the study was conducted in a wintering population of tits in wytham woods , u.k .
1 ) . 1018 nest - boxes suitable for great tits are installed at this site , with the vast majority of great tits breeding in boxes .
individuals are trapped as nestlings and breeding adults at nest - boxes and fitted with both a british trust for ornithology metal leg ring and a plastic leg ring containing a uniquely identifiable passive integrated transponder ( pit ) tag ( ib technology , aylesbury , u.k . ) .
there is a further mist - netting effort over autumn and winter to tag individuals immigrating into the population , and we estimate that over 90% of individuals were pit - tagged at the time of the study . in this population ,
great tits form loose fission - fusion flocks of unrelated individuals in autumn and winter .
flocks congregate at patchy food sources , and can be observed at bird feeders fitted with pit - tag detecting antennae .
experiments were conducted in eight sub - populations within wytham woods that had relatively little short - term between - area movement of individuals ( extended data fig .
the experimental apparatus consisted of an opaque plastic box with a perch positioned in front of a door that could be slid to either side with the bill to gain access to a feeder concealed behind .
the left side of the door was colored blue and the right side red , with a raised front section on the door to allow an easier grip .
the concealed feeder contained approximately 500 live mealworms and was refilled up to twice daily .
5 ) , and as live mealworms were used , solvers typically extracted one worm and then carried it away from the puzzle - box to kill and eat it ( confirmed with video observations ) ; supplementary video 1 - 2 .
each puzzle - box was surrounded by a 11 m cage with a 55 cm mesh that gave unlimited access to small birds , but prevented access by large non - target species such as corvids or squirrels . a freely accessible bird feeder filled with peanut granules
was also provided in the cage , at approximately 1 m from the puzzle - box .
peanut granules are a much less preferred food source ( extended data fig . 5 ) .
each peanut feeder had two access points fitted with rfid antenna and data - logging hardware .
this feeder was used to attract the original demonstrator to the location , and to record the identity of individuals that did not contact the puzzle - box .
all puzzle - boxes contained a printed circuit board ( pcb ) and motor , and were powered by a 12v sealed battery .
the perch also functioned as an rfid antenna that registered the visit duration ( time to nearest second ) and identity of the visiting individual .
solve  was recorded if the door was opened during an individual visit to the device , with the side direction also noted .
if a solution occurred without an accompanying identified individual , this was recorded as  unidentified solve  .
if further individuals visited before this happened , then a  scrounge  was recorded , as they were assumed to have taken food from the open door ( confirmed from video observations ) .
the door reset immediately after two individuals were registered scrounging , preventing more than two possible scrounging events per solve ( supplementary video 2 ) .
two males were captured from each sub - population ( 11 adults , 5 juveniles ) to act as demonstrators , either by removal from roosting boxes on sunday night , or by mist - netting at a sunflower - seed feeder on monday morning .
they were transferred to individual cages in indoor captive facilities , and over four days each pair of birds was subjected to one of three training regimes using step - wise shaping , either : ( i ) given no training and left in the cage with ab lib food ( control ) ; ( ii ) trained to solve the novel puzzle - box by pushing the blue side of the door to the right ( option b ) ; or ( iii ) trained to solve the novel puzzle - box by pushing the red side of the door to the left ( option a ) . with the exception of  control areas , which were clustered in the south of the woodland to avoid cross - contamination , sub - populations were randomly assigned to a training regime , with both demonstrators from a single sub - population trained on the same technique . during training , the demonstrators were initially exposed to an open puzzle - box baited with mealworms , which was then gradually closed over the course of four days until the subjects were reliably re - opening it .
the birds were released back at the site of capture in each respective sub - population ; puzzle - boxes at which both options were available and equally rewarding were installed at three sites 250 m apart on the following sunday night ( extended data fig .
these puzzle - boxes were run over a four - week period at each site , continuously operating from monday to friday and then removed on saturday and sunday , for a total of 20 days of data collection .
four replicates were conducted in the first year of data collection ( december 2012-february 2013 ; c1 - 2 , t1 , t3 ) . at three of these replicates ( c1 , t1 , t3 ) puzzle - boxes were simultaneously re - installed at the same locations for 5 days of further data collection in december 2013 .
no additional demonstrators were trained , and no individual had contact with the puzzle - box in the 9 months between the two data collection periods .
this second exposure aimed to test the long - term stability of social learning at the sub - population level .
they were run prior to the second year of data - collection for the cultural diffusion experiment in order to exclude the possibility that dispersing individuals from new replicates could be re - introducing the novel behaviour .
an additional four replicates were then conducted from december 2013 - february 2014 in new sub - populations , using the same initial protocol ( c3 , t2 , t4 , t5 ) .
the local population size for each replicate was defined as comprising all individuals in a replicate that had been recorded at least once at either : ( i ) the puzzle - box , ( ii ) the nearby peanut feeder , or ( iii ) the nearest network - logger feeders ( operated saturday - sunday , see below ) , during the experimental period ( i.e. from the weekend following the release of the demonstrators , to the weekend after the 20 day of operation of the puzzle - boxes ) .
persistence trial in the following year , the local population was defined just as ( i ) all individuals observed at the puzzle - box or ( ii ) nearby peanut feeder , so that areas were comparable . to analyse the results of the initial experiment we first compared control replicates and
treatment replicates , using welch two - sided t - tests , and by fitting linear and sigmoidal models to the data , with the best model ascertained by difference in aic values .
if individuals were using social information when learning about the puzzle - box , then we expected that there would be a difference between areas seeded with a trained demonstrator ( treatment ) and those without ( control ) .
replicates were thus compared in terms of latency to first solve ( seconds from beginning of the experimental period , excluding demonstrator ) , and the total number of solutions .
secondly , we compared the total number of solutions in the two different experimental treatments . here
if a more complex form of social learning than local enhancement to the feeding site was occurring , then we expected a consistent bias towards the seeded variant in the different treatments . to analyse the change in individual and population preferences for option a or b over time , we used a generalised estimating equation model ( gee ) where the dependent variable was the proportion of solutions using the seeded technique on each day of data collection , and the explanatory variables were the individuals and replicate , weighted by the overall number of solutions per day . the seeded technique ( a / b ) was initially also included as an explanatory variable , but was not significant ( coefficient  se = 0.130.22 , p = 0.55 ) . three individual variables were included in a gee model ; sex , age and natal origin .
sex was determined at capture using plumage coloration , age was either determined from breeding records or plumage coloration , and individuals were classed as 
immigrants if they had dispersed into the study site , and  locally - born if they had been ringed as a nestling in the study site .
only age was significant ( coefficient  se = 0.920.20 , p < 0.001 ) , and was included in the final model ( sex : coefficient  se = 0.380.22 , p = 0.08 ; natal origin : coefficient  se = 0.380.22 , p = 0.08 ) .
if population - level conformity was partly the result of a conformist transmission bias at first acquisition we would expect a sigmoidal relationship between population - level frequency of the variant and adoption probability , with adoption of the majority variant disproportionately more likely than its absolute frequency .
by contrast , copying the last individual observed , or random copying , should yield a linear relationship , with probability of adopting option a / b roughly equal to its proportion in the overall population . to investigate this , we isolated all individuals first observed solutions in all experimental replicates , and compared the option choice to the proportion of all previous solves as option a observed in the individual s group at that site .
group length was set at 245 sec , which was the average group length observed using gaussian mixture models on temporal patterns of flocking ( see below ) at network - logging sunflower feeders .
both linear and sigmoidal models were then fitted to the data , with the best model ascertained by difference in aic values .
we further examined the subset of individuals that moved between sub - populations ( n=40 ) .
this subset included all individuals recorded in more than one experimental replicate , whether within the season ( n=16 ) , or between seasons ( n=24 ) .
no individual was observed in more than two replicates , and this analysis did not include individuals in the  persistence trial. a preference for option a / b at each location was defined as more than 75% of all solves for either option a / b in that replicate . finally , in order to analyse the change in within - individual bias towards option a / b between the initial experiment and the second - year 
persistence trials , we used a general linear model where the dependent variable was the number of solves as the seeded variant over the total number of solves for each individual observed in both years .
explanatory variables were treatment type and year , with individual identity as a random effect .
sunflower bird - feeding stations were deployed at 65 locations around wytham woods on an approximate 250250 m square grid , as part of long - term research into social - network structure in tits ( see ) .
each station had two access points , each fitted with rfid antennae and data logging hardware .
feeding stations automatically opened from dawn to dusk on saturday and sunday , scanning for pit - tags every 16 of a second .
this study used the data from the eight nearest locations to each set of puzzle - boxes , for 10 dates within and surrounding the cultural diffusion experiment ( the standard logging protocol runs from september - february in wytham woods ) .
great tits were detecting visiting feeding stations and individually identified by their pit - tags .
we then applied a gaussian mixture model to the spatiotemporal data stream to detect distinct clusters of visits .
this method locates high - density periods of feeding activity , isolating flocks of feeding birds without imposing artificial assumptions about group boundaries .
a gambit of the group approach was used with a simple - ratio index to calculate social associations , where individual association strengths ( network edges ) were scaled between 0 ( never observed foraging together in the same group ) to 1 ( always observed in the same group , never observed apart ) . while a single co - occurrence may not be meaningful , our automated data collection method resulted in thousands of repeated group sampling events , allowing social ties between individuals to be built up from multiple observations of co - occurrences over time and across spatial locations .
networks contained 123 ( t1 ) , 137 ( t2 ) , 154 ( t3 ) , 95 ( t4 ) and 110 ( t5 ) nodes ; average edge strength was 0.09 ( t1 ) , 0.05 ( t2 ) , 0.08 ( t3 ) , 0.07 ( t4 ) and 0.07 ( t5 ) . to test whether networks contained significantly preferred and avoided relationships , we ran permutation tests on the grouping data , controlling for group size and the number of observations , restricting swaps within days and sites .
we tested whether observed patterns of associations were non - random by comparing the coefficient of variance in the observed network to the coefficient of variance in the randomised networks .
social networks for all replicates significantly differed from random , even at local scales ( t1 : p<0.0001 ; t2 : p=0.0005 ; t3 : p<0.0001 ; t4 : p=0.0002 ; t5 : p=0.0002 ) finally , we used network - based approaches to ask whether the behaviour was socially transmitted through foraging associations . network - based diffusion analysis ( nbda ) tests for social learning by assuming that if social transmission is occurring , then the spread of trait acquisition should follow patterns of relationships between individuals , with transmission rate linearly proportional to association strength .
we used nbda r code v.1.2 , with the time of each individual s first solution ( seconds since the beginning of the experiment ) entered into the continuous time of acquisition analysis function .
individuals that solved , but that did not appear in the social network ( i.e. had not been recorded in the standardised weekend logging ) were excluded from the analysis .
the effects of three individual level variables were also incorporated into the analysis : sex , age , and natal origin .
all combinations of nbda provided in the nbda r code v1.2 were run with social transmission rate allowed to vary for each replicate .
the study was conducted in a wintering population of tits in wytham woods , u.k .
1 ) . 1018 nest - boxes suitable for great tits are installed at this site , with the vast majority of great tits breeding in boxes .
individuals are trapped as nestlings and breeding adults at nest - boxes and fitted with both a british trust for ornithology metal leg ring and a plastic leg ring containing a uniquely identifiable passive integrated transponder ( pit ) tag ( ib technology , aylesbury , u.k . ) .
there is a further mist - netting effort over autumn and winter to tag individuals immigrating into the population , and we estimate that over 90% of individuals were pit - tagged at the time of the study . in this population ,
great tits form loose fission - fusion flocks of unrelated individuals in autumn and winter .
flocks congregate at patchy food sources , and can be observed at bird feeders fitted with pit - tag detecting antennae .
experiments were conducted in eight sub - populations within wytham woods that had relatively little short - term between - area movement of individuals ( extended data fig .
the experimental apparatus consisted of an opaque plastic box with a perch positioned in front of a door that could be slid to either side with the bill to gain access to a feeder concealed behind .
the left side of the door was colored blue and the right side red , with a raised front section on the door to allow an easier grip .
the concealed feeder contained approximately 500 live mealworms and was refilled up to twice daily .
5 ) , and as live mealworms were used , solvers typically extracted one worm and then carried it away from the puzzle - box to kill and eat it ( confirmed with video observations ) ; supplementary video 1 - 2 . each puzzle - box was surrounded by a 11 m cage with a 55 cm mesh that gave unlimited access to small birds , but prevented access by large non - target species such as corvids or squirrels . a freely accessible bird feeder filled with peanut granules
was also provided in the cage , at approximately 1 m from the puzzle - box .
each peanut feeder had two access points fitted with rfid antenna and data - logging hardware .
this feeder was used to attract the original demonstrator to the location , and to record the identity of individuals that did not contact the puzzle - box .
all puzzle - boxes contained a printed circuit board ( pcb ) and motor , and were powered by a 12v sealed battery .
the perch also functioned as an rfid antenna that registered the visit duration ( time to nearest second ) and identity of the visiting individual .
solve  was recorded if the door was opened during an individual visit to the device , with the side direction also noted .
if a solution occurred without an accompanying identified individual , this was recorded as  unidentified solve  .
if further individuals visited before this happened , then a  scrounge  was recorded , as they were assumed to have taken food from the open door ( confirmed from video observations ) .
the door reset immediately after two individuals were registered scrounging , preventing more than two possible scrounging events per solve ( supplementary video 2 ) .
two males were captured from each sub - population ( 11 adults , 5 juveniles ) to act as demonstrators , either by removal from roosting boxes on sunday night , or by mist - netting at a sunflower - seed feeder on monday morning .
they were transferred to individual cages in indoor captive facilities , and over four days each pair of birds was subjected to one of three training regimes using step - wise shaping , either : ( i ) given no training and left in the cage with ab lib food ( control ) ; ( ii ) trained to solve the novel puzzle - box by pushing the blue side of the door to the right ( option b ) ; or ( iii ) trained to solve the novel puzzle - box by pushing the red side of the door to the left ( option a ) . with the exception of  control areas , which were clustered in the south of the woodland to avoid cross - contamination , sub - populations were randomly assigned to a training regime , with both demonstrators from a single sub - population trained on the same technique . during training , the demonstrators were initially exposed to an open puzzle - box baited with mealworms , which was then gradually closed over the course of four days until the subjects were reliably re - opening it .
the birds were released back at the site of capture in each respective sub - population ; puzzle - boxes at which both options were available and equally rewarding were installed at three sites 250 m apart on the following sunday night ( extended data fig .
these puzzle - boxes were run over a four - week period at each site , continuously operating from monday to friday and then removed on saturday and sunday , for a total of 20 days of data collection .
four replicates were conducted in the first year of data collection ( december 2012-february 2013 ; c1 - 2 , t1 , t3 ) . at three of these replicates ( c1 , t1 , t3 ) puzzle - boxes were simultaneously re - installed at the same locations for 5 days of further data collection in december 2013 .
no additional demonstrators were trained , and no individual had contact with the puzzle - box in the 9 months between the two data collection periods . this second exposure aimed to test the long - term stability of social learning at the sub - population level .
they were run prior to the second year of data - collection for the cultural diffusion experiment in order to exclude the possibility that dispersing individuals from new replicates could be re - introducing the novel behaviour .
an additional four replicates were then conducted from december 2013 - february 2014 in new sub - populations , using the same initial protocol ( c3 , t2 , t4 , t5 ) .
the local population size for each replicate was defined as comprising all individuals in a replicate that had been recorded at least once at either : ( i ) the puzzle - box , ( ii ) the nearby peanut feeder , or ( iii ) the nearest network - logger feeders ( operated saturday - sunday , see below ) , during the experimental period ( i.e. from the weekend following the release of the demonstrators , to the weekend after the 20 day of operation of the puzzle - boxes ) .
persistence trial in the following year , the local population was defined just as ( i ) all individuals observed at the puzzle - box or ( ii ) nearby peanut feeder , so that areas were comparable . to analyse the results of the initial experiment we first compared control replicates and
treatment replicates , using welch two - sided t - tests , and by fitting linear and sigmoidal models to the data , with the best model ascertained by difference in aic values .
if individuals were using social information when learning about the puzzle - box , then we expected that there would be a difference between areas seeded with a trained demonstrator ( treatment ) and those without ( control ) .
replicates were thus compared in terms of latency to first solve ( seconds from beginning of the experimental period , excluding demonstrator ) , and the total number of solutions .
secondly , we compared the total number of solutions in the two different experimental treatments . here
if a more complex form of social learning than local enhancement to the feeding site was occurring , then we expected a consistent bias towards the seeded variant in the different treatments . to analyse the change in individual and population preferences for option a or b over time
, we used a generalised estimating equation model ( gee ) where the dependent variable was the proportion of solutions using the seeded technique on each day of data collection , and the explanatory variables were the individuals and replicate , weighted by the overall number of solutions per day . the seeded technique ( a / b ) was initially also included as an explanatory variable , but was not significant ( coefficient  se = 0.130.22 , p = 0.55 ) .
three individual variables were included in a gee model ; sex , age and natal origin .
sex was determined at capture using plumage coloration , age was either determined from breeding records or plumage coloration , and individuals were classed as 
immigrants if they had dispersed into the study site , and  locally - born if they had been ringed as a nestling in the study site .
only age was significant ( coefficient  se = 0.920.20 , p < 0.001 ) , and was included in the final model ( sex : coefficient  se = 0.380.22 , p = 0.08 ; natal origin : coefficient  se = 0.380.22 , p = 0.08 ) .
if population - level conformity was partly the result of a conformist transmission bias at first acquisition we would expect a sigmoidal relationship between population - level frequency of the variant and adoption probability , with adoption of the majority variant disproportionately more likely than its absolute frequency .
by contrast , copying the last individual observed , or random copying , should yield a linear relationship , with probability of adopting option a / b roughly equal to its proportion in the overall population . to investigate this , we isolated all individuals first observed solutions in all experimental replicates , and compared the option choice to the proportion of all previous solves as option a observed in the individual s group at that site
. group length was set at 245 sec , which was the average group length observed using gaussian mixture models on temporal patterns of flocking ( see below ) at network - logging sunflower feeders .
both linear and sigmoidal models were then fitted to the data , with the best model ascertained by difference in aic values .
we further examined the subset of individuals that moved between sub - populations ( n=40 ) .
this subset included all individuals recorded in more than one experimental replicate , whether within the season ( n=16 ) , or between seasons ( n=24 ) .
no individual was observed in more than two replicates , and this analysis did not include individuals in the  persistence trial. a preference for option a / b at each location was defined as more than 75% of all solves for either option a / b in that replicate .
finally , in order to analyse the change in within - individual bias towards option a / b between the initial experiment and the second - year  persistence trials , we used a general linear model where the dependent variable was the number of solves as the seeded variant over the total number of solves for each individual observed in both years .
explanatory variables were treatment type and year , with individual identity as a random effect .
sunflower bird - feeding stations were deployed at 65 locations around wytham woods on an approximate 250250 m square grid , as part of long - term research into social - network structure in tits ( see ) .
each station had two access points , each fitted with rfid antennae and data logging hardware .
feeding stations automatically opened from dawn to dusk on saturday and sunday , scanning for pit - tags every 16 of a second .
this study used the data from the eight nearest locations to each set of puzzle - boxes , for 10 dates within and surrounding the cultural diffusion experiment ( the standard logging protocol runs from september - february in wytham woods ) .
great tits were detecting visiting feeding stations and individually identified by their pit - tags .
we then applied a gaussian mixture model to the spatiotemporal data stream to detect distinct clusters of visits .
this method locates high - density periods of feeding activity , isolating flocks of feeding birds without imposing artificial assumptions about group boundaries .
a gambit of the group approach was used with a simple - ratio index to calculate social associations , where individual association strengths ( network edges ) were scaled between 0 ( never observed foraging together in the same group ) to 1 ( always observed in the same group , never observed apart ) . while a single co - occurrence may not be meaningful , our automated data collection method resulted in thousands of repeated group sampling events , allowing social ties between individuals to be built up from multiple observations of co - occurrences over time and across spatial locations .
networks contained 123 ( t1 ) , 137 ( t2 ) , 154 ( t3 ) , 95 ( t4 ) and 110 ( t5 ) nodes ; average edge strength was 0.09 ( t1 ) , 0.05 ( t2 ) , 0.08 ( t3 ) , 0.07 ( t4 ) and 0.07 ( t5 ) . to test whether networks contained significantly preferred and avoided relationships , we ran permutation tests on the grouping data , controlling for group size and the number of observations , restricting swaps within days and sites .
we tested whether observed patterns of associations were non - random by comparing the coefficient of variance in the observed network to the coefficient of variance in the randomised networks .
social networks for all replicates significantly differed from random , even at local scales ( t1 : p<0.0001 ; t2 : p=0.0005 ; t3 : p<0.0001 ; t4 : p=0.0002 ; t5 : p=0.0002 ) finally , we used network - based approaches to ask whether the behaviour was socially transmitted through foraging associations . network - based diffusion analysis ( nbda ) tests for social learning by assuming that if social transmission is occurring , then the spread of trait acquisition should follow patterns of relationships between individuals , with transmission rate linearly proportional to association strength .
we used nbda r code v.1.2 , with the time of each individual s first solution ( seconds since the beginning of the experiment ) entered into the continuous time of acquisition analysis function .
individuals that solved , but that did not appear in the social network ( i.e. had not been recorded in the standardised weekend logging ) were excluded from the analysis .
the effects of three individual level variables were also incorporated into the analysis : sex , age , and natal origin .
all combinations of nbda provided in the nbda r code v1.2 were run with social transmission rate allowed to vary for each replicate .
total area of wytham woods is 385 ha ; location and size of the separate woodland areas within this are labeled on the map .
( d ) indicates locations where trained demonstrators were caught from and released to . a , feeding station ( shut ) , with sunflower - feeder , rfid antennae , and data - logging hardware .
stations are approximately 250 m apart and open simultaneously dawn - dusk on saturday and sunday over winter .
c , grouping events are inferred from the temporal data stream gained from feeding stations , with individuals assigned to grouping events in a bipartite network .
d , repeated co - occurrences are used to create social networks ( adapted from psorakis et al .
red nodes are individuals that acquired the novel behaviour after 20 days of exposure , black nodes are nave individuals and yellow nodes are trained demonstrators .
networks are heavily thresholded to only show links above the average edge strength for each replicate ( t1 - 5 : 0.09 , 0.05 , 0.08 0.07 , 0.07 ) . a , social network for t1 replicate ( n=123 ) .
e , network for t5 replicate ( n=110 ) . only individuals that performed both options are included , and individuals that moved between replicates are excluded .
lines are running proportions of seeded variant for each individual over its last 10 visits . a , t1 ( option a ) , n=30 ; b , t2 ( option a ) , n=10 ; c , t3 ( option b ) , n=19 ; d , t4 ( option b ) , n=4 ; e , t5 ( option b ) , n=15 .
birds were presented with a freely available mix of 40 mealworms , peanut granules and sunflower seeds for 1 hr on 2 days over 1 week at 6 sites ( 3 sites in t4 and t2 ) .
trials were conducted 2 weeks after the end of the main experiment , in march 2014 .
food choice was identified from video camera footage , and the trial was halted when all of one prey item was taken . only great tits were included , but birds could not be individually identified . birds clearly preferred the live mealworms to either peanut granules or sunflower seeds .
 in human societies , cultural norms arise when behaviours are transmitted with high - fidelity social learning through social networks1 . 
 however a paucity of experimental studies has meant that there is no comparable understanding of the process by which socially transmitted behaviours may spread and persist in animal populations2,3 . here , 
 we introduce alternative novel foraging techniques into replicated wild sub - populations of great tits ( parus major ) , and employ automated tracking to map the diffusion , establishment and long - term persistence of seeded behaviours . 
 we further use social network analysis to examine social factors influencing diffusion dynamics . from just two trained birds in each sub - population , 
 information spread rapidly through social network ties to reach an average of 75% of individuals , with 508 knowledgeable individuals performing 58,975 solutions . 
 sub - populations were heavily biased towards the technique originally introduced , resulting in established local arbitrary traditions that were stable over two generations , despite high population turnover . 
 finally , we demonstrate a strong effect of social conformity , with individuals disproportionately adopting the most frequent local variant when first learning , but then also continuing to favour social over personal information by matching their technique to the majority variant . cultural conformity is thought to be a key factor in the evolution of complex culture in humans4 - 7 . in providing the first experimental demonstration of conformity in a wild non - primate , and of cultural norms in foraging techniques in any wild animal , 
 our results suggest a much wider evolutionary occurrence of such apparently complex cultural behaviour . 
Materials and Methods
Study Population and Area
Puzzle-box Design
Experimental Procedure
Data Analysis
Network Data Collection and Analysis
Extended Data
Supplementary Material