic zones, indicating that yellow coloration provides effective and universal protection for prey against diverse predators in forests across a large latitudinal gradient. ...
Full-text available
The strength of biotic interactions is generally thought to increase toward the equator, but support for this hypothesis is contradictory. We explored whether predator attacks on artificial prey of eight different colors vary among climates and whether this variation affects the detection of latitudinal patterns in predation. Bird attack rates negatively correlated with model luminance in cold and temperate environments, but not in tropical environments. Bird predation on black and on white (extremes in luminance) models demonstrated different latitudinal patterns, presumably due to differences in prey conspicuousness between habitats with different light regimes. When attacks on models of all colors were combined, arthropod predation decreased, whereas bird predation increased with increasing latitude. We conclude that selection for prey coloration may vary geographically and according to predator identity, and that the importance of different predators may show contrasting patterns, thus weakening the overall latitudinal trend in top-down control of herbivorous insects.
... A possible explanation for the distribution patterns of L. perturbatum and L. paradoxum is that principal avian hosts differ in each parasite. Color preferences in selecting foods are observed in birds [58]. It can be, therefore, hypothesized that the brown or green coloration of broodsacs is selectively attractive to particular birds. ...
Insectivorous birds serve as definitive hosts for trematodes of the genus Leucochloridium. The parasites exclusively use amber snails of the family Succineidae as intermediate hosts. A pulsating and colorful display of the larval broodsac in the snail's eyestalk seems to be a caterpillar mimic for attracting birds. A colored design of the broodsac is very useful for parasite identification. In Japan, characteristic broodsacs from amber snails have been recorded from 1980's, but their taxonomic discrimination from Asian, European, and North American species has not been achieved. In this study, old scientific records, sighting information on broodsacs from the general public, and direct molecular evidence by DNA barcoding clearly showed that at least three species of Leucochloridium are distributed in Japan. A vertical-striped broodsac found from Succinea sp. in Okinawa, the subtropical island of Japan, were treated as Leucochloridium sp., but being almost identical to that of Leucochloridium passeri in neighboring Taiwan. The European species of Leucochloridium perturbatum and Leucochloridium paradoxum were frequently detected from Succinea lauta in Hokkaido, the northernmost island of Japan. The former species was common in inland areas of Hokkaido, whereas the latter species was frequently seen in the coastal areas. A possible explanation for the parasite distribution pattern is that principal definitive hosts (migratory or resident birds) differ in each parasite. The conspecificity of Leucochloridium variae in North America and L. perturbatum in Europe and the Far East is also discussed.
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Birds can adapt to urban areas by modifying their foraging behaviours to exploit novel urban food sources, which are far more diverse than in the country. Neophobia, the fear of novelty, can lead to missed new sources of food. Urban populations of birds usually display a lesser level of neophobia than rural populations. We examined the response of birds in urban and rural habitats to the presence of new feeders. One feeder was green (the colour of preference, according to the literature), the other one was yellow (the colour avoided); feeders of these colours are not normally used in the study area, where the colour of bird feeders is usually the natural colour of wood. We hypothesised that the yellow feeder was more likely to be avoided by rural than urban birds because of the greater neophobia exhibited by the former. During the wintering season, we carried out 22 experiments in towns and 21 in villages in east-central Poland. The interaction between habitat and feeder colour was close to zero (number of visits to a feeder, choice of first feeder). However, we did find a smaller number of visits to yellow feeders and more frequent visits to feeders in urban areas. Birds may have treated the yellow colour as aposematic, hence their avoidance of yellow feeders, whereas more visits were made to feeders in urban areas because fewer natural food resources are available there than in rural habitats.
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Researchers demonstrated an elegant ability for red discrimination in zebra finches. It is interested to understand whether red activates exhibit much stronger response than other colors in neural network levels. To reveal the question, local field potentials (LFPs) was recorded and analyzed in two visual pathways, the thalamofugal and the tectofugal pathways, of zebra finches. Human studies demonstrate visual associated telencephalons communicate with higher order brain areas such as prefrontal cortex. The present study determined whether a comparable transmission occurs in zebra finches. Telencephalic regions of the thalamofugal (the visual Wulst) and the tectofugal pathway (the entopallium) with their higher order telencephalon, nidopallium caudolateral (NCL) were simultaneously recorded. LFPs of relay nuclei (the nucleus rotundus, ROT) of tectofugal pathway were also acquired. We demonstrated that LFP powers in the tectofugal pathway were higher than those in the thalamofugal pathway when illuminating blue lights. In addition, the LFP synchronization was stronger between the entopallium and NCL. LFPs also revealed a higher Granger causality from the direction of entopallium to NCL and from ROT to entopallium. These results suggest that zebra finches’ tectofugal pathway predominately processing color information from ROT to NCL, relayed by entopallium, and blue could trigger the strongest response.
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Quantitative measurements of colour, pattern and morphology are vital to a growing range of disciplines. Digital cameras are readily available and already widely used for making these measurements, having numerous advantages over other techniques, such as spectrometry. However, off‐the‐shelf consumer cameras are designed to produce images for human viewing, meaning that their uncalibrated photographs cannot be used for making reliable, quantitative measurements. Many studies still fail to appreciate this, and of those scientists who are aware of such issues, many are hindered by a lack of usable tools for making objective measurements from photographs. We have developed an image processing toolbox that generates images that are linear with respect to radiance from the RAW files of numerous camera brands and can combine image channels from multispectral cameras, including additional ultraviolet photographs. Images are then normalised using one or more grey standards to control for lighting conditions. This enables objective measures of reflectance and colour using a wide range of consumer cameras. Furthermore, if the camera's spectral sensitivities are known, the software can convert images to correspond to the visual system (cone‐catch values) of a wide range of animals, enabling human and non‐human visual systems to be modelled. The toolbox also provides image analysis tools that can extract luminance (lightness), colour and pattern information. Furthermore, all processing is performed on 32‐bit floating point images rather than commonly used 8‐bit images. This increases precision and reduces the likelihood of data loss through rounding error or saturation of pixels, while also facilitating the measurement of objects with shiny or fluorescent properties. All cameras tested using this software were found to demonstrate a linear response within each image and across a range of exposure times. Cone‐catch mapping functions were highly robust, converting images to several animal visual systems and yielding data that agreed closely with spectrometer‐based estimates. Our imaging toolbox is freely available as an addition to the open source ImageJ software. We believe that it will considerably enhance the appropriate use of digital cameras across multiple areas of biology, in particular researchers aiming to quantify animal and plant visual signals.
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The world in color presents a dazzling dimension of phenotypic variation. Biological interest in this variation has burgeoned, due to both increased means for quantifying spectral information and heightened appreciation for how animals view the world differently than humans. Effective study of color traits is challenged by how to best quantify visual perception in nonhuman species. This requires consideration of at least visual physiology but ultimately also the neural processes underlying perception. Our knowledge of color perception is founded largely on the principles gained from human psychophysics that have proven generalizable based on comparative studies in select animal models. Appreciation of these principles, their empirical foundation, and the reasonable limits to their applicability is crucial to reaching informed conclusions in color research. In this article, we seek a common intellectual basis for the study of color in nature. We first discuss the key perceptual principles, namely, retinal photoreception, sensory channels, opponent processing, color constancy, and receptor noise. We then draw on this basis to inform an analytical framework driven by the research question in relation to identifiable viewers and visual tasks of interest. Consideration of the limits to perceptual inference guides two primary decisions: first, whether a sensory-based approach is necessary and justified and, second, whether the visual task refers to perceptual distance or discriminability. We outline informed approaches in each situation and discuss key challenges for future progress, focusing particularly on how animals perceive color. Given that animal behavior serves as both the basic unit of psychophysics and the ultimate driver of color ecology/evolution, behavioral data are critical to reconciling knowledge across the schools of color research.
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Bird feeding is one of the most widespread direct interactions between man and nature, and this has important social and environmental consequences. However, this activity can differ between rural and urban habitats, due to inter alia habitat structure, human behaviour and the composition of wintering bird communities. We counted birds in 156 squares (0.25 km2 each) in December 2012 and again in January 2013 in locations in and around 26 towns and cities across Poland (in each urban area, we surveyed 3 squares and also 3 squares in nearby rural areas). At each count, we noted the number of bird feeders, the number of bird feeders with food, the type of feeders, additional food supplies potentially available for birds (bread offered by people, bins) and finally the birds themselves. In winter, urban and rural areas differ in the availability of food offered intentionally and unintentionally to birds by humans. Both types of food availability are higher in urban areas. Our findings suggest that different types of bird feeder support only those species specialized for that particular food type and this relationship is similar in urban and rural areas. Electronic supplementary material The online version of this article (doi:10.1007/s11356-015-4723-0) contains supplementary material, which is available to authorized users.
Consumer choice is often influenced by the context, defined by the set of alternatives under consideration. Two hypotheses about the effect of context on choice are proposed. The first hypothesis, tradeoff contrast, states that the tendency to prefer an alternative is enhanced or hindered depending on whether the tradeoffs within the set under consideration are favorable or unfavorable to that option. The second hypothesis, extremeness aversion, states that the attractiveness of an option is enhanced if it is an intermediate option in the choice set and is diminished if it is an extreme option. These hypotheses can explain previous findings (e.g., attraction and compromise effects) and predict some new effects, demonstrated in a series of studies with consumer products as choice alternatives. Theoretical and practical implications of the findings are discussed.