Mimus Polyglottos Research Articles

A Comparison of the mitochondrial performance between migratory and sedentary mimid thrushes.

Birds exhibit a variety of migration strategies. Because sustained flapping flight requires the production of elevated levels of energy compared to typical daily activities, migratory birds are well-documented to have several physiological adaptations to support the energy demands of migration. However, even though mitochondria are the source of ATP that powers flight, the respiratory performance of the mitochondria is almost unstudied in the context of migration. We hypothesized that migratory species would have higher mitochondrial respiratory performance during migration compared to species that do not migrate. To test this hypothesis, we compared variables related to mitochondrial respiratory function between two confamilial bird species-the migratory Gray Catbird (Dumetella carolinensis) and the non-migratory Northern Mockingbird (Mimus polyglottos). Birds were captured at the same location along the Alabama Gulf Coast, where we assumed that Gray Catbirds were migrants and where resident Northern Mockingbirds live year-round. We found a trend in citrate synthase activity, which suggests that Gray Catbirds have a greater mitochondrial volume in their pectoralis muscle, but we observed no other differences in mitochondrial respiration or complex enzymatic activities between individuals from the migrant versus the non-migrant species. However, when we assessed the catbirds included in our study using well-established indicators of migratory physiology, birds fell into two groups: a group with physiological parameters indicating a physiology of birds engaged in migration and a group with the physiology of birds not migrating. Thus, our comparison included catbirds that appeared to be outside of migratory condition. When we compared the mitochondrial performance of these three groups, we found that the mitochondrial respiratory capacity of migrating catbirds was very similar to that of Northern Mockingbirds, while the catbirds judged to be not migrating were lowest. One explanation for these observations is these species display very different daily flight behaviors. While the mockingbirds we sampled were not breeding nor migrating, they are highly active birds, living in the open and engaging in flapping flights throughout each day. In contrast, Gray Catbirds live in shrubs and fly infrequently when not migrating. Such differences in baseline energy needs likely confounded our attempt to study adaptations to migration.

Do vocal mimics learn their mimetic songs from heterospecifics or conspecifics?

Abstract Vocal mimicry can develop either through imitation of heterospecific models (primary mimicry) or through imitation of conspecifics already producing mimetic song (secondary mimicry). Distinguishing primary versus secondary mimicry is important from ecological, evolutionary, and neurobiological perspectives. We outline four empirical strategies for researchers to detect the usage of secondary mimicry: (1) model selection strategy (heterospecific model commonly mimicked but rare or absent locally), (2) usage frequency strategy (syllable types commonly mimicked but rarely used by the model), (3) acoustic structure strategy (acoustic divergence in how a syllable type gets produced by mimics versus models), and (4) syntax strategy (consistent variation between mimic and model in the ordering of syllable types). We then use these strategies to produce evidence for secondary mimicry in northern mockingbirds (Mimus polyglottos), focusing mostly on the mimicked songs of northern cardinals (Cardinalis cardinalis) and tufted titmice (Baeolophus bicolor). As further evidence of the mechanisms by which secondary mimicry might occur, we also demonstrate that mockingbirds match countersing much more frequently in response to conspecifics versus heterospecifics. Deeper questions about the precise extent of primary versus secondary mimicry in mockingbirds and other mimicking species still need answers.

Mocking Bird ( Mimus polyglottos ) calls potentially confound acoustic indices of bird diversity and provide a potential heuristic to distinguish them.

This study explores the increasing use of autonomous recording units (ARUs) in wildlife surveys. While ARUs offer cost-effective and efficient data collection, challenges arise in analyzing large datasets and accurately assessing species abundance. Our research focuses on avian communities, emphasizing the impact of vocal mimicry by Northern Mockingbirds ( Mimus polyglottos ) on survey accuracy. Utilizing the Merlin Bird ID application, we found an average accuracy rate of ~81.3%, with mockingbirds contributing ~31% of false positive identifications. Finding potential solutions for distinguishing mimics in bioacoustic survey data is crucial for enhancing accuracy as researchers increasingly adopt this methodology in the future.

Wild mockingbirds distinguish among familiar humans

Although individuals of some species appear able to distinguish among individuals of a second species, an alternative explanation is that individuals of the first species may simply be distinguishing between familiar and unfamiliar individuals of the second species. In that case, they would not be learning unique characteristics of any given heterospecific, as commonly assumed. Here we show that female Northern Mockingbirds (Mimus polyglottos) can quickly learn to distinguish among different familiar humans, flushing sooner from their nest when approached by people who pose increasingly greater threats. These results demonstrate that a common small songbird has surprising cognitive abilities, which likely facilitated its widespread success in human-dominated habitats. More generally, urban wildlife may be more perceptive of differences among humans than previously imagined.

Lead exposure is correlated with reduced nesting success of an urban songbird

Lead exposure is a concern in urban ecosystems, with physiological and behavioral effects well documented in humans. Wildlife inhabiting urban ecosystems are also exposed to lead, yet little work has documented the sublethal effects of lead exposure in urban wildlife. We studied northern mockingbirds (Mimus polyglottos) in three neighborhoods of New Orleans, Louisiana, two with high soil lead and one with low soil lead, to better understand how lead exposure may influence mockingbirds' reproductive biology. We monitored nesting attempts, measured lead concentrations in blood and feathers of nestling mockingbirds, documented egg hatching and nesting success, and assessed rates of sexual promiscuity in relation to neighborhood soil lead levels. We found that nestling mockingbirds’ blood and feather lead levels reflected the soil lead levels of their neighborhoods and nestling blood lead levels were similar to those of adult mockingbirds in the same neighborhoods. Nest success, as evaluated by daily nest survival rates, was higher in the lower lead neighborhood. Clutch sizes varied substantially across neighborhoods, but rates of unhatched eggs did not covary with neighborhood lead levels, suggesting that other drivers are influencing variation in clutch sizes and hatching success in urban habitats. At least one-third of nestling mockingbirds were sired by an extra-pair male, and there was no relationship between extra-pair paternity rates and neighborhood lead levels. This study provides insight on how lead contamination may influence reproduction in urban-dwelling wildlife and suggests that nestling birds could serve as useful bioindicators of lead levels in urban neighborhoods.

Singing on the nest is a widespread behavior in incubating Northern Mockingbirds and increases probability of nest predation

Abstract In this study, we documented for the first time singing on the nest (SOTN) in 74% of 65 Northern Mockingbird (Mimus polyglottos) nests that were monitored with continuous-running video cameras (8,353.9 hr sampled). As predicted, higher rates of SOTN significantly decreased daily survival rates of nests. SOTN occurred almost exclusively by females during the egg stage and in 86% (48 of 56) of nests for which we had sampling from the egg stage. While extensive at the population level, the average rate of SOTN per individual was low (5.24 ± 1.24 s SOTN per hour of video sampled). We found mixed support for the hypothesis that SOTN functions in territory maintenance. We found no support for the hypotheses that SOTN functions to coordinate parental care, defend nests, or aid in vocal learning. Given the limited attention SOTN has received and the mostly anecdotal accounts of it, our understanding of its costs and benefits is lacking. We conclude that while individual rates of SOTN are quite low, SOTN may be more widespread in populations than previously thought and that studies specifically designed to test hypotheses regarding potential functions are critically needed.

Effect of population size and selection on Toll-like receptor diversity in populations of Galápagos mockingbirds.

The interactions of evolutionary forces are difficult to analyse in free-living populations. However, when properly understood, they provide valuable insights into evolutionary biology and conservation genetics. This is particularly important for the interplay of genetic drift and natural selection in immune genes that confer resistance to disease. The Galápagos Islands are inhabited by four closely related species of mockingbirds (Mimus spp.). We used 12 different-sized populations of Galápagos mockingbirds and one population of their continental relative northern mockingbird (Mimus polyglottos) to study the effects of genetic drift on the molecular evolution of immune genes, the Toll-like receptors (TLRs: TLR1B, TLR4 and TLR15). We found that neutral genetic diversity was positively correlated with island size, indicating an important effect of genetic drift. However, for TLR1B and TLR4, there was little correlation between functional (e.g., protein) diversity and island size, and protein structural properties were largely conserved, indicating only a limited effect of genetic drift on molecular phenotype. By contrast, TLR15 was less conserved and even its putative functional polymorphism correlated with island size. The patterns observed for the three genes suggest that genetic drift does not necessarily dominate selection even in relatively small populations, but that the final outcome depends on the degree of selection constraint that is specific for each TLR locus.

Duet: Our Journey in Song with the Northern Mockingbird by Phillip Hoose

Duet: Our Journey in Song with the Northern Mockingbird by Phillip Hoose

First documentation of vocal mimicry in female northern mockingbirds

First documentation of vocal mimicry in female northern mockingbirds

First records of Ixodes brunneus (Acari: Ixodidae) in Delaware

Eight adult specimens of Ixodes brunneus (Acari: Ixodidae) were collected in Delaware via a combination of methods. The first was an engorged female recovered from a deceased Northern Mockingbird (Mimus polyglottos), a window strike victim, in Kent County. The other seven were four males and three females, all apparently unfed, collected by flagging and dragging vegetation in Kent, New Castle, and Sussex Counties during routine tick surveillance. These collections represent a new host record as well as new state and county records, and indicate a statewide presence of this species.

Demographic Dynamics of a Population of Northern Mockingbirds (Mimus polyglottus) in New Orleans, U.S.A., before and after Hurricane Katrina

Northern Mockingbirds (Mimus polyglottus) were studied between 1995 and 2015 on a university campus in New Orleans, U.S.A., spanning the 2005 landfall of Hurricane Katrina. The storm subjected the city to high winds and a prolonged flood. Nesting success showed a spike for 3 y after the storm, after which it gradually sank back to near pre-storm levels. Number of broods detected jumped from the first to the second year after the storm on campus and at two nearby residential sites. Success of males in acquiring mates improved from the first nesting season after the storm to the second across the three sites. Results draw attention to the importance of considering top-down effects in analyzing the recovery of storm-impacted birds.

Mockingbird Morphing Music: Structured Transitions in a Complex Bird Song.

The song of the northern mockingbird, Mimus polyglottos, is notable for its extensive length and inclusion of numerous imitations of several common North American bird species. Because of its complexity, it is not widely studied by birdsong scientists. When they do study it, the specific imitations are often noted, and the total number of varying phrases. What is rarely noted is the systematic way the bird changes from one syllable to the next, often with a subtle transition where one sound is gradually transformed into a related sound, revealing an audible and specific compositional mode. It resembles a common strategy in human composing, which can be described as variation of a theme. In this paper, we present our initial attempts to describe the specific compositional rules behind the mockingbird song, focusing on the way the bird transitions from one syllable type to the next. We find that more often than chance, syllables before and after the transition are spectrally related, i.e., transitions are gradual, which we describe as morphing. In our paper, we categorize four common modes of morphing: timbre change, pitch change, squeeze (shortening in time), and stretch (lengthening in time). This is the first time such transition rules in any complex birdsong have been specifically articulated.

Alarm calls of nesting Northern Mockingbirds (Mimus polyglottos) are associated with predator type

The alarm calls of many vertebrates encode predator-specific information such as the type of predator or the urgency of the threat. When an alarm call is only produced in a specific context and elicits specific behaviors from the recipients it is referred to as functionally referential. The pervasiveness of functionally referential alarm calls across bird species, however, remains to be established. In this study, we first classified Northern Mockingbird (Mimus polyglottos) alarm calls and then assessed if parental birds produced different alarm calls for different predators or nestling stages. To classify alarm calls we first isolated parental calls that preceded nest predation events from mockingbird nest camera footage and analyzed them using Raven Pro. Using a PCA analysis, we identified 9 different alarm calls based on 18 different predation events that resulted in 494 alarm calls given. To determine if the alarm calls were predator- or nest stage-specific we conducted a multinomial logistic regression. One call was given exclusively in association with snakes and 2 were given almost entirely in association with cats. In response to American Crows (Corvus brachyrhynchos), mockingbirds mainly produced a fourth alarm call, which was also frequently associated with Cooper's Hawks (Accipiter cooperii). The remaining 5 alarm calls were associated with Cooper's Hawks. While we have strong preliminary evidence for predator-specific alarm calls in nesting Northern Mockingbirds, many of these calls are also given in other contexts, such as in intraspecific interactions, which would exclude them from being considered functionally referential. These results highlight the challenges of categorizing alarm calls as functionally referential and the need to further integrate functional reference with context-dependent communication.

Coffee plantations, hurricanes and avian resiliency: insights from occupancy, and local colonization and extinction rates in Puerto Rico

Insights on impacts and resiliency of avian species with respect to hurricanes in the Caribbean have largely focused on responses measured in protected habitats. We assessed avian responses in non-protected habitat, specifically shade-restored coffee plantations, because their structural complexity retains many attributes of secondary forests, and may contribute to landscape scale species resiliency. We tallied species richness and estimated occupancy probability of 12 resident avian species, after adjusting for imperfect detection, to assess the impact of hurricane Maria (20 September 2017). For five of those species, we also estimated local colonization and extinction probabilities to assess their prospect of rebounding (resiliency) in the context of two stages of shade restoration. We used survey data collected March-June 2015–2017 (pre-hurricane) and 2018 (post-hurricane) in 58 coffee farms and satellite imagery to assess vegetation structure. Restored farms were grouped into two categories based on time-since-restoration: newly-restored and fully-restored. We predicted that mean percent forest cover in fully-restored farms (~30–40%) would revert to levels in newly-restored farms (<15%), with concomitant changes in occupancy by avian species. As predicted, mean percent forest cover (16.17±4.27%) in fully-restored farms post-hurricane reverted to pre-hurricane levels in newly-restored farms (15.00±5.61%). The loss represented 30–38% relative to the pre-hurricane cover levels. Detections of focal species dropped an average of 41% post-hurricane, with associated reductions in occupancy for 9/11 species. Occupancy of the Puerto Rican Bullfinch and Puerto Rican Spindalis reverted to levels detected in newly-restored plantations prior to the hurricane as predicted. Prospects of rebounding were more likely for species with invariant or increases in colonization probability (e.g., Yellow-faced Grassquit, Northern Mockingbird, Puerto Rican Spindalis). Rebounding for frugivores like the Puerto Rican Bullfinch would be protracted given that colonization rates dropped from 0.56±0.12 (pre-hurricane) to 0.04±0.2 (post-hurricane), regardless of restoration stage. Our work showed that the avian community associated with restored coffee farms exhibited a high degree of ecological resistance as the similarity in species composition before and after the hurricane was 81%, and all 12 focal species continued to occupy farms under both restoration stages. The prospect of the focal species to rebound (resiliency) was species-specific, and in some cases, mediated by their affinity to a particular farm restoration stage. The strength of hurricanes is projected to intensify with global warming. Pockets of undamaged or partially damaged shade-grown or fully-restored coffee plantations may contribute to species resiliency by increasing landscape level habitat redundancy, and facilitate habitat shifts to secure food resources or harbor source populations to colonize recovering, hurricane-damaged habitat tracts.

A Helminth Survey of Northern Bobwhite Quail (Colinus virginianus) and Passerines in the Rolling Plains Ecoregion of Texas.

The Northern bobwhite quail (Colinus virginianus) is a popular game bird that has been experiencing a well-documented decline throughout Texas since the 1960s. While much of this decline has been attributed to habitat loss and fragmentation, recent studies have identified other factors that may also contribute to decreasing quail populations. Parasites, in particular, have become increasingly recognized as possible stressors of quail, and some species, particularly the eyeworm (Oxyspirura petrowi) and cecal worm (Aulonocephalus pennula) are highly prevalent in Texas quails. Eyeworm infection has also been documented in some passerines, suggesting helminth infection may be shared between bird species. However, the lack of comprehensive helminth surveys has rendered the extent of shared infection between quail and passerines in the ecoregion unclear. Thus, helminth surveys were conducted on bobwhite, scaled quail (Callipepla squamata), Northern mockingbirds (Mimus polyglottos), curve-billed thrashers (Toxistoma curvirostre), and Northern cardinals (Cardinalis cardinalis) to contribute data to existing parasitological gaps for birds in the Rolling Plains ecoregion of Texas. Birds were trapped across 3 counties in the Texas Rolling Plains from March to October 2019. Necropsies were conducted on 54 individuals (36 quail and 18 passerines), and extracted helminths were microscopically identified. Nematode, cestode, and acanthocephalan helminths representing at least 10 helminth species were found. Specifically, A. pennula and O. petrowi had the highest prevalence, and O. petrowi was documented in all of the study species. This research adds to the body of knowledge regarding parasitic infections in quail and passerines of the Rolling Plains ecoregion and highlights the potential consequences of shared infection of eyeworms among these bird species.

Adverse weather conditions reduce food availability and increase glucocorticoid metabolite levels in barn swallow nestlings

Stimuli perceived as stressful by animals increase glucocorticoid secretion over basal levels. This is an adaptive response that by altering energy metabolism and animal behavior facilitates survival during acute stress. Secretion of corticosterone increases in adult insectivorous bird species after a short period of adverse weather conditions, which may determine a decreased availability of insect prey as well as thermoregulatory stress. Hormone response to stress in altricial nestlings is not yet clear. In some species (e.g. northern mockingbird, white-crowned sparrow) early age nestlings show a reduced or null response to stress stimulation, and the hypothalamus–pituitary–adrenal (HPA) axis seems to be fully active only at an age close to independence. In other species (e.g. barn swallow, canaries) the HPA axis seems to be active even in young nestlings. However, most of the data refer to experimentally induced stress while the physiological response to natural environmental perturbations has been scarcely investigated. The main aim of our study was to evaluate corticosterone secretion response to short periods of adverse weather conditions in two different age groups of barn swallow nestlings (7–14 days old and 15–21 days old). Furthermore, stress responses were compared between medium aged nestlings, late aged nestlings and adults, to understand whether HPA axis activity changed with age. A fecal non-invasive hormone assessment method was used.Our results showed that during adverse weather conditions, insect abundance decreased and corticosterone metabolites levels increased significantly and to a similar extent in droppings of medium and late aged barn swallow nestlings as well as in adults. Our data support previous findings, that the HPA axis is already fully functional in 7–14 days old nestlings. Further studies are required to verify the existence of a hyporesponsive period in younger barn swallow nestlings.

Composition and Potential Function of Fecal Bacterial Microbiota from Six Bird Species

Gut microbial communities play a fundamental role in health and disease, but little is known about the gut microbiota of pet bird species. This is important to better understand the impact of microbes on birds’ health but may also be relevant in a context of zoonoses. Total genomic DNA samples from pooled fecal samples from 30 flocks (4–7 pet birds per flock) representing over 150 birds of six different species (two Passeriformes: Northern Mockingbird (Mimus polyglottos) and Zebra Finch (Taeniopygia guttata), and four Psittaciformes: Lovebird (Agapornis, different species), Cockatiel (Nymphicus hollandicus), Red-rumped Parrot (Psephotus haematonotus), and Rose-ringed Parakeet (Psittacula krameri) were used for 16S rRNA gene analysis. Several taxa were found to be different among the bird species (e.g., lowest median of Lactobacillus: 2.2% in Cockatiels; highest median of Lactobacillus: 79.4% in Lovebirds). Despite marked differences among individual pooled samples, each bird species harbored a unique fecal bacterial composition, based on the analysis of UniFrac distances. A predictive approach of metagenomic function and organism-level microbiome phenotypes revealed several differences among the bird species (e.g., a higher proportion of proteobacteria with the potential to form biofilms in samples from Northern Mockingbirds). The results provide a useful catalog of fecal microbes from pet birds and encourage more research on this unexplored topic.

A cross-sectional field study of fall song in Northern Mockingbirds Mimus polyglottos

Studies of the acoustic structure of song in young birds have proven valuable at helping us understand song development, but nearly all existing studies have been performed on non-mimicking songbirds. We conducted a cross-sectional field study of song development in a prominent vocal mimic, the northern mockingbird, by comparing the fall songs of hatch-year vs. after-hatch-year birds. Although sample sizes of hatch-year birds were small, the data suggest a developmental trajectory in which both song stereotypy and the frequency of vocal mimicry increase with age. Thus, the acoustic structure of fall song may provide a reliable indicator of a bird’s age and performance.

Are northern mockingbirds classic open‐ended song learners?

AbstractThe northern mockingbird (Mimus polyglottos, Linnaeus) is considered a classic example of a species in which individuals learn songs throughout adulthood, but this assumption has not been tested rigorously. To assess whether mockingbirds should be categorized as open‐ended learners, I conducted a longitudinal study and a field‐based song‐tutoring experiment. I recorded songs from 15 free‐living, banded, adult males in an earlier year and a later year, and I classified 400 mimetic songs per year per individual, based on the species and vocalization type mimicked. For two of these “mimetic types,” I further classified all the song types of all individuals in their early and later samples. The number of song types increased significantly across years for both mimetic types, and the average number of observed mimetic types per individual was 46.4 and 47.7 in the early and late samples (p = .055). I found no evidence adults learned any tutor stimuli after six months of tutoring, but examples from the scientific literature suggest the tutoring regime might not have been adequate to pass the motivational threshold required for learning. I conclude that mockingbirds probably are open‐ended learners, but that future research is needed to verify experimentally that adults can indeed imitate novel song types.

Mockingbirds imitate frogs and toads across North America

Vocal mimicry is taxonomically widespread among birds, but little is known about mimicry of non-avian models. Prior studies show preferential imitation of avian models whose sounds are acoustically similar to the non-imitative songs of the vocal mimic. Based on these studies and anecdotes about frog imitations by northern mockingbirds (Mimus polyglottos), we hypothesized which anuran models would be most likely to get imitated by mockingbirds across their geographic range. We tested our hypothesis using >40 h of archived mockingbird recordings. Our results showed that mockingbirds imitated at least 12 anuran species, and calls were disproportionately mimicked when they contained dominant frequencies within the vocal range of the mockingbird (750–7000 Hz). Mockingbirds also frequently modified model anuran sounds by leaving out formants and/or truncating call duration. Our results represent the most comprehensive survey for any mimicking species of the imitation of anurans.