Population Energetics of Northern Pintails
Wintering in the Sacramento Valley, California
by Michael R. Miller1 and Wesley E. Newton2
Abstract: Recovery of northern pintail (Anas acuta) breeding populations may be facilitated by improved management of winter food and habitat resources. We estimated daily energy expenditure (DEE) of pintails, which included energy required from food and carcass reserves (DERfood, DERreserves), from mid-August to mid-March during a dry (1980-81) and a wet (1981-82) winter in the Sacramento Valley, California, using equations for existence metabolism (EM; kJ/day) and estimates of body mass, carcass composition, food habits, and apparent metabolizable energy (AME) of winter foods. We used these values and food density (kg/ha) to model population food and habitat (ha) requirements. Predicted DEE by monthly period ranged from 794 to 1,180 kJ/day for males and 700 to 1,044 kJ/day for females. Pintails consumed a predicted 49-82 g of food/day from wetlands and rice fields. The DEE was highest in September-October or October-November and again in January-February, and DERreserves was greater during November-December or December-January (up to 11.6% of DEE), and during the dry winter. Total food consumed by the larger pintail population present in the wet winter of 1981-82 exceeded that of the smaller population in the dry winter of 1980-81, both from wetlands (2.89 vs. 2.52 million kg) and harvested rice fields (11.4 vs. 9.37 million kg). Likewise, the cumulative area of wetlands and rice fields used to provide food was greater in the wet (2060 ha of wetlands, 41,456 ha of rice fields) than in dry winter (1,782 ha of wetlands, 33,941 ha of rice fields); these totals accounted for up to 23% of available rice fields and 9% of available wetlands. Population food and habitat requirements peaked in December-January, coinciding with peak pintail populations but not peak DEE (Jan-Feb). Model outcomes were most sensitive to variation in food density, AME, percentage of food obtained from wetlands and rice fields, and pintail abundance. Food and habitat seemed adequate for pintail populations wintering in the Sacramento Valley in the 1980s and presently; however, this conclusion must be validated by modeling bioenergetic requirements for other abundant waterfowl and wildlife that forage in rice fields and wetlands in this region.
Key words: Anas acuta, bioenergetics, California, food, northern pintail, populations, rice, Sacramento Valley, wetlands, winter.
This resource is based on the following source (Northern Prairie Publication 1067):
Miller, Michael R. and Wesley E. Newton. 1999. Population Energetics
of Northern Pintails Wintering in the Sacramento Valley, California.
Journal of Wildlife Management 63(4):1222-1238.
This resource should be cited as:
Miller, Michael R. and Wesley E. Newton. 1999. Population Energetics
of Northern Pintails Wintering in the Sacramento Valley, California.
Journal of Wildlife Management 63(4):1222-1238. Jamestown, ND:
Northern Prairie Wildlife Research Center Online.
http://www.npwrc.usgs.gov/resource/birds/popnrg/popcnrg.htm
(Version 17FEB2000).
Table of Contents
- Introduction
- Study Area
- Methods
- Population Energetics Model
- Calculation of Existence Metabolism
- Adjusting Existence Metabolism
- Energy Content of Composite Diets
- Population Food Requirements
- Statistical Analysis
- Results
- Daily Energy Expenditure
- Daily Food Intake
- Population Food Intake
- Foraging Habitat Required
- Sensitivity Analyses
- Discussion
- Daily Energy Expenditure
- Population Food and Habitat Requirements
- Management Implications
- Acknowledgments
- Literature Cited
- Appendix A -- Mean ambient temperatures, body mass, and changes in body mass, fat, and protein content of adult male and female pintails.
Tables and Figures
- Table 1 -- Daily energy expenditures, daily energy required from body reserves, daily energy obtained from food, and food intake of individual adult male and female pintails.
- Table 2 -- Mean daily populations and total and period use-days, estimated food intake, and habitat requirements of adult male and female pintails.
- Figure 1 -- Daily energy expenditure, daily energy required from food, and daily energy required from body reserves.
- Figure 2 -- Energy cost for fat synthesis during periods of body mass gain, and energy contributed by catabolism of fat during periods of body mass loss.
- Figure 3 -- Patterns of individual and population food intake of adult northern pintails by monthly periods.
- Figure 4 -- Patterns of population food intake and hectares of foraging habitat required by monthly periods.
- Figure 5 -- Percent change in area of wetlands and rice required by adult pintails to support daily energy expenditure.
- Figure 6 -- Area of wetlands and rice required by adult northern pintails to support daily energy expenditure when pintail use-days were held constant.
- Figure 7 -- Area of wetlands and rice required by adult northern pintails to support daily energy expenditure when food density was held constant.
1 U.S. Geological Survey, Biological Resources Division, Western Ecological Research Center, Dixon Field Station, 6924 Tremont Road, Dixon, CA 95620, USA. E-mail: michael_r_miller@usgs.gov
2 U.S. Geological Survey, Northern Prairie Wildlife Research Center, 8711 37th Street SE, Jamestown, ND 58401, USA
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