Core Questions & Objectives
Objective
Figures
Summary of Results
Consistency in comparison with habitat preferences
Comparison with conventional wisdom
Which species can be considered “boreal ducks” or “prairie ducks”?
How do we identify a boreal duck specialist?
Assess the importance of the boreal and prairie-parkland regions to each species, using models built from the Waterfowl Breeding Population and Habitat Survey
Sub-objective Highlight the importance of the boreal forest for waterfowl and encourage discussion and more research in the region
TS: We expect that species’ distributions/ranges and abundances are outcomes of selection for and adaptation to suitable environmental conditions.
TS: Historically, waterfowl species have been classified as either “prairie” or “boreal” species, meaning these species ‘represent’ or ‘are typical’ of a given region/biome.
TS: We expect that nesting habitat, food resources, growing season, climate, and other factors differ between different ecological regions (e.g. between prairies and boreal forest), and might therefore lead to differences in survival among difference species.
habitat & food resources
Due to topographical, hydrological, and climatic differences, wetlands generally differ from the prairie and parkland to the boreal region.
growing season and climate
The growing season is shorter further in the north, but so is the day length. Climatic conditions are more moist, less variable, and cooler (citation? - also consult with maps of environmental variables to make sure I’m correct).
TS: Our objective was to identify which species are highly adapted to boreal, hemiboreal, or prairie resources. [species that are not highly adapted to one region over the other can be considered “generalists”]
TS: Our study area represents the Canadian portion of the WBPHS (Figure already mentioned).
TS: We defined our regions following a combination of Brandt’s (2009) and the Bird Conservation Regions [?]
TS: We used waterfowl count data from the Waterfowl Breeding Population and Habitat Survey (WBPHS; Figure X
).
Figure Map of survey strata and transects
TS: We built predictive models of waterfowl abundance using boosted regression tree (BRT) analyses.
Figure Map of predicted abundances for one species with delineated range
TS: Range was delineated as the concave/alpha hull encompassing all densities above a species-specific density threshold.
TS: We calculated the amount of each species’ predicted population and delineated range contained within the boreal and prairie-parkland regions as a proportion of the total predicted population and predicted area within the study area.
Figure Point (or bar) plot showing the proportion of each species’ range within boreal, prairie-parkland, and “other” regions.
Figure Point (or bar) plot showing the proportion of each species’ population within boreal & prairies
Figure Point plot with abline at 0,1 to show where boreal ratio falls for each species. Colour-code/label specialization regions (e.g. above a given proportion and above/below 1 by a certain amount). Colour-code points by dabbler/diver
Figure Point plot with abline at 0,1 to show where prairie-parkland ratio falls for each species. Colour-code/label specialization regions (e.g. above a given proportion and above/below 1 by a certain amount). Colour-code points by dabbler/diver
Patterns of abundance/distribution vs. process of natural selection
[Are our results consistent with conventional wisdom regarding species for which the boreal is important? Prairies?]
Bethke & Nudds 1993 classify the following species as represenative of mixed prairie, aspen parkland, or boreal forest:
Duck abundance was most strongly associated with conserved soil moisture in the grassland region compared to the parkland (Bethke & Nudds 1995). Ephemeral and temporary wetlands are more common in the grassland region than the parkland (Adams 1988), and are important food resources in spring (Krapu 1974). - cited in Bethke & Nudds 1995.
—> Doesn’t necessarily say anything about species regionalizations. Just that abundance is more dependent on wetland conditions/precipitation in grassland compared to parkland.
Current patterns in distribution of species across a landscape are assumed to represent accumulated successes in survival, reproduction, and “choices” in habitat selection and dispersal
Check with Gaston notes for some citations
Natural selection can act on populations when there are differences in survival and reproduction among different habitats. Over time, species’ become adapted to particular ranges in habitat conditions in that they successfully reproduce and persist as populations in one set of conditions and not so outside of those conditions. The geographical area containing those conditions is the “range” (this idea based off a Martin 1998 citation in Clark & Hutler 1999 about natural selection occurring on nests in different habitats)
Prairie/grassland wetlands are generally highly productive, due to climatic variability and periodic droughts leading to high vegetation in shallower wetlands (Sheehan et al 1987, Adams 1988). - even compared to parkland wetlands (see Bethke & Nudds 1995)
or
Layout of the Waterfowl Breeding Population and Habitat Survey, showing strata boundaries and flight transects.
[Brief description of methods, but refer to my in-prep paper]
[species] pair abundance, as predicted from boosted regression trees (citation: Nic’s paper) and delineated range.
We identified each species’ density threshold as follows.
We extracted the cell-level predicted abundances from each cell in the prediction raster.
We ordered the abundances from highest to lowest and then calculated the cumulative sum abundance for each cell.
We converted this cumulative sum abundance into a proportion by dividing by the total predicted population in the full study area.
We plotted the proportional cumulative sum abundance as a function of abundance and then calculated the first and second derivative of this function.
We used the lowest density associated with a change point (identified as a minimum in the first derivative and a point where the second derivative equals zero).
Using each species’ density threshold, we separated presences from absences within the prediction raster, and then calculated the concave (i.e. alpha) hull of the resulting presences. This technique creates a polygon that encompasses the external points in a cluster of points (citation).
The proportion of each species’ range contained within the boreal, prairie-parkland, and other regions.
The proportion of each species’ range contained within the boreal, prairie-parkland, and other regions.
Boreal affinity of waterfowl species, where values above 1 indicate a boreal affinity and those below 1 indicate avoidance of the boreal. The green shaded region indicates the species classified as boreal due to the proportion of their range and/or population within the boreal.
Prairie-parkland affinity of waterfowl species, where values above 1 indicate a prairie-parkland affinity and those below 1 indicate avoidance of the prairie-parkland region. The yellow shaded region indicates the species classified as prairie-parkland due to the proportion of their range and/or population within the prairie-parkland.
We modelled and based our analyses off observed patterns in species distribution and abundance. However, since we used a relatively long-term dataset (15 years), we indirectly asked about persistence, which yields some information about the process driving range determination. Species may occur in some locations, at low abundance or only in one of many years. This pattern would be reflected as very low predicted abundance, which would exclude it from the predicted range in our analysis. Ergo, our ranges are likely to capture some pattern in long-term persistence of a population.