Looking back to several years ago, 2003 to be exact, and to my knowledge there was only one Agate Java sparrow known to be in the UK.

Rob Salem, who runs the popular www.javafinch.com website, stumbled across a lone Agate Java in a local pet shop. How and why such a rare specimen ended up for sale in pet shop we’ll never know, but Rob knew exactly what he was looking at and had no hesitation in purchasing the single bird with the intention to breed the mutation into his existing bloodlines. Sadly the bird did not live very long and Rob never managed to successfully breed from this bird.

It wasn’t until 2005 when the Agate was back in the UK when three committee members of the Java Sparrow Society UK www.javasparrow.org acquired a small stud from a breeder in Belgium that was retiring from the hobby. Thanks to those three original members the Agate has become more accessible to bird keepers although the availability is still rather limited.

If you are not familiar with Java sparrows then, at a glance, you would probably not notice the subtle differences between the normal wild type and the Agate. When comparing the Agate to the normal there are three differences that can be seen. The head is dark brown in contrast to the black cap of the normal, the eyes are a deep ruby red and the belly appears cream against the usual coral colouring of the normal.

The attributes of the Agate have often made me question its genetic inheritance. Is it a true mutation or has it been developed by hybridising with another species within the lonchura genus? I ask this question as my knowledge of genetics is somewhat limited and I am not in a position to make a definitive statement as to the true genetic make up.

Let's take a closer look at the Agate...

The Head – At a glance, the head of the Agate appears to be black but is actually a very dark brown; this can be seen more clearly in sunlight. The only other mutation that has a dark brown head is the fawn. The colouring of the fawn mutation is credited to a lack of eumomelanin and changes the overall colour of the bird. In the Agate, the body colour is unaffected and the only apparent lack of eumomelanin appears to affect the head.

I have noticed that this dark brown head can be an indication as to the sex of the bird. Drawing a comparison with the fawn mutation, I have found that Agate cock birds tend to have a much darker head than that of the hen. I don't want to state that this is fact correct as I have only bred around 15 visual Agates, but all of the examples I have bred appear to be like this.

The Eye – More commonly noticed in sunlight, the Agate’s eye colour is a deep ruby red. Red eyes are common in a few of the Java sparrow mutations such as the fawn, opal Isabel and in some whites.

An Agate can be identified in the nest almost as soon as it it hatched, the photo below shows an Agate and a normal chick (split for Agate). You can clearly see a difference in eye colour.

(Please Note: The photo (above) does not clearly illustrate the ruby red eye of the Agate, this was due to the flash of the camera).

Left - You can clearly see the ruby red eye of this young Agate. It shares the nest with a clutch of Agate splits (which are visually normal Java's). Even though their eyes are not open, you can see the eye colour throught the skin.

The Belly (Ventrum) - The Agate’s belly is a cream colour and does not occur, to my knowledge, in any other mutation. I suppose there could be case for this being attributed to the lack of eumomelanin as the colour does appear to be close to the fawn’s main feather colouring but, in my opinion, I don’t think this is the case.

It’s difficult to say where and how the Agate started but it’s slowly and surely being established as a new “mutation” within aviculture.

I recall a former member of the JSSUK being quite confident in saying that its origins lie in the silver (opal) mutation as his Agates threw this colour from his pairings. Couldn’t the reason be that the Agate paring in question were simply split for silver? I know from my experience that my Agates throw many colours, fawn, silver, opal Isabel and pastel Agate. Perhaps the Agate mutation is a combination of many colours?

If the Agate is a mutation then I believe its origins may have derived from the fawn (Isabel) as the dark brown head, cream feathering and red eye draw close parallels between the two and share the most characteristics when comparing mutations like-for-like.

Or maybe it is a result of hybridisation with the Java Sparrow’s closest relative, the Timor Sparrow (Lunchura Fuscata). The only true way to find out would be to breed experimental pairings. This is obviously a big task as the vast majority of hybrids are infertile, and the chances of breeding a fertile hybrid suitable for further breeding is slim. In addition to this, the availability of the Timor sparrow is extremely limited and could be lost within aviculture completely if breeders do not make a concerted effort to try and bolster the captive population.

Take a look at this photo (from a Japanese website) of Java Sparrow x F1 Timor Sparrow Hybrids and then compare it to the photo of the Agate above. I’m sure you’ll agree that there are definite similarities between the two….maybe the hybrid theory is possible?

So, what do you think? Is the Agate a mutation or a result of hybridisation? Like I said, my knowledge of genetics is limited and I’m sure there are plenty of people out there who can give a more qualified answer than I can.

Please remember, this page is based on a question as I don't know the answer. Hopefully this page will encourage more experienced bird keepers to look for the answer.

Either way, I'd love to hear your feedback...send me an email here.