A CRITIQUE OF INTERSPECIFIC TERRITORIALITY AND CHARACTER CONVERGENCE

BERTRAM G. MURRAY, JR.

Cody (1969) suggested that may con- (which, as Cody noted, were merged into verge in appearance or voice because simi- Malaconotus by Hall et al. 1966). Of this larities increase interspecific aggressiveness, case Cody (1969: 227) wrote, “Convergence which leads to the individuals of two species in advertising characters presupposes inter- maintaining mutually exclusive territories in specific territoriality in some form or to some a common habitat. The advantage of such extent, but no evidence has been found in behavior is that it results in the exclusion of the literature to indicate that the species of food competitors within the individuals ’ ter- the ‘ ’ group are in fact inter- ritories. Thus, according to Cody, interspecific specifically territorial with those of the Mala-‘ territoriality is adaptive. In 1971 I published conotus ’ group; rather, as this information is an interpretation of observed cases of inter- at present lacking, the inclusion of bush- specific territoriality, in which I assumed that shrikes in this paper amounts to a prediction interspecific territoriality was aggression that that when these are better known they evolved in intraspecific contexts but was mis- will be found to defend territories inter- directed toward individuals of other species specifically across the groups.” which possessed similar features that nor- (2) Concerning a pair of Asian wood- mally stimulated intraspecific territorial ag- peckers Cody (1969: 231) wrote, “NO one gression ( Murray 1971). I argued that mutual has reported interspecific territoriality be- interspecific territoriality is maladaptive for tween Dinopium and , and un- at least one of the species because the sub- til direct evidence is forthcoming the ulti- ordinate species would eventually be excluded mate test of my hypothesis cannot be made.” from otherwise optimal habitat, but I did not (3) Concerning another pair of Asian wood- exclude the possibility of the existence of peckers Cody (1969: 231) wrote “That cases of adaptive interspecific territoriality. 1Meiglyptes] jugularis and [ Hemicircus] can- The two hypotheses, then, seem contradictory. ente may be interspecifically territorial can- The first assumes that cases of mutual inter- not be verified from published observations.” specific territoriality are adaptive, while the (4) Concerning another pair of Asian second assumes that they are not. , LMicropternus hrachyurus and Some authors studying birds (Barlow et pyrrhotis, Cody (1969: 231) al. 1970, Brown and Orians 1970, Cheke 1971, wrote, “Again I!] the similarities may be at- Rohwer 1972, 1973, Kroodsma 1973, Emlen tributed to interspecific territoriality,” but also et al. 1975), fishes (Myrberg and Thresher again no references to such interspecific ter- 1974)) hermit crabs (Hazlett 1972 a, b), and ritoriality are reported. These species are not flowers (Levin and Schaal 1970) have found known to be sympatric (Short, in litt. 1975). Codys’ hypothesis reasonable. It has appeared (5) Concerning the Central American as an annual review article (Cody 1973) and woodpeckers, lineatus and Phloeo- as a portion of a book (Cody 1974), and has ceastes melanoleucos, Cody (1969: 232) wrote, been described in at least two ecology text- “As such observations [of both species feed- books (Ricklefs 1973, Smith 1974). Because ing in the same tree] are not dated in refer- Codys’ hypothesis is widely accepted and is ence to the breeding season, they do not contradictory to my own, I wish to examine preclude the possibility of interspecific terri- it and the evidence for it in some detail. toriality.” Subsequent observations by Kilham (1972) showed that D. lineatus and P. me- CODYS’ CASES OF INTER- Zanoleucos differ in the time of their breed- SPECIFIC TERRITORIALITY ing seasons, in their nest sites, and in their foraging behavior and that when they come One criterion for evaluating a theory is the into contact their relationship is “peaceful.” quality of the data presented as supporting Karr (1971) also failed to find evidence of evidence. conflict between these species in central Pan- (1) Cody first discussed the similarities in ama. color and pattern of the African bush-shrikes (6) Concerning the North American wood- of the genera Chlorophoneus and Malaconotus peckers, Dryocopus pileatus and

[5181 The Condor 78:518-525, 1976 INTERSPECIFIC TERRITORIALITY AND CHARACTER CONVERGENCE 519 principalis, Cody (1969: 233) wrote, “From bicolor), both competitors for acorns; they information in Tanners’ (1942) monograph behaved similarly toward Starlings (Sturnus on the Ivory-bill, the question of interspecific vulgaris), competitors for holes in trees, in- territoriality could not be resolved (one in- dicating the capacity of woodpeckers to be stance of apparent interspecific aggression interspecifically territorial against birds of dif- was observed), but it appears that territories ferent appearance and behavior. do in fact overlap somewhat between the two Finally, the interpretation of the wood- species (Tanner, pers. comm.) .” pecker cases depends upon ones’ conception Cody (1969: 233) summarized the results of their phylogenetic relationships. Cody of his survey of convergence and interspecific (1969) separated the woodpeckers into two territoriality in woodpeckers, “Although inter- groups of genera, the “logcocks” (Meiglyptes, specific territoriality has not been established Micropternus, Dinopium, and Dryocopus) for the above species pairs, it is commonly and the “ivory-bills” ( Hemicircus, Blythipicus, found in woodpeckers generally, e.g., for Chrysocolaptes, Campephilus, and Phloeo- breeding Centurus aurifrons, C. carolinus, and ceastes), following the classification in Peters C. uropygialis (Selander and Giller 1959, (1948). He cited but did not discuss the im- 1963), for wintering Centurus carolinus, Me- plications of Bocks’ (1963) arguments for lanerpes erythrocephalus, and Dendrocopos grouping Micropternus with Blythipicus, Di- pubescens (Kilham 1958)) for wintering Me- nopium with Chrysocolaptes, and Dryocopus lanerpes formicivorus and Asyndesmus lewis with Campephilus ( = Phloeoceastes) . Good- over acorn stores (Carl Bock, pers. comm.), win (1968) also considered Dinopium and and for Picus viridis, Dendrocopos major, Chrysocolaptes closely related and went so far and D. minor over nest sites (Howard 1920) .” as to merge the New World Dryocopus and One can only speculate why Cody did not Phloeoceastes into Campephilus. Short ( 1973) test his theory of convergence in appearance has described vocalizations and other displays and voice resulting from advantages gained by that indicate a close relationship between interspecific territoriality against these re- Meiglyptes and Hemicircus and, again, be- ported cases of interspecific territoriality. It tween Dinopium and Chrysocolaptes. is of interest that Centurus aurifrons and C. If the relationships are as de- carolinus are sibling species that are virtually scribed by Bock (1963), Goodwin (1968), allopatric, coming into contact only near Aus- and Short (1973), then the similarities of the tin, Texas (Selander and Giller 1959). Their woodpeckers cited by Cody are probably the similarity is almost certainly the result of result of close relationship rather than of se- common ancestry rather than the result of lection for similarities that promote inter- convergence that promotes interspecific ag- specific aggression, which has yet to be re- gression with potential competitors. The case ported. of interspecific territoriality between C. auri- (7) Codys’ seventh case was the reported frons and C. uropygialis is a casual specula- interspecific territoriality and similarity of tion (Selander and Giller 1963: 242). Even songs of the two closely-related wren species, if interspecific territoriality is confirmed, these Thryothorus felix and T. sinaloa in Mexico species are allopatric (Selander and Giller (Grant 1966). Because I believed that inter- 1963: 259) and closely related, forming a specific territoriality had not been sufficiently superspecies with C. carolinus (Mayr and documented, I did not consider this case in Short 1970). my earlier analysis of interspecific territorial- Interspecific territoriality between the Red- ity (Murray 1971). Grant studied popula- bellied Woodpecker, Red-headed Wood- tions of unmarked birds for one week and pecker, and Downy Woodpecker, between produced a map showing non-overlapping ter- the Acorn Woodpecker and Lewiss’ Wood- ritories. Although he was unable to distin- pecker, and between the Green Woodpecker guish the songs of the two species, the caption and the Greater Spotted and Lesser Spotted to his figure (Grant 1966: 268) stated, “Each woodpeckers seems to indicate that wood- seen or heard was recorded.” I am re- peckers which differ strikingly in plumage, luctant to accept this evidence for inter- voice, and behavior can be interspecifically specific territoriality because of my own ex- territorial. perience with populations of individually Further, Kilham (1958) reported that the color-marked sparrows ( Murray 1969)) war- Red-headed Woodpeckers were intensely and blers (Murray and Gill 1976), and a thrush persistently aggressive toward Blue Jays ( CY- (work in progress). For example, Blue- _ anocitta cristata) and Tufted Titmice (Parus winged Warblers (Vermivora pinus) and 520 BERTRAM G. MURRAY, JR.

Golden-winged Warblers (V. chrysoptera) of the 16 comparisons between sympatric and tend to sing from different perches even non-sympatric populations of Eastern and though their territories overlap entensively Western meadowlarks showed statistically sig- (Ficken and Ficken 1968, Gill and Murray nificant differences, all differences were in 1972, Murray and Gill 1976). A brief survey the direction of convergence. Because five of unmarked birds could lead one to believe of the significant differences were in male that they were interspecifically territorial. comparisons and because these characters Although Cody (1969: 235) considered the seemed to be associated with male aggres- similarity of the songs of the wrens “An in- sive display, Rohwer thought the convergence disputable case of vocal convergence,” Grant was caused by selection for signals related (1972) emphasized that there was no evi- to interspecific aggression. Yet, Rohwer has dence for convergence. Grant considered the not demonstrated that the small differences similarity of songs to be the result of a lack measured by his planimeter and reflectance of divergence. In fact, the songs may not be spectrophotometer are detectable by the birds as similar as Grant reported. Both Davis or that these differences in any way enhance (1972) and Edwards (1972) described dis- interspecific aggression. Inasmuch as all tinctively different songs for T. felix and T. changes in both species, including even the sinaloa, and J. W. Hardy (pers. comm.), who females, which are not aggressive, are to- has tape-recorded both species ’ songs in west- wards convergence, I think the parsimonious ern Mexico, identifies Grants’ (1966: 269) interpretation is that both species are re- audiospectrograms of the two species ’ songs sponding to their common physical environ- as belonging to the same species, T. sinaloa. ment. (8) The next case discussed by Cody is (9) The final case considered in detail by an undoubted case of mutual interspecific Cody (1969) concerned the similarity be- territoriality, between the Eastern and West- tween certain populations of the salamanders ern meadowlarks (Sturnella magna and S. Plethodon jordani and Desmognathus ochro- neglecta, respectively) as reported by Lanyon phaeus. Again, there are no references to (1956, 1957). Cody (1969: 235-236) sug- interspecific aggression or even to intraspe- gested that where these species are sym- cific territoriality. Historically this case has patric their primary songs have converged: been considered to be one of mimicry (Dunn “Throughout most of the zone of sympatry 1927 and following workers), a possibility the phenomenon of hybrid‘ song ’ has been re- that Cody considered and rejected. However, corded (Lanyon 1957: 23; J. Zimmerman, Brodie and Howard (1973) restudied these pers. comm.; and myself for Kansas), in populations in the field and laboratory, con- which it becomes exceedingly difficult to ducted further experiments on mimicry, and determine whether the vocalist is magna or concluded that mimicry of P. jordani by D. neglecta.” Cody implied that “hybrid song” ochrophaeus is the best interpretation of their is common, but other authors have found similarities. They found no evidence of either “hybrid song” rare. Lanyon (1957) cited intra- or interspecific territoriality. several published references to “hybrid song” These are the nine cases that Cody pre- and bivalent repertoires, but he found no sented in detail, No case unambiguously cases of “hybrid song” and only three cases links interspecific territoriality and conver- of bivalent song in four years ’ study in the gence. Indeed interspecific territoriality is northcentral United States. He has never unreported in seven of the nine cases. And found a case of “hybrid” song in later re- the similarities may be a consequence of close search throughout the zone of overlap (Lan- relationship rather than convergence in all yon, in litt. 1975). And in two years ’ field but the salamanders, which is an apparent work in the central and southern Great Plains case of mimicry. Rohwer (1972) found “hybrid” or intermedi- ate meadowlark songs “extremely rare.” THE MEXICAN FINCHES Rohwer ( 1973), however, reported con- Cody and Brown (1970) observed inter- vergence in appearance of these species, which specific territoriality between Pipilo ocai and he attributed to selection for interspecific Atlapetes brunneinucha and between P. ocai communication signals associated with inter- and P. erythrophthalmus during nine days ’ specific territoriality. Rohwer measured the field work on Cerro San Felipe, Oaxaca, size of the black V and the brightness, purity, Mexico. In the first case the two species and dominant wavelength of yellow breast of bear a striking resemblance to each other. both males and females. Although only six This resemblance has been noticed by others INTERSPECIFIC TERRITORIALITY AND CHARACTER CONVERGENCE 521

BO B 3 I3 c1 B > B 0 B 0

II - c '0 66 ,” IO- 22 IL 12 8 108 I 8 I 2 I 30 I 0 a7-is I 12 fn I I 3 4 I I 2 6 I I IO

4 16 I

I- CHIAPAS GUERRERO VERACRUZ SAN LUIS I I POTOSI OAXACA PUEBLA MICHOACAN JALISCO

FIGURE 1. Distribution of Atkzpetes hnneinucha (B ) and Pipilo ocai (0) in Mexico. The number of specimens is given for each species in each state at 500 ’ intervals. Data for P. ocai are from Sibley (1950), Sibley and West (1958), and Sibley and Sibley (1964). Data for A. hnneinucha are from specimens at the Moore Laboratory of Zoology, National Museum of Natural History, American Museum of Natural His- tory, University of California Museum of Vertebrate Zoology, California Academy of Sciences, and Carnegie Museum. and attributed to either close relationship species normally occupying different habitats (Short 1971) or parallelism (Wetmore 1943, within an area of sympatry. Sibley 1950), although their exact relation- The second case of interspecific territorial- ship is not known (Parkes 1954). That this ity involves the resemblance of songs of P. resemblance can be considered “convergence” ocai and P. erythrophthalmus. A problem that enhances interspecific territoriality, as here is whether the two forms are in fact suggested by Cody and Brown, seems un- species. Although P. ocai and P. erythroph- likely because, although P. ocais’ geographic thalmus interbreed extensively in central Mex- range is almost entirely included within A. ico, Sibley (1950) recognized the two forms brunneinuchas’ much more extensive range, as distinct species because at Cerro San Felipe the two species normally occur at different no interbreeding was detectable. Mayr (in elevations (fig. 1) and in different habitats Mayr and Short 1970) also considered them (Blake 1953, A. R. Phillips in lift.), contrary different species. However, Short (1969, and to Cody and Browns’ (1970: 309) statement in Mayr and Short 1970) prefered to consider that “within the range of sympatry the alti- them conspecific because the extent of inter- tudinal distribution of brunneinucha virtually breeding and introgression greatly exceeds coincides with that of ocai. . . .” They seem to the extent of coexistence without interbreed- meet in numbers only in Oaxaca, in particular ing. If the two forms are conspecific, then, on Cerro San Felipe. The extent of contact by definition, their mutual aggression cannot seems too small to account for convergence of be interspecific territoriality. But even if plumage, whose advantage is stimulation of considered conspecific the two populations at interspecific aggression. This case fits the Cerro San Felipe have certainly achieved re- pattern of interspecific territoriality I pre- productive isolation, and some may consider sented earlier (Murray 1971), being an ex- their aggression there to be interspecific ter- ample of interspecific territoriality between ritoriality. Surely, it is not intraspecific ter- 522 BERTRAM G. MURRAY, JR. ritoriality. The point, however, is that what- Bishop (Euplectes hordeacea) and Zanzibar ever taxonomic rank one gives the two Cerro Red Bishop (E. nigroventris) reported by San Felipe populations, they are clearly Fuggles-Couchman ( 1943)) ( e) several spe- closely related. The similarities between P. cies of bishops (Euplectes) and whydahs ocai and P. erythrophthalmus that stimulate (Coliuspasser, sometimes considered conge- the mutual aggression seem more likely at- neric with Euplectes) reported by Lack tributable to recent common ancestry than to ( 1935), Moreau and Moreau ( 1938), Emlen convergence. ( 1957), and Ruwet ( 1964)) ( f ) the Red- winged Blackbird (Agelaius phoeniceus) and OTHER CASES the Tricolored Blackbird (A. tricolor) re- Cody (1969, 1973, 1974) referred to other ported by Orians ( 1961) and Orians and Col- cases of actual or alleged interspecific ter- lier (1963), (g) the Redwinged Blackbird ritoriality or convergence. The actual cases and the Yellow-headed Blackbird (Xantho- are discussed in the next section of this paper. cephalus xanthocephalus) reported by Lins- The alleged cases include unpublished or in- dale (1938), Fautin (1940), Orians and Will- completely published observations of Cody son ( 1964), and Miller ( 1968), and (h) the and others. To evaluate each of these cases Sedge Warbler ( Acrocephalus schoenobae- as evidence for or against one theory or an- nus) and the Reed Warbler (A. scirpaceus) other seems to depend upon the publication reported by Brown and Davies (1949) and of details. For instance, Cody (1973, 1974) later by Catchpole (1972). Finally, (i) Mur- referred to an abstract by Ferry and De- ray (1969, 1971) has interpreted the non-ter- schaintre, in the abstracts of the Fourteenth ritorial behavior of the Sharp-tailed Sparrow International Ornithological Congress, which (Ammospiza caudacuta) and the sporadic I have not seen. Evidently, in a narrow zone aggression of the Le Contes’ Sparrow (Am- of sympatry the Melodious and Icterine war- mospiza leconteii) toward the Sharp-tailed blers (Hippolais polyglotta and H. icterina, Sparrow to be the consequences of selection respectively) are interspecifically territorial against mutual interspecific territoriality, and have similar songs. Further investigation which had occurred in the past. of this case by Ferry and Deschaintre (1974) A pattern in this diversity of situations can resulted in the conclusion (p. 307), “En be discerned. Cases of mutual interspecific somme, nous admettons que, dans le cas de territoriality occur between species that either nos contrefaisants et comme le dit Murray are largely allopatric (cases a and b) or oc- (I97I), interspecific‘ territoriality is misdi- cupy different habitats in areas of sympatry rected intraspecific territoriality.”’ (cases c, d, e, h). Species that are widely Evaluation of particular cases should await sympatric and occupy the same habitats either detailed reporting. differ in their intra- and interspecific terri- torial behavior (cases f and i) or they are ACTUAL CASES OF INTER- quite different in appearance (case g). This SPECIFIC TERRITORIALITY pattern indicates that mutual interspecific ter- A second criterion for evaluating a theory is ritoriality in widely sympatric species ex- its generality. Cody did not claim gener- tensively occupying the same habitat is rare, ality, and thus the fact that he did not dis- if it occurs at all. I therefore suggested that cuss all known cases of interspecific terri- mutual interspecific territoriality is disadvan- toriality is in itself of no great consequence. tageous for one of the species and should not Nevertheless, consideration of these cases be selected for (Murray 1971). This con- will help in understanding interspecific ter- clusion is contrary to the assumption of the ritoriality in general, and this understanding “convergence” hypothesis that mutual inter- may allow us to evaluate the theory. specific territoriality is advantageous. In addition to the cases involving (a) the Red-bellied and Golden-fronted woodpeckers THE “CONVERGENCE” HYPOTHESIS (Selander and Giller 1959) and (b) the There are other reasons for finding the “con- Eastern and Western meadowlarks (Lanyon vergence” hypothesis less than satisfying. Of 1956, 1957), already discussed above, other particular concern is the fact that the pre- cases that seem adequately described (Mur- dictions of the “convergence” hypothesis are ray 1971) involve (c) the Dusky Flycatcher explicitly contrary to those of the Competi- (Empidonax oberholseri) and the Gray Fly- tive Exclusion Principle. As Cody wrote, “To catcher (E. wrightii) reported by Johnson many ecologists the idea that selection may (1963, 1966), (d) the Black-winged Red actually favor increased similarity between INTERSPECIFIC TERRITORIALITY AND CHARACTER CONVERGENCE 523 species in character value until they even- sumes that the degree of territorial exclusion tually coincide is contraintuitive and contra- depends upon the degree of similarity, but, as dictory to what has been since the fifties a noted above, completely exclusive interspe- blanket application of the so-called Volterra-‘ cific territoriality occurs between dissimilar Gause ’ principle” ( Cody 1973: 190; para- species (e.g., some species of Euplectes and phrased in Cody 1974: 216). For one to ac- Coliuspasser, Emlen 1957, Ruwet 1964). And cept the “convergence” hypothesis, then, one the Red-headed Woodpecker is persistently ag- must reject the Competitive Exclusion Prin- gressive toward intruding Red-bellied Wood- ciple as a principle, applying it to certain com- peckers, Downy Woodpeckers, Blue Jays, petitive situations and not to others. Earlier Tufted Titmice, and Starlings (Kilham 1958). authors ( Wynne-Edwards 1962, Hamilton It seems that if interspecific aggression lead- 1964) had recognized that if cases of mutual ing to exclusion of competitors were ad- interspecific territoriality between species oc- vantageous, interspecific territoriality should cupying the same habitat were stable and had evolve regardless of dissimilarities in the ap- evolved by natural selection, then they con- pearances or voices of the species involved. tradicted the Competitive Exclusion Principle. Finally, it is not clear how the exclusion Challenging currently held principles is surely of individuals from otherwise suitable por- respectable scientific activity, but in this case tions of a species ’ habitat necessarily results there is no substantial body of fact to support in the exposure of those individuals to greater the challenge. At the same time, an enormous food density. It seems at least equally pos- amount of observation seems to be consistent sible that exclusion from suitable portions of with the predictions of the Competitive Ex- the habitat could result in those individuals clusion Principle, including one interpretation occupying less suitable areas with lesser food of the documented cases of interspecific ter- densities. Numerous reports, summarized by ritoriality (Murray 1971). Hinde (1956) and Brown ( 1969), indicate Next, consider the “convergence” hypoth- that within species some individuals are forced esis: “increased similarity could evolve con- to occupy marginal areas because of intra- currently with a decreasing territorial overlap specific territoriality. Interspecific territorial- between two species and actually promote a ity probably has the same consequences; in- behavioral response which separates territories dividuals of the subordinate species are forced to economic advantage. Suppose a mutation to occupy marginal areas and thus presumably in a male of one territorial species causes a reproduce less successfully. change in plumage coloration which results in a closer resemblance to males of an eco- SUMMARY logically-similar second species. This change The hypothesis that species converge in ap- could result in its partial exclusion from the pearance or voice because such convergence territories of this strong competitor, and this enhances mutual interspecific territoriality exclusion would be advantageous because the that results in the exclusion of food competi- food density to which the individual is then tors is examined. The cases presented in sup- exposed would be increased” (Cody 1969: port of this “convergence” hypothesis do not 224). link any case of convergence with any case This hypothesis explicitly assumes that an of interspecific territoriality; hence, the advantage of interspecific territoriality is in hypothesis does not explain any real situation, reducing competition for food. Yet in several much less a substantial body of fact. There proved cases of interspecific territoriality (e.g., exist cases of interspecific territoriality that the Redwinged and Tricolored blackbirds, are unexplained by the “convergence” hypoth- Orians 1961, Orians and Collier 1963; the esis. These known cases indicate that mutual Sedge and Reed warblers, Catchpole 1972) interspecific territoriality between species ex- much of the food is gathered outside the ter- tensively coexisting in the same habitat is ritories. In other cases, the birds do not nor- rare. They also indicate that interspecific mally occupy the same habitat but are inter- territoriality occurs between species which specifically territorial where their habitats occupy different habitats, forage outside their abut (e.g., Gray and Dusky flycatchers, John- territories, and differ in appearance, voice, or son 1963, 1966; the Black-winged Red Bishop both. Finally, the predictions of the “con- and Zanzibar Red Bishop, Fuggles-Couchman vergence” hypothesis are contrary to the pre- 1943, Moreau and Moreau 1938). dictions of the Competitive Exclusion Prin- The “convergence” hypothesis further as- ciple. 524 BERTRAM G. MURRAY, JR.

ACKNOWLEDGMENTS EDWARDS, E. P. 1972. A field guide to the birds of Mexico. Privately published, Sweetbriar, Vir- I thank all those persons who have assisted me in ginia. preparing this paper. I am particularly grateful to EMLEN, J. T., JR. 1957. Display and mate selec- J. W. Hardy, J. R. Jehl, Jr., M. Gochfeld, W. tion in the whydahs and bishop birds. Ostrich Shields, and F. B. Gill for reading and commenting 28:202-213. on one or more drafts of this paper. I have also EMLEN, S. T., J. D. RISING, AND W. L. THOMPSON. benefitted from comments on portions of this paper 1975. A behavioral and morphological study by W. E. Lanyon, K. C. Parkes, A. R. Phillips, S. of sympatry in the Indigo and Lazuli buntings A. Rohwer. and L. L. Short. L. C. Binford (Cali- of the Great Plains. Wilson Bull. 87:145-179. fornia Academy of Sciences), J. W. Hardy (then FAUTIN, R. W. 1940. The establishment and main- at the Moore Laboratory of Zoology at Occidental tenance of territories by the Yellow-headed Black- College ) , L. Baptista and Elizabeth Thompson bird in Utah. Great Basin Nat. 1:75-91. (Moore Laboratory of Zoology), N. K. Johnson FEIIRY, C., AND A. DESCHAINTRE. 1974. Le chant, (University of California Museum of Vertebrate signal interspecifique chez Hippolais icterina et Zoology), and K. C. Parkes (Carnegie Museum ) polyglotta. Alauda 42:289-311. kindly forwarded information on specimens at their FICKEN, M. S., AND R. W. FICKEN. 1968. Terri- institutions. D. Amadon (American Museum of torial relationships of Blue-winged Warblers, Natural Historv). R. W. Storer (University of Golden-winged Warblers. and their hvbrids. Michigan Museum of Zoology), and R. L. . Zusi Wilson Bully 80:442-451. ’ (National Museum of Natural History) allowed me FUGGLES-COUCHMAN, N. R. 1943. 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