Trappnman--I was almost sure I would hit someones button with that one. If you hadn't asked, Wiley almost certainly would have. What we saw in examining pregnant female red fox (about 150) and coyotes (about 300) was a tendency for younger females of both species to have somewhat more males in the litters and older females having somewhat more females in the litters. There was not a really strong difference, but it was there. This, of course, will then likely vary annually, because the age structure of the female population of both species varies annually. I'm sure you remember our discussions earlier about age-related increases in reproductive performance in both species. Thus, if there was a high number of young females in the spring population that typically had somewhat smaller litters than older females, intuitively one could expect the embryonic sex ratio to be somewhat heavy to males.
Now, the "strong variable" part of the comment was referring to the impact of a variable embryonic sex ratio in models of population dynamics (e.g. computer population models). I found that even varying the sex ratio of the incoming pup cohort from 50:50 to say 49.5:50.5 or 50.5:49.5 impacted the population size 10-15 years later quite a bit. A change to say 48.5:51.5 or vice versa really made dramatic changes. I know it doesn't seem like very much until ones examines computer printouts, and starts making the calculations that the computer did to check. Sure enough, the computer was right on the dot; to as many decimals as one wants. Additionally, I used 2 different computer population models, and saw the same results with both of them.
However, we may not see these dramatic population changes 10 years later resulting exclusively from changes in this variable, because the female population next spring will likely have a different age structure than the population did this spring--maybe really different if pelt prices change dramatically and fur harvesters really get after stuff. So you don't think I'm against fur harvesting, my attitude was always and still is "with special consideration for the population in future years, happiness now is a bigger pile of pelts!"
Hopefully, I didn't muddy up the whole thing for you. Post back again if I left something unclear, and we will keep talking.