Male Swamp Sparrows Research Articles

Developmental overproduction and selective attrition: new processes in the epigenesis of birdsong.

All phases of song development from infancy to adulthood were studied intensively in a group of laboratory-reared birds. Male swamp sparrows, Melospiza georgiana, trained with tape-recorded songs in infancy, developed song some 8 months later, averaging 2.2 song types per bird. Analysis of the intermediate stage of plastic song revealed that the birds generated 4 to 5 times more song material than was needed for the species-specific song repertoire. The excess was discarded at the time of full song crystallization. Indications that the attrition process is selective include tendencies to retain imitated rather than nonimitated elements, and the rejection of heterospecific elements. Attrition may also be influenced by vocal stimulation at the time of song crystallization, providing an opportunity for behavioral adjustment even though new themes can no longer be learned. Attrition has been described in the transition in human infants from babbling to speech.

Long-term storage of learned birdsongs prior to production

Sixteen male swamp sparrows, Melospiza georgiana, were reared by hand in the laboratory and exposed in infancy to tape-recorded songs. Training ended around 2 months of age. Samples of singing were tape recorded sporadically from the age of 50 to 90 days and on a weekly basis from about 95 to 400 days. Analysis revealed that explicit rehearsal of learned songs did not begin, on the average, until 240 days after the last exposure to training songs. Swamp sparrows can commit song syllables to memory and produce imitations of them 8 months later with no rehearsal in the interim.

Species song discrimination in adult female song and swamp sparrows

Six female song sparrows ( Melospiza melodia) and six female swamp sparrows ( Melospiza georgiana) were treated with oestradiol, and their response to song measured by frequency and intensity of copulation-solicitation display. Test stimuli were synthetic songs composed of either song sparrow or swamp sparrow syllables assembled in either song-sparrow-like or swamp-sparrow-like temporal patterns. Female song sparrows responded preferentially to songs containing their own species' syllables and to songs containing their own species' temporal patterns. Swamp sparrows were also sensitive to both syllable type and temporal, pattern, in contrast to male swamp sparrows, which show no preference for swamp sparrow temporal patterns.

Sparrows Learn Adult Song and More from Memory

Male swamp sparrows reared in the laboratory and exposed to taped songs during infancy produce accurate imitations of the material following an 8-month interval with no rehearsal. When the first rehearsal occurs, at about 300 days of age, large numbers of syllables are perfected. They are developed through invention and improvisation as well as imitation. Most are discarded at the time of song crystallization. Hence, these songbirds learn more than they manifest in full adult song.

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.

Species song discrimination in choice experiments with territorial male swamp and song sparrows

Playbacks of synthetic and normal songs were used to determine what song parameters are important to species song recognition by territorial male swamp sparrows ( Melospiza georgiana) and song sparrows ( Melospiza melodia). Syllable morphology influences the discrimination of conspecific song from song sparrow song in adult swamp sparrows, but temporal pattern does not; this result duplicates that found in studies of song learning of the young in this species. Species song recognition is influenced by both syllable morphology and temporal pattern in adult song sparrows, in contrast to the situation in young sparrows, which seem not to distinguish their own species' song from that of swamp sparrows on either cue.

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.

Polygamy among Swamp Sparrows

Polygamy among Swamp Sparrows.-Systems of mating are of considerable biological interest; the field observations reported herein are relevant to the consideration of the evolution of polygamy presented by J. Verner and M. F. Willson (Ecology, 47, 143-147, 1966). These authors have shown that polygamy in North American passerines is most common in species inhabiting vegetation that presents a small vertical dimension, i.e., marshes, prairies, and savannahs, and that most of the regularly polygynous species breed in marshes. Swamp Sparrows (Melospiza georgiana) are common breeding passerines of marshes in eastern Massachusetts. During June, 1965, I made several trips to the marshes of Great Meadows National Wildlife Refuge, Concord, Massachusetts, and to a large marsh along the Sudbury River, west of Wayland, Massachusetts. In these marshes, male Swamp Sparrows most frequently held territories over shallow water near shore, in mixed stands of sparse cat-tail (Typha), grasses, and weeds (and sometimes bur-reed, Sparganium), but were occasionally found in vegetation composed of shrubs and arrowhead (Sagittaria). Territories varied greatly in size, but whether their territories were large or small, males and females foraged in the woods and shrubbery on shore as well as in the marsh. One male at the Wayland marsh, on a territory comprised largely of a dense stand of shrubs, was unpaired and was singing vigorously even as late as mid-June. Another male at Wayland was bigamous; each of his females had a on which she foraged. The male's favored singing perches were between the females' centers of activity, and he frequently flew into both subterritories. On 12 June the male was attentive to both females, but concentrated his activity in the area of one of them and carried food to her brood. Three days later the male paid little attention to either female. By this time the young of the earlier brood were out of the nest and the female was feeding them close to shore. One male at Great Meadows was also bigamous; here, too, each female had a subterritory within the male's territory. This male followed both females on 15 June and sang frequently from both subterritories. Two days later, one of the females left to spend most of her time in the woods, perhaps feeding fledglings, and was seldom seen on the marsh. The male at this time was closely attentive to the second female, and by 26 June, both male and female were feeding fledglings. When the first female left the marsh, the territory utilized by the male contracted until it was only slightly larger than the subterritory of his second female. In both cases of bigamy observations began too late to ascertain if the males fed nestlings of the first females, but both males fed young of their second females. In neither case did the nestling periods of the two broods overlap extensively. Eight males at Great Meadows each had only one mate in evidence at the times of observation. However, it is possible that, earlier in the season, some of these may have been mated to other females. Two of these apparently monogamous males assisted their mates in feeding the offspring. The female of another male was not seen, but the male fed fledglings on and after 17 June. This male sang more frequently than any of his neighbors through 27 June; a female was carrying nesting material on his territory on 22 June, but was not seen again. The present observations of Swamp Sparrows revealed that, of 12 males observed, 1 was unpaired, 8 had one mate each at the times of observation, and 2 (or about 18 per cent) were bigamous. Thus it is possible that Swamp Sparrows are among the regularly polygynous passerines nesting in marshes. So far as I know, polygamy has not previously been reported for this species.-MARY F. WILLSON, Department of Zoology, Vivarium Building, University of Illinois, Champaign, Illinois.