# Manipulating badges of status only fools strangers

Alexis S Chaine, Daizaburo Shizuka, Theadora A Block, Lynn Zhang, Bruce E Lyon

► To cite this version:

Alexis S Chaine, Daizaburo Shizuka, Theadora A Block, Lynn Zhang, Bruce E Lyon. Manipulating badges of status only fools strangers. Ecology Letters, 2018, 21 (10), pp.1477-1485. 10.1111/ele.13128 . hal-04967668

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1 Manipulating badges of status only fools strangers

2

3 Alexis S. Chaine¹,²*, Daizaburo Shizuka³, Theadora A. Block⁴, Lynn Zhang⁴, Bruce E. Lyon⁴

4

5 ¹Station d'Ecologie Théorique et Expérimentale du CNRS (UMR5321), Evolutionary Ecology

6 Group, 2 route du CNRS, 09200 Moulis, France

7 ²Institute for Advanced Studies in Toulouse, Toulouse School of Economics, 21 allée de

8 Brienne, 31015 Toulouse, France

9 ³School of Biological Sciences, University of Nebraska-Lincoln, NE 68588 USA

10 ⁴Department of Ecology and Evolutionary Biology, University of California, Santa Cruz, CA

11 95064, USA

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13 *Corresponding author: alexis.chaine@cnrs.fr ; tel: +33561040378

14

15 Short Title: Dominance by badges vs. recognition

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17 Key words: badge of status; individual recognition; social dominance; social recognition; social

18 structure

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20 Article Type: Letter

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22 Total Words: 5166 [148 in abstract]

23 Total Figures: 3

24 References: 72

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26 Data Accessibility: Data is available at https://doi.org/10.6084/m9 figshare.6626675.v1

27

28 Author contributions

29 ASC, DS, and BEL designed research. ASC, TAB, LZ and BEL conducted trapping and aviary

30 experiments. ASC performed analyses. ASC and BEL wrote the initial manuscript and all

31 authors contributed to revisions.
32 **Abstract:**

33 Conflict is risky, but mechanisms that allow animals to assess dominance status without
34 aggression can reduce such costs. Two different mechanisms of competitor assessment are
35 expected to evolve in different contexts: badges of status are expected in larger, anonymous
36 groups whereas individual recognition is feasible in small, stable groups. However, both
37 mechanisms may be important when social interactions occur both within and across stable
38 social groups. We manipulated plumage in golden-crowned sparrows (*Zonotrichia atricapilla*)
39 and found that two known badges of status—gold and black head plumage patch sizes—
40 independently affect dominance among strangers but manipulations had no effect on dominance
41 among familiar flockmates. Moreover, familiar flockmates showed less aggression and increased
42 foraging relative to strangers. Our study provides clear experimental evidence that social
43 recognition affects badge function, and suggests that variation in social contexts maintains
44 coexistence and context-dependent use of these two dominance resolution mechanisms.
45 **Introduction**

46
Conflict over resources is ubiquitous among organisms. When the fitness stakes are high,
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conflict can entail extreme aggression and even lethal fights, for example, when males battle for
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access to females in polygynous mating systems. In contrast, when organisms compete over
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resources with modest effects on fitness, such as a meal, animals often settle conflicts with
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mechanisms that avoid the costs of overt aggression and injury (Maynard Smith & Price 1973;
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Maynard Smith & Harper 2003). Two such mechanisms for competitor assessment have been
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proposed: individual recognition and badges of status (Rohwer 1975; Barnard & Burk 1979;
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Maynard Smith & Harper 2003; Searcy & Nowicki 2005; Dale 2006; Tibbetts & Dale 2007;
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Bradbury & Vehrencamp 2011). Individual recognition allows an organism to tailor its behavior
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in aggressive interactions with familiar opponents based on past interactions (Barnard & Burk
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1979; Tibbetts & Dale 2007) or through observations of interactions between other individuals of
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known rank (i.e., transitive inference: Paz-Y-Miño C et al. 2004; Grosenick et al. 2007). In
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contrast, badges of status are signals that correlate with an individuals' fighting ability that allow
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any random pair of individuals to assess their chances of winning a given contest and therefore
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avoid costly fights (Rohwer 1975, 1977, 1982). Both mechanisms are supported by ample
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experimental evidence in the literature (Dale et al. 2001; Whiting et al. 2003; Senar 2006;
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Tibbetts & Dale 2007), but there is relatively little data on whether and under what
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circumstances these two mechanisms might co-occur (Sheehan & Bergman 2016b, but see Järvi
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& Bakken 1984; Whitfield 1988; Sheehan & Tibbetts 2010; Sheehan et al. 2014).
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Social structure—particularly group size and stability—should affect whether individual
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recognition or badges of status are favored as assessment strategies (Figure 1) (Rohwer 1982;
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Whitfield 1987; Shultz & Gersick 2016). Individual recognition is thought most likely to occur
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in small, stable groups for two reasons: the number of individuals an animal can remember may
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be constrained (Dukas 1999; Burns et al. 2011), and the benefits of memorizing individual
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identities and adjusting dominance behavior accordingly are greater when the same individuals
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repeatedly interact (Figure 1a) (Whitfield 1987; Ydenberg et al. 1988; Johnstone 1997; Tibbetts
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& Dale 2007). Conversely, badges of status do not require memory of past encounters, and thus
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could function in large groups where most interactions occur between newly interacting
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individuals (Rohwer 1975, 1982; Whitfield 1987) (Figure 1c). Taken together, individual
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recognition should be favored in societies that feature small stable groups, while badges of status
should be favored in systems with large groups where repeated contests are relatively rare, and also where individual recognition may not be feasible (Figure 1a vs c) (Rohwer 1982; Whitfield 1987; Shultz & Gersick 2016). This contrast in conditions has sometimes led to the perception that the two conflict resolution mechanisms are unlikely to coexist.

The debate over assessment strategies has often implied that the social organization of a species can be neatly categorized into the two extremes—small and stable versus large and fluid—that each favors different assessment strategies (Shields 1977; Rohwer 1982). However, the social structure of many animal populations cannot be characterized along a simple gradient of group size or group stability. Fission-fusion dynamics are pervasive in animals, even among species that were not previously considered to be socially complex (Aureli *et al.* 2008; Mourier *et al.* 2012; Silk *et al.* 2014), and social network analysis can help uncover these complex patterns of social stability (Wey *et al.* 2008; Pinter-Wollman *et al.* 2014; Silk *et al.* 2014). For example, stable long-term associations can exist in clusters, or ‘social communities’ within social networks, but individuals in different social communities may nevertheless be connected weakly through transient interactions. In such multilevel societies, stability of social associations can be heterogeneous, where individuals often have encounters with both familiar and unfamiliar competitors—i.e., contexts in which different dominance assessment mechanisms may be favored (e.g. Figure 1b) (Whitfield 1987; Shultz & Gersick 2016). Even within stable social communities, new recruits will be initially unfamiliar and may use badges of status to establish dominance relationships prior to making use of individual recognition once established in the group. In such cases, the function of badges of status would be context-dependent: they may play an important role in mediating interactions between unfamiliar individuals but may be less important between familiar individuals that can assess each other through individual recognition.

In this study, we investigated whether the use of badges of status depends on the familiarity of contestants in a winter population of the migratory golden-crowned sparrow (*Zonotrichia atricapilla*). In previous work, we provided evidence for multiple badges of status: contests with both natural variation (Chaine *et al.* 2011) and experimental manipulation (Chaine *et al.* 2013) showed that individuals with larger gold or larger black plumage patches win contests among strangers (i.e. individuals from different populations). However, social network analysis based on flock co-membership in a free-living population revealed these sparrows live in small, stable winter social groups that are connected together by relatively weaker associations
across groups (Shizuka et al. 2014). Moreover, these groups are stable across years and many
individuals form affiliations that last many years; these affiliations reform anew each year after
migration to and from the breeding grounds. The fact that a significant amount of variation in
flocking patterns is explained by the effect of the previous year's affiliation, even after
controlling for the amount of overlap in home ranges (Shizuka et al. 2014), indicates that these
birds likely show individual recognition in some aspects of their social behavior. We already
know that sparrows use badges in some dominance contexts; the golden-crowned sparrow social
network may provide conditions under which both badges of status and individual recognition
are beneficial in resolving social dominance.

Empirical tests of individual recognition and badges of status adopt somewhat different
methods; showing that both occur in the same population requires careful experiments that
control for familiarity, the context that should determine which mechanism the birds use. Badges
of status are often documented through correlations between the size of a putative signal and
dominance rank [e.g. lizards (Thompson & Moore 1991), insects (Tibbetts & Dale 2004), birds
(Senar 2006; Tibbetts & Safran 2009), and mammals (Setchell & Wickings 2005)]. Confirmation
that a specific trait is used as a badge requires manipulation of the presumed badge, which
should trigger a change in the outcome of specific contests (Rohwer & Rohwer 1978; Pryke &
Andersson 2003; Chaine et al. 2013). Experimental contests to test for badges of status typically
involve unfamiliar contestants to remove the potential effect of prior information on the contest
outcome. In contrast, individual recognition is documented in one of three ways: by comparing
interactions between familiar and unfamiliar individuals (Hazlett 1969; Caldwell 1985; Watt
1986), by measuring changes over time in the behaviors and interactions of a pair of individuals
that become increasingly familiar with each other (Karavanich & Atema 1998; Tibbetts 2002;
Vedder et al. 2010) or, more rarely, through manipulation of a putative identity signal (Whitfield
1988; Tibbetts 2002). Here, we investigated the potential co-occurrence of badges of status and
social recognition by conducting experimental badge size manipulations in two types of
contests—dyads of birds that are familiar with each other and dyads of unfamiliar birds. This
design allowed us to determine if the badges that we have already shown to be effective among
unfamiliar birds (Chaine et al. 2011, 2013) are also used among familiar birds or, alternatively, if
these badges are ignored as would be expected if individuals use some form of social recognition
(individual or group). We provide definitive evidence that sparrows use both badges of status
and social recognition and demonstrate that variation in social context plays a key role in the coexistence of these two dominance-resolving mechanisms. Because our experimental approach was not designed specifically to discriminate between individual and group recognition, we could not directly test for individual recognition, the form of recognition most discussed in the extensive literature on badges of status (e.g. Rohwer 1975; Whitfield 1982). However, several considerations suggest that the social recognition we observed involved individual recognition, as we discuss below.

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## 146 Materials and Methods

We used staged competition in aviaries to assess whether previous familiarity affected the role of plumage traits on social dominance. We caught golden-crowned sparrows at four different sites in January and February using Potter traps baited with millet seed. From 2007-2009, we trapped birds at two locations near Pogonip City Park (36°59'25.6"N 122°02'12.9"W and 36°59'04.2"N 122°02'49.0"W) and the University of California Santa Cruz (UCSC) campus (36°58'40.1"N 122°03'04.8"W). In 2012-2014 we added a site at the Santa Cruz Waldorf School (37°00'22.4"N 122°04'26.7"W). Birds were transported to the UCSC Arboretum soon after capture. We measured all birds (mass, wing chord, tarsus, beak length), banded them with color bands and a USFWS metal band for identifying individuals within experiments, and photographed their crowns as in past studies (Chaine et al. 2011, 2013). All birds were then placed in one of two outdoor aviaries for habituation before use in experimental trials the following morning—these two aviaries were visually and acoustically isolated from each other, had shelter, and both food and water *ad libitum*. The two birds used in each trial were put in separate over-night aviaries to ensure a lack of contact immediately prior to the trial. Before running the trials we measured size of gold and black crown patches (mm²) from photos with Adobe Photoshop CS and these patch sizes were then used to assign birds to a trial such that the two birds had similar pre-manipulation patch size, as in previous work (Chaine et al. 2011, 2013). Sex was not used as a criterion for assigning birds to a trial because previous work showed that gender does not predict social dominance in this species (Chaine et al. 2011).

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We conducted two different types of social dominance trials. “Unfamiliar trials” (N = 62) used birds caught on the same day from two different populations >800m apart (often much greater distances). This distance is much larger than the average home range of individual
169 sparrows (Shizuka et al. 2014) so the birds in the trial were very unlikely to have interacted with
170 each other prior to the trial. The “Familiar trials” involved birds that were trapped at the same
171 site and within a short time period (<30min); based on our detailed understanding of flocking
172 and feeding behavior from our color-banded population (Shizuka et al. 2014, unpubl. data), these
173 were birds that would be very likely to have been in the same flock when captured (2012-2014
174 only; N = 60). Unfamiliar trials analyzed here include some trials also used in a previous
175 publication (N = 32) (Chaine et al. 2013) as well as new Unfamiliar trials (N = 30) conducted at
176 the same time as Familiar trials to control for possible year effects and collect new data on
177 distance between birds not gathered in the earlier experiments (see below).

178 Social dominance trials were conducted in the morning between 8-11 AM in a third contest
179 aviary (same dimension as overnight aviaries) and each trial lasted 30 minutes. Food was
180 removed from the overnight aviaries at sundown the evening before the trials so birds in
181 dominance trials were motivated to access the single feeding tray at the center of the contest
182 aviary. Prior to the trial, one of the birds, chosen at random, had one of their color patches (either
183 black or gold) increased in size while the other received a sham manipulation using clear thinner
184 (gold) or brown permanent marker (black). Gold patch size was increased using acrylic paint
185 while black crown size was increased using a permanent ink pen; both colors were spectrally
186 similar to natural color patches (Chaine et al. 2013). As in our previous experiment (Chaine et al.
187 2013), the birds in each dyad did not differ in patch size before manipulation and the
188 manipulation significantly increased badge size (Supplemental Information). Because pre-
189 manipulation patch size of the two birds was similar, we would expect manipulated birds to be
190 dominant in half of the trials if patch size manipulation had no influence on dominance (Chaine
191 et al. 2011, 2013). As in our previous experiment, gold (N = 62) and black (N = 60)
192 manipulations showed similar outcomes, so we present combined results in the main text (results
193 split by treatment in Figure S1).

194 We scored social behavior in two ways. First, an observer watched trials from ~30m away
195 with binoculars and scored social interactions as aggression (peck, supplant), avoidance
196 (subordinate avoided challenging a dominant), or tolerance (no aggression while in close
197 proximity), and we also tallied feeding behaviors (Chaine et al. 2011, 2013) for the first and
198 second 15min time periods separately. We used the sum of the social interactions to determine
199 which bird was dominant or, in some cases, to conclude that dominance was not clear (Chaine *et*
al. 2011, 2013). We concluded that dominance was clear when one bird consistently won encounters through supplants or avoidance behavior (Chaine et al. 2011, 2013). In contrast, dominance was not clear when birds had the opportunity to interact (i.e. they moved around), but either no dominance behaviors occurred or both birds won an equal number of encounters (very rare). In a second approach, we scored tolerance behavior as a measure of flocking and social affinity from videos taken from above the contest aviary. Generally, tolerance is a measure of whether birds socialize at close proximity without any aggression, and we quantified this as the number and duration of instances where the birds were within two body lengths of each other for more than 3 seconds and did not show aggressive behaviors (i.e. no dominance interactions; 2012-2014 only). The person who conducted the trials was not blind to treatment but dominance was evaluated as the sum of behaviors post data collection. In contrast, videos used to quantify tolerance and social clustering were scored blind to treatment which should eliminate observer bias. The results of the two approaches are concordant.

To evaluate the impact of our plumage manipulation on social dominance, and particularly to be able to compare across the two sets of experiments, we examined two different outcomes: the proportion of trials that showed a clear dominance winner and then the proportion of this subset of trials where the manipulated (i.e. enlarged) bird was dominant. For the latter, the null expectation is that each bird has a 50% chance of winning so we evaluated the impact of the manipulation on dominance as the deviation from an expected 50:50 ratio using a binomial test. This null expectation applies because pre-manipulation badge sizes were matched for each dyad and because badge size predicted dominance in past studies (Chaine et al. 2011, 2013). In contrast, there is no clear null expectation of what proportion of trials should show clear dominance, so we simply provide the raw data for evaluation. We used Z-tests to compare the differences between Familiar and Unfamiliar treatments in the probability of observing clear dominance, as well as the probability of the bird with the experimentally enlarged patch winning the contest (Fleiss et al. 2003). We used ANOVA to compare rates of each behavior (aggression, avoidance, tolerance and feeding) between Familiar and Unfamiliar trials. Data were analyzed in R 3.1.3 (R Development Core Team 2009) and are available on DRYAD (upon acceptance).

All protocols were approved by the UCSC IACUC (Animal Welfare Permit Number A3859-01 to B. Lyon). Capture and banding was done under permits to B. Lyon: a California
230 Department of Fish and Wildlife Scientific Collecting permit, a Federal Fish and Wildlife Permit
231 and a Federal Banding Permit.

232

233 **Results**

234 Familiarity affected the likelihood of a trial showing clear dominance patterns. Trials with
235 unfamiliar birds (i.e., birds caught at different sites) nearly always had a clear dominant
236 individual (53 of 62 trials). In contrast, only about half of the familiar dyads (birds caught at the
237 same site at the same time) had clear dominance (27 of 60 trials). The proportion of trials where
238 dominance was clear was significantly greater in Unfamiliar trials than in Familiar trials
239 (comparison of two probabilities: Z = 4.71, P < 0.0002, Figure 2a).

240 The plumage manipulations influenced the outcome of dominance in trials involving
241 unfamiliar birds but not familiar birds. In the subset of trials where dominance was clear, the
242 manipulated bird was dominant over the sham individual in a significantly larger proportion of
243 trials between unfamiliar birds relative to trials between familiar birds (comparison of two
244 probabilities: Z = 4.20, P < 0.0002, Figure 2b). Indeed, the manipulated bird was dominant in
245 nearly all cases during Unfamiliar trials (49 of 53 trials, binomial test based on null expectation
246 of 0.5 probability that an individual will be dominant based on pre-manipulation crown size: P <
247 0.001). The sample here includes trials conducted in our previous study using the same methods
248 (Chaine *et al.* 2013), and thus simply increases the robustness of the previously reported patterns.
249 In contrast, the manipulated bird was not more likely to be dominant than the sham individual
250 among familiar dyads, which is what we would expect only if birds ignored the patch
251 manipulation (14 of 27 trials, binomial test with null expectation of 0.5 probability that
252 individual will be dominant based on pre-manipulation crown size: P = 1). These results are the
253 same regardless of which plumage patch was manipulated (i.e., black or gold: Figure S1).

254 Birds in Familiar trials had fewer costly social behaviors and spent more time feeding
255 relative to unfamiliar dyads. Familiar trials had fewer aggressive interactions (ANOVA: F₁,₁₂₀ =
256 3.46, P = 0.065; Figure S2a), fewer avoidance interactions (ANOVA: F₁,₁₂₀ = 24.63, P < 0.0001;
257 Figure 3a), and a higher rate of tolerance (a lack of aggression when close; ANOVA: F₁,₁₂₀ =
258 96.50, P < 0.0001; Figure S2b). Familiar birds also spent significantly more time in close
259 proximity relative to unfamiliar dyads (ANOVA: F₁,₅₇ = 4.77, P = 0.033; Figure 3b). Finally,
260 while birds in both types of trials accessed food at similar rates (ANOVA: F₁,₁₂₀ = 1.31, P = 0.25;
Figure S2c), birds in Familiar trials spent a significantly longer time at the feeder on each visit compared to birds in Unfamiliar trials (ANOVA: F<sub>1,101</sub> = 13.07, P = 0.0004; Figure 3c).

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## Discussion

Our experiments revealed that plumage manipulations affect dominance status in staged contests among strangers (confirming the results of Chaine *et al.* 2013), but not among birds previously familiar with each other. These contrasting results provide evidence that the familiar birds recognized each other, either individually or at the group level, and that this recognition allowed them ignore experimental changes to plumage badges. This also implies that the crown plumage patches we manipulated were not the traits the birds use for social recognition. Finally, our experiments suggest how familiar birds can benefit from social recognition during such encounters—reduced aggression, tighter flocking, and increased access to resources.

The differences we observed between the familiar and unfamiliar trials imply some form of recognition among familiar birds. We did not quantify the amount of prior social interaction leading to this social recognition, nor did our experiments directly test for individual recognition so there is a question of what type of recognition was involved—individual recognition or group level recognition (e.g. familiar vs unfamiliar)? Regardless of the level of social recognition, our results indicate that birds caught in the same place within a short time—i.e., those that are typically very socially familiar due to close associations over long periods of time (Shizuka *et al.* 2014)—disregard manipulation of badges of status. However, distinguishing between these two forms of recognition can be difficult and direct evidence for individual recognition requires demonstrating that individuals vary their behavior in response to an individual specific cue like an individually distinct vocalization or visual features, and not some group level attribute (Tibbetts *et al.* 2008). For example, group recognition is common in social insects where individuals respond differently to familiar (same colony) and unfamiliar (different colony) individuals on the basis of colony specific olfactory cues (cuticular hydrocarbons, Hölldobler & Wilson 1990). Thus, simply showing that these insects respond differently to familiar and unfamiliar individuals may only show a group level response and not individual recognition. In birds, there is some evidence for group-specific calls in various contexts, including seasonally stable flocks (e.g., Nowicki 1983; Hausberger *et al.* 1995). However, we never observed vocalizations in any of our trials so acoustic features cannot explain our results. Furthermore, our
past work suggests that recognition between familiar sparrows generally goes beyond group
membership and reflects true individual recognition. When winter social communities form anew
each fall after fall migration, variation in the strength of pair-wise affiliations is explained in
large part by the degree of affiliations between those individuals in the previous year, even after
controlling for shared space use by individuals, which strongly suggests individual recognition
(Shizuka et al. 2014). Based on these considerations, we believe that individual recognition is the
most likely explanation for the differences between familiar and unfamiliar trials. Identifying the
trait or traits used in individual recognition remains an interesting, if challenging, question for
future work.

Our study demonstrates how both badges of status and social recognition can mediate
social competition within the same population. Prior work shows that badges of status and
recognition (in particular, individual recognition) each provide a way to avoid costly conflict
over resources, yet each has different benefits and constraints. For example, badges of status may
allow rapid assessment of competitive ability and can function reliably even when groups are
large and fluid and individual recognition is not feasible (Rohwer 1982). However, badges can,
in theory, be susceptible to cheating (Rohwer & Ewald 1981). In contrast, individual recognition
could allow for more reliable assessment of competitive ability, but it is only beneficial when
there are repeated interactions between competitors (Ydenberg et al. 1988; Johnstone 1997;
Tibbetts 2004; Tibbetts & Dale 2007), and it may require investment in neural mechanisms to
allow for memory of the outcomes of past interactions associated with each contestant (Dukas
1999; Tibbetts & Dale 2007; Sheehan & Tibbetts 2011). There also may be a limit to the size of
the social group where individual recognition is cognitively feasible (Dunbar 1992).
Traditionally, researchers have sought evidence for either badges of status or individual
recognition for a given species, and evidence for one type of assessment strategy was held as
evidence against the other (e.g., Shields 1977). Our study provides valuable empirical data to
show that conditions favorable for both types of assessment strategies coexist in one social
system, and that golden-crowned sparrows selectively use badges of status or social recognition
depending on the social context. These findings should spur further progress in development of
theory related to the evolution of competitor assessment strategies, which has been highlighted in
a recent review by Sheehan and Bergman (2016b) and responding commentary (Barrett & Henzi
2016; Ridley et al. 2016; Sheehan & Bergman 2016a; Shultz & Gersick 2016).
We suggest that the context-dependent use of both badges of status and individual recognition in the same species may be more common than currently suspected. In a handful of species, both mechanisms of assessment have been tested but only one was found—e.g., the various *Polistes* wasps studied in the impressive body of work by Tibbetts and colleagues (Tibbetts 2004; Tibbetts & Dale 2004; Sheehan & Tibbetts 2010). However, the results are more mixed in avian systems, with a few cases that hint at the co-occurrence of badges and recognition. For example, blue tits (*Parus caeruleus*) use badges of status (Rémy *et al.* 2010), but also show changes in the importance of badges for dominance across repeated interactions suggestive of individual recognition (Vedder *et al.* 2010), although winner/loser effects cannot be ruled out for this pattern (Hsu *et al.* 2006; Rutte *et al.* 2006). Likewise, white-crowned sparrows (*Zonotrichia leucophrys*), a congener of the sparrows we studied, use badges of status (Fugle *et al.* 1984), yet our reanalysis of experiments by Watt (1986) show that interactions between familiar birds show fewer aggressive interactions than between unfamiliar birds (reanalysis of data in Table 3 in (Watt 1986): comparison of the proportion of aggressive interactions between familiar and unfamiliar birds: Z = -2.67, P = 0.008). This difference between familiar and unfamiliar birds in levels of aggression suggests that individual recognition may exist in white-crowned sparrows. Parsons and Baptista (1980) also showed that white-crowned sparrows with manipulated crowns maintain status within their flock, further suggestive of individual recognition. For these two sparrow species, careful experiments are now required to confirm that individual recognition occurs.

An open question is whether there are predictable conditions under which a species or population might use just one form of assessment or both assessment strategies. Complex social structure may favor the use of both assessment strategies. Four decades ago, Whitfield (1987) hypothesized that social organization might be sufficiently variable in many species to favor both assessment mechanisms, and lamented the lack of understanding of social organization as an impediment for understanding the evolution of badges and individual recognition. More recently, Shultz and Gersick (2016) suggested that the dual use of quality signaling and social recognition would be favored in multilevel animal societies in which close-knit social clusters exist within a larger population because individuals would interact with both familiar and unfamiliar individuals (e.g. Figure 1b). Our study system provides evidence to support this idea. Golden-crowned sparrows in our population live in a complex social network characterized by cohesive
social clusters embedded within a larger population that interacts more loosely (Shizuka et al. 2014). This social structure is not driven by kinship (Arnberg et al. 2015), but rather preferences for familiar flock-mates, even across years (Shizuka et al. 2014). Our experiments now show that familiarity not only affects flock associations, but also the way competitors use badges of status to mediate competition. In the natural social network context where interactions may occur with a mix of familiar and unfamiliar competitors, within-cluster (familiar) interactions may be mediated by recognition whereas interactions among clusters (unfamiliar) may use badges of status, precisely as Whitfield (1987) predicted. The basic features of this social system—fission-fusion dynamics characterized by a mix of stable long-term associations and diffuse short-term associations—are likely widespread in avian systems (Silk et al. 2014). Even for systems in which long-term stable social relations dominate, we suggest that there are likely periods of time during which interactions among unfamiliar individuals occur and badge use would be favored, such as during migration, the integration of new recruits into stable social groups, or periods of social instability following the breakdown of some groups. A better understanding of the natural patterns of social interactions throughout the annual cycle for birds generally may reveal common patterns that favor the use of one or both mechanisms of competitor assessment.

Our study demonstrates how controlling the social context of contests is paramount to accurately understand the dynamics of status signaling. This poses a challenge for researchers because it also requires a detailed understanding of the social structure of the population—i.e., the extent to which social interactions are naturally confined to familiar *versus* unfamiliar competitors. For example, earlier observational studies of badges of status suggested that the failure of putative badges to accurately predict dominance cast doubt on whether they served as badges (e.g. Whitfield 1987). However, it is also possible those studies contained a large proportion of within group interactions where individual recognition rather than badges of status mediated dominance. Moreover, testing the function of putative badges through observations in the wild, rather than with experiments, may often produce weaker correlations between badge and dominance when interactions involve a mix of strangers and familiar birds. Our results suggest the relationship between putative badges and dominance in the wild will depend critically on the frequency of interactions that are within groups of familiar individuals versus between strangers, and highlight the importance of distinguishing between these two different contexts.
Our experimental results also have implications for the maintenance of honest signaling.

A key question for badges of status has long been, why not cheat? Why don't poor fighters
produce badges that signal high fighting ability? In theory, the stability of badges of status as a
signaling system relies on some mechanism to prevent cheating, such as condition dependence
(Johnstone & Norris 1993; Tibbetts & Curtis 2007) or social punishment of cheaters (Webster et
al. in press; Rohwer 1982; Tibbetts & Dale 2004). However, our plumage manipulation with
familiar individuals apparently did not result in the rapid social punishment seen in similar
experiments in other systems (Tibbetts & Izzo 2010; Ligon & McGraw 2016). This begs the
question whether social recognition could change the dynamics of social enforcement of honesty
in badges of status. We suggest that, given individual recognition, it may be possible for delayed
social punishment to play out at timescales beyond the duration of a given dominance
experiment. In theory, the value of a dishonest badge should be diminished in systems where
both badges and individual recognition are used, because interactions within a social group no
longer rely only on badges of status. Specifically, badges of status might be used to settle
dominance when a bird initially joins a group, but recognition subsequently modulates
interactions. If detection makes it less likely that cheaters can join a group, or if they
subsequently develop weaker or more negative affiliations (i.e. individuals reduce interactions
with cheaters or affiliations involve more hostility), then social costs linked to individual
recognition could guard against cheating. For animals that live in stable long-lived groups, the
presence of such 'punishment' could have dire long-term consequences such as reduced
cooperation or even exclusion from a group. If there are important benefits to stable group
membership the risks of dishonest status signaling in the presence of individual recognition may
make it unlikely.

Finally, our experiments also demonstrate potential benefits of interacting with familiar
individuals, such as reduced aggression and increased food intake which are key components of
winter survival. Birds in Familiar trials spent much less time in conflict and more time in non-
aggressive (tolerant) interactions relative to those in Unfamiliar trials. Familiar birds also spent
much longer times at the feeder than unfamiliar birds, which in general would increase their food
intake. Finally, familiar birds spent much more time close to each other than unfamiliar birds and
such clustering could provide benefits such as reduced predation risk (Hamilton 1971; Lima et
al. 1999). These benefits, which result from recognition rather than badges of status, may be key
components that favor the stable community structure we see in golden-crowned sparrows (Shizuka et al. 2014). Thus, our experimental results may provide a key link between competitor assessment strategies and the social network structure of foraging flocks. The cues used for recognition—which we have not yet identified—may play an outsized role in the winter social system of golden-crowned sparrows by mediating flock membership as well as modulating the function of badges of status in contests over food.

Special thanks to Allison Roth and Melanie Laure for help collecting aviary data and the UCSC Arboretum for generously providing us with space for our aviaries, use of an indoor office space for banding, and other logistic support. We thank the City of Santa Cruz Park Services and the Santa Cruz Waldorf School for permission to conduct part of this study on their land. This work was funded by a UCSC Special Research Grant to B.E.L. and support from the CNRS and ANR-JCJC NetSelect and HFSP RGP0006/2015 to A.S.C. This work is part of the Laboratoire d'Excellence (LABEX) entitled TULIP (ANR -10-LABX-41).

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594
595 **Figure Legends**

596 Figure 1: Schematic representation of social networks predicted to favor different dominance
597 resolving mechanisms. A) Social (individual or group) recognition is expected to be favored in
598 smaller, stable groups where each individual only interacts with a few others on a regular basis
599 but only rarely encounters new or unfamiliar individuals. B) Intermediate networks that include
600 both frequent, repeated interactions within a stable group and some interactions with extra-group
601 individuals could favor the coexistence of both badges and social recognition. C) Badges of
602 status alone should be expected in fluid groups where individuals are likely to encounter a large
603 number of other individuals so that the costs of remembering this large number outweighs the
604 relative low benefit from rare repeat encounters. In each figure, circles represent individuals (e.g.
605 nodes), lines represent the frequency of interaction between two individuals (e.g. edges), and
606 colors represent social communities that are defined by high within-community interaction and
607 low among-community interaction.

608

609 Figure 2: Comparisons between Familiar (open) and Unfamiliar (grey) trials in the proportion of
610 trials where A) a dominance was clear and B) where the manipulated bird was dominant among
611 trials where dominance was clear. Confidence intervals were calculated using Wilson's
612 procedure described by (Newcombe 1998).

613

614 Figure 3: Comparison between Unfamiliar and Familiar trials in behaviors that reflect costs and
615 benefits of grouping behavior when dominance resolution occurs by recognition. A) The number
616 of dominance interactions where a subordinate avoided challenging a dominant (avoidance). B)
617 The total time the two birds spent very near each other without showing aggression (within two
618 body lengths). C) The average duration of feeding bouts. Figures show standard box and whisker
619 plots.