Year of Award

2014

Document Type

Thesis

Degree Type

Master of Science (MS)

Degree Name

Wildlife Biology

Department or School/College

College of Forestry and Conservation

Committee Chair

Creagh Breuner

Commitee Members

Lisa Bate, Mark Hebblewhite

Keywords

harlequin duck, resource selection, occupancy, human disturbance, feather corticosterone, stress

Abstract

Annual reproductive variation is the central focus of many ecological studies. Variation in reproductive success is an important vital rate to study because it can lead to inferences about population health, extinction risk, human disturbance and habitat quality. The identification of the causes of reproductive variability can help guide conservation and management efforts of a species. In Glacier National Park, Montana I studied causes of annual reproductive variation and behavioral responses to human disturbance in a breeding population of harlequin ducks (Histrionicus histrionicus). Harlequins are rare sea ducks with a Holarctic distribution and winter along rocky coast lines of North America. Females reach reproductive maturity at age 3. At this time they bond with a male that they will breed with for life. Recent band re-sighting has revealed that these ducks can live up to at least 21 years. In spring pairs migrate inland to the female’s natal montane stream to breed. My study focused on the breeding season from April – September on Upper McDonald Creek, Glacier National Park, Montana. My objective was to study 3 potential indirect and direct sources of reproductive variation in Harlequin ducks on this breeding stream; 1) stream flow effects on annual reproductive success, 2) human presence and effects on stream patch occupancy and resource selection, and 3) carry-over effects of physiological measures of body condition, baseline corticosterone levels (primary stress hormone in birds), and integrated measures of corticosterone deposition in feathers. For my first objective I identified 4 different parameters of stream flow that accounted for 32% of the annual variation in reproductive success. I conclude that these parameters will be very sensitive to climate change, making reproduction challenging for harlequins into the future. For my second objective I found greater probability of occupancy of ducks in high human use sites and in stream patches closer to roads. I also found greater occupancy in pool habitat; surprisingly, this pool habitat also had a greater distribution close to road. I conclude from this analysis that there were no strong negative effects of human disturbance on harlequin duck occupy and resource selection, but recommend that harlequin habitat near to human use areas be monitored closely. For my third objective I found that concentrations of corticosterone deposited in feathers grown just prior to reproduction predict reproductive success for that year. I did not find any predictive value of body condition or baseline corticosterone levels. The carry-over effects that I documented in the feathers grown during the prenuptial molt indicate that is an import period that reflects reproductive decision (may be 2 month separation from feather growth to egg lay). These 3 lines of inquiry identified important sources of annual reproductive variation and will help guide management and conservation efforts. I recommend further study to better understand important resources that harlequins select for on the breeding stream and intensive study of harlequin wintering habitat, especially prenuptial molt areas.

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© Copyright 2014 Warren Kevin Hansen