Geis, A. D. , R. K. Martinson and D. R. Anderson. 1969. Establishing hunting 

 regulations and allowable harvest of Mallards in the United States. J. 

 Wildl. Manage. 33: 848-859. 



Greenwood, R. J. 1969. Mallard hatching from an egg cracked by freezing. Auk 

 86: 752-754. 



Heath, R. G. , J. W. Spaan and J. F. Kreitzer. 1969. Marked DDE impairment of 

 Mallard reproduction in controlled studies. Nature 224: 47-48. 



Lehner, P. N. and A. Egbert. 1969. Dieldrin and eggshell thickness in ducks. 

 Nature 224: 1218-1219. 



Lockner, F. R. and R. E. Phillips. 1969. A preliminary analysis of the de- 

 crescendo call in female Mallards ( Anas platyrhynchos L.). Behaviour 35: 

 281-287. 



Maley, M. J. 1969. Electrical stimulation of agnostic behaviour in the Mal- 

 lard. Behaviour 34: 138-160. 



Post, W. 1969. Breeding birds of Williston Bay. Chat 33: 83-84. 



Prince, H. H., P. B. Siegel and G. W. Cornwell. 1969a. Incubation environment 

 and the development of Mallard embryos. J. Wildl. Manage. 33: 589-595. 



. 1969b. Hatchability , clutch position, and hatching sequence in Mallards. 



Auk 86: 762-763. 



1968 



Balat, F. 1968. Influence of repeated disturbance on the breeding success in 

 the Mallard, Anas platyrhynchos Linn. Zool. Listy 18: 247-252. 



Bjarvall, A. 1968. The hatching and nest exodus behaviour of Mallard. Wild- 

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Coulter, M. and W. Miller. 1968. Nesting biology of Black Ducks and Mallards 

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Dindal, D. L. and T. J. Peterle. 1968. Wing and body tissue relationships of 

 DDT and metabolite residues in Mallard and Lesser Scaup ducks. Bull. En- 

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Duebbert, H. F. 1968. Two female Mallards incubating on one nest. Wilson 

 Bull. 80: 102. 



Martinson, R. K. and A. S. Hawkins. 1968. Lack of association among duck 

 brood-mates during migration and wintering. Auk 85: 684-686. 



Nickell, W. P. 1968. Mallards nest in trees and on walls. Jack-Pine Warbler 

 46: 28-30. 



191 



