The proximate effects of food supply on intraclutch egg-size variation in American kestrels

1996 ◽  
Vol 74 (1) ◽  
pp. 118-124 ◽  
Author(s):  
Karen L. Wiebe ◽  
Gary R. Bortolotti
Keyword(s):  
Food Supply ◽  
Egg Size ◽  
Size Variation ◽  
Food Supplementation ◽  
Laying Order ◽  
American Kestrels ◽  
Good Body Condition ◽  
Adaptive Explanation ◽  
Food Shortages

Egg size can be an important determinant of offspring survival in birds. We measured eggs from 275 clutches of wild American kestrels (Falco sparverius) to study the degree of intraclutch variability in egg size. We also performed two food-supplementation experiments to investigate the proximate role of food supply during laying in determining egg size. Females with relatively abundant food and those in good body condition did not lay eggs that were more uniform in size than those laid by control females. This result is contrary to hypotheses that propose an adaptive explanation for intraclutch egg-size variation and also to ideas of energy depletion during laying. Patterns of egg size versus laying order were different between years, suggesting that females did not adaptively manipulate laying order and egg size within a clutch. The food-supplementation experiments showed that laying female kestrels probably depend on both stored energy reserves and on daily energy surpluses to form eggs. It appears that slight intraclutch variations in egg size occur in response to short-term food shortages during laying, but that these variations are probably nonadaptive. This is in marked contrast to interclutch (among females) variation in egg size, which we have shown varies significantly with food supply.

scholarly journals Effects of Environmental Conditions and Parental Quality on Inter- and Intraclutch Egg-Size Variation in the Collared Flycatcher (Ficedula Albicollis)

The Auk ◽  
2005 ◽  
Vol 122 (2) ◽  
pp. 509-522 ◽  
Author(s):  
Rita Hargitai ◽  
János Török ◽  
László Tóth ◽  
Gergely Hegyi ◽  
Balázs Rosivall ◽  
...  
Keyword(s):  
Egg Size ◽  
Size Variation ◽  
Laying Date ◽  
Life History Trait ◽  
Ficedula Albicollis ◽  
Collared Flycatcher ◽  
Egg Formation ◽  
Adaptive Explanation ◽  
Breeding Condition

AbstractEgg size is a particularly important life-history trait mediating maternal influences on offspring phenotype. Females can vary their egg-size investment in relation to environmental circumstances, their own breeding condition, and the quality of their mate. Here we analyzed inter- and intraclutch variation in egg size in the Collared Flycatcher (Ficedula albicollis) on the basis of eight years of data. According to our results, mean egg size increased with female condition, but did not differ among young, middle-aged, and old females. The male’s age, body size, and forehead patch size did not influence egg size; thus, we found no evidence for differential investment in egg size in relation to male quality. We found no effect of laying date on egg size when controlling for ambient temperature during the egg formation period, yet temperature had a significant effect on egg size. That result indicates proximate constraints on egg formation. Furthermore, we report on annual differences in intraclutch egg-size variation. Egg size increased within clutches in years with a warm prelaying period; whereas in years when the weather during that period was cold, there was no significant intraclutch trend. Proximate considerations seem to explain the observed patterns of intraclutch egg-size variation; however, we cannot reject the adaptive explanation. Mean egg size and intraclutch egg-size variation were unrelated to clutch size. Therefore, we found no evidence for a trade-off between size and number of eggs within a clutch.

Parental effort of American kestrels: the role of variation in brood size

2003 ◽  
Vol 81 (5) ◽  
pp. 852-860 ◽  
Author(s):  
Russell D Dawson ◽  
Gary R Bortolotti
Keyword(s):  
Brood Size ◽  
Size Variation ◽  
Parental Effort ◽  
Proximate Determinant ◽  
American Kestrels ◽  
Experimental Variation ◽  
Proximate Determinants ◽  
Proximate Factor ◽  
And Control

Brood size has the potential to determine the allocation of resources between parents and offspring, as well as influence the relative contributions of each sex to parental effort. However, it is unclear whether brood size is the proximate determinant of parental effort, or conversely whether parental effort is the proximate factor to which brood size is adjusted. If brood size determines parental effort, then theory suggests that parental effort should vary with experimental changes in brood size. In contrast, if parental effort determines brood size, then parental effort is expected to be independent of experimental variation in brood size. To distinguish between these hypotheses, we experimentally reduced brood sizes of American kestrels (Falco sparverius). Our results suggest that male parents responded to brood-size variation and adjusted their provisioning behaviour accordingly. Conversely, female parents did not adjust provisioning in response to brood size, and as a result, offspring in reduced broods received more food on a per-nestling basis. However, condition and survival of offspring were similar in reduced broods and control young, which may have been the result of larger food requirements of small broods, owing to increased thermoregulatory costs compared with control broods. Female parents with reduced broods also did not brood offspring more often, further suggesting that females do not respond to variation in brood size. We conclude that the proximate determinants of parental effort are sex-specific in American kestrels: for males, brood size determines behaviour, whereas for females, behaviour may be a proximate factor determining brood size.

The role of calcium in constraining egg synthesis in the Audouin’s Gull (Ichthyaetus audouinii)

2013 ◽  
Vol 91 (9) ◽  
pp. 640-645 ◽  
Author(s):  
F. Ramirez ◽  
M. Garcia-Tarrasón ◽  
L. Rami ◽  
M. Genovart ◽  
L. Jover ◽  
...  
Keyword(s):  
Physiological Response ◽  
Reproductive Strategies ◽  
Egg Size ◽  
Potential Role ◽  
Size Variation ◽  
Eggshell Thickness ◽  
Egg Volume ◽  
Causal Inferences ◽  
The Relationship

Understanding how resources are allocated to form eggs is crucial to our better understanding of avian reproductive strategies. However, little is currently known about how egg synthesis in wild birds might be constrained by the availability of specific micronutrients. Here, we investigated the potential role of calcium (Ca) in constraining egg synthesis in the Audouin’s Gull (Ichthyaetus audouinii (Payraudeau, 1826)). In particular, we evaluated the relationship between plasma Ca levels (mg/dL) in incubating females (as an indicator of the physiological response of females to increased Ca demand associated with clutch production) and several fitness-related egg traits such as egg size (i.e., egg volume), egg shape, and eggshell thickness from three-egg clutches. Egg size was positively related with incubating female plasma Ca levels, with the slope of this relationship being significantly higher for later-laid eggs. The observational nature of this study and reversed timing precludes causal inferences, but observed relationships supported the constraining role of Ca in egg synthesis and suggested that Ca may also have a role in modulating the intraclutch pattern of egg-size variation typical of this gull species.

Significance of Intraclutch Egg-Size Variation in Common Eider: The Role of Egg Size and Quality of Ducklings

1998 ◽  
Vol 29 (1) ◽  
pp. 3 ◽  
Author(s):  
Kjell Einar Erikstad ◽  
Torkild Tveraa ◽  
Jan Ove Bustnes
Keyword(s):  
Egg Size ◽  
Size Variation ◽  
Common Eider

The role of nitrogen in transforming British agricultural productivity production prior to and during the First World War

2020 ◽  
Vol 13 (3) ◽  
pp. 583-609
Author(s):  
John Martin
Keyword(s):  
Agricultural Production ◽  
First World War ◽  
World War ◽  
Coal Gas ◽  
Major Threat ◽  
The First World War ◽  
Food Shortages ◽  
War Effort ◽  
First World

This paper explores the reasons why artificial or mineral sources of nitrogen, which were more readily available in Britain than in other European countries, were only slowly adopted by farmers in the decades prior to and during the First World War. It considers why nitrogen in the form of sulphate of ammonia, a by-product of coal-gas (town-gas) manufacture, was increasingly exported from Britain for use by German farmers. At the same time Britain was attempting to monopolise foreign supplies of Chilean nitrate, which was not only a valuable source of fertiliser for agriculture but also an essential ingredient of munitions production. The article also investigates the reasons why sulphate of ammonia was not more widely used to raise agricultural production during the First World War, at a time when food shortages posed a major threat to public morale and commitment to the war effort.

scholarly journals Increased summer food supply decreases non-breeding movement in black-legged kittiwakes

2020 ◽  
Vol 16 (1) ◽  
pp. 20190725 ◽  
Author(s):  
Shannon Whelan ◽  
Scott A. Hatch ◽  
David B. Irons ◽  
Alyson McKnight ◽  
Kyle H. Elliott
Keyword(s):  
Breeding Season ◽  
Food Supply ◽  
Light Level ◽  
Food Supplementation ◽  
Reproductive Phenology ◽  
Rissa Tridactyla ◽  
Breeding Behaviour ◽  
Unlimited Supply ◽  
Migration Phenology ◽  
Carry Over

Individual condition at one stage of the annual cycle is expected to influence behaviour during subsequent stages, yet experimental evidence of food-mediated carry-over effects is scarce. We used a food supplementation experiment to test the effects of food supply during the breeding season on migration phenology and non-breeding behaviour. We provided an unlimited supply of fish to black-legged kittiwakes ( Rissa tridactyla ) during their breeding season on Middleton Island, Alaska, monitored reproductive phenology and breeding success, and used light-level geolocation to observe non-breeding behaviour. Among successful breeders, fed kittiwakes departed the colony earlier than unfed controls. Fed kittiwakes travelled less than controls during the breeding season, contracting their non-breeding range. Our results demonstrate that food supply during the breeding season affects non-breeding phenology, movement and distribution, providing a potential behavioural mechanism underlying observed survival costs of reproduction.

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