Vocalizations and nesting behaviour of the Pacific-slope Flycatcher, Empidonax difficilis

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dc.contributor.authorAinsley, Darryl Thomas Josephen_US
dc.date.accessioned2024-07-31T22:14:31Z
dc.date.available2024-07-31T22:14:31Z
dc.date.copyright1992en_US
dc.date.issued1992
dc.degree.departmentDepartment of Biologyen_US
dc.degree.levelMaster of Science M.Sc.en
dc.description.abstractVariation in vocal characteristics within a population of Pacific-slope Flycatchers (Empidonax difficilis) has not been described in detail. Species status of the PacificĀ­-slope Flycatcher and the Cordilleran Flycatcher (E. occidentalis) has only recently been established. The Western Flycatcher(E. difficilis) was reclassified into these two species, partially on the basis of geographic variation in voice. This study provides a basis for comparison of this variation among populations to variation within a population of E. d. difficilis on the Queen Charlotte Islands, British Columbia. Seven breeding pairs were studied in detail. Tape and written recordings of vocalizations were made on a regular basis. Inventories of the amounts and types of vocalizations produced by each bird were compiled. The context in which each vocalization was used was noted. Vocal behaviour and behaviour around the nest were observed. The date of each stage of breeding was noted. The song of E. difficilis consists of three syllables presented in a semi-regular sequence. A 'Pee-ist' call is commonly inserted into this sequence. A 'Tsip' call is the most commonly heard female vocalization. Other calls include 'Chrrip', 'Ti-ti-ti', 'Weet-weet-weet', 'Seet', and 'Zeet'. Spectrograms are presented for all but the Zeet call. Extensive variation among individuals was found in proportions of syllables (including the Pee-ist call) within song, sequence of syllables, syllable durations, intervals between syllables, and frequencies. Some variation among individuals in spectrographic form of song syllables was also noted. Significant temporal variation was found in syllable proportions, in sequence of syllables, in intervals between syllables, and in low frequencies. On the basis of these patterns of variation, I recommend protocols for gathering and analyzing vocal data used for the purpose of geographic comparison. Singing begins shortly after dawn and declines to nil around noon. Males sing extensively before females arrive, and while females build the nest and incubate. On the basis of these patterns of variation, I recommend that population surveys on this species be conducted within three hours of sunrise and prior to the arrival of females. Phenomena underlying variation in vocal features are investigated. The probability of two-syllable sequences appears to depend on the abundance of the second syllable of the sequence, on predilection for sequences, on the kind of syllable preceding the sequence, and on the length of the interval between syllables. Correlations among frequencies, syllable durations, and intervals between syllables are moderate. Song appears to be used primarily in mate attraction, while Pee-ist calls are used in interactions between neighbouring males and in communication between mates. This study provides the first documentation of polygyny in this species. There is no apparent association between song complexity and mating system in Empidonax. Frequencies, frequency spreads, and one interval measurement are greater than any reported previously in E. difficilis or in E. occidentalis. The physical structure of song syllables is similar to those of other difficilis populations described previously. Pee-ist calls, however, are less frequency-modulated than previously reported.en
dc.format.extent200 pages
dc.identifier.urihttps://hdl.handle.net/1828/16898
dc.rightsAvailable to the World Wide Weben_US
dc.subjectUN SDG 14: Life Below Wateren
dc.titleVocalizations and nesting behaviour of the Pacific-slope Flycatcher, Empidonax difficilisen_US
dc.typeThesisen_US

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