Sex Imbalance

Have you ever wondered why some breeding seasons you produce an imbalance of one sex or another?

When this happened in the research flock of Gouldians our scientists set out to find the reason why.

They decided there could be three reasons:

1: Sperm Competition

Amazingly, it has now been proven that in birds, the females have the ability to determine the sex of their offspring.

Females paired to well coloured males tend to produce more males.

This is because well coloured males are more attractive to females than their less well coloured peers. So the best way for a female which is paired to a well coloured male to get her genes out there into the market place is to produce attractive, well coloured male offspring.

But here again, the reason well coloured males are attractive to females is not quite as obvious as you might think; while the females use strong colouring as a signal it’s not the fancy colour itself that they are after.

We all know that birds use carotenes to create colour in their feathers, however, carotenes are heaps more important than that. They are one of the key nutritional components used in many body functions, amongst which a couple of the ones we would recognise are the important part they play in strengthening the immune system and in building fertility. Only surplus carotene which is left over after being used for everything else is used in feather colour.

And we know that in nature carotenes are hard to come by, so well coloured males are attractive to females because they have proven themselves to be good foragers. They have gathered so much quality food they have been able to use the surplus carotene to put into feather colour. This of course indicates to the females they are going to be good fathers to their nestlings and give them plenty of food so that he will fledge a full brood of youngsters – and yes, back to where we started, get the maximum number of her genes out there into the market place.

Ruthless these ladies!

Females who were a bit slow off the mark and missed out on the chance to pair to one of the well coloured males are therefore forced to make do with the poorly coloured blokes. But all is not lost, because they produce more female offspring to provide partners for the well coloured young males the other lot produce.

Now here’s the sneaky bit, these well coloured young gentlemen have inherited the good forager gene – yes you’ve got it; surplus carotene – so this way these females are best able to get lots of their genes out into the market place.

So there we have it, if you are producing too many cocks, chances are you have been selecting for the best colour which is what most of us have done. So to get a few more females keep some poor coloured males too.
I used to have a friend who was heavy into showing and he used to have a hen producing line and a separate cock breeding line.

2: Protein Deficiency

However, just in case you think the solution is that simple, your sex bias may have nothing to do with sperm competition, because diet can also have an effect on the balance.

Research has shown pairs which are fed a protein deficient diet produce more males, they are also likely to produce fewer fledglings and the fledglings themselves are likely to be smaller and have a lower immune system.

Of course the sad thing is that, other than the work done by Save The Gouldian scientists, there has been little to no research on finch diets; in fact almost none has ever been done on any cage bird diet, so therefore it begs the question, what is the correct protein level?

Partially funded by NATURALLY FOR BIRDS shareholders, the Save the Gouldian Fund researchers did an analysis of the crop contents of wild Gouldians at four different times of the year. This was also compared with the crop contents of two other finches.

Now as we know, wild Gouldians do not eat insects. For years this led us to believe that the Gouldian had evolved to live on a sparse, low nutrition diet. Not a bit of it!!

During the breeding season the wild Gouldians feed almost exclusively on natural wild sorghum seed. When this seed was analysed, we discovered to our surprise that it contained a much higher protein level than most grass seeds. Wild sorghum contains 247mg of protein per gram of seed (24.7% protein) well above the levels of most grasses. Recent scientific publications by Dr Anna Weier and colleagues (Weier et al 2017) working on wild sorghum around Wyndham confirm this level of 22-25% protein. By being able to specialise on highly nutritious sorghum seed the Gouldian has no need to spend energy chasing insects, it has a richer diet ready to hand and much easier to collect.

When the analysis of the Gouldian diet was cross checked with that of the Crimson Finch, it was discovered the nestlings nutritional crop analysis was very similar but derived from different food sources. In other words approximately 250mg of protein per gram of food, but the crimsons achieved that through a combination of lower quality seeds and insects which are much higher protein (40-50%).

So therefore, it would seem reasonable to guess that somewhere around the 250mg of protein per gram of food intake would probably suit many if not most other finches too [and maybe many other largely seed eating birds as well].

NATURALLY FOR BIRDS were sponsoring additional research work into this area to see if the theory worked out across additional species. So of course this had to be a combination of field work and captive bird research.

The research team already had diet supplements (now sold as PRIMA) that had been formulated as a complete diet to support other research work, but now they needed to be able to vary the intake of protein so they could measure any differences in birds fed a protein deficient diet and those fed at what was deemed the correct level.

So this is how PROTEIN BOOST came to be developed. It was designed so it could be added to any base diet to increase the protein levels to whatever was required. Today it too is available through Naturally for Birds Pty Ltd (

The early research work would seem to indicate that we were heading down the right track. The nestlings of birds fed on 250mg of protein per gram of food grew faster, fledged sooner, had fewer deaths and had a stronger immune system.

Sadly, before the research could be deemed academically conclusive, our chief scientist became ill. The research will be continued with support from Save the Gouldian Fund as soon as we can interest another scientist in the project.

So there we have it. It is highly likely, no matter what species of finch you keep, if you ensure they get an adequate level of protein in their diet, you will produce a higher number of healthy chicks which will have the benefit of also being less prone to disease.
However, there are a couple of caveats – told you nothing was simple – protein is not just one food item. There are literally thousands of proteins with slightly different composition and conducting different functions in living things. They might be structural protein, muscle protein, enzymes catalyzing biochemical reactions to drive metabolism, storage proteins in seeds – all are proteins and all are synthesised by the body from just 20 amino acids. So all you have to do is make sure your birds get the full complement of amino acids in appropriate levels.

I have included a table to show you what I mean by that. The table shows that all 20 amino acids are present in the three supplements from Naturally for Birds (PRIMA, PROTEIN BOOST and MICRONUTRIENT) and in insects and wild sorghum. Dry seeds, white millet in this example, can be deficient in some amino acids. The bottom line is the one to look at. This shows the total protein content and emphasises the nutritional value of green wild sorghum seed – at least 10% higher than green white millet for example.

The other caveat is more of a warning – cultivated sorghum is completely different to the native sorghum and certain varieties are reported to contain a toxin. So the message there is that it is probably a good idea if you don’t use it.


  • Anna Weier, Ian J. Radford, Alan Manson, Lesley J. Durrans and Michael J. Lawes (2017 in press) published online March 14, 2017
  • Frequent fires reduce the nutritional quality of Sorghum stipoideum seed, a keystone food resource for the Gouldian finch (Erythrura gouldiae). The Rangeland Journal

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