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M. I.c.h.a.e.l.d. Beecher - One of the best experts on this subject based on the ideXlab platform.
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Song Sparrows do not discriminate between their own Song and stranger Song.
Behavioural processes, 2020Co-Authors: Çağlar Akçay, M. I.c.h.a.e.l.d. BeecherAbstract:Abstract Bird Song is socially learned. During Song learning, the bird’s hearing its own vocalization is important for normal development of Song. Whether bird’s own Song is represented and recognized as a special category in adult birds, however, is unclear. If birds respond differently to their own Songs when these are played back to them, this would be evidence for auditory self-recognition. To test this possibility, we presented Song Sparrow males (Melospiza melodia) playbacks of their own Songs or stranger Songs and measured aggressive responses as well as type matching. We found no evidence of behavioral discrimination of bird’s own Song relative to the (non-matching) stranger Song. These findings cast doubt on an earlier proposal that Song Sparrows display auditory self-recognition and support the common assumption in playback experiments that bird’s own Song is perceived as stranger Song.
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Extrapair paternity, Song, and genetic quality in Song Sparrows
Behavioral Ecology, 2010Co-Authors: Christopher E. Hill, S. Elizabeth Campbell, Çağlar Akçay, M. I.c.h.a.e.l.d. BeecherAbstract:Most Songbirds are socially monogamous, yet molecular studies have found that in most species, some offspring in the nest are sired by males other than the social mate of the female. The functional significance of extrapair paternity (EPP) in social monogamy is poorly understood, despite numerous theoretical and empirical studies in the last decades. We have examined EPP in the Song Sparrow (Melospiza melodia) using microsatellites and tested whether females choose as extrapair mates males that 1) had larger Song repertoires, 2) shared more Songs with their neighbors, 3) were more heterozygous, or 4) were less related to the females than the social mate of these. We found that 24% of offspring were sired by extrapair males and that the extrapair sires were invariably neighbors. However, neither Song repertoire size nor Song sharing with neighbors predicted a male’s EPP success. Furthermore, neither heterozygosity of a male nor his relatedness to the female predicted EPP success. At the same time, males that did not lose paternity in their own nest or gain paternity in other nests tended to be younger. These results indicate that females are not using Song repertoire size or Song sharing as a basis for extrapair mate choice and are not likely to accrue significant genetic benefits from EPP. Instead, the occurrence and level of EPP in this population might be primarily governed by behavioral trade-offs between mate guarding and pursuing extrapair copulations. We suggest that detailed behavioral studies are needed to understand extrapair mating in this species. Key words: bird Song, compatible genes, extrapair paternity, good genes, Song Sparrow. [Behav Ecol]
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Song perception in the Song Sparrow importance of different parts of the Song in Song type classification
Ethology, 2010Co-Authors: Cynthia L. Horning, Philip K Stoddard, M. I.c.h.a.e.l.d. Beecher, Elizabeth S CampbellAbstract:Song Sparrow (Melospiza melodia) males have repertoires of 6 to 12 Song types, each Song consisting of four or five contrasting phrases. Song types vary both within individuals (a singer varies successive renditions of a type within a singing bout) and between individuals (neighbors sing slightly different versions of a type), and in both cases this variation is concentrated in the later parts of the Song. We speculated that type variation in the later parts of the Song might be correlated with a perceptual tendency to classify Song types primarily on the basis of the earlier parts of the Song. We tested this hypothesis using a laboratory conditioning technique, supplemented by a field playback experiment. In the lab, Song Sparrows and white crowned Sparrows were trained to discriminate between two distinct Song types. In test sessions, they were presented with hybrid Songs synthesized from varying proportions of the two training Song types. For most birds and most Song pairs, Song classification was influenced by all parts of the Song, with the beginning elements being most important. The field playback experiment used Song type matching as the response measure. Each subject was presented a hybrid stimulus Song consisting of the first half of one of his Song types and the second half of another of his Song types. Subjects replied with both ‘front matches’ and ‘back matches’ (60% were front matches).
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Geographic Variation in the Organization of Song Sparrow Repertoires
The Auk, 2000Co-Authors: Susan Peters, M. I.c.h.a.e.l.d. Beecher, William A Searcy, Stephen NowickiAbstract:Abstract We asked whether geographic variation exists in the complexity of Song repertoires in Song Sparrows (Melospiza melodia) by quantitatively comparing four measures of repertoire organization across four geographically distant populations: (1) repertoire size (the number of distinct Song types), (2) the number of “minimal units of production” per repertoire, (3) mean similarity among variants of the same Song type (“within-type” similarity), and (4) mean similarity among Song types in a repertoire (“between-type” similarity). We found significant geographic differences among populations in three of these four measures, with mean similarity among Song types being the exception. In general, relatively sedentary populations in North Carolina and Washington were more similar to each other than to migratory populations in Pennsylvania and Maine. Contrary to our expectation based on prior interspecific analyses of variation in repertoire complexity, the relatively sedentary populations in our sample had more complex repertoires than did the more migratory populations. The origin and functional significance of population differences in repertoire complexity in this species remain uncertain.
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geographic variation in the organization of Song Sparrow repertoires
The Auk, 2000Co-Authors: Susan Peters, M. I.c.h.a.e.l.d. Beecher, William A Searcy, Stephen NowickiAbstract:Abstract We asked whether geographic variation exists in the complexity of Song repertoires in Song Sparrows (Melospiza melodia) by quantitatively comparing four measures of repertoire organization across four geographically distant populations: (1) repertoire size (the number of distinct Song types), (2) the number of “minimal units of production” per repertoire, (3) mean similarity among variants of the same Song type (“within-type” similarity), and (4) mean similarity among Song types in a repertoire (“between-type” similarity). We found significant geographic differences among populations in three of these four measures, with mean similarity among Song types being the exception. In general, relatively sedentary populations in North Carolina and Washington were more similar to each other than to migratory populations in Pennsylvania and Maine. Contrary to our expectation based on prior interspecific analyses of variation in repertoire complexity, the relatively sedentary populations in our sample had m...
John C Wingfield - One of the best experts on this subject based on the ideXlab platform.
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the presence of water influences reproductive function in the Song Sparrow melospiza melodia morphna
General and Comparative Endocrinology, 2012Co-Authors: John C Wingfield, Kimberley Sullivan, Jessica Jaxionharm, Simone MeddleAbstract:Abstract Cumulative evidence indicates that Song Sparrows, Melospiza melodia morphna, of western Washington State prefer territories close to water. Densities of territories were higher within 50 m of open water and analysis of stomach contents revealed aquatic organisms. An unusually dry period (less open water) in May and June 1997 had no effect on latency of territorial males to respond to a simulated territorial intrusion (STI), but the number of Songs and closest approach to the decoy were lower than those recorded in June 1988 (no major dry periods). A laboratory experiment was conducted in which males and females were exposed to long days to stimulate reproductive development. One group received a bath with water daily and the other group received a dry bath (both groups had ad libitum access to drinking water through a glass tube). Birds with a dry bath tended to show reduced photoperiodically-induced gonadal growth compared with birds that had access to water in the bath. Plasma levels of luteinizing hormone (LH) and follicle-stimulating hormone (FSH) increased following photostimulation in all groups. However, LH levels were higher in females with access to water. There were no differences in hormone levels in any of the other groups. Taken together these novel data indicate that presence and access to open water could be an important environmental cue for Song Sparrows in western Washington State. Implications for global climate change and droughts are suggested.
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Combined effects of DHEA and fadrozole on aggression and neural VIP immunoreactivity in the non-breeding male Song Sparrow
Hormones and Behavior, 2008Co-Authors: Douglas W Wacker, Barney A. Schlinger, John C WingfieldAbstract:The male Song Sparrow, Melospiza melodia morphna, shows high levels of aggression in its non-breeding season, concomitant with basal levels of circulating testosterone (T) and estradiol (E(2)). However, administration of fadrozole, an aromatase inhibitor, decreases non-breeding aggression in the field. Circulating levels of dehydroepiandrosterone (DHEA), an androgen/estrogen precursor, correspond to the seasonal expression of aggression in this species, with high levels in the breeding and non-breeding seasons when aggression is also high, and lower levels during the molt when aggression is low. We test the hypothesis that circulating DHEA up-regulates non-breeding aggression via an aromatase-mediated mechanism. We also hypothesize that this up-regulation of aggression is partially mediated by changes in vasoactive intestinal polypeptide (VIP) in the lateral extent of the bed nucleus of the stria terminalis (BSTl) and lateral septum (LS). Birds were administered either DHEA, fadrozole, or both for 2 weeks and tested for aggression in a lab-based paradigm. As predicted, birds given DHEA were significantly more aggressive. However, fadrozole did not block this effect, and, when administered without DHEA, also led to increased aggression over controls. These results may be explained by the fact that the behaviors measured in field tests, which include more direct attack behaviors, may be under different hormonal regulation than the behaviors measured in the lab paradigm, which represent warning, or threat, behaviors. VIP immunoreactivity (VIP-ir) changed across multiple brain regions with this treatment regimen, most notably in the LSO/VFI subdivision of the lateral septum.
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Seasonality and Hormonal Control of Territorial Aggression in Female Song Sparrows (Passeriformes: Emberizidae: Melospiza melodia)
Ethology, 2000Co-Authors: Michelle M. Elekonich, John C WingfieldAbstract:Male and female Song Sparrows perform similar aggressive behaviors including flights, wing-wave threat displays, and growls. Females very rarely sing, however. To investigate the seasonal variation and hormonal control of territorial aggression in females, we simulated female intrusions during the pre-breeding, breeding and post-molt seasons in the field. Circulating levels of testosterone, dihydrotestosterone, estradiol, progesterone and corticosterone in females experiencing simulated intrusion were compared to those of passively netted females matched for breeding stage. Female aggressive responses to female intrusion dropped from the pre-breeding to the post-molt seasons. Levels of circulating androgens were significantly higher in control females than in females experiencing a simulated intrusion. There were no significant differences in any of the other hormones measured. Although Song Sparrow female-female aggression appears to be behaviorally similar to male-male aggression, the seasonal variation and hormonal support of aggression differ between the sexes.
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regulation of territorial behavior in the sedentary Song Sparrow melospiza melodia morphna
Hormones and Behavior, 1994Co-Authors: John C WingfieldAbstract:Male Song Sparrows (Melospiza melodia morphna) of western Washington State show year-round territoriality. Although territorial aggression during the breeding season was accompanied by high circulating levels of luteinizing hormone (LH) and testosterone (T), similar aggression in the non-breeding season occurred when gonadal hormone levels were basal. Experimental removal of territorial males in autumn resulted in new males taking over the territory within a few days. These males had basal levels of LH and T despite establishing a new territory and the accompanying high level of aggression. There was also no difference in plasma levels of corticosterone in replacement versus established territorial males suggesting that social stress was not a factor. To test the possibility that low levels of gonadal steroids, or potentially some gonadal hormone not measured here, might regulate territorial aggression in the non-breeding season, free-living male Song Sparrows were castrated in early autumn and their aggressive territorial behavior was quantified by a simulated territorial intrusion (STI). Castrates showed the same aggressive responses to STI as controls indicating that establishment and maintenance of a territory was not dependent upon hormones of gonadal origin. Castrated males retained territories throughout the autumn and winter and even into the following breeding season. Further experiments were conducted to establish a role, if any, for T in territorial behavior in this species. During the breeding season when males had high levels of T, the responses to STI continued after the stimuli (caged conspecific male and tape-recorded Songs) were withdrawn. Some males continued to patrol the territory and sang for long periods after STI. In contrast, males exposed to STI in autumn showed a strong aggressive response during the challenge, but then territorial aggression abated rapidly when the stimuli were withdrawn. Implants of T into males in autumn reinstated the high level of aggression after withdrawal of STI in a manner similar to that seen during the breeding season. These data suggest that in M. m. morphna T does not activate territorial aggression per se, but may increase the intensity of an aggressive response to STI, and persistence of the behavior after STI is withdrawn.
Simone Meddle - One of the best experts on this subject based on the ideXlab platform.
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the presence of water influences reproductive function in the Song Sparrow melospiza melodia morphna
General and Comparative Endocrinology, 2012Co-Authors: John C Wingfield, Kimberley Sullivan, Jessica Jaxionharm, Simone MeddleAbstract:Abstract Cumulative evidence indicates that Song Sparrows, Melospiza melodia morphna, of western Washington State prefer territories close to water. Densities of territories were higher within 50 m of open water and analysis of stomach contents revealed aquatic organisms. An unusually dry period (less open water) in May and June 1997 had no effect on latency of territorial males to respond to a simulated territorial intrusion (STI), but the number of Songs and closest approach to the decoy were lower than those recorded in June 1988 (no major dry periods). A laboratory experiment was conducted in which males and females were exposed to long days to stimulate reproductive development. One group received a bath with water daily and the other group received a dry bath (both groups had ad libitum access to drinking water through a glass tube). Birds with a dry bath tended to show reduced photoperiodically-induced gonadal growth compared with birds that had access to water in the bath. Plasma levels of luteinizing hormone (LH) and follicle-stimulating hormone (FSH) increased following photostimulation in all groups. However, LH levels were higher in females with access to water. There were no differences in hormone levels in any of the other groups. Taken together these novel data indicate that presence and access to open water could be an important environmental cue for Song Sparrows in western Washington State. Implications for global climate change and droughts are suggested.
Peter Arcese - One of the best experts on this subject based on the ideXlab platform.
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Data used in the analysis of Lifetime number of adult offspring produced by adult individuals.
2017Co-Authors: Pirmin Nietlisbach, Peter Arcese, Lukas Keller, Glauco Camenisch, Frédéric Guillaume, Jane Reid, Erik PostmaAbstract:Data file with one row per individual Song Sparrow used in the analysis of Lifetime number of adult offspring produced by adult individuals, with the following columns. Fecundity: Relative lifetime number of adult offspring produced by adult individuals, i.e. number of offspring reaching adulthood (i.e. one year old) produced by the focal individual across its lifetime divided by the mean number of adult offspring of all individuals in this dataset (all focal individuals in this dataset are adults). Sex: Sex of the individual, i.e. Male or Female. F: Pedigree-based inbreeding coefficient. MLH: Mean heterozygosity across 160 microsatellite markers. hi_*: 160 columns with heterozygosity data at each of 160 microsatellite markers, with 0=homozygous, 1=heterozygous, NA=unknown
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Data used in the analysis of Lifespan.
2017Co-Authors: Pirmin Nietlisbach, Peter Arcese, Lukas Keller, Glauco Camenisch, Frédéric Guillaume, Jane Reid, Erik PostmaAbstract:Data file with one row per individual Song Sparrow used in the analysis of Lifespan, with the following columns. Age: Relative lifespan, i.e. lifespan (in years) divided by mean lifespan of all individuals in this dataset. Sex: Sex of the individual, i.e. Male or Female. F: Pedigree-based inbreeding coefficient. MLH: Mean heterozygosity across 160 microsatellite markers. hi_*: 160 columns with heterozygosity data at each of 160 microsatellite markers, with 0=homozygous, 1=heterozygous, NA=unknown
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nest defense and parental investment in Song Sparrows melospiza melodia
Canadian Journal of Zoology, 2016Co-Authors: Nina Morrell, Kate M Johnson, Corey E Tarwater, Peter ArceseAbstract:Individual variation in nest defense behaviour is common in altricial birds, but despite clear predictions about why such variation exists, there is no consensus on its causes. We tested for an influence of five predictors of individual variation in nest defense behaviour, including time of season, offspring age, parental age and sex, and clutch size in a well-studied Song Sparrow (Melospiza melodia (A. Wilson, 1810)) population. We recorded parental responses to a standardized human approach and used model selection to assess support for each predictor. Parents tended to approach observers less closely and alarm-call less as the breeding season progressed, indicating a modest seasonal decline in parental nest defense, which is consistent with the hypothesis that the reproductive value of offspring influenced parental defense behaviour. Clutch size effect estimates were insignificant, but it was weakly supported as a predictor of nest defense, which is expected if parental investment in defense and curren...
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Inbreeding coefficient and heterozygosity-fitness correlations in unhatched and hatched Song Sparrow nestmates.
Molecular Ecology, 2010Co-Authors: Sabrina S. Taylor, Peter Arcese, Jane M. Reid, Rebecca J. Sardell, Thomas Bucher, Nathan Taylor, Lukas F. KellerAbstract:Heterozygosity-fitness correlations use molecular measures of heterozygosity as proxy estimates of individual inbreeding coefficients (f) to examine relationships between inbreeding and fitness traits. Heterozygosity-fitness correlations partly depend on the assumption that individual heterozygosity and f are strongly and negatively correlated. Although theory predicts that this relationship will be strongest when mean f and variance in f are high, few studies of heterozygosity-fitness correlations include estimates of f based on pedigrees, which allow for more thorough examinations of the relationship between f, heterozygosity and fitness in nature. We examined relationships between pedigree-based estimates of f, multilocus heterozygosity (MLH) and the probability of survival to hatch in Song Sparrow nestmates. f and MLH were weakly, but significantly negatively correlated. Inbreeding coefficient predicted the probability of survival to hatch. In contrast, MLH did not predict the probability of survival to hatch nor did it account for residual variation in survival to hatch after statistically controlling for the effects of f. These results are consistent with the expectation that heterozygosity-f correlations will be weak when mean and variance in f are low. Our results also provide empirical support for recent simulation studies, which show that variation in MLH among siblings with equal f can be large and may obscure MLH-fitness relationships.
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a metapopulation approach to the population biology of the Song Sparrow melospiza melodia
Ibis, 2008Co-Authors: James N M Smith, Peter Arcese, Lukas F. Keller, Mary J. Taitt, Christopher Rogers, Alice Cassidy, Wesley M HochachkaAbstract:In this paper, we describe spatial variation in the demography of the Song Sparrow Melospiza melodia. Long-term population studies of birds have generally considered only single sites in optimal habitat, but recent theory has shown the value of taking spatial variation in population dynamics into account. In this theory, collections of local populations in habitat patches connected by dispersal are defined as metapopulations. We review metapopulation models briefly and then use these ideas in a study of the Song Sparrow. Sparrows were studied on islands of varying size and degree of isolation from the North American continent. For analysis, these islands are grouped into three areas. Sparrows on the isolated Mandarte Island usually reproduced and survived well over 17 years but suffered from catastrophic mortality in some winters. After such events, the population recovered quickly without much immigration. Sparrows on smaller islets near Mandarte also survived and reproduced well during 4 years, and they did not experience severe mortality in a winter in which those on Mandarte declined by over 90%. These small islets frequently exchanged first year birds, but only one yearling bird moved between the small islets and the more isolated Mandarte. Sparrows at one of two sites on the larger Westham Island, near the continental mainland, survived less well than on the small offshore islands. Reproduction on Westham Island was poor because of frequent nest failure and high levels of brood parasitism by Brown-headed Cowbirds Molothrus ater. Despite this poor reproduction and survival, the Westham population remained stable as a result of immigration. We interpret the dynamics of these Sparrow populations in terms of H.R. Pulliam's source-sink metapopulation model.
S. Elizabeth Campbell - One of the best experts on this subject based on the ideXlab platform.
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Extrapair paternity, Song, and genetic quality in Song Sparrows
Behavioral Ecology, 2010Co-Authors: Christopher E. Hill, S. Elizabeth Campbell, Çağlar Akçay, M. I.c.h.a.e.l.d. BeecherAbstract:Most Songbirds are socially monogamous, yet molecular studies have found that in most species, some offspring in the nest are sired by males other than the social mate of the female. The functional significance of extrapair paternity (EPP) in social monogamy is poorly understood, despite numerous theoretical and empirical studies in the last decades. We have examined EPP in the Song Sparrow (Melospiza melodia) using microsatellites and tested whether females choose as extrapair mates males that 1) had larger Song repertoires, 2) shared more Songs with their neighbors, 3) were more heterozygous, or 4) were less related to the females than the social mate of these. We found that 24% of offspring were sired by extrapair males and that the extrapair sires were invariably neighbors. However, neither Song repertoire size nor Song sharing with neighbors predicted a male’s EPP success. Furthermore, neither heterozygosity of a male nor his relatedness to the female predicted EPP success. At the same time, males that did not lose paternity in their own nest or gain paternity in other nests tended to be younger. These results indicate that females are not using Song repertoire size or Song sharing as a basis for extrapair mate choice and are not likely to accrue significant genetic benefits from EPP. Instead, the occurrence and level of EPP in this population might be primarily governed by behavioral trade-offs between mate guarding and pursuing extrapair copulations. We suggest that detailed behavioral studies are needed to understand extrapair mating in this species. Key words: bird Song, compatible genes, extrapair paternity, good genes, Song Sparrow. [Behav Ecol]
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Song sharing in two populations of Song Sparrows (Melospiza melodia)
Behavioral Ecology and Sociobiology, 1999Co-Authors: Christopher E. Hill, S. Elizabeth Campbell, J. Cully Nordby, John M. Burt, M. I.c.h.a.e.l.d. BeecherAbstract:Sharing Song types with immediate neighbors is widespread in birds with Song repertoires, and sharing Songs may confer a selective advantage in some cases. Levels of Song sharing vary between different geographical populations of several bird species, and ecological differences often correlate with differences in singing behavior; in particular, males in migratory subspecies often share fewer Songs than males in resident subspecies. The Song Sparrow (Melospiza melodia) appears to fit this pattern: resident Song Sparrows in western North America generally share 20–40% of their repertoire (of about eight Songs) with each neighbor, while migratory subspecies from eastern North America often share 10% or less. We compared Song sharing in two populations within a single subspecies of Song Sparrow (M. m. morphna) in Washington State. These populations, separated by only 120 km, nonetheless differ in migratory tendencies and several other ecological and life history variables. We recorded complete Song repertoires from 11 male Song Sparrows in a high-elevation, migrating population at Gold Creek in west-central Washington, and compared them to two samples (n = 15 and n = 36) from a coastal, resident population at Discovery Park, Seattle, Washington. Despite major differences in habitat, population density, and migratory tendencies, Song sharing among Gold Creek males was as high as that among Discovery Park males. In both populations, sharing was highest between immediate neighbors, and declined with distance. We conclude that at the within-subspecies level, neither migration nor population density affect Song sharing in Song Sparrows, a Song repertoire species.
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Song-type matching in the Song Sparrow
Canadian Journal of Zoology, 1992Co-Authors: Philip K Stoddard, M. I.c.h.a.e.l.d. Beecher, S. Elizabeth Campbell, Cynthia L. HorningAbstract:Song playback to Song Sparrows (Melospiza melodia) in a resident population in Washington state showed that the tendency of birds to respond with the same Song type (match) depended on the identity of the singer. Matching rates were high to 'self Song (60%) and 'stranger' Song (50%) and low to 'neighbor' Song (20%, not significantly above chance level). The higher matching rate to stranger Song was particularly interesting, since the neighbor test Songs were generally more similar to the subjects' Songs than were the stranger test Songs (the self Songs, of course, were the most similar). The importance of the neighbour–stranger contrast, in addition to Song similarity, in eliciting Song matching confirms similar conclusions from earlier studies on the great tit (Parus major) and western meadowlark (Sturna neglecta).
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Memory Does Not Constrain Individual Recognition in a Bird With Song Repertoires
Behaviour, 1992Co-Authors: Philip K Stoddard, M. I.c.h.a.e.l.d. Beecher, Patricia Loesche, S. Elizabeth CampbellAbstract:Summary We tested the hypothesis that memory or perceptual limitations imposed by Song repertoires contrain the ability of Song birds to recognize their neighbours by Song. Using operant conditioning procedures, we trained male Song Sparrows (Melospiza melodia) (median repertoire size = 8) to discriminate between two artificial Song Sparrow repertoires of 32 Songs each (64 Songs total). Both Song Sparrows learned to discriminate concurrently between all 32 Song pairs. The birds learned later Songs as quickly as they learned earlier Songs. These results suggest that Song Sparrows are capable of memorizing the full Song repertoire of their neighbours under natural conditions. In a second experiment we found that Song Sparrows readily generalize from one exemplar of a Song type to other variations of that Song type. We conclude that the evolution of Song repertoires of Song Sparrows have neither constrained nor been constrained by individual recognition of neighbours by Song.
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Recognition of individual neighbors by Song in the Song Sparrow, a species with Song repertoires
Behavioral Ecology and Sociobiology, 1991Co-Authors: Philip K Stoddard, M. I.c.h.a.e.l.d. Beecher, Cynthia L. Horning, S. Elizabeth CampbellAbstract:Previous theory and research have suggested that bird species with Song repertoires in general, and Song Sparrows (Melospiza melodia) in particular, cannot readily discriminate between the Songs of neighbors and strangers. In a recent study (Stoddard et al. 1991) we showed that Song Sparrows can in fact discriminate neighbors from strangers on the basis of Song. In this study we sought to demonstrate that Song Sparrows can make the finer discrimination between individual neighbors and that they can do so on the basis of a single Song type. We compared the response of territorial males to Song playback of neighbors and strangers at three locations: the neighbor's regular boundary, the opposite boundary, and the center of the territory. The birds showed strong neighbor-stranger discrimination at the regular boundary but not at the opposite boundary, nor in the center of the territory. The differences in Song discrimination between different boundary locations indicate that Song Sparrows associate particular Songs with particular territories, effectively discriminating between individual neighbors on the basis of Song. Song repertoires themselves do not interfere with neighbor recognition to the extent originally postulated. As speakers are moved inside the territory from the border, however, the degree of discrimination diminishes. We believe that differences in speaker placement may have contributed to the variability in neighbor-stranger discrimination observed in previous studies of the Song Sparrow and perhaps other repertoire species as well. This interpretation is consistent with data from another Song Sparrow population showing that half the territory takeovers are by immediate neighbors.