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Abstract

High spring temperatures also seemed to induce early nesting. The mallard, which nested earliest, was most affected by temperatures during April, whereas the other species were most affected by temperatures during late April and May. Peak hatching dates were also earlier in years with higher temperatures in May. Earlier peaks were associated with early first nests, so it was difficult to separate the effects of weather and date of initial nesting. Peaks at Woodworth occurred earlier than at Salyer, after temperature differences were taken into account. The period of most active nesting was longest for the early-nesting mallard, shortest for the late-nesting gadwall, and intermediate for the blue-winged teal and redhead. For two species, precipitation during the breeding season may have prolonged nesting activities. We also found that late nesting seasons tend to be compressed.

Productivity at Salyer, measured by the brood to pair ratio, was generally greater in years with higher temperatures during 23 April-3 June. Effects were more pronounced among early-nesting species. Average brood size for Classes I and II tended to decline during the 1947-62 period at Salyer; pair populations generally increased. Consequently, it was nearly impossible to distinguish the effects of pair density on brood size from those of yearly trend. In addition, Class II broods were smaller in years when temperatures were higher during late May and June.

¹Present address: Silverton, British Columbia, V0G 2B0 Canada.

Hammond, Merrill C. and Douglas H. Johnson.  1984.  Effects of weather on breeding 
     ducks in North Dakota.  U. S. Fish and Wildlife Service, Fish and Wildlife 
     Technical Report No. 1.  17pp.

Hammond, Merrill C. and Douglas H. Johnson.  1984.  Effects of weather on breeding 
     ducks in North Dakota.  U. S. Fish and Wildlife Service, Fish and Wildlife 
     Technical Report No. 1.  Jamestown, ND: Northern Prairie Science Center Online.  
     http://www.npwrc.usgs.gov/resource/birds/dukweath/index.htm
     (Version 16JUL97).

Contents

• Study Areas
• Methods
  • Weather Data
  • Duck Arrival Dates
  • Breeding Pair Populations
  • Nesting Studies and Brood Counts
  • Data Analysis
• Results and Discussion
  • Duck Arrival Dates
  • Breeding Pair Populations
  • Nest Initiation Dates
  • Peak Hatching Dates
  • Span of Nesting
  • Productivity
  • Brood Size
• Conclusions
• Acknowledgments
• References

This is the first issue of Fish and Wildlife Technical Reports. It combines material previously published in the series as Special Scientific Reports—Wildlife and Technical Papers.

This publication series of the Fish and Wildlife Service (formerly the Bureau of Sport Fisheries and Wildlife) comprises reports of investigations related to fish or wildlife. Each is published as a separate paper, but for economy several may be issued in a single cover. The Service distributes a limited number of these reports for the use of Federal and State agencies and cooperators.

Copies of this publication may be obtained from the Publications Unit, U.S. Fish and Wildlife Service, Washington, DC 20240 or may be purchased from the Government Printing Office, Superintendent of Documents, Washington, DC 20402 and National Technical Information Service (NTIS), 5285 Port Royal Road, Springfield, VA 22161