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Using multiple methods to describe breeding, stress response, and disturbance of marbled murrelets, Brachyramphus marmoratus

Using multiple methods to describe breeding, stress response, and disturbance of marbled murrelets, Brachyramphus marmoratus

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Title: Using multiple methods to describe breeding, stress response, and disturbance of marbled murrelets, Brachyramphus marmoratus
Author: McFarlane Tranquilla, Laura
Abstract: I investigated the breeding biology of
Marbled Murrelets using (a) vitellogenin
(VTG) analyses, (b) brood patch (BP)
scores (thought to imply incubating
adults), and (c) radio telemetry data.
VTG analyses allowed description of the
5-month breeding season for Marbled
Murrelets, the timing of which did not
vary between years (1999-2000). Of the
females caught between April to July
(the 'egg-production period'), 55% were
producing eggs. Using brood patches (BP)
to infer reproductive status is an
approach that should be used cautiously:
53% Marbled Murrelets caught with
fully-developed BP never incubated, and
likewise, 50% of fecund, radio-tagged
females never incubated (failed
incubators?). Of a sample of fecund
females, 40% started incubation about 15
days later than expected (delayed
incubators?). This suggests large
numbers of birds that failed to start
incubation, for reasons that were not
clear. While investigator disturbance
explained some cases, seasonal date
also had an effect on breeding success.
We detected a seasonal decline in br3eeding success in Marbled Murrelets, with failed incubators occurring later int he season (by 18 days) than successful incubators, and 'delayed' incubators initiating incubation later (by 24 days) than those not delayed. Thus, while capturing murrelets sometimes affected individual breeding status, later breeders were affected more than earlier breeders. This finding suggests that researchers should aim to campture Marbled Murrelets early in the breeding season. My investigation of capture effects also included an analysis of the stress respsonse to capture, using corticosterone. Like other birds, Marbled Murrelets reach maximum corticosterone levels at 30 min. Corticosterone increased with mass in females (but not males), suggesting that females are more sensitive to stress when they are heaviest, during egg-production.
Type: Thesis
URI: http://hdl.handle.net/10315/14820
Published: Ottawa : National Library of Canada = Bibliothèque nationale du Canada
Citation: Thesis (M.Sc.)--Simon Fraser University, 2001.
ISBN: 0612818926
Date: 2004

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