| Summary: | Animal vocalizations vary greatly between and within species. Male oscines
acquire song by imitation of others, in much the same way that humans learn language. I
investigate song variation and the source and timing of song learning by Song Sparrows
(Melospiza melodia) in this thesis. I recorded 33,843 songs of 134 birds from 1988-1991
on 12 islands in southwest coastal British Columbia. Birds were colour-banded, usually
in the nest, and many were followed from their birth place through to territory
establishment in the following spring. The age and “phenotypic” father of every bird
born on Mandarte Island was known during this 4-year period.
Individual Song Sparrows did not change their unique repertoires of 5-13 complex
Song Types across a range of ages covering their life span. Complete repertoires
recorded from this species at any age are the same as those in the first year of life, when
song is learned. Two hundred and six continuously recorded songs or 280 songs from
pooled sessions were required to achieve 95% confidence that the complete repertoire
was recorded.
Birds averaged 8.2 Song Types over all islands and did not sing smaller repertoires
than those birds in mainland populations. Higher population density and an increased
number of neighbours at the time of song learning both resulted in larger repertoires.
More singing males provide greater acoustic stimulation at the time of song learning.
From whom do wild birds learn their songs, and how do individuals choose among
the models available? Two opposing hypotheses predict that tutors are most likely either
fathers or neighbours. Twenty-one birds born on Mandarte Island matched no songs with
their fathers. However, three birds that dispersed from a small island (0.8 ha) with few
tutors to a very poor song environment with only one tutor retained some songs they
heard from their fathers before dispersal (22-68 days of age) and also learned other songs
from their neighbours after dispersal (273+ days of age). Birds as young as 124 days of
age uttered note sequences that were destined to be in their adult repertoires. Previous
studies had shown this to occur at 241 days in the laboratory and 169 days in the field.
Juvenile birds that progress rapidly through the stages of song development may obtain
territories more readily than birds who do so more slowly or at older ages.
Using the 1989 cohort of juveniles, I could assign every song learned to a particular
tutor. I found that while most focal birds shared no songs with older non-neighbours,
some birds matched up to nine Song Types with them. These patterns indicate the
existence of preferred tutors. Particular Song Types were copied precisely, and persisted
across up to four generations and eleven years on Mandarte Island. This thesis shows
that Song Sparrows share more identical songs, and learn song over a longer period than
previously determined. Both the timing and the source of song learning depends on the
quality of the learning environment, measured by the number of tutors and the amount of
singing. === Science, Faculty of === Zoology, Department of === Graduate
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