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Northern Prairie Wildlife Research Center

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Fall and Winter Foods of Northern Pintails in the Sacramento Valley, California

Tables

Table 1.  Esophageal contents and preference ranks of major ≥1% aggregate % dry wt) foods of northern pintails collected while feeding diurnally in unharvested rice fields left flooded (Aug-Sep) and rice fields flooded after harvest (Oct, Jan, and Feb-Mar) on 3 northern California wildlife refuges, 1979-82.
Food item Aug-Sep (N = 34) Oct-Jan (N = 4) Feb-Mar (N = 7)
% occa Agg %b Prefc % occ Agg % Pref % occ Agg % Pref
Seeds
  Arnmannia coccinea 5.9 trd   50.0 2.5        
  Flatsedge spp. 41.2 2.1   50.0 27.5 +0.83 14.3 tr +2.00
  Common barnyardgrass 29.4 tr +1.30 75.0 20.2 −0.17 28.6 tr +5.64
  Waterstar mudplantain
    (Heteranthera dubia)		 11.8 tr −0.72 50.0 1.3   42.9 2.2 +5.50
  Southern naiad 55.9 tr   100.0 15.6 +4.00 85.7 18.0 +0.29
  Smartweed spp. 17.6 tr   100.0 2.3 −1.50 28.6 tr -6.93
  Rice 100.0 93.9 −0.04 50.0 1.1 −4.50 28.6 17.6 +3.50
  Common arrowhead 41.2 tr   100.0 1.1 +3.33 28.6 tr +0.57
  Roughseed bulrush 85.3 0.5 +0.22 50.0 1.3 −2.33 28.6 tr −5.29
  Other seeds 58.8 1.2   75.0 4.0   42.9 0.6  
Misc. vegetation 85.3 1.7   75.0 21.6   85.7 20.4  
Total plant 100.0 99.7   100.0 98.5   100.0 59.3  
Animal
  Midges and other flies 26.5 tr         100.0 28.2 +2.64
  Snails 23.5 tr   50.0 1.3   28.6 9.4 −1.64
  Other invertebrates 20.6 tr   50.0 tr   42.9 1.0  
  Misc. fragments 35.3 tr   50.0 tr +0.33 42.9 2.1 +2.36
Total animal 67.6 0.3   100.0 1.5 −1.33 100.0 40.7 −0.36
a % occurrence = no. of pintails consuming a food item ÷ no. of pintails in the sample.
b Aggregate % dry wt = wt of food item ÷ wt of all food items determined for each pintail, then averaged over all pintails.
c Preference rank values are average differences between ranks of usage and availability. The larger the value, the stronger the selection (+) or rejection (−) of the food. Listed only for foods available or consumed ≥1% dry wt, but ranks do not sum to 0 in each column because not all ranked foods are included in the table. Foods eaten but not available at the feeding site, and food available but not eaten, were not included in preference analyses.
d tr = <0.5%.

 

Table 2.  Esophageal contents and preference ranks of major ≥1% aggregate dry wt) foods of northern pintails collected while feeding diurnally in summer-dry seasonal marshes on 3 northern California wildlife refuges, 1979-82.
Food item Aug-Sep (N = 31) Oct-Jan (N = 33) Feb-Mar (N = 4)
% occa Agg %b Prefc % occ Agg % Pref % occ Agg % Pref
Seeds
  Saltbush spp.       9.1 3.3        
  Boisduvalia cleistogama 12.9 trd   9.1 1.2   25.0 tr  
  Bermuda grass 16.1 3.4 +1.58 6.1 5.4 +1.52 25.0 1.8 −0.50
  Flatsedge spp. 9.7 tr   15.2 3.2 +1.85      
  Spikerush spp. 6.5 tr −0.40 30.3 1.9 +1.75 25.0 tr −1.25
  Swamp timothy 93.5 77.9 +0.17 84.8 46.4 −0.11 75.0 33.9 +1.25
  Smartweed spp. 45.2 1.5 +0.58 15.2 2.3 −1.04 25.0 0.5 −1.75
  Woolly marbles 35.5 1.1 +3.33 15.2 2.0 +3.32      
  Dock spp. 29.0 tr −0.42 15.2 3.6 −4.48      
  Pickleweed (Salicornia spp.) 38.7 tr   15.2 1.6 −0.24 25.0 tr +1.38
  Alkali bulrush 19.4 tr −4.21 24.2 6.4 −1.20 25.0 6.0 +0.38
  Bulrush (Scirpus spp.) 22.6 1.0 +1.45 6.1 tr        
  Other seeds 25.8 0.5   15.2 0.1   25.0 1.0  
Misc. vegetation 77.4 11.1   63.6 21.1   100.0 27.4  
Total plant 100.0 97.9   100.0 98.8   100.0 71.1  
Animal
  Beetles 22.6 tr   3.0 tr   50.0 12.8 +2.25
  Midges and other flies 32.3 1.7 −0.04 12.1 tr −1.19 75.0 10.4 +1.50
  Dragonflies (Odonata) 3.2 tr   3.0 tr   50.0 2.2 +0.63
  Snails 6.5 tr   6.1 0.8 +0.78 25.0 3.1 -0.63
Total animal 51.6 2.1 −0.81 27.3 1.2 −3.09 75.0 28.9 −0.25
a,b,c,d As in Table 1.

 

Table 3.  Esophageal contents and preference ranks of major ≥1 % aggregate dry wt) foods of northern pintails collected while feeding diurnally in summer-irrigated seasonal marshes on 3 northern California wildlife refuges, 1979-82.
Food item Aug-Sep (N = 13) Oct-Jan (N = 5) Feb-Mar (N = 4)
% occa Agg %b Prefc % occ Agg % Pref % occ Agg % Pref
Seeds
  Centromadia pungens       20.0 1.5        
  Goosefoot spp.       40.0 26.8        
  Common barnyardgrass 92.3 73.6 −0.09 100.0 36.5 0.00 25.0 6.8 −2.00
  Spikerush spp. 7.7 trd   40.0 3.7 −1.00      
  Bearded sprangletop 23.1 2.7 −2.96 20.0 tr   50.0 2.4 −1.38
  Knotgrass paspalum 7.7 1.1 +1.46            
  Smartweed spp. 61.5 20.5 −0.82 60.0 4.6 +1.00 25.0 1.3 +0.75
  Dock spp.       40.0 4.3        
  Alkali bulrush       40.0 1.3   25.0 tr −0.50
  Other seeds 7.7 tr   40.0 0.6   50.0 0.8  
Misc. vegetation 23.1 0.8   40.0 18.7   100.0 23.0  
Total plant 100.0 99.4   100.0 98.0   100.0 34.4  
Animal
  Midges and other flies             100.0 46.0 +0.75
  Snails       40.0 tr   25.0 9.0 +0.63
  Misc. fragments plus other
    invertebrates		 15.4 0.5 0.00 20.0 1.7   50.0 10.6 +1.75
Total animal 30.8 0.6 −0.82 60.0 2.0 0.00 100.0 65.6 0.00
a,b,c,d As in Table 1.

 

Table 4.  Esophageal contents and preference ranks of major ≥1% aggregate dry wt) foods of northern pintails collected while feeding in marshes of 3 northern California wildlife refuges shortly after returning from feeding in commercial rice fields (Oct and Feb-Mar); 1979-82 (rice portion of esophageal contents deleted to emphasize foods consumed at feeding site).
Food item Oct (N = 10)a Feb-Mar (N = 9)b
% occc Agg %d Prefe % occ Agg % Pref
Seeds
  Common barnyardgrass  20.0 9.3   100.0 4.8 +1.56
  Swamp timothy 50.0 5.8 +1.71 33.3 0.7 +2.94
  Southern naiad 50.0 8.9   44.4 2.4 +2.56
  Smartweed spp. 40.0 trf +0.43 88.9 60.1 −0.06
  Dock spp. 60.0 2.7 −1.86 55.6 0.7 −5.33
  Alkali bulrush 40.0 2.5 −1.29 11.1 tr −3.11
  Other seeds 40.0 0.5   77.8 1.4 −4.50
Misc. vegetation 40.0 30.5 0.00g 100.0 18.0  
Total plant 100.0 59.8   100.0 88.2  
Animal
  Beetles 50.0 7.3   55.6 0.7 +2.56
  Midges and other flies 60.0 10.3   100.0 8.7 +2.17
  Mayflies (Ephemeroptera) 20.0 0.5 −1.36      
  Water boatmen 60.0 16.8 −2.29 66.7 tr −1.44
  Water fleas (Cladocera) 20.0 0.8 +0.86      
  Misc. fragments plus other invertebrates 50.0 4.5   100.0 2.1 +1.84
Total animal 90.0 40.2 +3.79 100.0 11.8h +0.88
a Seven ducks in summer-dry habitat and 3 in flooded, fallow rice field.
b Eight ducks in summer-irrigated and 1 in summer-dry habitat.
c,d,e,f As in Table 1, respectively, a,b,c,d.
g Bulrush seedlings.
h 33.3% if 2 ducks with very high percentages of smartweeds (71-83%) are deleted.

 

Table 5.  Esophageal contents of northern pintails collected returning to roost on 3 national wildlife refuges before sunrise from nocturnal feeding in harvested commercial rice fields, northern California, 1979-82.
Food item Oct-Jan (N = 20) Feb-Mar (N = 13)
% occa Agg %b % occ Agg %
Seeds
  Common barnyardgrass 20 trc 76.9 30.5
  Southern naiad 45 0.6 53.8 2.4
  Rice 100 97.1 100.0 62.6
  Roughseed bulrush 20 0.7 30.8 tr
Misc. vegetation 75 1.0 92.3 1.3
Total plant 100 99.7 100.0 97.3
Total animald 60 tr 92.3 2.7
a,b As in Table 1.
c tr = <0.5%.
d Midges, snails, and misc. fragments.

 

Table 6.  Aggregate percent (dry wt) of invertebrates in habitat samples taken at pintail collection sites on 3 northern California national wildlife refuges, 1979-82. (No. of sample sites in parentheses.)
Habitat Aug-Sep Oct-Jan Feb-Mar P values
Refuge ricea trf (5) 5.6 (2) 29.9 (4) P < 0.02
Summer-dryb 5.0 (15) 10.7 (16) 31.3 (4) P < 0.10
Summer-irrigatedc 0.1 (9) 3.3 (1) 32.3 (4) P < 0.02
MFWRd 48.6 (1) 22.7 (3)g 21.2 (4) P > 0.10
P valuese P < 0.01 P > 0.10 P > 0.10   
a See Table 1 for habitat description.
b See Table 2 for habitat description.
c See Table 3 for habitat description.
d Marsh feeders with rice; see Table 4 for description.
e Kruskal-Wallis 1-way ANOVA.
f tr = <0.1%.
g Oct only.

 

Table 7.  Proximate analysis (% dry wt) and apparent metabolizable energy (AME) (kcal/g) of selected foods making up ≥5% dry weight of the esophageal content of northern pintails from 3 northern California wildlife refuges, 1979-82.
Food AME Crude protein Crude fat NFEa Ash Crude Fiber Source if other than this studyb
Swamp timothy 3.71 13.9 2.0 74.9 3.6 5.6  
Rice 3.53 6.7 1.4 78.3 5.1 8.5  
Common barnyardgrass (fall) 2.51 9.0 1.5 50.6 10.9 28.1  
Com. barnyardgrass (winter) 3.33 9.5 2.2 69.1 7.1 12.1  
Goosefoot 3.27 15.3 6.4 53.1 8.3 16.9 Spinner and Bishop (1950)
Alkali bulrush 3.24 8.3 3.2 65.8 6.4 16.2 Bardwell et al. (1962)
Smartweed spp. 3.16 9.5 2.2 66.5 3.5 18.3 Bardwell et al. (1962)
Flatsedge spp. 3.08 9.0 4.0 59.4 8.1 19.5  
Bermuda grass 3.08 8.0 0.3 68.4 4.2 19.1  
Dock spp. 2.94 10.8 2.0 58.6 3.8 24.8 Spinner and Bishop (1950)
Southern naiad 2.84 15.5 1.8 52.1 8.7 21.9  
Roughseed bulrush 2.72 6.5 1.4 58.5 4.7 28.9  
Bulrush seedlings 2.13 13.5 0 40.3 19.0 27.3  
Water beetles 4.32 45.6 27.6 5.2 2.1 19.5 Reinecke (1977)
Midge larvae 3.59 66.4 5.8 14.9 13.1 0 Krapu and Swanson (1975)
Water boatmen 3.12 71.1 5.0 0.8 4.7 18.4 Reinecke (1977)
Snails (without shell) 3.09 58.9 <0.1 21.9 18.4 0.7 Krapu and Swanson (1975)
Snails (with shell) 0.93 16.9 0.7 5.8 64.2 12.4 Sugden (1973)
a Nitrogen-free extract.
b Except metabolizable energy.