Seasonal patterns of vocal mimicry in northern mockingbirds Mimus polyglottos

2014 ◽  
Vol 45 (6) ◽  
pp. 545-550 ◽  
Author(s):  
David E. Gammon

Behaviour ◽  
2013 ◽  
Vol 150 (12) ◽  
pp. 1375-1397 ◽  
Author(s):  
David E. Gammon

Many animal species imitate the sounds of other species, but we know little about why vocal mimics copy some species while failing to copy other species, i.e., ‘model selection’. In this observational study of free-living northern mockingbirds (Mimus polyglottos), I tested five hypotheses of model selection: (1) Proximity hypothesis: preferential imitation of species found in close proximity to the vocal mimic, (2) Aggression hypothesis: preferential imitation of species with which the mimic interacts aggressively, (3) Passive sampling hypothesis: preferential imitation of species heard frequently by the mimic, (4) Acoustic similarity hypothesis: preferential imitation of species whose sounds are acoustically similar to the non-imitative songs of the vocal mimic and (5) Alarm hypothesis: preferential imitation of alarm-associated vocalisations. The data supported only the acoustic similarity hypothesis. Given that this hypothesis has been supported in two additional mimicking lineages, it suggests a potential non-adaptive explanation for the evolution of vocal mimicry. Species that learn vocalisations are already predisposed toward learning sounds with key acoustic characteristics. Whenever natural selection favours a widening of the auditory template that guides model selection, vocal imitation of heterospecifics becomes more likely because of ‘learning mistakes’.





The Auk ◽  
2002 ◽  
Vol 119 (3) ◽  
pp. 855-858
Author(s):  
Brian D. Peer ◽  
Spencer G. Sealy


The Auk ◽  
2002 ◽  
Vol 119 (3) ◽  
pp. 855 ◽  
Author(s):  
Brian D. Peer ◽  
Kevin S. Ellison ◽  
Spencer G. Sealy


The Auk ◽  
1987 ◽  
Vol 104 (2) ◽  
pp. 198-207 ◽  
Author(s):  
Kim C. Derrickson

Abstract The singing behavior of 4 male Northern Mockingbirds (Mimus polyglottos) was studied during 1980 and 1981. Over 10,000 song bouts (repetition of a particular song type) were analyzed spectrographically. Between 102 and 412 distinct song types were identified for each male in a given year. Many of these song types (25.8-57.4%) occurred only once in this sample of singing behavior. Repertoire size was estimated by fitting an exponential curve to a cumulative plot of distinct song types as a function of consecutive bouts sampled. The resulting asymptote was the estimate of repertoire size. Sequences of at least 50 consecutive bouts were used in estimating repertoire size. The technique of using consecutive bouts was required because of the high proportion of rare song types. Several estimates were made for each male and resulted in mean repertoire size estimates of 100-200 song types for the four males. Long sequences (125-150 bouts) of consecutive bouts are preferred to estimate repertoire size accurately. In addition, the social situation in which the singing behavior occurred can alter significantly the estimate of repertoire size. For example, estimates produced from singing during patrolling or countersinging were smaller than estimates generated from singing while associating with a female. The repertoire size estimate increased between 1980 and 1981 for 3 of 4 males. The one male not showing an increase spent much time patrolling and interacting with neighboring males before dying early in 1981. These results are consistent with the impression that repertoire size increases with age.



1996 ◽  
Vol 6 (3) ◽  
pp. 271-283 ◽  
Author(s):  
Juan E. Martínez-Gómez ◽  
Robert L. Curry

SummaryThe Socorro MockingbirdMimodes graysoniis endemic to Socorro Island, Mexico, and has declined dramatically in this century. Study of its population size, distribution, and structure is currently under way to help assess its conservation status. In 1993 and 1994 215 Socorro Mockingbirds were ringed; a modified Lincoln index yielded a population estimate of 353 ± 66 individuals in 1994. Most of the birds observed occupied a small region at high elevation that covered less than 10% of the island's area. Average territory size was 1.48 ± 0.71 ha,n= 11. Of the 86 birds banded in 1993 67% were adults and 33% subadults. Of the 170 birds detected in 1994, including new captures and ringed individuals from the previous year, 44% were adults and 56% subadults. In 1993 62% were male and 38% female; in 1994 56% were male and 44% were female. The sex ratio of the population was similar to that of other undisturbed Mimid populations, which argues against the possibility that cats might prey disproportionately on incubating females. Moreover, the presence of young birds in both years indicates that successful reproduction was occurring and that the population was not suffering catastrophic nest failure, as might be caused by cat predation on nestlings or fledglings. Northern MockingbirdsMimus polyglottos, which first arrived on Socorro in the 1970s, occupied mainly open areas produced by sheep grazing, which suggests that the Socorro Mockingbird is not being competitively displaced. Our observations indicate that habitat degradation by sheep is the most probable cause of the Socorro Mockingbird's decline.





The Auk ◽  
2002 ◽  
Vol 119 (3) ◽  
pp. 855-858 ◽  
Author(s):  
Brian D. Peer ◽  
Kevin S. Ellison ◽  
Spencer G. Sealy

Abstract We experimentally parasitized Northern Mockingbird (Mimus polyglottos) nests to determine whether that species is more likely to eject immaculate eggs of the Bronzed Cowbird (Molothrus aeneus) or the spotted eggs of the Brown-headed Cowbird (M. ater); the latter species lays eggs that more closely resemble mockingbird eggs. Mockingbirds ejected 69% of model Bronzed Cowbird eggs, indicating that contrary to previous evidence Northern Mockingbirds eject Bronzed Cowbirds eggs at a high frequency. Mockingbirds also ejected 60% of model and real Brown-headed Cowbird eggs. Bronzed Cowbird eggs were ejected faster than Brown-headed Cowbird eggs (1.3 and 2.1 days, respectively). Ejection by mockingbirds may account for the lack of observed parasitism at our study sites in southern Texas, but it is more likely that cowbirds did not parasitize mockingbirds.



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