133 
methods used and the abundant brood cover available, more broods were accurately 
observed for divers ‘than for dabblers. Ari analysis of total broods seen per species 
causiet be used as an index to Production. | 
Over the two years 80 juvenile ducks were found dead. Unknown causes 
accounted for 35 (44 percent); hawk kills; 28°(25 percent) and mink kills, 17 (21 per- 
cent). While in only five instances was a marsh hawk actually flushed from a fresh 
kill, this abundant species was apparently the chief avian predator. It was the only 
hawk regularly seen hunting over the marsh. ; 
Banding Record 
Before the inauguration of this study there was apparently no previous banding 
done at Gray's Lake. Of the 6 recoveries of the 85 ducks banded last summer 3 were 
outside of Idaho; one each from California, New Mexico, and Louisiana. 
Banding commenced on August 27 and ceased on September 11, this year. The 
water trap used was constructed out of one-inch mesh chicken wire situated in shallow 
water averaging a foot in depth with the holding boxes on the shore. Trap materials, 
bait, and other assistance during the banding operation were furnished by the Idaho Fish 
and Game Department through Robert L. Salter, State Waterfowl Biologist. 
Table 4. -- Average Hatch and Record of Brood Size Averages by Age Class at 
Gray's Lake, 1949 and 1950 
a 

Av. Hatch 
-Per Success- No. 
Species Year ful Nest Class l Class 11 Class 111 Broods 
Mallard 1949 726 7.6 (18)* _5.2 (13) 5,0( 8) 39 
; 1950 7.0 6.5( 4) 5.3( 4) . 10 
Pintail 1949 7.1 7.3 (9) 7.1 (8) 6.7 (13) 30 
1950 — 7.0 5.3 (3) 7,.0(1) 6.0( 1) 5 
Gadwall 1949 7.9 (27) 7.2 (19) 46 
' 1950 7.8 (19) 3.0 (1) 20 
Baldpate 1949 ; 
1950 ; "i 5,0 (4) 4 
Shoveler 1949 
1950 - - 8.0( 1) 7.0 ( 1) 2 
B-w/Cinn. teal 1949 © 7.4 8.9 (16) 7.5 (11) 5.7 ( 6) 33 
1950 10.2 4.1( 7) 5.4( 5) 6.0( 1) 13 
G-w. teal _ 1949 
1950 z.0( 1) _ 1 
Canvasback 1949 7,8 7.2(50) 5.9(97) 5.0(72) 219 
; : 1950 5.9 (5.8(46) 5.4 (49) 5.4(30) 125 
Redhead 1949 7.5 7.1 (58) 6.1 (63) 5.5 (41) 162 
1950 7.2 5.9 (56) 6.5(23) 6.3( 4) 83 
Lesser. scaup 1949 7.1 (81) 6.2 (94) | 175 
“1960 6.5 (64) ~ 5.4 (18) 82 
Ruddy duck 1949 ~ 6.3 (130) '5.2(78) 208 
; 1950 5.8(98) = 4. 4 6) 104 
Canada.géese . 1949. 4.4 (41) 4.1 (20) _ 4.1 (18) 79 
:s, 1950 “4.5 (29) 2.5( 2), 3.7(10) 41 


) “*Figures in parenthesis are numbers of brooc counts from which 
- brood size figure was computed, 
