Abstract
A negative relationship, or trade-off, between egg size and clutch size is a central and long-standing component of life-history theory, yet there is little empirical evidence for such a trade-off, especially at the intraspecific level. Here, I show that female zebra finches (Taeniopygia guttata) treated chronically during egg formation with the anti-oestrogen tamoxifen lay smaller eggs (by 8%) but produce larger clutches (on average two eggs more) than controls. Decreased egg mass in tamoxifen-treated females was associated with a 50% decrease in plasma levels of the two yolk precursors, vitellogenin and very-low-density lipoprotein. Although tamoxifen-treated females laid more, smaller eggs (and had a higher total expenditure in their clutch), they did not differ from controls in the number of chicks fledged, the mass or size of these chicks at fledging, or the chicks' egg-production performance at three months of age. However, tamoxifen-treated females had lower relative hatching success: they laid more eggs but hatched the same number of chicks. Among individual tamoxifen-treated females, birds that laid the smallest eggs early in their laying sequence laid the largest number of additional eggs, that is, there was a negative correlation, or trade-off, between egg size and clutch size.
Full Text
The Full Text of this article is available as a PDF (145.3 KB).
Selected References
These references are in PubMed. This may not be the complete list of references from this article.
- Delville Y., Balthazart J. Hormonal control of female sexual behavior in the Japanese quail. Horm Behav. 1987 Sep;21(3):288–309. doi: 10.1016/0018-506x(87)90016-x. [DOI] [PubMed] [Google Scholar]
- Finkler M. S., Van Orman J. B., Sotherland P. R. Experimental manipulation of egg quality in chickens: influence of albumen and yolk on the size and body composition of near-term embryos in a precocial bird. J Comp Physiol B. 1998 Feb;168(1):17–24. doi: 10.1007/s003600050116. [DOI] [PubMed] [Google Scholar]
- Hill W. L. Importance of prenatal nutrition to the development of a precocial chick. Dev Psychobiol. 1993 Jul;26(5):237–249. doi: 10.1002/dev.420260502. [DOI] [PubMed] [Google Scholar]
- Jaccoby S., Arnon E., Snapir N., Robinzon B. Effects of estradiol and tamoxifen on feeding, fattiness, and some endocrine criteria in hypothalamic obese hens. Pharmacol Biochem Behav. 1995 Jan;50(1):55–63. doi: 10.1016/0091-3057(94)00251-d. [DOI] [PubMed] [Google Scholar]
- Jaccoby S., Pinchasov Y., Snapir N., Robinzon B. Hypothalamic obese, functionally castrated hens are hypersensitive to estrogenic modulation of lipid metabolism. Physiol Behav. 1996 Sep;60(3):913–918. doi: 10.1016/0031-9384(96)00089-3. [DOI] [PubMed] [Google Scholar]
- Jordan V. C., Robinson S. P. Species-specific pharmacology of antiestrogens: role of metabolism. Fed Proc. 1987 Apr;46(5):1870–1874. [PubMed] [Google Scholar]
- doi: 10.1098/rspb.1998.0495. [DOI] [PMC free article] [Google Scholar]
- Shanawany M. M., Morris T. R., Pirchner F. Influence of sequence length on the response to ahemeral lighting late in lay. Br Poult Sci. 1993 Dec;34(5):873–880. doi: 10.1080/00071669308417647. [DOI] [PubMed] [Google Scholar]
- Williams T. D. Experimental (tamoxifen-induced) manipulation of female reproduction in zebra finches (Taeniopygia guttata). Physiol Biochem Zool. 2000 Sep-Oct;73(5):566–573. doi: 10.1086/317748. [DOI] [PubMed] [Google Scholar]
- Williams T. D. Parental and first generation effects of exogenous 17beta-estradiol on reproductive performance of female zebra finches (Taeniopygia guttata). Horm Behav. 1999 Apr;35(2):135–143. doi: 10.1006/hbeh.1998.1506. [DOI] [PubMed] [Google Scholar]
- Wilson S. C., Cunningham F. J. Effects of an anti-oestrogen, tamoxifen (ICI 45,474), on luteinizing hormone release and ovulation in the hen. J Endocrinol. 1981 Feb;88(2):309–316. doi: 10.1677/joe.0.0880309. [DOI] [PubMed] [Google Scholar]