Sparrow Species Research Articles

Role of Handling Time in Selection of Extruded Food Morsels by Two Granivorous Bird Species

After producing food morsels resembling seeds of different shapes and sizes, we determined the effect of these variables on food morsel selection by Harris' Sparrows (Zonotrichia querula) and American Tree Sparrows (Spizella arborea). Harris' Sparrows have larger bodies and bills than American Tree Sparrows. During pairwise feeding trials, where consumption (mass) was the measure of selection, both species of sparrows selected food items that required the least handling time, not those that maximized energy gain per unit of time. Extruder-processed food morsels may provide a new means to distinguish predictions of various foraging theories and hypotheses.

Action-Based Learning: a New Form of Developmental Plasticity in Bird Song

Two forms of developmental plasticity in bird song are contrasted. The classical 'memory-based' or sensorimotor process includes a sensory phase during which a song model is memorized followed by a motor phase during which the bird matches his own song to the model via auditory feedback. In contrast, 'action-based learning' refers to the selection of songs that are already produced for retention in the mature repertoire. Evidence for action-based learning appears in the form of a large (overproduced) repertoire of songs in the plastic phase of song development. During the transition from plastic to crystallized song, social interactions selectively reinforce performance of certain song types, while non-reinforced song types are discarded. We review evidence from three species of sparrow which suggests that song sharing among territorial males, a common form of vocal plasticity usually thought to solely involve memory-based learning, may be the result of action-based learning. These forms of song learning are complementary in that memory-based learning provides the raw song material upon which the selective forces of action-based learning act. We suggest that action-based learning may be widespread among behaviour patterns that involve overproduction of motor patterns in youth.

Comparing Actual and Random Distributions of Nearest Neighbors

Pearson (1991) watched (Spizella pusilla) and White-throated (Zonotrichia albicollis) feeding on artificial patches of three sizes. He compared the observed distributions of distances between nearest neighbors in small groups with computer-generated expected distributions. Two principal results were given (presented here in reverse order from Pearson's paper). First, both species occurred disproportionately often on portions of the patches near a nearby pile. Pearson concluded the birds were attracted to Second, observed distributions of distances between birds differed from Monte Carlo (computer-generated) distributions and differed between the two species for most combinations of group size and patch size. The Monte Carlo method was complete spatial randomness (CSR; Diggle 1983: 4), presumably accomplished by generating a pseudorandom X-value and Y-value for each point. The points were constrained only to be at least 1 cm apart; 1,000 nearest-neighbor distances were generated for each group size in this manner. Pearson's (1991) conclusions were derived from differences between the spacing of real and Monte Carlo-generated birds, although he stated that spacing behavior could not be separated from these birds' affinity for cover. The conclusions are valid only to the extent that CSR represents a realistic expectation of the birds' behavior in the absence of social interactions. However, because the birds were attracted to the pile, we know that they did not conform to CSR. In the absence of social interactions, one would expect nearest-neighbor distances on average to be less than those predicted by the purely random model, because the birds were bunched at one end. Fortunately, Pearson's (1991) detailed data allow construction of a more suitable alternative model. Values for X are computed pseudorandomly, as in Pearson's study. Values for Y are computed by using a weighted pseudorandom number generator (Robertson 1977), based on the known distributions in Pearson's figures 4 and 5. The weighted values cast birds on the plane with a preference for proximity to a brush pile at Y of zero; for instance, they place 72% of the computer-generated Field Sparrows within the closest 5 cm of a small patch when group size is two. The alternative model (Fig. 1) differs greatly from Pearson's (1991) figure 1. Although the mean may not be a meaningful measure of central tendency in these distributions, the recalculated means are 0.61 to 0.64 those of Pearson's model. They differ by 3 to 14 cm. Although Pearson's interesting conclusions about differences between spacing behaviors of the two species of sparrows may be unaffected, his conclusions about the degree of randomness in their spacing (Pearson 1991:fig. 3) are not supported by his data when a more realistic distribution of birds is used for comparison. The alternative model for random spacing with a preference for cover (Fig. 1) assumes that the sparrows have no overall preference for certain regions in the X direction, that the six zones described in Pearson (1991) are an accurate description of the birds' use of space, and that positions in X and Y are uncorrelated. Pearson did not test these assumptions, nor can they be tested from the published data. Comparison of the alternative weighted model with observed distributions, though more valid, is probably less powerful than comparison of Pearson's (1991) purely random model. This is because the birds' distribution in the Y direction is determined both by a known preference for Y of zero and by a suspected minimum or preferred distance between birds. Thus, using the observed Y distribution taints the model with an unknown component of social spacing itself. Monte Carlo methods allow testing for spatial patterning when conventional methods fail (Diggle 1983, Krebs 1989, Manly 1991). The technique of using weighted number generators (Larkin 1982) extends Monte Carlo methods to some situations in which distributions in one or more dimensions are not purely random.

Weather and Reproductive Variation in Shrubsteppe Sparrows: A Hierarchical Analysis

We used a hierarchial approach to investigate the relationships among within— and between—year variation in precipitation and temperature in the northern Great Basin and components of reproductive success in two species of common shrubsteppe sparrows. During a 5—yr period we monitored clutch sizes, brood sizes, and fledging success in Sage (Amphispiza belli) and Brewer's (Spizella breweri) Sparrows in shrubsteppe habitat in central Oregon. During the 5 yr of our study, the Pacific Northwest experienced precipitation extremes, with the driest bioyear (October—April) in 65 yr of records (1976—1977) followed by one of the wettest. Within each breeding season daily temperature and precipitation fluctuated widely and in most cases unpredictably over a scale of a few days. Both species achieved significantly greater final reproductive success (as measured by number of fledglings produced) in wetter, presumably more biologically productive years. In Brewer's Sparrows this was achieved through higher clutch sizes in wetter years, whereas Sage Sparrows had higher hatching rates. For Sage Sparrows, within—year weather variables accounted for a significant amount of variation in reproductive parameters beyond that statistically explained by bioyear precipitation alone. However, in Brewer's Sparrows addition of within—year weather variables was not significant, and thus this species appeared buffered from the effects of short—term variation in abiotic conditions. The observed patterns suggested that clutch—size variation in Brewer's Sparrows may represent adaptive flexibility, the ability to assess potentially favorable environmental conditions and adjust reproductive investment accordingly. In contrast, in Sage Sparrows the association between bioyear precipitation and final reproductive success seemed most likely to be a proximate consequence of resource availability at the time of oogenesis, and to be further modified by the effects of weather that each nest experienced.

Hearing in the swamp sparrow, Melospiza georgiana, and the song sparrow, Melospiza melodia

Operant conditioning techniques and a psychophysical tracking procedure were used to measure thresholds for pure tones in two congeneric species of sparrows: swamp sparrows and song sparrows. Thresholds were measured both in quiet conditions and in the presence of white noise. The two species were similar in their gross pattern of auditory sensitivity with most sensitive thresholds in the frequency region of 1·0–8·0 kHz and poor hearing above and below this range. However, the best sensitivity occurred at 2 kHz for the song sparrows and at 4 kHz for the swamp sparrows. This pattern was also observed in song spectra of the two species. The songs of song sparrows had more power in lower frequencies than the songs of swamp sparrows. Masked auditory thresholds for both species were very similar, showing a generally increasing signal-to-noise ratio with increasing frequency. The similarity between swamp and song sparrows in these measures of basic auditory sensitivity suggests that the primary mechanisms underlying selective vocal learning in these sparrows probably reside at higher levels than the peripheral auditory sensitivities.

GEOGRAPHIC VARIATION OF SEXUAL DIMORPHISM IN SIZE OF SAVANNAH SPARROWS (PASSERCULUS SANDWICHENSIS): A TEST OF HYPOTHESES.

The Savannah Sparrow (Passerculus sandwichensis) is a widespread and common North American bird that shows both geographic variation and sexual dimorphism in size. I used information from 24 measurements on 1,791 individuals from 51 populations to test two hypotheses (sexual-selection and niche-partitioning) about the evolution of sexual dimorphism. Throughout their range male Savannah Sparrows are larger, on average, than females. This doubtless reflects Darwinian sexual selection, for territorial fights usually involve males, many of whom fail to obtain mates. In some parts of their range, Savannah Sparrows are commonly polygynous, whereas in others they are characteristically monogamous. Among species of American sparrows (subfamily Emberizinae) sexual size dimorphism is generally greater in polygynous species than in monogamous ones. However, I did not find a similar trend among populations of Savannah Sparrows. The amount of dimorphism in all populations of Savannah Sparrows is equivalent in magnitude to that of other species of sparrows that are commonly or regularly polygynous, and it is greater than that of other sparrow species that are characteristically monogamous. The amount of sexual dimorphism, either in overall size or in bill size, does not correlate with species diversity and does not differ between island and mainland populations. These results do not support the niche-variation hypothesis. Size dimorphism is relatively great in populations of Savannah Sparrows that are resident in southwestern salt marshes, and these birds are the only sparrow-like birds that generally breed in these marshes. Dimorphism is, in general, relatively great in marsh-dwelling species in the family Emberizidae. These species are commonly, but not always, polygynous; the mating systems of the salt-marsh Savannah Sparrows are not known. There are no significant differences in the extent of dimorphism among populations of salt-marsh sparrows, and there are few among the non-salt-marsh ones, probably reflecting conservatism in the evolution of size dimorphism.

Chromosomal evolution in finches and their allies (families: Ploceidae, Fringillidae, and Emberizidae)

Five species of sparrows, weavers, and finches belonging to the Ploceidae, Fringillidae, and Emberizidae were examined cytogenetically by G- and C-banding. There was significant G-band homology between the families, with pericentric inversions being the principal form of chromosome change both at the intra- and inter-specific levels. In some instances there was more homology between species from different families than there was between species within a family. Possible explanations for this phenomenon are discussed.Key words: chromosome banding, inversion polymorphism, Passeriformes, Aves.

A Lesson in the Limitations of Field Experiments: Shrubsteppe Birds and Habitat Alteration

We manipulated the habitat composition and structure within territories of birds breeding in the Artemisia—dominated shrubsteppe of central Oregon in order to assess how closely individuals track habitat in features such as territory placement of size or behavioral budgeting and space. We removed 75, 50, 25, and 0% of the shrub individuals from 625—m2 blocks in a checkerboard designs. Over the following 7 yr we monitored territorial locations and sizes and breeding densities of Horned Larks (Eremophila alpestris), Sage Sparrows (Amphispiza belli), and Brewer's Sparrows (Spizella breweri) on the manipulated area and adjacent unaltered control area. Activity and substrate use patterns and intensity of use of the different treatment blocks within the manipulated area were also determined for the two sparrow species. Sage Sparrows, which from our previous studies appear to be more closely linked to shrub (sagebrush) coverage than the other species, did not respond to the manipulation at a local population level. The manipulation apparently did affect territory placement and densities of Brewer's Sparrows and Horned Larks in 1980—1982, but these trends were not consistent over the entire postmanipulation period. Densities of all species varied among years. For Brewer's Sparrows and Horned Larks these variations did not parallel those in nearby census locations, but Sage Sparrow densities varied in the same ways over all the locations. These variations appeared to parallel variations in bioyear (October—April) precipitation, with a 1—yr time lag. Individuals of both sparrow species altered the details of their activity budgeting, but not their substrate—use patterns, in response to the manipulation. Both species clearly expressed an affinity for unmanipulated blocks within the manipulation area. This experimental manipulation is complicated by influences of time lags on individual and population responses that may stem in part from site tenacity by breeding adults, leading them to return to previous breeding locations in years following the manipulation despite the habitat changes. Further, the spatial scale on which the manipulation was conducted may have been inappropriate to gauge responses at the population level. We suggest that these complications may plague many field experiments in ecology.

Niche Expansion and Contraction in a Variable Environment

When food is abundant, sparrows are found in great variety of habitats and appear to specialize on particularly profitable types of seeds. However, during periods of food scarcity, each sparrow species occupies a very narrow range of habitats but consumes a great variety of seeds within each occupied habitat. As a result, average dietary overlap may underestimate the potential for competition for food within habitats during periods of food shortage whereas average habitat overlap overestimates the potential for competition since each species occupies a different habitat during periods of food shortage.

Foraging Efficiency, Resource Partitioning, and the Coexistence of Sparrow Species

The relationship between seed size and handling time was documented for three species of sparrows. Handling times were measured in the laboratory by presenting field-collected seeds to birds caught in the wild. Large species of sparrows were more efficient than small species at handling large seeds, but large and small sparrow species were about equally efficient at handling small seeds. Based on the relationships between seed size and handling time, a function was constructed relating profitability (measured in milligrams per second) to seed size for each sparrow species. These results, with information on the abundance and size distribution of seeds in the habitats frequented by the sparrows, were used to show that different species of sparrows are likely to have broadly overlapping diets whenever seeds are scarce enough for the consumption of seeds by one species to have much impact on the availability of seeds to another species.

Response of Breeding Passerine Birds to Rangeland Alteration in a North American Shrubsteppe Locality

SUMMARY (1) During 1980, a large area of sagebrush (Artemisia tridentata Nutt.)-dominated rangeland in southern Oregon, U.S.A., was sprayed with the herbicide 2,4-D, the dead shrubs removed, and crested wheatgrass (Agropyron cristatum (L.)) planted as part of a range improvement programme carried out by government agencies. We monitored breeding bird populations in the treated area for 3 years prior to and 3 years following the alteration. (2) The treatment produced major changes in habitat composition and structure. Before treatment, sagebrush cover was 19-24% and grass cover 1-4%. Afterwards, sagebrush cover decreased to 4-12%, while grass cover increased during the post-treatment period to 10-57% as the wheatgrass became established and cheatgrass (Bromus tectorum L.) invaded. The area of bare, unvegetated ground also decreased, and the height profile of the vegetation changed substantially. (3) There was no evidence of an immediate response by the bird populations to these habitat changes. In the year following the treatment, abundances of sage sparrows (Amphispiza belli (Cassin)) did not change, while the density of Brewer's sparrows (Spizella breweri Cassin) decreased. During the following 2 years, however, Brewer's sparrows fluctuated in abundance, sage sparrow abundance gradually decreased, numbers of horned larks (Eremophila alpestris (Linnaeus)) increased, and vesper sparrows (Pooecetes gramineus (Gmelin)) first appeared on the area. These density changes were not related to population changes occurring elsewhere in this shrubsteppe region. (4) Results from earlier work on unaltered rangelands in the region were used to predict the population densities that would be expected on the basis of the structure and floristic composition of the study area following the treatment. Horned lark densities approximated the predicted values, but for both sparrow species the fit was poor. Incorporating a 1 year time lag improved the fit of observed to predicted values in a few cases, but overall made no significant difference. (5) The failure of such bird populations to respond rapidly to major habitat changes may relate to time lags produced by site tenacity of breeding individuals. Such time lags complicate attempts to formulate management policies on the basis of short-term before and after surveys. They also suggest that conducting field experiments in ecology may require longer periods of post-treatment study than has normally been the case.

Keypeck conditioning with reinforcements in two different locations in thrush, tit and sparrow species

Twenty-one individuals each of the species great tits (Parus major), blue tits (Parus caeruleus), marsh tits (Parus palustris), blackbirds (Turdus merula), songthrushes (Turdus philomelos), tree sparrows (Passer montanus) and house sparrows (Passer domesticus) were conditioned to a keypeck response by means of food reinforcement. The site where the reward was given was then changed. The number of reinforcements were then counted until the keypeck response followed immediately (within 10 seconds) on three successive occasions, and a comparison was made between species. Of the species studied the blackbird needed significantly fewer instances of reinforcement in order to re-establish an immediate keypeck response. A significant difference was also seen between the performance of the great tit and marsh tit, as well as between the blue tit and the marsh tit. No significant difference was found between the performance of the house sparrow and the tree sparrow.

Ontogeny of Song Recognition in Birds

SYNOPSIS. This paper reviews song recognition in two congeneric species of sparrow the swamp sparrow ( Melospiza georgiana ) and song sparrow ( Melospiza melodia ). Data from psychophysical studies of hearing, tutoring experiments with young birds, and field playback studies with adult birds are considered together in order to gain insight into the mechanisms of species recognition through song development. In aggregate, the evidence suggests a multi-stage process of song development consisting of an early perceptual preference for learning conspecific song, a sensorimotor phase of song development during which vocal output matches an auditory memory as if through trial and error, and a final phase of full song which functions in territorial defense and mate attraction.

Birds in Isolated Bogs in Central Michigan

A study of the avifaunas of three different types of bog-black sprucetamarack, white cedar-tamarack and open bog-at approximately the same latitude in central Michigan, indicated that only the black spruce-tamarack bog attracted boreal species of birds during the breeding season. The bog characterized by white cedar had species found in deciduous forest and edge habitat. Few, if any, bird species appear to be closely associated with white cedar. Open dry bogs had only species occupying early successional habitats and no boreal species of birds. The common yellowthroat (Geothlypis trichas) and song sparrow (Melospiza melodia), early successional or ecotonal species having small territories, were the only species found in all three types of bog in central Michigan. It appears that at least the structure of the vegetation and plant species composition determine which boreal species of birds inhabit these isolated bogs.

Summer Rainfall and Winter Sparrow Densities: A Test of the Food Limitation Hypothesis

We used published data on winter sparrow densities (from Christmas Bird Counts) and summer precipitation to test the hypothesis that local densities of wintering sparrows in southeastern Arizona are affected by the abundance of food. Our analyses rest on the assumption, justified by previous studies, that the abundance of seeds available to wintering granivorous birds is correlated with the quantity of rainfall the previous summer. Our results strongly supported two a priori predictions: (1) the density of sparrows should be positively correlated with summer rainfall, and (2) the density of individual sparrow species should be positively correlated with the total density of all other sparrow species. Our findings provide further evidence that winter finch populations are food-limited and suggest that interspecific competition may be important in at least some avian communities.

A comparison of auditory evoked potentials in two species of sparrow

Auditory evoked potentials were recorded from the surface of the brain in young swamp and song sparrows. Responses to pure tones indicate that both species have similar auditory sensitivity during the sensitive period for song learning. Responses to the song syllables extracted from the normal adult song of both species show evidence of hemispheric differences for swamp sparrows listening to conspecific syllables but not to song sparrow syllables. Song sparrows showed no evidence of selective responsiveness to conspecific syllable type.

Response of Male Song and Swamp Sparrows To Neighbour, Stranger, and Self Songs

Abstract We examined the responsiveness of territorial male swamp sparrows (Melospiza georgiana) and song sparrows (Melospiza melodia) to neighbor, stranger, and self songs. In two speaker tests (with two song bouts played simultaneously from separate speakers), male swamp sparrows failed to discriminate between neighbor and stranger songs and between self and stranger songs. In single speaker presentations, male swamp sparrows responded more aggressively to stranger song than to neighbor song and gave intermediate responses to self song. Male song sparrows showed no significant discrimination between neighbor, stranger, and self songs. We hypothesized that male birds may learn what other conspecific songs should sound like by listening to their own songs. In its most stringent form this hypothesis might predict maximal responsiveness to playback of a male's own song. This prediction was not verified for these two sparrow species. There was less of a difference in responsiveness toward neighbor and stranger songs in song sparrows than in swamp sparrows; this result is compatible with the hypothesis that larger repertoires make neighbor recognition more difficult.

Optimal size of territory in the clay-colored sparrow, Spizella pallida

Territory size in two populations of clay-colored sparrows in Manitoba averaged smaller than those in other open-country species of sparrows. This is probably because the territory was not used by adults for feeding or for gathering food fur the young. Experimental removals of territorial males in mid-May revealed the existence of a surplus of nonterritorial birds, indicating that there is some resistance to taking too small a territory. Investigation of several factors which could influence territory size indicated that nest predation was the most important factor in preventing the territory from becoming a very small size and that the upper limit to territory size was determined proximately by a number of factors including nesting cover and pressure from adjacent territory holders. Most male clay-colored sparrows appeared to preferentially defend an optimal size range of territories in which they maximized their reproductive fitness.

Selective Vocal Learning in a Sparrow

Male swamp sparrows learn their songs; they fail to learn songs of the sympatric song sparrow. Syllables from tape recordings of both species of sparrow were spliced into an array of swamp sparrow-like and song sparrow-like temporal patterns. Swamp sparrows learned only those songs made of swamp sparrow syllables. They did so irrespective of whether the temporal pattern was swamp sparrow-like or song sparrow-like. Selectivity was retained by birds reared in total isolation from adult conspecific sounds.

TRANSMISSION OF AVIAN POX FROM STARLINGS TO ROTHCHILD'S MYNAHS

Several wild species of birds, including starlings (Sturnus vulgaris), house sparrows (Passer domesticus) and pigeons (Columba livia) gained access to an aviary housing Rothchild's mynahs (Leucospar rothchildii) and over 100 additional birds representing a variety of species. Six of approximately 15 mynahs became infected with avian pox and all of them died. None of the other birds in the aviary developed lesions. Pox virus was isolated from mynah facial lesions on chicken chorioallantoic membrane and in duck embryo fibroblast cell culture. It did not produce lesions in white Leghorn chickens, but did produce lesions in 4 of 11 wild starlings captured outside the aviary. Results indicated the agent was an indigenous starling pox capable of infecting and producing disease in mynah birds. Destruction of the captive starlings and isolation of the remaining mynahs immediately stopped the mortality.