Ht pobi Intermediate Relatively immobile 
Canvasback Blue-winged teal Baldpate 
Redhead Shoveler Ruddy 
Mallard 
Fintail 
This rating is based mainly on appearances of broods not previsusly 
observed or disappearances of broods of the same anecies, age, and number 
from other potholes. In aome easee 1t was nossihle to repeatedly locate 
brooda fro some distances in thelr wanderings. Too few bDroods of gadwall 
and green-winged teal were observed to give reliable data. 
Preferred Pothole Types 
Ime to the mobility of the broods, 1t was porsible to obtain data on 
preferred types of potholes. A preliminary review of the data obtained from 
cover mapping, checking of water level¢ and brood locations gives an indica- 
tion of what constitutee a preferred brood area. The main requirements 
appear to concern size and escape cover. Heavily used potholes were generally 
two acres or more in area and had marginal cover which allowed unseen movements 
of young birds around the margin. The distribution of Fluminen Carex cover 
aeemed optimal as usually it aceurred es clumpe adjacent to open water and 
became more dense near shore. One pothole. aleo heavily utilized was dotted 
with cattall islands interspersed with canal-like pasesager. Hardatem bulreh 
provided eimllar conditions on two other potholes which were moderately ueed. 
Water levele, in their relationship to cover, are important. It wae 
noted in one cacé that when the water Level drapped below the base of the 
cover used, many broods deserted the pothole. 
The eréat majority of desirmble potholes were found on ungrized or 
lightly grazed areas, usunlly in arege under cultivation. ‘Severely erazed 
potholes generally contained dence bede of water milfoil (Myriophyllum ep.} 
and bladderwort (Utricularia sep.). They became eapecially undesirable late 
in the season when the plants hed grown to such an extent that ther often 
completely covered the surface of the water. ‘Suck areas often had a dense 
marginal cover of bulrush or ¢attail, which provided good nesting aites for 
diving ducks and coots, but which were appsrently relatively undesimble as 
bread cover. 
Brocd Count Factores 
A preliminary study cf the data gained in brood ocheervation and 
eearchee for brocde indicate that time of day and wind are the moet important 
factors affecting trood counte. 
Early morning and evening were the best houra for finding broods in 
the open, The latter period proved to be the best az many broods are still 
renting in the shore cover two hours or more after sunrise and could not be 
geen, Doring the day, most broods were under cover, and with a wind of over 
15 M.PF.E, it was generally imposelble for even two men to drive them from 
it. 
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