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‘The thieving magpie’? No evidence for attraction to shiny objects
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T.V. Shephard, S.E.G. Lea, N. Hempel de Ibarra
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Centre for Research in Animal Behaviour, University of Exeter, Perry Road, Exeter, EX4 4QG,
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UK
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Corresponding Author:
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Dr Toni Vernelli Shephard
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T.Shephard@exeter.ac.uk
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Abstract
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It is widely accepted in European culture that magpies (Pica pica) are unconditionally attracted
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to shiny objects and routinely steal small trinkets such as jewellery, almost as a compulsion.
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Despite the long history of this folklore, published accounts of magpies collecting shiny objects
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are rare and empirical evidence for the behaviour is lacking. The latter is surprising considering
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that an attraction to bright objects is well documented in some bird species. The present study
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aims to clarify whether magpies show greater attraction to shiny objects than non-shiny objects
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when presented at the same time. We did not find evidence of an unconditional attraction to
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shiny objects in either captive or free-living birds. Instead, all objects elicited responses
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indicating neophobia in free-living birds. We suggest that humans notice when magpies
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occasionally pick up shiny objects because they believe the birds find them attractive, while it
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goes unnoticed when magpies interact with less eye-catching items. The folklore may therefore
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result from observation bias and cultural inflation of orally-transmitted episodic events.
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Introduction
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It is widely believed across Europe that magpies (Pica pica) are unconditionally attracted to, and
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collect, shiny objects. A Google search on the term 'magpie shiny object' produced 60,100 results
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in 0.28 seconds (February, 2014). Most of these are descriptions of magpies that make reference
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to their 'weakness for shiny things' (Winterman, 2008) or reputation for 'stealing jewellery'
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(BBC, 2003). Although such assertions are usually stated as fact, no references or examples are
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given. The belief is so ingrained in our culture that one definition given for ‘magpie’ in the
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Collins English Dictionary is 'a person who hoards small objects' (Collins, 2013). Perhaps the
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most famous example of this folklore penetrating popular culture is Rossini's opera 'The thieving
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magpie', first performed in 1817, where a servant girl is executed for a series of silver thefts
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which were actually committed by a magpie. Despite the folklore’s long history and widespread
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acceptance, published accounts of magpies stealing or collecting shiny objects are rare and
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empirical research on the subject is lacking.
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An extensive internet search uncovered just two published accounts of magpies stealing shiny
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things: a missing engagement ring that was discovered in a magpie nest (Telegraph, 2008) and a
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magpie in Rochdale stealing keys, coins and a spanner (a shiny tool) from an automotive garage
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(Manchester Evening News, 2007). Without empirical research, it is not known whether these
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birds had an unconditional attraction to shiny objects, or if the folklore has caused observation
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bias in the human population. In other words, we notice when magpies collect shiny objects
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because we 'know' they are attracted to shiny objects but we do not notice when they interact
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with less eye-catching items. A non-specific attraction to objects was demonstrated by Heinrich
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(1995) with four hand-raised juvenile ravens, birds who are also reputedly attracted to shiny
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objects. The young birds contacted novel items placed in their familiar aviary significantly more
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than familiar items; however, their attraction depended solely on the novelty of the item "without
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relevance to its palatability or shininess."
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Research investigating cognitive abilities and object interaction in magpies is scarce. However,
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attraction to shiny or bright objects has been documented in several other bird species, with
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many using them as non-body ornaments, to attract mates or influence parental investment
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(outlined in Schaedelin and Taborsky 2009). Black kites (Milvus migrans) place them in the nest
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to act as threats to conspecifics, revealing the viability and conflict dominance of the signaller
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(Sergio et al. 2011). Some corvid species are known to collect and cache non-food objects and
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this may be an expression of exploration, although this behaviour does not appear to be colour
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specific (Jacobs et al. 2014). We performed experiments with captive wild-born magpies and
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free-living magpies (during breeding and non-breeding periods) to test for an unconditional
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attraction to shiny objects or any sign of collection of non-food objects, and to investigate
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possible explanations for such behaviour. In the absence of such an attraction, a neophobic
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response to objects might be expected; accordingly we recorded behaviour that could indicate
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either neophobia or ambivalence towards the objects. Neophobia was measured as a reduction in
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the rate of feeding in the presence of the test objects. Five behaviours, approach/withdrawals
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(see Greenberg and Mettke-Hoffman, 2001), walk-bys, fly-overs, jumping jacks (see Heinrich,
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1988) and neck extensions, were classified as ambivalent behaviour, and ambivalence scores
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were calculated as the sum of the numbers of all these behaviours exhibited in a session. Full
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operational definitions of these behaviours are given in Table S1.
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Methods
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Captive Study
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Eight magpies were obtained from three wildlife rescue centres in the UK. All birds were
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deemed to be suitable for release back into the wild at the time of acquisition. They were housed
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in an aviary on the roof of the laboratory. The accommodation provided a shed and a flight cage
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(Fig. S1). There was a large, hinged hatch in the wall of the shed adjacent to the flight cage. A
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large tray filled with soil was situated in the flight cage (outside of the test arena) so the birds
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could cache food or other objects. A second large tray filled with water was provided for
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bathing. The birds were colour banded for individual identification. All birds that arrived in a
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group were housed as a group. They were locked in the shed overnight, and while test materials
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were being set out; during experimental sessions, birds not being tested were also locked in. At
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all other times, all birds had free access to both the shed and the flight cage.
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On arrival at the laboratory, the birds were habituated to feeding from two plastic trays situated
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at the opposite ends of the main aviary (test arena, Figure S1). The shiny-object tests formed part
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of a random sequence of novel object tests that followed habituation; the other tests involved
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presenting birds with familiar shaped trays in novel colours (black, silver and red or blue) and
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novel shaped trays (8cm deeper) in the familiar colour. In all tests, the trays contained
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mealworms. In the shiny objects test, two piles of six zinc-plated steel woodscrews were placed
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in the aviary, each 20cm from a feeding tray. One pile contained silver screws and the other blue
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screws. This test was only performed once with each bird. The screws were 7cm long. Before
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the study began, half of the screws were painted blue with matt aerosol paint. The remaining
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screws were left in their original shiny silver colour.
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All sessions were videotaped with a tripod-mounted video camera situated inside an observation
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hide located approximately 20m from the flight cage. The tests were performed between May
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and August 2010.
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Field Study
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The field experiment was conducted at eight sites on the university campus, where magpies are
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accustomed to regular human activity, allowing observations to be conducted from a close
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proximity (<20m). To prevent pseudoreplication, the sites were separated by a minimum of
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500m, about twice the maximum extent of territories defended by breeding magpies across
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northern Europe (Birkhead 1991, p. 43). Each study site had a resident pair of magpies,
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identified as the same pair in each session by their habituation to the observer and to the feeding
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protocol, as well as their defence of the feeding area when other magpies approached. This
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provided a total of 16 birds in the field study, but, as the two birds at each site could not be
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reliably individually identified they are treated as one unit for analyses of mean feeding latency
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and frequency and the mean ambivalence score.
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The experiment took place in two phases. The first series of tests were performed at six sites
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during the non-breeding season, from August to September 2011. The same tests were then
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repeated at four of the same sites and two new sites throughout the breeding season, February to
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April 2012. The new sites were required as the birds from two summer sites did not re-engage in
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the breeding season.
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The test objects were screws as used in the captive study, small foil rings (3cm diameter) and a
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small rectangular piece of aluminium foil (7cm x 5cm). Half of the screws and rings were
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painted blue with matt aerosol paint, and the rest left in their original shiny silver colour, as was
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the piece of aluminium foil.
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Before the beginning each phase, food was provided in two loose piles on the ground daily at
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each study site for two weeks, and the observer recorded data as in the intended tests. The birds
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were considered to be habituated when all of the food provided was taken in the presence of the
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observer and within 20 minutes of provisioning. Food continued to be provided throughout the
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study, with test objects placed next to the food during test sessions. Once the birds were
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habituated, three control sessions were conducted to determine the birds' feeding motivation and
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whether they had a side preference (right or left side of the feeding area). Two equal portions of
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nuts were placed in loose piles on the ground approximately three metres apart, and at roughly
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equal distance from the observer and from tree cover. Figure S2 illustrates these procedures.
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Shiny object tests were conducted once three successful control sessions had been completed
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(success was defined as the birds appearing within 15 minutes and feeding from the piles). Two
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loose piles of nuts were placed on the ground in the same locations as in the control sessions but
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with the addition of two piles of objects (screws or rings), each placed 30cm from a nut pile. One
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object pile contained four silver objects and the other four blue objects. During the breeding
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season, a further test was conducted with a rectangular piece of aluminium foil placed on the
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ground next to one nut pile and secured with a small hair pin (Fig. S2). In the non-breeding
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phase two object tests were performed at each site, one with screws and one with rings. In the
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breeding phase a minimum of eight tests were performed at each site, with multiple exposures to
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the rings and screws and one test with the foil rectangle. The tests were spaced out to incorporate
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early nest-building, final nest-building and incubation and were performed in a random
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sequence. In both phases, the sequence of tests varied across sites. Control sessions lasted for 30
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minutes or until the food was depleted, whichever came first. All test sessions lasted for 30
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minutes, even if the food was depleted sooner, to give the birds ample time to investigate the
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objects. If no magpies arrived in the first 15 minutes of an experimental session it was
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abandoned and its data were discarded.
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Binoculars (10x magnification) were used to confirm the number of food items taken in each
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visit. All sessions were videotaped with a tripod-mounted video camera situated 15 to 20m from
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the food and positioned to give a panoramic view of the feeding area. The video footage was
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viewed to measure feeding latency and feeding frequency, which were considered to be
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measures of neophobia, and to record ambivalent behaviours. One person coded the sessions
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from the non-breeding phase and another coded those from the breeding phase, and also recoded
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three sessions from the non-breeding phase. Pearson's correlations and comparisons of means
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confirmed consistent coding: the correlations between coders were 1.00, 0.99 and 0.99 for
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feeding latency, feeding frequency and ambivalence scores respectively, P<.05 in all cases, and
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the Means ±se for the two observers were 246s ±202 and 245s ±202 for feeding latency, 7.33
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±1.09 and 8.67 ±1.61 for feeding frequency, and 11 ±5.86 and 12 ±6.49 for ambivalence score.
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Statistical procedures
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Data from the captive test and the foil test were analysed using Wilcoxon Rank Sum tests.
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General Estimating Equations (GEE) were used to analyse the remaining field data to
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accommodate the non-normal distribution and the use of repeated measures (Garson, 2012). The
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most appropriate model type, working correlation matrix structure and subset of predictors were
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chosen based on the Goodness of Fit statistics QIC (quasi-likelihood under independence
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criterion) and QICC (a corrected version that rewards parsimony). Feeding latency data were
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analysed using identity-inverse Gaussian regression whereas feeding frequency and ambivalence
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data were analysed using negative binomial regression. Least Significant Difference tests were
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used to examine pairwise contrasts. Spearman Correlation Coefficients were used to explore
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whether ambivalent behaviour changed with repeated exposure to the objects in the field study.
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GEE analyses on feeding latency, feeding frequency and ambivalence scores were first run with
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the control sessions split into multiple phases, each comprised of the three sessions preceding a
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test. No qualitative differences between the control sessions across the different phases were
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found so their data were combined and treated as one control condition. This resulted in a better
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model fit for each of the analyses. All analyses were carried out using SPSS v20.
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Results
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Captive study
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None of the eight birds made contact with any object, shiny or blue. The presence of the objects
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did not deter them from feeding from the trays next to the objects. Feeding latencies in this test
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were not significantly different to the preceding control session (means ±se: control = 42s ±13,
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screw test = 23s ±19; W = 16, N = 8, P = 0.313). Additionally, there was no significant
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difference in feeding latency between the trays next to silver and blue screws (means ±se: silver
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= 325s ±161, blue = 370s ±223; W = 4, N = 8, P = 0.844). The birds exhibited little ambivalence
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in the presence of the screws, with scores in this test lower than the other novel object tests
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conducted during the study (mean score ±se: shiny object test = 3.13 ±1.34, other tests in captive
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study ranged from 8.88 ±2.70 to 25.88 ±7.97).
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Field study
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Magpies only made contact with a shiny object twice in 64 tests. Both incidents occurred at the
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same site, once in the non-breeding phase and once during early nest-building. One silver ring
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was picked up and immediately discarded in both instances. No other object interactions
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occurred at any site.
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Figure 1 shows that birds in the field appeared to find the test objects aversive, with significant
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differences in feeding latencies and frequencies for the food piles across three conditions
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(control, ring test, screw test; feeding latency: χ2 = 23.52, df = 2, P <0.001; feeding frequency: χ2
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= 12.68, df = 2, P = 0.002). Pairwise contrasts between conditions confirm that magpies fed from
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the piles significantly faster and took significantly more nuts in the control condition than when
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objects were present. In the foil test, magpies showed a preference for the control pile over the
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pile next to the foil rectangle, feeding from the control pile sooner (W = 1, N = 6, P = 0.080;
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Figure 1a) and taking significantly more nuts from it (W = 0, N = 6, P = 0.041; Figure 1b). The
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aversion to feeding from food piles beside objects remains when the non-breeding and breeding
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phases are examined separately (test*season interaction: feeding latency: χ2 = 5.87, df = 2, P =
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0.053; feeding frequency: χ2 = 1.28, df = 2, P = 0.527).
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Figure 1 also shows that screw colour (shiny or blue) did not affect magpies’ reactions to the
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food piles during either phase (breeding and non-breeding). The birds took significantly longer
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to feed from piles beside blue rings in the breeding season (test*colour*season interaction:
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feeding latency: χ2 = 14.16, df = 4, P = 0.007; Figure 1a) but there was no difference in the non-
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breeding phase. Ring colour did not affect feeding frequency in either phase (test*colour*season
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interaction: feeding frequency: χ2 = 5.09, df = 4, P = 0.278, Figure 1b). Colour comparisons were
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not confounded by a positional bias (mean feeding latency ±se: right pile = 350s ±49, left pile =
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298s ±40, χ2 = 1.62, df = 1, P = 0.203; mean feeding frequency ±se: right pile = 4.65 ±0.31, left
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pile = 4.90 ±0.41, χ2 = 2.62, df = 1, P = 0.106).
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Figure 2 shows that the pattern of ambivalent behaviour also implies that the birds were wary of
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the objects. There was a significant difference in ambivalence scores across the four conditions
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(control, ring test, screw test, foil test; χ2 = 27.5, df = 3, P <0.001). Pairwise contrasts between
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conditions reveal the magpies displayed significantly more ambivalence in the ring and screw
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tests than in the control sessions. Ambivalence scores decreased with repeated exposure to the
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objects (N = 6, n = 163, r = -0.187, P = 0.017).
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Discussion
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This study exonerates Rossini’s magpie, finding no evidence to suggest the species is
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unconditionally attracted to shiny objects. The birds either ignored or avoided both shiny and
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blue objects, with little difference observed between breeding and non-breeding seasons. There
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were two interactions with shiny rings at one site, but these occurred after the food was depleted
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rather than when the objects were first presented, suggesting investigations into a potential food
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item rather than unconditional attraction.
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Rather than being attractive to magpies, the objects appeared to induce neophobia in most of the
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birds in the field - demonstrated by increased feeding latency, decreased feeding frequency and
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more ambivalent behaviour when objects were present than during control sessions. The free-
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living birds reacted this way to both shiny and blue objects, as well as to different shaped
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objects. The decline in ambivalence scores with repeated exposure to the objects suggests the
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birds did habituate to their presence over time. This agrees with descriptions of object neophobia
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in other corvid species (Greenberg 2003; Greenberg and Mettke-Hofmann 2001) and we have
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investigated it more fully in other studies (Vernelli, 2013). Birds in captivity did not show any
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object-related avoidance. Similar differences between wild and captive populations have been
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observed in kea (Huber & Gajdon 2006) and spotted hyenas (Benson-Amram, Weldele &
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Holekamp 2013). They may reflect the artificial nature of captive settings where animals are
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confined in close proximity to novel stimuli, whereas wild animals are free to avoid fear-
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provoking objects.
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We suggest the widely-held belief that magpies are unconditionally attracted to shiny objects
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results from cultural generalisation of anecdotal evidence, demonstrating how biases in
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observations of animals may determine the broad public perception of species and their impact
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on the environment.
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Acknowledgements:
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We thank RSPCA, Secret World Wildlife Rescue and Crows are Us for providing rescued
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magpies for the captive study. TVS was funded by the University of Exeter Research
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Studentship. The authors declare that they have no conflict of interest.
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Figure captions
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Figure 1. Feeding behaviour of free-living magpies (6 sites, 202 total trials). Birds (a) fed more
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quickly and (b) took more food items when no objects were present. The two columns in control
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condition represent the left and right food piles. Error bars show the standard error. *P <0.05,
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**P <0.005.
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Figure 2. Ambivalence scores (±se) for field-tested magpies (6 sites, 202 total trials). Birds
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showed more ambivalence when test objects were present. *P = 0.050, **P ≤0.026.
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Figure 1. Feeding behaviour of free-living magpies (6 sites, 202 total trials). Birds (a) fed more
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quickly and (b) took more food items when no objects were present. The two columns in control
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condition represent the left and right food piles. Error bars show the standard error. *P <0.05,
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**P <0.005.
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Figure 2. Ambivalence scores (±se) for field-tested magpies (6 sites, 202 total trials). Birds
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showed more ambivalence when test objects were present. *P = 0.050, **P ≤0.026.
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