American dippers (Cinclus mexicanus) and montane streams :habitat selection, nesting ecology, and movements in relation to stream conditions


Strickler, Katherine Maureen.. (2008). American dippers (Cinclus mexicanus) and montane streams :habitat selection, nesting ecology, and movements in relation to stream conditions. Theses and Dissertations Collection, University of Idaho Library Digital Collections.

American dippers (Cinclus mexicanus) and montane streams :habitat selection, nesting ecology, and movements in relation to stream conditions
Strickler, Katherine Maureen.
American dipper--Habitat--Idaho American dipper--Nests--Idaho American dipper--Habitat--Montana American dipper--Nests--Montana
Forestry, Wildlife, and Range Sciences
Effective species management strategies can only be formulated after relationships between aspects of a species' ecology and environmental factors have been identified. In this dissertation, I piece together aspects of habitat use, nesting ecology, and movement patterns of the American dipper (Cinclus mexicanus), a stream habitat specialist.;To evaluate the degree to which dippers rely on continuous waterways as dispersal corridors, I examined thirteen polymorphic microsatellite DNA loci to determine the genetic structure of dippers in four watersheds in Idaho and Montana that are separated by similar over-land but varying over-water distances. I found that F ST values were generally low (0.01 to 0.09) and were not significantly correlated with either over-land or over-water distance (Mantel test, over-land: r 2 = 0.03; over-water: r 2 = 0.19). The lack of genetic structure among watersheds suggests widespread dispersal by this aquatic songbird. Given the lack of correlation between F ST and over-water distance for the four Idaho and Montana watersheds, I conclude that dipper movements among watersheds are not exclusively limited to streams.;I investigated watershed, stream reach, and benthic invertebrate community characteristics that can be used to predict the presence of American dippers. Dipper presence was best predicted by a combination of stream reach and watershed factors; benthic invertebrate community characteristics were poor predictors of dipper presence. Dippers were more likely to occur on streams that were wider, more turbulent, dominated by boulder and cobble substrates, and had lower conductivity and fine sediment compared to streams without dippers. These reach stream conditions were strongly linked to watershed-scale characteristics, including road densities and stream crossings, that were also important predictors of dipper presence.;When animals select the best habitat available, we should find congruence between habitat use and reproductive success. I compared factors associated with habitat selection and reproductive success at two scales, territory and nest site, and considered the effect of conspecific territory holders on habitat selection and nest success. Presence of neighboring territories was associated with reduced territory size and with lower nest success at both the territory and nest site scales, and may have moderated the importance of different stream and prey characteristics on habitat use and nest success. From this work, it appears that intraspecific competition can alter habitat use or nest success and may provide an alternative explanation for apparent mismatches between habitat preferences and fitness.;Dippers have frequently been proposed as indicator species because of their apparent sensitivity to impaired stream water quality. I reviewed existing criteria for selection of indicator species and assessed the suitability of dippers as indicators of biological integrity in streams in light of these requirements. American dippers satisfy only eight of 16 published criteria for selection of effective ecological indicators. Most importantly, dipper tolerance levels for most stream disturbances have not been well-studied (with the exception of stream acidity), and correlations between dippers and other ecosystem components have been shown only infrequently. This review identified notable shortcomings in the use of dippers as ecological indicators of stream health. However, several weaknesses could be reduced with more focused research, and others may be outweighed by the advantages of using dippers as ecological indicators. A possible resolution is to include dippers in multispecies indices of biological integrity.
Thesis (Ph. D., Forestry, Wildlife, and Range Sciences)--University of Idaho, May 8, 2008.
Major Professor:
Kirk Lohman.
Defense Date:
May 8, 2008.
Format Original:
xxi, 170 leaves :ill., map ;29 cm.

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