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IntroductionUrban areas are expanding rapidly worldwide because
the human population is growing very fast, and many
people are moving to such areas (UNDESA 2014). The
effects of urbanisation have huge consequences for the 1194 Journal of Ornithology (2021)
162:1193–11981 3
life history, demography, communities and biodiversity of
birds through the extinction of some species and changes
in the distributions of others (Gil and Brumm 2013; Sepp
et al. 2018). Birds can adapt to urban areas by modify-
ing their behavioural responses (Sol et al. 2013; Audet
et al. 2016; Marzluff 2017), for example, to predators
or competitors (Beckerman et al. 2007; Hasegawa et al.
2010), and also their foraging tactics (Seress et al. 2011;
Møller et al. 2015). Urban populations of some bird spe-
cies have been found to exhibit less neophobia than rural
populations of the same species, e.g. House Sparrow Pas-
ser domesticus and Common Myna Acridotheres tristis
(Liker and Bókony 2009; Sol et al. 2011). Comprehen-
sive studies in Poland have also shown a lesser degree of
neophobia in assemblages of overwintering birds, such as
Great Tit Parus major, in urban than in rural areas. The
most probable explanation for this is that the urbanisa-
tion of birds involves the differential recruitment to urban
habitats of individuals with lower levels of neophobia and
earlier experiences with different food sources (Tryjanow-
ski et al. 2016). Urban environments are rich in various
sources of food for birds, such as refuse dumps, leftover
pet food, waste human food and bird feeders (Tryjanowski
et al. 2015; Ciach and Fröhlich 2017).
Neophobic behaviour may be influenced by the fea-
tures of an object such as its colour (Gamberale-Stille et al.
2007), and many birds possess a preference for, or aversion
to, food of different colours (Mastrota and Mench 1995).
Many diurnal birds have the most complex (tetrachromatic)
colour vision of all vertebrates and use it in every aspect of
life, e.g. for recognising and discriminating objects (Osorio
and Vorobyev 2008). Preferences for particular food col-
ours have been reported in birds (Hartley et al. 2000; Duan
et al. 2014), but studies relating to the colours of bird feeders
have focussed mainly on the preferences of hummingbirds
Trochilidae. Experimental studies at such feeders have not
shown that hummingbirds consistently prefer one particular
colour over another, although earlier studies did suggest a
preference for red, because this colour was associated with
the red flowers of nectar-rich plant species (Cronk and Ojeda
2008; Handelman and Kohn 2014). It is likely that other fac-
1
, tors, such as location, previous experience and nectar qual-
ity, are more important in governing the choices of these
birds. Apart from these studies of hummingbirds, only Roth-
ery et al. (2017) demonstrated that garden birds in the UK
preferred feeders of particular colours: higher numbers of
several species visited silver and green feeders than red and
yellow ones. Those authors stated that the former colours
could have been preferred because feeders of these colours
are often used in the UK, so the birds are familiar with them.
There may, however, be a wider but unknown reason behind
this preference for the colour green: Brown (2006) stated
that tits preferred green nesting boxes to brown ones, yet
brown is the colour of their natural nesting sites. The colour
preferences of birds are, therefore, not well understood.
The aim of this paper was to examine the colour prefer-
ence of two populations of birds: one that was exposed to
novel items (urban), and the other not exposed to such items
(rural—naïve), the hypothesis being that previous exposure
affects the level of neophobia. We used bird feeders of two
colours—yellow and green—in this investigation because
birds are sensitive to these colours, and because of the
results obtained by Rothery et al. (2017). We hypothesised
that urban birds come into contact with novel, coloured
objects such as bird feeders, garbage and other anthropo-
genic items more often than rural birds. Hence, we predicted
that urban birds, potentially less neophobic, would feed more
often at yellow feeders than their rural counterparts. For the
same reason, birds in an urban habitat would not display
a preference for any particular colour when approaching a
feeder for the first time. We conducted the experiments in
towns and villages in east-central Poland.
Methods
Data collection
Data were collected during December–February in the
winters of 2018/2019 and 2019/2020 in 5 towns (urban)
and 12 villages (rural) in east-central Poland. The popula-
tions of the towns (Siedlce, Węgrów, Sokołów Podlaski,
Łuków, and Siemiatycze) ranged from 12 600 to 78 000
(mean = 31 000), whereas the villages had from 136 to 550
(mean = 232) inhabitants (https:// bip. gov. pl). Across the
years, a total of 43 experimental trials, each in a different
place (21 and 22 in rural and urban areas, respectively), were
carried out in good weather, i.e. no snow or rain, or strong
wind. The experimental sites were set up in places where
small passerines, especially tits, were frequently observed,
but no closer than 50 m from existing feeders. These sites
were chosen during a slow drive around the study area. The
minimum distance between two adjacent experimental sites
was 1 km. Two feeders of the same type were used in the
experiment: they were shaped like a small house with a roof
and were mounted on a 120 cm-tall tripod. The two dif-
2
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