Influence of forced renesting, seasonal date of laying, and female characteristics on clutch size and egg traits in captive American Kestrels

Bird, David M.; Laguë, Paul C.

doi:10.1139/z82-009

Cited by 38 publications

(7 citation statements)

References 32 publications

(26 reference statements)

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“…However, many studies of piscivorous, gallinaceous, and passerine birds showed no association between PCB exposure of adults and eggshell thinning (Koeman et al, 1973). In this study, eggshells of PCB eggs were not different from those of control eggs, and the thickness of shells was similar to that previously reported for this species (Bird & Laguë, 1982). In this study, eggshells of PCB eggs were not different from those of control eggs, and the thickness of shells was similar to that previously reported for this species (Bird & Laguë, 1982).…”

Section: Discussionsupporting

confidence: 90%

Changes in Egg Composition of American Kestrels Exposed to Dietary Polychlorinated Biphenyls

Fernie¹

2000

Journal of Toxicology and Environmental Health, Part A

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Changes in the quality of eggs of birds exposed to polychlorinated biphenyls (PCBs) have been described, but have never been directly attributed to PCBs. Polychlorinated biphenyl residues in eggs have been associated with reduced reproductive success and embryonic deformities in wild birds. Egg size and composition, specifically the amount of albumen, yolk, and water in an egg, also influence the growth and viability of embryos and hatchlings, and consequently the reproductive success of birds. To deter mine whether PCB exposure of adult birds affected the size and composition of their eggs, 25 pairs of captive American kestrels (Falco sparverius) were fed a mixture of PCB-spiked (1248:1254:1260) food to give an approximate exposure of 7 mg/kg body weight/d, beginning 1 mo prior to pairing, and continuing throughout the courtship, egg-laying, and incubation periods. This dietary level in the adult female kestrels resulted in mean total PCB residues in the eggs of 34.1 microg/g wet weight (geometric mean), which is environmentally relevant. PCB residues in eggs increased with the time of female exposure to the contaminated diet and laying date. Variation in egg size within PCB clutches was significantly greater than within control clutches, although absolute egg mass and volume did not differ markedly by treatment. Only infertile eggs and only one egg per clutch were used for egg composition analysis. Yolks in the PCB-contaminated eggs were heavier, with less wet and dry albumen relative to control eggs. Water content and eggshell thickness were not significantly affected by PCB exposure. These results suggest that eggs from the PCB treatment have relatively more lipid and less protein available for embryonic development. Changes in egg composition were not associated with egg size, lay date, ambient temperature, humidity, or precipitation, which are factors known to affect these variables in bird eggs. The PCB-induced changes in egg composition described here provide insight into possible mechanisms contributing to reduced reproductive performance in wild birds exposed to PCBs.

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Section: Discussionsupporting

confidence: 90%

Changes in Egg Composition of American Kestrels Exposed to Dietary Polychlorinated Biphenyls

Fernie¹

2000

Journal of Toxicology and Environmental Health, Part A

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“…Quite simply, body size of some female kestrels, and hence likely most males (the smaller sex), may be too small for proper incubation of their modal clutch size of five eggs. The fact that egg size and female size are not correlated (see Results, andPorter andWiemeyer 1972, Bird andLague 1982) would further add to the problems of small birds during incubation. We do not know to what degree such problems might be exacerbated by cool temperatures experienced at the relatively high latitude of our study population.…”

Section: Discussionmentioning

confidence: 97%

Incubation Behaviour and Hatching Patterns in the American Kestrel Falco sparverius

Bortolotti¹,

Wiebe²

1993

Ornis Scandinavica

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“…In the vast majority of single-brooded species, females lay more eggs when they initiate clutches early in the season than when they initiate clutches late in the season (Klomp, 1970). The American kestrel is no exception (Bird & Laguë, 1982;. Data collected on wild, free-living American kestrels over three breeding seasons revealed that females initiating clutches early in the season tend to lay five-or six-egg clutches, whereas those initiating clutches late in the season tend to lay four-eggs or fewer .…”

Section: Determinants Of Reproductive Effortmentioning

confidence: 99%

Orchestration of avian reproductive effort: an integration of the ultimate and proximate bases for flexibility in clutch size, incubation behaviour, and yolk androgen deposition

2007

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How much effort to expend in any one bout of reproduction is among the most important decisions made by an individual that breeds more than once. According to life-history theory, reproduction is costly, and individuals that invest too much in a given reproductive bout pay with reduced reproductive output in the future. Likewise, investing too little does not maximize reproductive potential. Because reproductive effort relative to output can vary with predictable and unpredictable challenges and opportunities, no single level of reproductive effort maximizes fitness. This leads to the prediction that individuals possessing behavioural mechanisms to buffer challenges and take advantage of opportunities would incur fitness benefits. Here, we review evidence in birds, primarily of altricial species, for the presence of at least two such mechanisms and evidence for and against the seasonal coordination of these mechanisms through seasonal changes in plasma concentrations of the pituitary hormone prolactin. First, the seasonal decline in clutch size of most bird species may partially offset a predictable seasonal decline in the reproductive value of offspring. Second, establishing a developmental sibling-hierarchy among offspring may hedge against unpredictable changes in resource availability and offspring viability or quality, and minimize energy expenditure in raising a brood. The hierarchy may be a product, in part, of the timing of incubation onset relative to clutch completion and the rate of yolk androgen deposition during the laying cycle. Because clutch size should influence the effects of both these traits on the developmental hierarchy, we predicted and describe evidence in some species that females adjust the timing of incubation onset and rate of yolk androgen deposition to match clutch size. Studies on domesticated precocial species reveal an inhibitory effect of the pituitary hormone prolactin on egg laying, suggesting a possible hormonal basis for the regulation of clutch size. Studies on the American kestrel (Falco sparverius) and other species suggest that the seasonal increase in plasma concentrations of prolactin may regulate both a seasonal advance in the timing of incubation onset and a seasonal increase in the rate of yolk androgen deposition. These observations, together with strong conceptual arguments published previously, raise the possibility that a single hormone, prolactin, functions as the basis of a common mechanism for the seasonal adjustment of reproductive effort. However, a role for prolactin in regulating clutch size in any species is not firmly established, and evidence from some species indicates that clutch size may not be coupled to the timing of incubation onset and rate of yolk androgen deposition. A dissociation between the regulation of clutch size and the regulation of incubation onset and yolk androgen deposition may enable an independent response to the predictable and unpredictable challenges and opportunities faced during reproduction.

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Influence of forced renesting, seasonal date of laying, and female characteristics on clutch size and egg traits in captive American Kestrels

Cited by 38 publications

References 32 publications

Changes in Egg Composition of American Kestrels Exposed to Dietary Polychlorinated Biphenyls

Changes in Egg Composition of American Kestrels Exposed to Dietary Polychlorinated Biphenyls

Incubation Behaviour and Hatching Patterns in the American Kestrel Falco sparverius

Orchestration of avian reproductive effort: an integration of the ultimate and proximate bases for flexibility in clutch size, incubation behaviour, and yolk androgen deposition

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