Foraging habits of spring migrating waterfowl in the upper mississippi river and great lakes region
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- ________________________________________________________________________ Mallard Diets
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a/b d/e c f a d b e c f Species 
Figure 1.3. Percent of seeds and invertebrates in the diet of 6 species (BWTE = blue-winged teal, MALL = mallard, GADW = gadwall, LESC = lesser scaup, RNDU = ring-necked duck) collected in the Upper MS River and Great Lakes Region during spring 2006 and 2007 (least-squares means ± standard error). Different letters indicate significantly different means. s
ignificantly by date and the percentage of seeds varied significantly among study sites and by date (Table 1.11). Blue-winged teal exhibited a daily increase of 0.79% ± 0.29% in invertebrate consumption (P = 0.006). Additionally, the proportion of seeds in the diet was moderately lower (P = 0.065) for blue-winged teal collected at Saginaw Bay than blue-winged teal collected at Wisconsin (Figure 1.4). The final reduced MANCOVA model evaluating longitudinal variation in diets of blue-winged teal included the main effects of transect, date, habitat, reproductive status, year, and a transect by year interaction (Table 1.12). Because of the significant interaction term, I analyzed data by year (i.e., removed interaction term), and found invertebrate consumption varied significantly with transect in 2006 and date in 2006 and 2007 (Table 1.13 and Table 1.14), whereas seed consumption varied with transect in 2006 (Table 1.13) and only date in 2007 (Table 1.14). Blue-winged teal collected in the eastern transect consumed 30.4% ± 9.1% more invertebrates and 31.3% ± 9.1% less seeds than teal collected in the western transect in 2006 (Figure 1.5). Blue-winged teal collected in 2006 increased invertebrate consumption by 0.81% ± 0.38% daily. In 2007, invertebrate and seed consumption varied only by date (Table 1.14 and Figure 1.6). Invertebrate consumption increased daily by 0.82% ± 0.37% and seed consumption decreased daily by 0.89% ± 0.37% in 2007. Table 1.10. Date of first and last dabbling duck collected at each study site in 2006 and 2007. ________________________________________________________________________ 2006 2007 SPECIES FIRST LAST FIRST LAST ______________________________________________________________________________________
Cache River 23 March 19 April 18 March 26 April Illinois River 14 March 01 May 22 March 29 April
Table 1.11. Results from a MANCOVA model evaluating the effects of site, date (Jul), habitat (Hab), reproductive status (RS), and year (Yr) on proportions of invertebrates and seeds consumed by blue-winged teal in the Upper MS River and Great Lakes Region during spring 2006 and 2007. ________________________________________________________________________ Source DF Type III SS Mean Square F value Pr > F ________________________________________________________________________
Figure 1.4. Percent of seeds and invertebrates consumed by blue-winged teal at 6 locations (SR = Scioto River, LE = Lake Erie, SAG = Saginaw Bay, CA = Cache River, IR = Illinois River, WI = Wisconsin) in the Upper MS River and Great Lakes Region during spring 2006 and 2007 (least-squares means ± standard error). Different letters indicate significantly different means. Table 1.12. Results from a MANCOVA model evaluating the effects of transect (Tran), date (Jul), habitat (Hab), reproductive status (RS), year (Yr), and transect by year (Tran*Yr) on proportions of invertebrates and seeds consumed by blue-winged teal in the Upper MS River and Great Lakes Region during spring 2006 and 2007.
Source DF Type III SS Mean Square F value Pr > F ________________________________________________________________________
Table 1.13. Results from a MANCOVA model evaluating the effects of transect (Tran), date (Jul), habitat (Hab), and reproductive status (RS) on proportions of invertebrates and seeds consumed by blue-winged teal in the Upper MS River and Great Lakes Region during spring 2006. ________________________________________________________________________ Source DF Type III SS Mean Square F value Pr > F ________________________________________________________________________
Table 1.14. Results from a MANCOVA model evaluating the effects of transect (Tran), date (Jul), habitat (Hab), and reproductive status (RS) on proportions of invertebrates and seeds consumed by blue-winged teal in the Upper MS River and Great Lakes Region during spring 2007. ________________________________________________________________________ Source DF Type III SS Mean Square F value Pr > F ________________________________________________________________________
One-hundred and eighty-eight mallards (n = 95 in 2006 and n = 93 in 2007) were included in analyses evaluating diet at the scale of study site (Table 1.1). Likewise, 188 mallards (n = 105 from eastern transect and n = 83 from western transect) were included in the analysis evaluating diet at the scale of transect (n = 56 in 2006 and n = 49 in 2007 from the eastern transect and n = 39 in 2006 and n = 44 in 2007 from the western transect). In 2006, the first mallard was collected on 16 February and the last on 25 April and in 2007, the first was collected on 22 February and the last on 4 May (Table 1.10). The final reduced MANCOVA model evaluating latitudinal variation in diets (invertebrates and seeds) of mallards included the main effects of site, date, habitat, reproductive status, and year; none of which were significant with regard to the proportions of invertebrates or seeds in the diet (Table 1.15 and Figure 1.7). The final reduced MANCOVA model evaluating longitudinal variation in diet of mallards included the main effects of transect, date, habitat, reproductive status, and year. The reduced model included only a date effect for the proportions of invertebrates and seeds in the diet (Table 1.16 and Figure 1.8). Mallards exhibited a daily increase of 0.47% ± 0.18% in invertebrate consumption (P = 0.002) and a daily decrease of 0.55% ± 0.19% in seed consumption (P = 0.004).
Figure 1.5. Percent of seeds and invertebrates consumed by blue-winged teal at western/eastern transect in the Upper MS River and Great Lakes Region during spring 2006 (least-squares means ± standard error). Different letters indicate significantly different means. 
Transect 
a b a b 
Figure 1.6. Percent of seeds and invertebrates consumed by blue-winged teal at western/eastern transect in the Upper MS River and Great Lakes Region during spring 2007 (least-squares means ± standard error). Different letters indicate significantly different means. Table 1.15. Results from a MANCOVA model evaluating the effects of site, date (Jul), habitat (Hab), reproductive status (RS), and year (Yr) on proportions of invertebrates and seeds consumed by mallards in the Upper MS River and Great Lakes Region during spring 2006 and 2007.
Source DF Type III SS Mean Square F value Pr > F ________________________________________________________________________
Figure 1.7. Percent of seeds and invertebrates consumed by mallards at 6 locations (SR = Scioto River, LE = Lake Erie, SAG = Saginaw Bay, CA = Cache River, IR = Illinois River, WI = Wisconsin) in the Upper MS River and Great Lakes Region during spring 2006 and 2007 (least-squares means ± standard error). Different letters indicate significantly different means. Table 1.16. Results from a MANCOVA model evaluating the effects of transect (Tran), date (Jul), habitat (Hab), reproductive status (RS), year (Yr), and transect by year (Tran*yr) on proportions of invertebrates and seeds consumed by mallards in the Upper MS River and Great Lakes Region during spring 2006 and 2007.
Source DF Type III SS Mean Square F value Pr > F ________________________________________________________________________
Figure 1.8. Percent of seeds and invertebrates consumed by mallards at western/eastern transect in the Upper MS River and Great Lakes Region during spring 2006 and 2007 (least-squares means ± standard error). Different letters indicate significantly different means. Gadwall Diets One-hundred and sixteen gadwalls (n = 42 in 2006 and n = 74 in 2007) were included in analyses evaluating diet at the scale of study site (Table 1.1). Likewise, 116 gadwalls (n = 55 from eastern transect and n = 61 from western transect) were included in the analysis evaluating diet at the scale of transect (n = 20 in 2006 and n = 35 in 2007 from the eastern transect and n = 22 in 2006 and n = 39 in 2007 from the western transect). In 2006, the first gadwall was collected on 3 March and the last on 19 April and in 2007, the first was collected on 22 February and the last on 3 May (Table 1.10). The final reduced MANCOVA model evaluating latitudinal variation in diet (vegetation, invertebrates, and seeds) of gadwalls included the main effects of site, date, habitat, and year; sample sizes were insufficient to include date by site and site by year interactions. There was a marginally significant year effect on percentage of invertebrates in gadwall diets (Table 1.17), with invertebrate consumption being greater in year 2 than year 1 (P = 0.080). Proportions of vegetation, invertebrates, and seeds did not differ among study sites (Figure 1.9). The final reduced MANCOVA model evaluating longitudinal variation in diet (vegetation, invertebrates and seeds) of gadwalls included the main effects of transect, date, habitat, year, and a transect by year interaction (Table 1.18). Because of the significant interaction term, I separated data by years (i.e., removed interaction term), and found invertebrate consumption of gadwalls in 2006 was not effected by transect, date, or the habitat they were collected in. However, the proportion of seeds and vegetation consumed by gadwalls in 2006 varied significantly with date and transect (Table 1.19). Gadwalls collected in the western transect in 2006 consumed 40.8% ± 15.4% more seeds Table 1.17. Results from a MANCOVA model evaluating the effects of site, date (Jul), habitat (Hab), and year (Yr) on proportions of invertebrates, seeds, and vegetation consumed by gadwalls in the Upper MS River and Great Lakes Region during spring 2006 and 2007.
Source DF Type III SS Mean Square F value Pr > F ________________________________________________________________________
Figure 1.9. Percent of seeds, vegetation and invertebrates consumed by gadwalls at 6 locations (SR = Scioto River, LE = Lake Erie, SAG = Saginaw Bay, CA = Cache River, IR = Illinois River, WI = Wisconsin) in the Upper MS River and Great Lakes Region during spring 2006 and 2007 (least-squares means ± standard error). Different letters indicate significantly different means. Table 1.18. Results from a MANCOVA model evaluating the effects of transect (Tran), date (Jul), habitat (Hab), year (yr), and transect by year (Tran*yr) on proportions of invertebrates, seeds, and vegetation consumed by gadwalls in the Upper MS River and Great Lakes Region during spring 2006 and 2007.
Source DF Type III SS Mean Square F value Pr > F ________________________________________________________________________
Source DF Type III SS Mean Square F value Pr > F ________________________________________________________________________
than gadwalls collected in the eastern transect in 2006 (Figure 1.10). Seed consumption decreased daily by 1.4% ± 0.5% and vegetation consumption increased daily by 1.5% ± 0.6% in gadwalls collected in 2006. Gadwalls collected in the eastern transect in 2006 consumed 39.2% ± 15.7% more vegetation than gadwalls collected in the western transect in 2006 (Figure 1.10). There was no effect of transect, date, or habitat on seeds, invertebrates, and vegetation consumed by gadwalls in 2007 (Table 1.20 and Figure 1.11). Lesser Scaup Diets One-hundred and thirty-five lesser scaup (n = 49 in 2006 and n = 86 in 2007) were included in analyses evaluating diet at the scale of study site (Table 1.1). Likewise, 135 lesser scaup (n = 91 from eastern transect and n = 44 from western transect) were included in the analysis evaluating diet at the scale of transect (n = 37 in 2006 and n = 54 in 2007 from the eastern transect and n = 12 in 2006 and n = 32 in 2007 from the western transect). In 2006, the first lesser scaup was collected on 08 March and the last on 29 April and in 2007, the first was collected on 27 February and the last on 2 May (Table 1.21). The final reduced MANCOVA model evaluating latitudinal variation in diets (invertebrates and seeds) of scaup included the main effects of site, date, habitat, and year. The percentage of invertebrates and seeds in the diet varied significantly among study sites and habitats (Table 1.22). More invertebrates (P = 0.006) were consumed by scaup at the Saginaw Bay study site (77.0% ± 9.0%) than all other study sites except the Scioto River (52.0% ± 12.7%). Moderately fewer seeds (P = 0.073) were consumed by Table 1.20. Results from a MANCOVA model evaluating the effects of transect (Tran), date (Jul), and habitat (Hab) on proportions of invertebrates, seeds, and vegetation consumed by gadwalls in the Upper MS River and Great Lakes Region during spring 2007. ________________________________________________________________________ Source DF Type III SS Mean Square F value Pr > F ________________________________________________________________________
Figure 1.10. Percent of seeds, vegetation and invertebrates consumed by gadwalls at western/eastern transect in the Upper MS River and Great Lakes Region during spring 2006 (least-squares means ± standard error). Different letters indicate significantly different means. 
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