breding results & thoughts

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lardles
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Joined: 23 Jul 2010, 10:59
Location: Central Vic
Location: Central Victoria

After speaking to a couple of other breeders of red siskens, It got me thinking about a couple of things with respect to last years breeding season ( in Vic anyway)

Last summer/breeding season was very wet and humid here ( shocking for my tomatoes), and my pair produced 2 males from their only clutch. In trying to find hens to make pairs this year I learnt that some other breeders also produced more males than females for that season which was considered unusual. Actual numbers in clutches were also down apparently.
I do know that one breeder have all theirs in outdoor avairies, but not sure of others.

This got me wondering if climatic conditions can influence the sex of of potential youngsters?

Now, I realise that there may be other variables which could influecne this, so only speaking in broad/general terms.
Someone has probably done a study on it I imagine. With African Cichlids, it has been suggested that raising the water temp in the tanks of some species (not all -I think) leads to more males than females being produced?

Will be intereting to see what happens this breeding season, I will hopefully have 2 pairs to test the theory???
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Tiaris
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Joined: 23 Apr 2011, 08:48
Location: Coffs Harbour

Its hard to know whether these things are general rules when we only have small samples of young birds from a small number of breeders. I do certainly think that Red Siskin breeding activity is very dependent upon rainfall and temperatures occurring at the right time in relation to their normal seasonal breeding impulses. There are usually slightly more cocks bred compared to hens in Red Siskins Australia-wide and if you've bred extra hens in any year they are nearly always far easier to dispose of than spare cocks. I've also heard that sexes of young crocodiles depends on incubation temperatures.
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Myzomela
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Joined: 24 Jan 2011, 18:44
Location: Melbourne Vic

This is an interesting topic.

Despite the findings in crocodiles, it doesn't appear that manipulating incubation temperatures of the eggs once laid has any bearing on sex ratios produced in species such as ostriches or parrots. I daresay that if this were the case the poultry industry would be setting incubation temps to achieve 100% hens for the egg laying industry for example.

With finches, we just don't know.

However, temperature and or humidity may have an effect on determining sex ratios in some species immediately before and up to the time of egg laying, for example, than after eggs are laid.

Just as in some passerine species where hens determine the gender of their offspring depending on the "credentials" of their male mates, perhaps they can do so in response to certain climatic triggers.

Sounds like a great PhD project for someone I reckon!!
Research; evaluate;observe;act
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Niki_K
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Joined: 23 Oct 2011, 12:18
Location: Melbourne, VIC

I'm currently working on sex ratio in zebbies in relation to stress hormone levels, and I imagine a lot more work is going to be done with other species as sex allocation theory is a hot topic at the moment :)
Sex ratio has been shown to be affected by maternal condition and environmental conditions in a few avian species (even social hierarchy has played a role in some species), but this needs a lot more work, and I don't know how much has been done with siskins. As yet, the mechanisms controlling sex allocation are unknown, but I believe it's in relation to hormone concentrations (hence my project!).
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Tiaris
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Joined: 23 Apr 2011, 08:48
Location: Coffs Harbour

Do you have a hypothesis that higher concentrations of stress hormones result in more males (for eg.) or are you just testing the effect of stress on sex ratio of young generally with Zebra Finches?
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desertbirds
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Location: Alice Springs

Alice Springs - Black breasted Button Quail - 10 straight cocks before i bred a hen.
- Pictorellas - 18 young - 3 cocks and 15 hens.

I think seasons can have a huge impact on the ratio of males to females but it varies with different species. Pig nose turtles are another species where the temperature of nests only has to vary by a few degrees and all the turtles will hatch either male or female. I noticed with lessers that over two years and 25 young i ended up with 5 spare cocks, the first season (very wet ) produced heaps of cocks and the second season produced more hens.
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Niki_K
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Tiaris wrote:Do you have a hypothesis that higher concentrations of stress hormones result in more males (for eg.) or are you just testing the effect of stress on sex ratio of young generally with Zebra Finches?
Yes, I believe that stressed mothers will produce more males than females. It's an unusual hypothesis, as generally mothers (in other species) in poorer condition produce more females as males are energetically more expensive to produce than females (generally, due to differences in size and colouration), but in zebra finches, its the other way around. A number of other studies have shown that the factors affecting sex allocation also happen to be correlated with increased circulating stress hormone concentrations, so I believe that 'stress' (and I use this term broadly) has far more of an effect on physiological mechanisms than previously thought.
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dukem
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This is a old topic but very interesting. I have every year the same problem with Red Siskin i have alot of males and a very few females in 3 years i had: 29 males and 4 females i suspect is genetic.
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