Hi Belinda and others,
It is obvious that if a male bird mates with lots of females, he is more
likely to produce a greater number of offspring than if he mates with
only one bird. If his male offspring inherit the behavioural propensity
to mate with lots of females, then the proportion of multiple-mating
males in the population will increase, and so it goes on. Those that
only mate with one female, will be relatively scarce.
If a female bird mates with several males, she will be more likely to
produce young with a wide variety of characteristics (sperm competition
aside). Depending on environmental conditions, this may increase the
number of offspring that survive to sexual maturity. If the survivors
inherit the propensity to mate with several partners, then the chances
of their offspring surviving will also increase, etc.
On the other hand, if a female mates with only one male, even a really
good quality one, if environmental conditions change, then the offspring
might not be well suited to the new conditions and may not survive to
maturity. However, if environmental conditions are unchanging, then
mating with the best (fittest for the current conditions) available male
will produce the greatest number of surviving offspring.
Similarly, under certain circumstances, young will be more likely to
survive if they have more than one carer, i.e. both mother and father
(and sometimes older siblings as well). These survivors will inherit the
capacity to care for young in a socially stable partnership along with
whatever mating system was employed by their parents (single or multiple
partners).
It's all about inheritance and survival.
Cheers,
Merrilyn
Belinda Cassidy wrote:
Hi Kurtis, John, Rosemary, Storm, and everyone,
I must apologise for being so curt. I don't know whats got into me today;
anyway I didn't mean to put everyone off side. Its been an emotional week
for me and I guess I sprung a leak.
I think we all agree that the scientific evidence demonstrates that some
birds pair for life, and some do not. I don't even know why this is being
hotly debated, but like I said, I have my suspicions as to the reasons.
You're right though Kurtis, suspicions are not the same as scientific fact.
Cheers,
Bel
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