Zonotrichia Leucophrys Research Articles

Not so sexy in the city: urban birds adjust songs to noise but compromise vocal performance

Anthropogenic noise affects the behavior of a variety of animal taxa around the world. In many taxa, minimum frequencies of acoustic signals increase with ambient noise levels, and males and females respond less strongly to these adjusted signals. Lower response may be due to higher minimum frequencies or to the associated decrease in frequency bandwidth. There is a performance challenge to producing notes rapidly at a wide bandwidth, and any reduction in bandwidth necessarily reduces the performance value. This measure of vocal performance is a trait under sexual selection in many taxa. We investigated the relationship between anthropogenic noise amplitude and male white-crowned sparrow vocal performance in San Francisco, CA. Males on louder territories produced songs at higher minimum frequencies but also with reduced bandwidth and lower vocal performance. These results suggest that behavioral adjustments to anthropogenic noise reduce vocal performance of songs. We conducted playback experiments to test if lower responses to urban songs are due to higher minimum frequencies or to narrower bandwidths. Males responded more strongly to normal than to reduced bandwidth songs, but equally to high- and low-pass filtered songs. Our results therefore suggest that reduced bandwidth and performance—not higher minimum frequency—could be the reason that urban birds are less responsive to songs adjusted for anthropogenic noise. Ultimately, the lower vocal performance of birds on territories with high levels of anthropogenic noise could result in fewer mating opportunities and more challenges in defending their territory.

The Effects of Acute Restraint Stress on Plasma Levels of Prolactin and Corticosterone across Life-History Stages in a Short-Lived Bird: Gambel's White-Crowned Sparrow (Zonotrichia leucophrys gambelii).

The general reproductive effort model attempts to predict the resources that will be allocated to a current reproductive bout or to future survival by aborting the current reproductive attempt. Life-history theory predicts that short-lived species should devote more resources toward a reproductive event because brood value is far greater compared with that of long-lived species that have multiple breeding opportunities. Previous bird studies have used patterns of hormone secretion to understand the regulation of parental investment in response to environmental challenges, such as stress. The two key hormones investigated have been prolactin, which promotes parental investment, and corticosterone, which can reduce parental investment. Research on long-lived seabirds showed that prolactin levels decrease in response to a stressor, but the magnitude of the decline was positively correlated with future reproductive potential. However, little is known about the role of prolactin in short-lived species. Here we present prolactin and corticosterone data from a short-lived Arctic breeding, migratory songbird-the white-crowned sparrow, Zonotrichia leucophrys gambelii-at multiple stages of the breeding and nonbreeding seasons following standardized acute restraint stress. These data show that both prolactin and corticosterone are modulated seasonally. Corticosterone levels increased significantly in response to acute restraint stress during the breeding season in both sexes, but prolactin levels did not change in response to acute restraint stress at any stage of the annual cycle. We found no relationship between corticosterone or prolactin at either baseline or peak induced levels during any stage of breeding.

New records of the Lyme disease bacterium in ticks collected from songbirds in central and eastern Canada

This study highlights the collection of ticks from wild-caught birds in central and eastern Canada. Using polymerase chain reaction (PCR), 32 (33%) of 98 Ixodes species ticks tested were positive for the Lyme disease bacterium, Borrelia burgdorferi sensu lato (s.l.) Johnson, Schmid, Hyde, Steigerwalt, and Brenner (hereafter B. burgdorferi). Immature blacklegged ticks, Ixodes scapularis Say, which are competent vectors of B. burgdorferi, constituted the predominant Ixodes species tick collected from parasitized songbirds; specifically, 31(35%) of 89 I. scapularis nymphs were positive for B. burgdorferi. Notably, we report the first B. burgdorferi-positive I. scapularis (nymph) on a migratory passerine in Prince Edward Island; this is the first record of a tick on a bird in this maritime province. First-time records of B. burgdorferi-infected, I. scapularis nymphs on passerines in northwestern Ontario include rose-breasted grosbeak, Pheucticus ludovicianus (Linnaeus), eastern bluebird, Sialia sialis (L.), and indigo bunting, Passerina cyanea (L.). Similarly, we furnish a new host record in Canada for an I. scapularis (nymph) on a worm-eating warbler, Helmitheras vermivorus (Gmelin); this engorged nymph tested positive for B. burgdorferi. We document the first recorded collection of a B. burgdorferi-infected Ixodes muris Bishopp and Smith (female) on a songbird in Ontario. We provide the first account of a live culture of B. burgdorferi from an I. scapularis (nymph) collected from a brown-headed cowbird Molothrus ater (Boddaert) in Manitoba. We make available new host records for I. scapularis on a clay-coloured sparrow Spizella pallida (Swainson) and a Gambel’s white-crowned sparrow Zonotrichia leucophrys gambelii (Nuttall). An I. scapularis on a songbird during southward autumn migration in northwestern Ontario is a first record reported. As well, we document the first-ever account of a reptile-associated tick, a nymph of Amblyomma sabanerae Stoll, on a veery Catharus fuscescens (Stephens) in northwestern Ontario. Migratory songbirds play an integral role in the wide dispersal of B. burgdorferi-infected ticks, especially during northward spring migration. Clinicians need to be aware that people can be bitten by B. burgdorferi-infected ticks released by songbirds across Canada.

Haemoproteus infected birds have increased lifetime reproductive success.

The impact of haematozoan infection on host fitness has received substantial attention since Hamilton and Zuk posited that parasites are important drivers of sexual selection. However, short-term studies testing the assumption that these parasites consistently reduce host fitness in the wild have produced contradictory results. To address this complex issue, we conducted a long-term study examining the relationship between naturally occurring infection with Haemoproteus and Plasmodium, and lifetime reproductive success and survival of Mountain White-crowned Sparrows. Specifically, we tested the hypothesis that birds infected with haematozoan parasites have reduced survival (as determined by overwinter return rates) and reproductive success. Contrary to expectation, there was no relationship between Haemoproteus and Plasmodium infection and reproduction or survival in males, nor was there a relationship between Plasmodium infection and reproduction in females. Interestingly, Haemoproteus-infected females had significantly higher overwinter return rates and these females fledged more than twice as many chicks during their lifetimes as did uninfected females. We discuss the impact of parasitic infections on host fitness in light of these findings and suggest that, in the case of less virulent pathogens, investment in excessive immune defence may decrease lifetime reproduction.

Peter Robert Marler FRS (1928-2014)

Peter Robert Marler FRS (1928-2014)

Seasonal plasticity of precise spike timing in the avian auditory system.

Vertebrate audition is a dynamic process, capable of exhibiting both short- and long-term adaptations to varying listening conditions. Precise spike timing has long been known to play an important role in auditory encoding, but its role in sensory plasticity remains largely unexplored. We addressed this issue in Gambel's white-crowned sparrow (Zonotrichia leucophrys gambelii), a songbird that shows pronounced seasonal fluctuations in circulating levels of sex-steroid hormones, which are known to be potent neuromodulators of auditory function. We recorded extracellular single-unit activity in the auditory forebrain of males and females under different breeding conditions and used a computational approach to explore two potential strategies for the neural discrimination of sound level: one based on spike counts and one based on spike timing reliability. We report that breeding condition has robust sex-specific effects on spike timing. Specifically, in females, breeding condition increases the proportion of cells that rely solely on spike timing information and increases the temporal resolution required for optimal intensity encoding. Furthermore, in a functionally distinct subset of cells that are particularly well suited for amplitude encoding, female breeding condition enhances spike timing-based discrimination accuracy. No effects of breeding condition were observed in males. Our results suggest that high-resolution temporal discharge patterns may provide a plastic neural substrate for sensory coding.

Androgens Increase Persistence But Do Not Affect Neophobia in a Problem-Solving Context in a Songbird

Gonadal steroid hormones enhance cognitive performance, particularly spatial and vocal learning, in mammals and birds. However, it is unknown whether problem-solving ability is similarly regulated. We propose that androgens, such as testosterone and 5α-dihydrotestosterone, play a role in mediating problem-solving behavior as well. As a test, male white-crowned sparrows (Zonotrichia leucophrys gambelii) were either castrated and administered a blank (Blank-castrate) or testosterone-filled implant (T-castrate) or were sham operated and were exposed to a novel feeder, which they had to open to receive a food reward, in two trials. Testosterone treatment affected neither a neophobic response nor problem-solving performance. However, T-castrates were more persistent in manipulating the feeder than Blank-castrates or Shams. Furthermore, their persistence correlated positively with circulating levels of both testosterone and 5α-dihydrotestosterone. We suggest that a positive correlation between sex steroids and persistence in foraging and problem-solving contexts may lead to an adaptive increase in resource acquisition in the breeding season. Given the overall low success on the problem-solving test, we cannot confidently conclude that androgens do not play a role in mediating problem-solving behavior. However, unlike in mammals, it seems these hormones do not significantly influence neophobia in foraging contexts in birds.

Nuevos pájaros en la ciudad de México: primeros registros de Vireo philadelphicus y Zonotrichia leucophrys para el Distrito Federal

El Distrito Federal (DF) es la entidad más pequeña de México; en ella contrasta la presencia de un elevado desarrollo urbano y una compleja variedad de ecosistemas naturales. Tanto en la periferia como en el interior de la Zona Metropolitana de la ciudad de México, las áreas verdes proveen de refugios importantes para la vida silvestre. En este trabajo, reportamos dos especies de aves que no habían sido registradas con anterioridad en el DF: el víreo de Filadelfia (Vireo philadelphicus) y el gorrión corona blanca (Zonotrichia leucophrys). Ambas especies son migratorias de invierno en México y se conoce su amplia capacidad de dispersión. Si bien no es posible asociar factores causales de manera definitiva, consideramos que algunos fenómenos que pudieron haber propiciado la presencia inusual de estos individuos en la región son la reducción de sus hábitats invernales, el severo invierno que se vivió en EUA y Canadá en 2013-2014 y la posible presión inducida por fenómenos de cambio climático global. Consideramos que la creciente comunidad de observadores de aves y de usuarios de plataformas como aVerAves permitirán mejorar nuestro conocimiento en torno a las aves de la entidad.

Divergence of vocal culture among isolated alpine habitats is inconsistent among three Oscine species

Divergence in song culture has been well documented among isolated bird populations. Montane populations separated by unsuitable lower-elevation habitats thus appear to be excellent candidates for cultural divergence, and existing data support this conjecture. To explore the generality of this phenomenon, we investigated song sharing patterns in songbird species breeding in isolated alpine life zones in the Rocky Mountains of Colorado. We recorded songs of American Pipits (Anthus rubescens alticola), Wilson’s Warblers (Cardellina pusilla pileolata), and White-crowned Sparrows (Zonotrichia leucophrys leucophrys) across 19 sites among 6 mountain ranges. We used spectrographic cross-correlation to calculate song similarity coefficients between individuals within and among populations. White-crowned Sparrows exhibited significantly elevated song sharing within isolated mountain ranges, but Wilson’s Warbler and the American Pipit did not. Cluster analyses showed that White-crowned Sparrow songs diverged among alpine fragments but were generally similar among sites within contiguous alpine habitat within mountain ranges. There was no such clustering within American Pipit or Wilson’s Warbler populations. Song similarity declined with distance between sites within contiguous alpine habitat in White-crowned Sparrows but not in American Pipits or Wilson’s Warblers. Our results provide convincing evidence for the existence of geographically structured vocal culture in White-crowned Sparrow populations in Colorado, and this geographic pattern may be explained by clinal variation rather than by a mosaic pattern of divergence among isolated alpine fragments.

Decreases in mineralocorticoid but not glucocorticoid receptor mRNA expression during the short Arctic breeding season in free-living Gambel's white-crowned sparrow (Zonotrichia leucophrys gambelii).

The acute stress response in vertebrates is a highly adaptive suite of physiological and behavioural mechanisms that promote survival in the face of deleterious stimuli from the environment. Facultative changes of physiology and behaviour are mediated through changes in circulating levels of glucocorticoids (corticosterone, cortisol) and their subsequent binding to the high-affinity mineralocorticoid receptor (MR) or the low-affinity glucocorticoid receptor (GR). Free-living male wild Gambel's white-crowned sparrows (Zonotrichia leucophrys gambelii) display annual fluctuations in the stress response with marked attenuation during the transition from the pre-parental to the parental stage. We investigated whether this rapid reduction in the stress response is mediated through changes in MR and GR mRNA expression in the brain using in situ hybridisation. MR mRNA expression was found to be significantly lower in the hippocampus as the male birds became parental. No changes were observed in GR mRNA expression in the paraventricular nucleus (PVN) or preoptic area (POA) at this time. No significant correlations were found between initial capture levels of corticosterone and GR or MR mRNA expression. No differences were found in basal levels of corticosterone between pre-parental and parental in birds collected for in situ hybridisation. Stress response data revealed no difference at baseline but reductions in peak levels of corticosterone as birds became parental. These data suggest that changes in MR expression may be important for the regulation of the stress response or behavioural stress sensitivity with respect to promoting parental care and investment.

Greater shrub dominance alters breeding habitat and food resources for migratory songbirds in Alaskan arctic tundra.

Climate warming is affecting the Arctic in multiple ways, including via increased dominance of deciduous shrubs. Although many studies have focused on how this vegetation shift is altering nutrient cycling and energy balance, few have explicitly considered effects on tundra fauna, such as the millions of migratory songbirds that breed in northern regions every year. To understand how increasing deciduous shrub dominance may alter breeding songbird habitat, we quantified vegetation and arthropod community characteristics in both graminoid and shrub dominated tundra. We combined measurements of preferred nest site characteristics for Lapland longspurs (Calcarius lapponicus) and Gambel's White-crowned sparrows (Zonotrichia leucophrys gambelii) with modeled predictions for the distribution of plant community types in the Alaskan arctic foothills region for the year 2050. Lapland longspur nests were found in sedge-dominated tussock tundra where shrub height does not exceed 20cm, whereas White-crowned sparrows nested only under shrubs between 20cm and 1m in height, with no preference for shrub species. Shrub canopies had higher canopy-dwelling arthropod availability (i.e. small flies and spiders) but lower ground-dwelling arthropod availability (i.e. large spiders and beetles). Since flies are the birds' preferred prey, increasing shrubs may result in a net enhancement in preferred prey availability. Acknowledging the coarse resolution of existing tundra vegetation models, we predict that by 2050 there will be a northward shift in current White-crowned sparrow habitat range and a 20-60% increase in their preferred habitat extent, while Lapland longspur habitat extent will be equivalently reduced. Our findings can be used to make first approximations of future habitat change for species with similar nesting requirements. However, we contend that as exemplified by this study's findings, existing tundra modeling tools cannot yet simulate the fine-scale habitat characteristics that are critical to accurately predicting future habitat extent for many wildlife species.

Reactive neurogenesis in response to naturally occurring apoptosis in an adult brain.

Neuronal birth and death are tightly coordinated to establish and maintain properly functioning neural circuits. Disruption of the equilibrium between neuronal birth and death following brain injury or pharmacological insult often induces reactive, and in some cases regenerative, neurogenesis. Many neurodegenerative disorders are not injury-induced, however, so it is critical to determine if and how reactive neurogenesis occurs under noninjury-induced neurodegenerative conditions. Here, we used a model of naturally occurring neural degradation in a neural circuit that controls song behavior in Gambel's white-crowned sparrows (Zonotrichia leucophrys gambelii) and examined the temporal dynamics between neuronal birth and death. We found that during seasonal-like regression of the song, control nucleus HVC (proper name), caspase-mediated apoptosis increased within 2 d following transition from breeding to nonbreeding conditions and neural stem-cell proliferation in the nearby ventricular zone (VZ) increased shortly thereafter. We show that inhibiting caspase-mediated apoptosis in HVC decreased neural stem-cell proliferation in the VZ. In baseline conditions the extent of neural stem-cell proliferation correlated positively with the number of dying cells in HVC. We demonstrate that as apoptosis increased and the number of both recently born and pre-existing neurons in HVC decreased, the structure of song, a learned sensorimotor behavior, degraded. Our data illustrate that reactive neurogenesis is not limited to injury-induced neuronal death, but also can result from normally occurring degradation of a telencephalic neural circuit.

What is the sound of fear? Behavioral responses of white-crowned sparrows Zonotrichia leucophrys to synthesized nonlinear acoustic phenomena

Abstract Fear and anxiety may be adaptive responses to life-threatening situations, and animals may communicate fear to others vocally. A fundamental understanding of fear inducing sounds is important for both wildlife conservation and management because it helps us understand how to design repellents and also how (and why) animals may be negatively impacted by anthropogenic sounds. Nonlinear phenomena—sounds produced by the desynchronization of vibrations in a sound production system—are commonly found in stress-induced animal vocalizations, such as in alarm calls, mobbing calls, and fear screams. There are several functional hypotheses for these nonlinear phenomena. One specific hypothesis is the unpredictability hypothesis, which suggests that because nonlinear phenomena are more variable and somewhat unpredictable, animals are less likely to habituate to them. Animals should, therefore, have a prolonged response to sounds with nonlinear phenomena than sounds without them. Most of the studies involving nonlinear phenomena have used mammalian subjects and conspecific stimuli. Our study focused on white-crowned sparrows (Zonotrichia leucophrys ssp. oriantha) and used synthesized acoustic stimuli to investigate behavioral responses to stimuli with and without nonlinear phenomena. We predicted that birds would be less relaxed after hearing a stimulus with a nonlinear component. We calculated the difference from baseline of proportion of time spent in relaxed behaviors and performed pair-wise comparisons between a pure tone control stimulus and each of three experimental stimuli, including a frequency jump up, a frequency jump down, and white noise. These comparisons showed that in the 30‒60 s after the playback experiment, birds were significantly less relaxed after hearing noise or an abrupt frequency jump down an octave but not an abrupt frequency jump up an octave or a pure tone. Nonlinear phenomena, therefore, may be generally arousing to animals and may explain why these acoustic properties are commonly found in animal signals associated with fear [Current Zoology 60 (4): 534–541, 2014].

Tutor choice and imitation accuracy during song learning in a wild population of the Puget Sound white-crowned sparrow

Songbirds learn to sing by modeling their songs on the songs of other males through a process of social learning. Models of social learning predict that animals should be selective in what and when they learn. In this study, we asked whether young males in a wild population of the Puget Sound white-crowned sparrow, Zonotrichia leucophrys pugetensis, were selective in their choice of tutor models and what factors influenced how accurately they imitated tutors’ songs. We first examined two strategies for tutor choice: whether pupils have a conformity bias and/or a preference for high-quality tutors. In keeping with a conformity bias, tutors that sang song types that were relatively common within a radius of about 500 m of their territory were more likely to be imitated than were tutors that sang rarer song types. Most potential tutors were not imitated by pupils. Aspects of tutor quality, such as age, pairing status, and survival to the next year had no effect on whether a tutor’s song was imitated. Secondly, we tested whether pupil repertoire size, pupil quality, and local abundance of tutor models affected the accuracy of song imitations. We found a trade-off between repertoire size and tutor imitation accuracy with males that sang two or more song types developing significantly poorer imitations than males that sang one type. We discuss possible functions of a conformity learning strategy and factors that could produce a trade-off between imitation accuracy and repertoire size.

Changes in plasma concentrations of progesterone, dehydroepiandrosterone and corticosterone in response to acute stress of capture, handling and restraint in two subspecies of white-crowned sparrows

The aim of this study was to determine circulating patterns of the three major adrenal steroids in blood in response to stress during acute restraint handling in two subspecies of white-crowned sparrow. Gambel's white-crowned sparrows (Zonotrichia leucophrys gambelii) are long distance migrants that breed at high latitudes and Nuttall's white-crowned sparrows (Zonotrichia leucophrys nuttalli) are residents of coastal California. Column partition chromatography was developed to separate progesterone, dehydroepiandrosterone (DHEA), and corticosterone from a small plasma sample. Each of these steroids has the capability to modulate the stress response through various mechanisms. For example, progesterone is bound to corticosterone binding globulin (CBG) with a higher affinity than corticosterone. If plasma levels of progesterone rise during acute stress, then this could displace corticosterone from CBG and increase the amount of biologically active, free, corticosterone in blood. Dehydroepiandrosterone (DHEA) has been implicated to have many anti-stress properties with the potential to mitigate some of the actions of corticosterone. Results indicate that progesterone levels in both subspecies are elevated in response to acute stress handling. DHEA levels declined in Gambel's but did not change in Nuttall's. Thus DHEA does not follow the same secretory pattern as in mammals. Corticosterone levels were elevated in response to acute stress handling in both subspecies. This study provides new insight into an integrated stress response among three steroids.

Brain transcriptome sequencing and assembly of three songbird model systems for the study of social behavior.

Emberizid sparrows (emberizidae) have played a prominent role in the study of avian vocal communication and social behavior. We present here brain transcriptomes for three emberizid model systems, song sparrow Melospiza melodia, white-throated sparrow Zonotrichia albicollis, and Gambel’s white-crowned sparrow Zonotrichia leucophrys gambelii. Each of the assemblies covered fully or in part, over 89% of the previously annotated protein coding genes in the zebra finch Taeniopygia guttata, with 16,846, 15,805, and 16,646 unique BLAST hits in song, white-throated and white-crowned sparrows, respectively. As in previous studies, we find tissue of origin (auditory forebrain versus hypothalamus and whole brain) as an important determinant of overall expression profile. We also demonstrate the successful isolation of RNA and RNA-sequencing from post-mortem samples from building strikes and suggest that such an approach could be useful when traditional sampling opportunities are limited. These transcriptomes will be an important resource for the study of social behavior in birds and for data driven annotation of forthcoming whole genome sequences for these and other bird species.

Regulatory mechanisms for the development of the migratory phenotype: Roles for photoperiod and the gonad

This article is part of a Special Issue “Energy Balance”.Male white-crowned sparrows, Zonotrichia leucophrys gambelii, were studied to investigate roles of natural day length and the testes in regulating development and expression of the vernal migration phenotype. Previous work suggested that a pulse of androgen during winter months followed by the vernal increase in photoperiod promotes fueling (fat deposition) to support long distance flight; however, other traits required for successful migration remain untested. To investigate these points, birds were captured on their wintering grounds and castrated prior to winter solstice following Mattocks (1976). A subset of the castrates received 8mm Silastic implants of testosterone (T-castrates) and others blank implants (Blank-castrates) for 16days in February. Shams were surgical controls. Migratory traits measured were as follows: 24h locomotor activity, prenuptial molt, body mass, fat score, flight muscle profile, cloacal protuberance (CPL) and plasma androgens measured over 28weeks divided into 3 experimental periods (pre-implant, implant, and post-implant). Under short day lengths, castration increased diurnal locomotor activity over Shams. Testosterone implants temporarily enhanced CPL, plasma androgens and flight muscle enlargement, but failed to induce migratory restlessness. Whereas all groups exhibited seasonal increases in mass, fat score and muscle profile, only Shams showed timely onset and completion of prenuptial molt and migratory restlessness. Thus, for castrated males exposed to naturally increasing day lengths, the organizational effects of a transient testosterone surge were not sufficient to actuate a timely spring molt and migratory behavior. A fully functional testis that can organize central processes is required for the entire expression of the spring migratory phenotype.

Early song discrimination by nestling sparrows in the wild

Songs play an important role in premating isolation in birds. However, when songs are learned, experience with both conspecific and heterospecific songs in early life could lead to the development of both mixed songs and mixed preferences. One way that such learning errors can be prevented is if birds can discriminate between songs of different species prior to learning and preferentially memorize conspecific songs. Prior captive studies have shown that white-crowned sparrows, Zonotrichia leucophrys, are able to discriminate songs early in the process of song memorization, after about 10 days since hatching. I studied early song discrimination in wild golden-crowned sparrows, Zonotrichia atricapilla, the sister species of white-crowned sparrow. The two species occur syntopically in the study population, and therefore sparrows were expected to selectively learn conspecific songs. Playbacks of songs elicited vocal responses from nestlings as young as 6 days old, and nestlings responded more to conspecific songs than to songs of the sympatric white-crowned sparrow subspecies. These results suggest that conspecific song templates exist at the onset of song memorization, and this could allow golden-crowned sparrows to learn the songs of their own species correctly despite syntopy with their sister species. I suggest that studying species recognition prior to learning could provide fresh insights into the evolution of reproductive isolation and song divergence.

Song exposure during juvenile dispersal in Mountain White-crowned Sparrows

ABSTRACT The degree to which local song structure reflects the singer's population of origin is a long-standing and contentious issue. Young songbirds that settle to breed outside their natal song-dialect area may learn to produce nonnatal dialect by hearing and memorizing these songs during juvenile dispersal. We quantified adult singing rates in a population of Mountain White-crowned Sparrows (Zonotrichia leucophrys oriantha) in the Sierra Nevada in 2 yr, and compared them with the arrival schedule of juveniles not hatched on the study area. Our results show that opportunities for juveniles to learn new (nonnatal) song types become highly limited during the premigratory dispersal phase, because adult singing rates are very low by the time nonlocal juveniles begin to arrive. Thus, if individuals learn nonnatal songs during dispersal, they must do so hearing relatively few repetitions of the unfamiliar dialect.

Habitat suitability through time: using time series and habitat models to understand changes in bird density

Confronted with a rapidly changing world and limited resources for conservation, ecologists are increasingly challenged with predicting the impact of climate and land‐use change on wildlife. A common approach is to use habitat‐suitability models (HSMs) to explain aspects of species' occurrence, such as presence, abundance, and distribution, utilizing physical habitat characteristics. Although HSMs are useful, they are limited because they are typically created using spatial rather than temporal data, which omits temporal dynamics. We explored the value of combining spatial and temporal approaches by comparing HSMs with autoregressive population models. We investigated a 28‐year period of bird community dynamics at a field site in northern California during which time the plant community has been transitioning from scrub to conifer forest. We used the two model frameworks to quantify the contribution of vegetation change, weather, and population processes (autoregressive models only) to variation in density of seven bird species over the first 23 years. Model predictive ability was then tested using the subsequent five years of population density data. HSMs explained 58% to 90% of the deviance in species' density. However, models that included density dependence in addition to vegetation covariates provided a better fit to the data for three of the seven species, Song Sparrow (Melospiza melodia), White‐crowned Sparrow (Zonotrichia leucophrys), and Wrentit (Chamaea fasciata). These three species have more localized dispersal compared to the other four species, suggesting that dispersal tendency may be an important life‐history trait to consider when predicting the impact of climate and land‐use change on population levels. Our results suggest that HSMs can effectively explain and predict variation in species' densities through time, however for species with localized dispersal, it may be especially informative to include population processes.