Nutrient Reserves and Clutch-Size Regulation of Northern Shovelers in Alaska

Abstract We determined patterns of nutrient-reserve use by female Northern Shovelers (Anas clypeata) nesting at Minto Flats, Alaska, and compared them with those of female shovelers nesting in the Prairie Pothole Region of Manitoba, Canada. Individual variation in somatic lipid was best explained by nest initiation date; females that initiated nests early had larger lipid reserves than females that delayed nest initiation. These results contrast with those from Manitoba, which showed that females used lipid reserves and stored protein during egg production. Incubating females from Alaska did not use protein or mineral reserves, but lipid reserves decreased significantly throughout incubation. Females in Alaska and Manitoba used lipid reserves similarly during incubation. We conclude that endogenous nutrient availability does not proximately limit clutch size during laying for this population of shovelers, possibly due to the high productivity of wetlands in interior Alaska and/or the long photoperiod that allow females to forage extensively. Successful completion of incubation or brood rearing may be an ultimate factor that controls clutch size for this population of shovelers.

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Nutrient Reserve Dynamics of Breeding and Molting Brant

The Auk ◽

10.1093/auk/101.2.361 ◽

1984 ◽

Vol 101 (2) ◽

pp. 361-370 ◽

Cited By ~ 93

Author(s):

C. Davison Ankney

Keyword(s):

Body Weight ◽

Northwest Territories ◽

Egg Production ◽

Muscle Protein ◽

Nutritional Stress ◽

Egg Laying ◽

Branta Bernicla ◽

Nutrient Reserve ◽

Males And Females ◽

Nutrient Reserves

Abstract I collected 150 Brant (Branta bernicla) at East Bay, Southampton Island, Northwest Territories, Canada, in 1979 and 1980 to evaluate how much these birds rely on reserves of fat, protein, and calcium during egg production, incubation, and the subsequent wing molt. Egg laying resulted in decreases in body weight and nutrient reserves of females. These decreases could have accounted for all of the fat but only 70% of the protein in an average clutch. Neither males nor females had sufficient reserves when incubation began to enable them to fast during that period. Only 11% and 22% of the energy required by males and females, respectively, could have been derived from their reserves during incubation. Brant evidently did not use body reserves to obtain nutrients for feather growth during wing molt. Rather, molting males and females accumulated muscle protein, which supports my hypothesis that wing molt is not a nutritional stress for waterfowl.

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Effects of Water Conditions on Clutch Size, Egg Volume, and Hatchling Mass of Mallards and Gadwalls in the Prairie Pothole Region

The Condor ◽

10.1093/condor/102.4.936 ◽

2000 ◽

Vol 102 (4) ◽

pp. 936-940 ◽

Cited By ~ 1

Author(s):

Pamela J. Pietz ◽

Gary L. Krapu ◽

Deborah A. Buhl ◽

David A. Brandt

Keyword(s):

North Dakota ◽

Clutch Size ◽

Prairie Pothole Region ◽

Prairie Pothole ◽

Egg Volume ◽

Water Conditions ◽

Breeding Grounds ◽

Using Data ◽

The Relationship ◽

Basin Area

AbstractWe examined the relationship between local water conditions (measured as the percent of total area of basins covered by water) and clutch size, egg volume, and hatchling mass of Mallards (Anas platyrhynchos) and Gadwalls (A. strepera) on four study sites in the Prairie Pothole Region of North Dakota and Minnesota, 1988–1994. We also examined the relationship between pond density and clutch size of Mallards and Gadwalls, using data collected at another North Dakota site, 1966–1981. For Mallards, we found no relationships to be significant. For Gadwalls, clutch size increased with percent basin area wet and pond density; hatchling mass marginally increased with percent basin area wet. These species differences may reflect, in part, that Mallards acquire lipid reserves used to produce early clutches before they reach the breeding grounds, whereas Gadwalls acquire lipid reserves locally; thus Gadwall clutches are more likely to be influenced by local food resources.

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Changes in lipid and protein reserves and in diet of breeding House Sparrows

Canadian Journal of Zoology ◽

10.1139/z88-141 ◽

1988 ◽

Vol 66 (4) ◽

pp. 950-956 ◽

Cited By ~ 8

Author(s):

David G. Krementz ◽

C. Davison Ankney

Keyword(s):

Clutch Size ◽

Egg Production ◽

Passer Domesticus ◽

Threshold Level ◽

Egg Laying ◽

High Protein ◽

House Sparrows ◽

Fat Reserves ◽

Egg Formation ◽

Nutrient Reserves

We collected House Sparrows (Passer domesticus) around London, Ontario, weighed their protein and fat reserves, and determined their food habits and egg production to test the effects of reserve levels on the timing of egg formation and the control of clutch size. Although consumption of high-protein foods was apparently related to insect availability, females consumed more high-protein foods than did males, especially during the laying period. Before egg production began, protein and fat reserves of males declined but those of females were constant. After egg production began, reserves of males remained constant through postreproduction. Neither protein nor fat reserves were accumulated by females before egg formation began, suggesting that an elevated threshold level of nutrient reserves was not necessary to commence egg formation. Protein reserves of females did not decline during egg production; fat reserves increased just before the first ovulation and declined rapidly thereafter. Neither fat reserve levels on the first day of ovulation nor the decline in fat reserves thereafter were related to clutch size. Postlaying females had, on average, enough fat reserves to produce an additional egg. We conclude that although female House Sparrow use fat reserves during egg laying, their clutch size is not controlled thereby.

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Patterns of Variation in Clutch Sizes in a Guild of Temperate-Nesting Dabbling Ducks

The Auk ◽

10.1093/auk/121.3.695 ◽

2004 ◽

Vol 121 (3) ◽

pp. 695-706

Author(s):

Gary L. Krapu ◽

Ronald E. Reynolds ◽

Glen A. Sargeant ◽

Randy W. Renner

Keyword(s):

Significant Variation ◽

Egg Production ◽

Prairie Pothole Region ◽

Interspecific Variation ◽

Egg Laying ◽

Dabbling Ducks ◽

Prairie Pothole ◽

Risk Of Mortality ◽

Species Declines ◽

Nesting Season

Abstract We investigated patterns and causes of variation in clutch sizes in a guild of five species of temperate-nesting dabbling ducks (Mallard [Anas platyrhynchos], Northern Pintail [“pintail,” A. acuta], Gadwall [A. strepera], Blue-winged Teal [“teal,” A. discors], and Northern Shoveler [“shoveler,” A. clypeata]) during 1993-1995 in the Prairie Pothole Region of midcontinental North America. Clutch sizes (mean ± SE) were largest for teal (10.80 ± 0.03), followed in descending order by those of shoveler (10.31 ± 0.05), Gadwall (9.92 ± 0.04), Mallard (8.91 ± 0.04), and pintail (7.66 ± 0.06). In Mallard, pintail, and shoveler, predicted clutch sizes at onset of nesting exhibited minimal variation. Clutch sizes of Gadwall and teal displayed statistically significant variation among years at onset of nesting; pintail clutch sizes showed significant variation late in the nesting season. Clutch sizes declined seasonally in all species. Declines in clutch sizes of teal and shoveler were approximately linear; whereas clutch sizes of Mallard, pintail, and Gadwall usually declined at progressively decreasing rates. Linear declines in teal and shoveler clutches suggest that those species experienced greater difficulty securing lipids for egg production late in the nesting season than did Mallard, pintail, and Gadwall. That disparity may result because egg-laying female teal and shoveler feed almost exclusively on animal foods, which are primarily protein; whereas female Mallard, pintail, and Gadwall consume more carbohydrate-rich plant foods. Our findings, when examined in context with existing information, suggest that interspecific variation in clutch sizes results from innate differences in several traits—including body size, diet, timing of lipid acquisition, and nesting—all of which can affect the amount of lipid available for egg production. Temperate-nesting dabbling ducks have evolved traits that facilitate laying of large clutches early in the nesting season, because risk of mortality is lower among early-hatched young. Annual differences in clutch sizes of all five species were not significant when effects of annual variation in nest-initiation dates were accounted for, reflecting the key role of environmental influences on intraspecific variation in clutch sizes among years.

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Consequences of rainfall variation for breeding wetland blackbirds

Canadian Journal of Zoology ◽

10.1139/z04-107 ◽

2004 ◽

Vol 82 (8) ◽

pp. 1316-1325 ◽

Cited By ~ 27

Author(s):

Robert J Fletcher, Jr. ◽

Rolf R Koford

Keyword(s):

Clutch Size ◽

Nest Predation ◽

Community Dynamics ◽

Prairie Pothole Region ◽

Abiotic Factors ◽

Reproductive Failure ◽

Water Levels ◽

Prairie Pothole ◽

Rainfall Variation ◽

Population And Community Dynamics

Annual variability in abiotic factors can be pronounced, especially in systems that rely on precipitation, such as arid regions and prairie potholes. We report how annual variation in precipitation from 1999 to 2002 in the Prairie Pothole Region of Iowa, USA, affected both density and reproduction of two interspecific competitors: yellow-headed blackbirds, Xanthocephalus xanthocephalus (Bonaparte, 1826), and red-winged blackbirds, Agelaius phoeniceus (L., 1766). During dry years, yellow-headed blackbirds, an obligate wetland-breeding species, showed a marked reduction in density and a complete reproductive failure in which none of the nests we monitored fledged young. The reproductive failure was attributed primarily to nest predation, which was negatively correlated with water levels in wetlands. Conversely, red-winged blackbirds, a facultative wetland-breeding species, showed little variation in density and nest success. Both species exhibited similar patterns of reduced clutch size and later nest initiation dates in dry years, measures often tied to bottom-up effects of food availability and (or) age of individuals. Yet top-down effects of nest predation had a stronger influence, because lower clutch size did not result in fewer young fledged per successful nest. Incorporating how rainfall variation can affect wetland songbird demography will be critical for understanding population and community dynamics in changing environments.

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