I investigated the relationship between harlequin duck (Histrionicus
histrionicus) behavior and lack of recovery from the Exxon Valdez oil spill in
Prince William Sound, Alaska. First, I evaluated the hypothesis that harlequin
ducks in winter have little flexibility to increase foraging time in response to
disturbance because they are constrained to forage during daylight. Eight radio-tagged
harlequin ducks wintering in Resurrection Bay, Alaska were monitored for
evidence of dive-feeding at night. Each radio-tagged individual was detected
during an average of 19.5 of 22 nocturnal monitoring sessions and signal loss
indicative of diving behavior was not detected during a total of 780 minutes of
signal monitoring. In contrast, the same 8 radio-tagged birds were detected during
an average of 9.1 of 12 daytime signal monitoring sessions and signal loss
indicated diving behavior during an average of 62 �� 7% of 5-minute daytime
monitoring periods (total of 364 minutes of signal monitoring). Thus the harlequin
ducks monitored in this study rarely, if ever, fed by diving at night, possibly due to
reduced foraging efficiency and (or) increased predation risk at night. This result
suggests that harlequin ducks in mid-winter may be severely time-limited in their
foraging, especially in northern parts of their winter range. Therefore, subtle
changes in energy requirements and (or) time-activity budgets as a result of
continued exposure to residual oil from the Exxon Valdez oil spill may affect the
ability of harlequin ducks to meet their daily energy requirements.
Second, I tested the hypothesis that exposure to crude oil affects time-activity
budgets of harlequin ducks. Controlled oil-dosing and plumage-oiling
experiments were conducted using adult female harlequin ducks in captivity. I
found no evidence that ingestion of weathered Prudhoe Bay crude oil affected the
occurrence of feeding activity during 30-minute observation periods, nor was there
evidence of effects on time spent feeding. Effects of crude oil ingestion on
maintenance activity were detected, but were neither consistent between the 2 years
of the study, nor dose-dependent for the 2 doses administered (2 and 20 mL kg�����
wk�����), and therefore did not strongly support an oil-dosing effect on maintenance
activity. Consequently, these results provided little support for the hypothesis that
oil ingestion affects time-activity budgets of captive harlequin ducks, at least for
the doses and conditions of captivity used in this study. Plumage-oiling reduced
feeding activity in captive harlequin ducks. The estimated probability of feeding
during 30-minute observation periods for birds in the high-exposure oiling group (5
mL of crude oil) was 53% less than that of non-oiled controls. Oiled birds
exhibited a trend of reduced time feeding with increasing level of external-oiling;
this effect was greatest among birds in the high-exposure oiling group, which spent
43% less time feeding than non-oiled birds. Reduced feeding was associated with
less time in the water dive-feeding and presumably lower heat loss. Trends in the
occurrence of maintenance activity and time spent in maintenance activity for birds
in the high-exposure treatment suggested plumage-oiling increased maintenance
activity, but results were not conclusive. The behavioral changes associated with
plumage-oiling in captivity would likely reduce fitness in the wild, where a high
proportion of time must be spent in the water feeding. If residual Exxon Valdez oil
sequestered in beach sediments enters the water column where it may be
encountered by harlequin ducks, external exposure may lead to reduced feeding
activity. This, in turn, may compromise survival, particularly during mid-winter
when the time available for diurnal foraging is low and maintenance energy
requirements are high. / Graduation date: 2004
| Identifer | oai:union.ndltd.org:ORGSU/oai:ir.library.oregonstate.edu:1957/30132 |
| Date | 05 February 2004 |
| Creators | Rizzolo, Daniel J. |
| Contributors | Roby, Daniel D., Jarvis, Robert L. |
| Source Sets | Oregon State University |
| Language | en_US |
| Detected Language | English |
| Type | Thesis/Dissertation |
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