The lesser scaup (Aythya affinis, henceforth scaup) population decreased during the 1980s and has remained below conservation objectives. With two-thirds of the breeding population nesting in boreal forests, it is imperative to understand how changes in habitat features and landscape changes could negatively impact breeding scaup; this information could also help to guide waterfowl conservation and management programs. It has been hypothesized that landscape modifications, such as agricultural and oil exploitation activities, could adversely affect scaup reproductive performance. Female scaup were collected by shooting in the boreal forest fringe of central Alberta during within the first two weeks of June 2008 and 2009, corresponding to the early laying period. Collection location was determined using a hand-held GPS device and body mass (BM, g) was recorded immediately. When scaup carcasses were dissected, ovaries were removed and weighed. Rapidly growing follicles (RGF) and oviductal follicles (OF) were subjected to radioimmunoassay to quantify amount of ovarian corticosterone (OCORT) deposited into follicles. Nest initiation date (NID) was determined by counting and subtracting the number of postovulatory follicles (POF) from collection date.
Natural landscape features and habitat disturbances within 100 m, 250 m, 500 m, 1500 m, and 5000 m buffers of each scaup collection location were quantified, and then normalized using z-score transformation. General linear modeling was applied to BM, OCORT and NID across each of the five buffer sizes using a priori candidate models. Natural landscape and habitat disturbance parameters were model-averaged to obtain 85% confidence intervals to determine which habitat features best predicted BM, NID, and OCORT. Model-averaging revealed that the amount of natural water body habitats were negatively correlated to scaup OCORT at the 100 m and 500 m buffer zones, and negatively correlated to scaup BM at 1500 m and 5000 m buffer zones. A combination of natural water bodies (BOGSFENS, SWAMP, WATER, and WETLAND) were negatively correlated to NID across all buffer sizes tested, AGRIC disturbance was positively correlated to NID at the 100 m and 1500 m buffer zones, WELLS were negatively correlated to NID at the 1500 m buffer zone, while TRANSPORT showed varied responses at the 1500 m and 5000 m buffer zones. Post-hoc exploratory analyses were conducted to assess whether variation in OCORT, BM, and NID was related to habitat features operating at more than one spatial scale. This analysis revealed models incorporating more than one spatial scale were competitive when compared to the original a priori model sets at the 250 m buffer zone, with post-hoc models performing better than a priori models. This study highlights the need for a holistic approach to conservation management, considering not only local habitat characteristics and disturbances in the immediate vicinity of breeding waterfowl, but extending beyond and incorporating regional landscape attributes.
| Identifer | oai:union.ndltd.org:USASK/oai:ecommons.usask.ca:10388/ETD-2012-12-875 |
| Date | 2012 December 1900 |
| Contributors | Machin, Karen L. |
| Source Sets | University of Saskatchewan Library |
| Language | English |
| Detected Language | English |
| Type | text, thesis |
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