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ovulation order in songbirds

Posted by er12 on 23 Jun 2008 at 10:43 GMT

As the title of the paper indicates, ovulation order is claimed as the mediator of the trade-off. Ovulation order is not what was actually measured. Instead, laying order was used as a proxy for ovulation order, assuming that they would be the same and citing a classic book on avian eggs. This is probably a reasonable assumption (how could one ovum pass another in the oviduct?). It serves as a reminder, however, that most of what is known about such matters is based on chickens and a few other domestic birds. Remarkably little is known about ovulatory cycles and their physiology in songbirds (oscine passerines), even though this is by far the largest avian clade. It is hoped that by emphasizing ovulation order the study will motivate research into ovulation mechanisms in female songbirds.

RE: ovulation order in songbirds

kwsockman replied to er12 on 04 Jul 2008 at 02:34 GMT

Hi Elizabeth,

Thank you very much for initiating this discussion on my paper. I am sorry for the delay in responding, but I am in the field and have only occasional internet access.

You are absolutely correct that I assume laying order reflects ovulation order, an assumption based largely on chicken research. I had thought about this concern when writing the paper but then thought, like you did, that it seems far-fetched for an ovum to pass another in the single oviduct of the songbird. But, who knows? Given the fact that Alex Badyaev has evidence in house finches that individual follicles can developmentally overtake other follicles in the ovarian hierarchy, perhaps it is possible for an ovum to pass another within the oviduct. This issue of whether or not ovulation and laying order are one and the same becomes particularly interesting in Falconiformes that, if I remember correctly, have retained the bilateral pair of ovaries and oviducts and sometimes have two- to three-day latencies between eggs.