Nuttall's White-crowned Sparrows Research Articles

Song and genetic divergence within a subspecies of white-crowned sparrow (Zonotrichia leucophrys nuttalli).

Animal culture evolves alongside genomes, and the two modes of inheritance-culture and genes-interact in myriad ways. For example, stable geographic variation in culture can act as a reproductive barrier, thereby facilitating genetic divergence between "cultural populations." White-crowned sparrows (Zonotrichia leucophrys) are a well-established model species for bird song learning and cultural evolution, as they have distinct, geographically discrete, and culturally transmitted song types (i.e., song dialects). In this study, we tested the hypothesis that divergence between culturally transmitted songs drives genetic divergence within Nuttall's white-crowned sparrows (Z. l. nuttalli). In accordance with sexual selection theory, we hypothesized that cultural divergence between mating signals both preceded and generated genetic divergence. We characterized the population structure and song variation in the subspecies and found two genetically differentiated populations whose boundary coincides with a major song boundary at Monterey Bay, California. We then conducted a song playback experiment that demonstrated males discriminate between songs based on their degree of divergence from their local dialect. These results support the idea that discrimination against non-local songs is driving genetic divergence between the northern and southern populations. Altogether, this study provides evidence that culturally transmitted bird songs can act as the foundation for speciation by sexual selection.

Territory Quality Predicts Avian Vocal Performance Across an Urban-Rural Gradient

Human activity around the globe is a growing source of selection pressure on animal behavior and communication systems. Some animals can modify their vocalizations to avoid masking from anthropogenic noise. However, such modifications can also affect the salience of these vocalizations in functional contexts such as competition and mate choice. Such is the case in the well-studied Nuttall's white-crowned sparrow (Zonotrichia leucophrys nuttalli), which lives year-round in both urban San Francisco and nearby rural Point Reyes. A performance feature of this species' song is salient in territorial defense, such that higher performance songs elicit stronger responses in simulated territorial intrusions; but songs with lower performance values transmit better in anthropogenic noise. A key question then is whether vocal performance signals male quality and ability to obtain high quality territories in urban populations. We predicted white-crowned sparrows with higher vocal performance will be in better condition and will tend to hold territories with lower noise levels and more species-preferred landscape features. Because white-crowned sparrows are adapted to coastal scrub habitats, we expect high quality territories to contain lower and less dense canopies, less drought, more greenness, and more flat open ground for foraging. To test our predictions, we recorded songs and measured vocal performance and body condition (scaled mass index and fat score) for a set of urban and rural birds (N = 93), as well as ambient noise levels on their territories. Remote sensing metrics measured landscape features of territories, such as drought stress (NDWI), greenness (NDVI), mean canopy height, maximum height, leaf area density (understory and canopy), slope, and percent bare ground for a 50 m radius on each male territory. We did not find a correlation between body condition and performance but did find a relationship between noise levels and performance. Further, high performers held territories with lower canopies and less dense vegetation, which are species-preferred landscape features. These findings link together fundamental aspects of sexual selection in that habitat quality and the quality of sexually selected signals appear to be associated: males that have the highest performing songs are defending territories of the highest quality.

Morning recital accelerates migrating sparrow moult

![Figure][1] Juvenile Nuttall's white-crowned sparrows. Photo credit: Helen Chmura. There's always so much to remember when you're packing for a long journey, and when migrating species begin their preparations for departure they focus on building their muscles and fat stores in readiness

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.

RESPONSES OF ADULT WHITE-CROWNED SPARROWS TO PLAYBACK OF SONG PHRASES: IMPLICATIONS FOR THE ONTOGENY OF SONG RECOGNITION

Abstract We examined the contribution of individual song phrases to territorial behavior in Nuttall's White-crowned Sparrows (Zonotrichia leucophrys nuttalli) in the Bodega, California, dialect area. We presented territorial adult males with playbacks of five song types: local conspecific song, three single phrase types of local conspecific song, and Song Sparrow (Melospiza melodia) song. Local conspecific song evoked the strongest response, measured in latency to flight, number of flights, average and closest distance from playback speaker, and vocal response. Of individual song phrases, the trill evoked the strongest response, and the whistle evoked the weakest. Combining these results with those of previous studies on young birds, we describe a model of developmental change from responsiveness to all phrase types in dependent fledglings, through reliance on a species-universal phrase as a cue for song learning, to the use of a more variable, dialect-distinct phrase as a territorial signal by adults. Re...

Song learning and vocal tradition in Nuttall's white-crowned sparrows

We investigated song sharing and dispersion of song types in the wild in a colour-marked population of the non-migratory Nuttall's white-crowned sparrow,Zonotrichia leucophrys nuttalli. The songs of fathers, their male progeny (sons), and the neighbours of the sons at recruitment sites were analysed spectrographically and compared qualitatively and quantitatively. To determine whether a son's song more closely matched that of his father or a neighbour at the site settled, we subjected frequency and temporal characteristics of songs within each father–son–neighbour triad to multivariate cluster analysis. The songs of 14 of 16 sons clustered with their neighbours’ rather than their fathers’ songs, confirming that song matching of neighbours is an integral component of territory settlement by juveniles. Principal components analysis of frequency and temporal measurements of song within a dialectal area show that songs group into neighbourhoods and are non-randomly distributed. Multivariate analysis suggests that sons may entrain on frequency and temporal characteristics of a neighbour's song without matching phrases or complex syllables. Implications for models of instructive versus selective learning are discussed. The timing of closure of the sensitive phase, the length of the silent interval between the sensory phase and plastic song stage, and the time to song crystallization remain open questions in song ontogeny.

Seasonal plasticity of the song control system in wild Nuttall's white-crowned sparrows.

Seasonal plasticity in the morphology of telencephalic nuclei that control song behavior has been reported for diverse species of songbirds. The only published report of a lack of seasonal changes in the song nuclei of a seasonally breeding bird is that of Baker et al. in the Nuttall's subspecies of white-crowned sparrow (Zonotrichia leucophrys nuttalli). In this study, they brought wild birds into the laboratory and exposed them to either "summer" or "winter" photoperiods. Previous studies have shown that exposing wild-caught white-crowned sparrows to long-day photoperiods in the laboratory may not induce circulating concentrations of testosterone (T) as high as those seen in wild breeding birds. Changes in circulating T are primarily responsible for the seasonal morphological changes in the song nuclei. To determine whether there is seasonal plasticity of the song system in this subspecies, we measured circulating T, morphological attributes of the song nuclei, and song behavior in wild Nuttall's white-crowned sparrows during the spring and fall. Testis size and circulating T concentrations were greater in spring than fall birds. The absolute volumes of the song nuclei HVc, RA, and Area X, and their volumes relative to those of either the total telencephalon or three thalamic nonsong nuclei, were significantly greater in the spring than fall sparrows. Song behavior also changed seasonally; fall birds sang shorter songs than did spring birds. These results show that there is seasonal plasticity of the song system in wild Nuttall's white-crowned sparrows. Seasonal plasticity can now be regarded as a common feature of the seasonally breeding songbirds studied thus far.

Overproduction in song development: an evolutionary correlate with migration

Many songbirds overproduce songs during development and shrink the repertoire at the time of adult crystallization. The amount of overproduction varies between species. The hypothesis was tested that overproduction of learned songs during ontogeny is correlated with a migratory annual cycle. It is argued that in migrants, overproduction permits song matching between territory neighbours when song memorization is restricted to an early sensitive phase and young males subsequently disperse relatively long distances to their first breeding territory. Song development was compared in the sedentary Nuttall's white-crowned sparrow, Zonotrichia leucophrys nuttalli, and two migratory taxa, the Puget Sound white-crowned sparrow, Z. l. pugetensis , and the mountain white-crowned sparrow, Z. l. oriantha . Although the Puget Sound and Nuttall's white-crowned sparrows are sister taxa, male Puget Sound sparrows more closely resembled the more distantly related, but migratory, mountain white-crowned sparrow on every measure of song development studied. It is concluded that a migratory annual cycle is a better explanation of diversity in vocal development in this species than recency of common ancestry.

BEHAVIOURAL RESPONSE TO SONG PLAYBACK BY MALE AND FEMALE WHITE-CROWNED SPARROWS OF TWO SUBSPECIES

ABSTRACT Nuttall's white-crowned sparrow Zonotrichia leucophrys nuttalli and the Puget Sound white-crowned sparrow Z. i. pugetensis intergrade through a zone of hybridization in northern California. The songs of the two differ in the sequence of syllable types and in the phonology of the complex syllables. We did a playback experiment to males of both subspecies in the field and to females of both subspecies in the laboratory to determine their response to the two subspecies songs. By making alterations of features of the songs, we also attempted to identify characteristics that account for subspecific recognition. Males of both subspecies were more responsive to their own subspecies song than to that of the other subspecies. Substitution of Puget Sound complex syllables into the Nuttall's song caused a reduction in response by male Nuttall's, but alteration of a Nuttall's song to a Puget Sound sequence of syllables had no effect. Females of both subspecies gave more sexual displays when played a song of ...

Song Development and Territory Establishment in Nuttall's White-Crowned Sparrows

Song development and territory establishment were studied in the permanently resident Nuttall's White-crowned Sparrow (Zonotrichia leucophrys nuttalli). Hatching-year birds (juveniles) begin subsong in July, and the first crystallized songs are heard in late September. Social interaction with territorial adults accelerates song development so that song crystallizes earlier in wild juveniles than in hand-raised laboratory birds. Some juveniles begin staking out territories in September and October. At this time individuals may sing up to four song types. As time progresses settling juveniles use only one or sometimes two song types which match those of neighbors with whom they interact. Singing is performed circumannually, even during the molt in this subspecies, reflecting its year-round territo- riality.

Microgeographic Song Variation in the Nuttall's White-Crowned Sparrow

Intradialect variation in the song of 138 male Nuttall's White-crowned Sparrows (Zonotrichia leucophrys nuttalli) was examined using multivariate cluster analyses on both quantitative (frequency and temporal) and qualitative (structural) variables. Mapping of song groups revealed local song clusters with a high degree of spatial overlap and the occurrence of satellite males located well outside the spatial cluster of their song type. This pattern is suggestive of predispersal song learning and is thus more consistent with the genetic adaptation hypothesis than with one version of the deceptive mimicry hypothesis.

Dispersal in White-Crowned Sparrows: A Computer Simulation of the Effect of Study-Area Size on Estimates of Local Recruitment

Abstract Consideration of the problem of sampling a population within a finite study area suggested that recruitment results might be related to the size of the study area. Specifically, the proportion of recruits observed within a defined study area that originate in that area (local recruits) should be a function of the proportion of the population that the study area represents. Computer simulations of dispersal, using Nuttall's White-crowned Sparrow (Zonotrichia leucophrys nuttalli) as a model, were designed to test this hypothesis, and the effect of territory size and population size on this relationship. The simulations confirmed that local recruitment is a function of the proportion of the population sampled in the study area. Additionally, these simulations demonstrated that by holding the distribution of dispersal distances constant, local recruitment for a given proportion of the population sampled increased with territory size and population size. These latter results, however, are artifacts of the simulations and have no biological significance. Finally, the proportion of local recruits predicted for a natural population was remarkably close to that obtained from fieldwork. I suggest that conclusions about dispersal and population structure should not be drawn from proportions of local recruitment within finite study areas, and require more detailed analysis of dispersal.

Assortative mating by white-crowned sparrows at song dialect boundaries

We tested the hypothesis that female Nuttall's white-crowned sparrows ( Zonotrichia leucophrys nuttalli) mate assortatively with males from the same dialect population. Young birds of both sexes learn their natal dialect during an early sensitive period, and for females, this early experience may be the basis of future mate choice. A total of 32 female sparrows were mist-netted for three experiments at or near dialect boundaries just inside the Limantour, Drake and Clear dialect populations in Marin Co., California. The mates of all captured females sang the home dialect. All females were implanted with testosterone and maintained in captivity. Of the females which began to sing, 25 sang recognizable white-crowned sparrow songs. Of those 25 females, 24 had mated assortatively, thus supporting the assortative mating hypothesis.

The behavioral response of female Nuttall's White-crowned Sparrows to male song of natal and alien dialects

Female Nuttall's White-crowned Sparrows (Zonotrichia leucophrys nuttalli) were tested in a laboratory experiment to determine their response to stimulation by songs from their natal dialect (Clear) and by songs from three different alien dialects (Fig. 1). The greatest number of copulation solicitation displays and amount of locomotor activity were caused by songs of the subject's natal dialect (Clear); the next most potent stimulus was the contiguously adjacent dialect (Buzzy); the least effective stimuli were songs from a dialect 25 km distant (McClure), representing the same non-migratory subspecies, and a dialect 1,900 km distant (Sand Creek), representing a migratory montane subspecies of White-crowned Sparrow (Figs. 2–4).

SONG DIALECTS AND GENETIC DIFFERENCES IN WHITE-CROWNED SPARROWS (ZONOTRICHIA LEUCOPHRYS).

Song dialects have been described in several bird species (Marler and Tamura, 1962; Lemon, 1966; Nottebohm, 1969). Clear examples are found in the resident white-crowned sparrows (Zonotrichia leucophrys nuttalli) of coastal California and in populations of the chingolo (Zonotrichia capensis) of Argentina. Where dialects occur in these species an area of breeding habitat is occupied by territorial males that with few exceptions sing a very similar song. Contiguous and allopatric with this area males of another population sing a different song type. It has been shown (Marler and Tamura, 1964; Marler, 1970) that in the white-crown (Z. 1. nuttalli) the dialect is learned during the first few weeks of life. The contiguity of the populations with discretely different vocalizations could be related to several interesting questions in population genetics, vocal communication, and evolutionary processes. On a general level, however, the dialect phenomenon leads to two central issues: (1) How do dialects arise? and (2) What role, if any, do they play in the biology of the birds? In this paper I provide a speculation on the first question and some data that may clarify the second. Following a suggestion by Marler and Tamura (1962), Nottebohm (1969) proposed that females might preferentially mate with males of their own dialect, thereby constraining a locally adapted gene pool. This hypothesis, that dialects reduce gene migration, came from the observation that Z. capensis on altitudinal gradients in Argentina exhibits a series of dialect populations possibly corresponding to different selective regimes, whereas a single dialect is found over vast areas of lowland pampas where selection may be spatially homogeneous (Nottebohm, 1969; Nottebohm and Selander, 1972). There, are other possible explanations of song dialects in birds. First, song dialects, a consequence of vocal learning, may play no important role. Perhaps during the early learning phase, young birds acquire population specific calls that promote flocking, foraging efficiency, predator avoidance, or individual recognition, that are important for winter survival. Thus, the selective advantage of vocal learning would be explained by winter ecological conditions and not territorial breeding behavior. Second, dialects could maximize outcrossing in small populations. Females would mate with males having a song type unlike that of their early experience. Third, dialects may be a result of intrasexual selection and bear no direct relationship to mate selection. Perhaps vocal convergence bestows some advantage in gaining and holding a territory but females do not use dialect information for mate choice. Using an electrophoretic analysis of alloenzymes, I investigated populations of Nuttall's white-crowned sparrow (Z. 1. nuttalli) in California and populations of the mountain white-crown (Z. 1. oriantha) in Colorado to determine if song dialects were correlated with genetic differentiation.

A Distinctive Song Pattern in Gambel's White-Crowned Sparrow

The purpose of this communication is to report a distinctive song pattern of Gambel's Sparrows (Zonotrichia leucophrys gambelii) recorded in southern Alaska during the summer of 1967. It is well known that the songs of White-crowned Sparrows breeding in different localities differ in pattern, or dialect. Banks (Univ. Calif. Publ. Zoil. 70:1-123, 1964) reviews references in the literature to geographic variations in White-crowned Sparrow songs. Marler and Tamura (Science 146:1483-1486, 1964) found that the dialect patterns of males of the permanently resident Nuttall's White-crowned Sparrow (Z. 1. nuttalli) develop through learning from older birds in the first month or two of life. If gambelii is similar to nuttalli in this respect, the songs described below represent local dialects characteristic of specific breeding populations. Also, the song pattern of a given individual should, once it achieves adult form, be constant throughout life, whether uttered on the breeding grounds, in migration, or on the wintering grounds. A year ago, with support from the Institute of Arctic Biology and the Arctic Institute of North America, we began a study of variation in song pattern in the Gambel's Sparrow. To date one of us (Leonard Peyton) has tape-recorded the songs of this race in early summer in Alaska at College, Gulkana, Glennallen, Anchorage, Skilak Lake, and Kenai Lake. The other author (Barbara DeWolfe) recorded songs in fall, winter, and early spring at Santa Barbara, California, and during spring migration at Watson Lake, Yukon Territory. Sonagrams of the recordings were made, and analysis of the variations in song patterns is under way. The birds near Anchorage, and at Skilak Lake and Kenai Lake on the Kenai Peninsula, uttered songs that are similar to each other in basic pattern and that differ from all songs of Gambel's Sparrows we have heard or recorded elsewhere. At this early stage of our study we do not know how localized this distinctive pattern is. We describe it below in hopes that, once ornithologists are alerted to its existence, this same pattern may be detected either at other points in the vast breeding range of this race or, even better, on migration routes or in the wintering range. Fortunately, the pattern is sufficiently distinctive to be recognizable with the unaided ear. ---1-..-. ---2--3 4-4-56-

Continuity of Behavior in the Nuttall White-Crowned Sparrow

Continuity of Behavior in the Nuttall White-Crowned Sparrow