Most of my readers already know that I track huge amounts of data about my birds in an effort to learn what makes them tick. I do this in part because there is very little scientific information about finches in general, let alone information about Gouldian finches that is relevant for the average captive Gouldian keeper.   But in addition to my "need to know what makes the birds tick", there are other reasons I track all of this data. Read below to find out why!

Egg Size & Weight Are Telling

It should be understood that I use every bit of data I collect to decide which birds to breed, which should be retired, how to pair breeders, whether the nutrition needs to be reevaluated, etc. I also use age and a multitude of other factors in this decision, but egg size & weight are the tells that I use the most.

Most Gouldian eggs in my aviary fall within the specific range of 18.5-19.5mm, while Societies and other species have very different ranges - some larger, some smaller. But regardless of species, smaller than average eggs or weights often mean the parents are not getting "something" nutritional they need, are not assimilating calcium properly, or possibly have some kind of disease process going on. Breeding hormones lower the immune system opening the birds up to a host of potential issues, but hidden illnesses or bugs in carrier birds will show up in the eggs and offspring. It's very important to pay attention to egg size and weight to uncover issues early.

Every bird in the aviary is evaluated for overall health BEFORE being paired, so when changes occur during breeding or averages fall below or above normal, I must take action and find the cause. When I see small eggs, I watch closely to see exactly what seeds and supplements the birds are eating (literally count seed hulls, weigh & measure mineral content, drinker content, etc.) and tweak their mixes. I test droppings, run cultures, and take the parents in hand for another overall health check. If I find nothing wrong, I just keep observing. If I see the birds consuming large amounts of any given seed or supplement, I reevaluate their entire nutritional program to discover what it is they are looking for - each type of seed holds a different nutritional makeup, grit and charcoal in large amounts may be a need to replace calcium, but may also point to an internal issue such as parasites. In most cases, it's merely a matter of tailoring the nutrition to meet the needs of each pair. However, improper nutrition can lead to smaller eggs, breeding older birds can lead to smaller eggs (and in some cases, is expected). It may be time to retire a bird if the eggs are too small, and they aren't always old when they need to retire.
Small eggs produce small chicks - if they hatch at all. Smaller chicks tend to be weaker and more prone to disease processes. Hens who produce consistently small eggs are retired - regardless of age. In most cases, we retire hens between 4-6yrs old.

Overly large eggs can be caused by nutritional issues as well, so the same (above) applies. Young hens tend to produce larger eggs than older hens, so I expect to see eggs at the large end of the scale from these girls. I typically pair larger hens with smaller mates because the hen tends to produce the size in offspring. But even being larger than the cock bird, they are sometimes unable to pass those eggs easily and must be watched for signs of egg binding. Calcium intake must be closely monitored. If the hen refuses to eat shaved cuttlebone or grit, she is pulled from the breeding program and held until the following season before being allowed to breed again. If it appears she isn't processing her calcium intake properly - perhaps she sits low on the perch or can't sit up on her legs, is passing soft shelled eggs, or shell-less eggs - her D3 is increased via Inca Honey and liquid calcium in the drinking water, and again, she is pulled from the program and held for a season before breeding again.

But because I try to pair in the hopes of producing birds more likely to appeal to the judges, I pair larger birds with smaller ones to put some size on the chicks. I have to keep a close eye on them. We all know what it's like to be short a cock or hen for breeding season, and sometimes less than favorable pairings must be made. In cases like this, egg size is again an indicator. Good pairs produce eggs within normal range. A cock bird larger than a hen may cause her to have issues passing eggs. And because pairing is crucial and done once both cocks & hens are in condition, any abnormalities I see may mean one or the other was an undetected carrier bird. The birds are kept in like-sexed flights away from one another. They can easily hide issues that don't mix well once paired - strains of bacteria, like what we acclimate them to when bringing new birds from one aviary to another, or mixing lines that have never been mixed before. Catching signs of illness or overall weariness in the parent birds can prevent chick losses and/or weak chicks. In many cases, the eggs will be the first indicator of a problem. When we check eggs regularly, we can detect early signs of dead in shell, clear eggs, infertility, etc. While it's not advisable that all breeders check all eggs, it should still be done at least once around the 7 day mark to detect issues early. Of course there are species who don't tolerate nest checks well, but if you've spent time with your Gouldians, they should readily accept a few nest checks without too much fuss.

Egg Size Issues

Like breeding a Chihuahua to a Great Dane - if the female is too small or male too large, she won't be able to safely birth the pups which can end up destroying her. Of course that is a bit of an exaggeration, but I'm trying to give an example of why I track this information! In the birds, sometimes eggs can be overly large and not pass easily from a smaller hen resulting in egg binding, torn cloaca, or a horribly exhausted hen. If I see this, I pull the pair and review my pairing to see where I went wrong. The hen is released to the resting flight to recover and not paired until the following season. The cock may be used in another pairing if I still have hens to be paired. These new pairings aren't always successful after a pair has bonded, so good initial pairing is crucial.

There is a very fine line I won't cross when pairing. A lot of it is instinct, but I use my records in my overall choice for breeding pairs!

Every bird bred here has their own records, so I compare not only the hen's birth records, but her clutch results to the birth records of the cock bird. If he hatched from an overly large egg, chances are any hen he is paired with will end up producing overly large eggs. It's not an exact science - nutrition and overall health also play a crucial role - but it has worked well for me over the years.

Yes, I suppose it IS a lot of work! But it has become a normal part of my routine. I NEED to know what makes these birds tick, so I do what it takes - and I see correlations regularly! I don't even think about "why" I do it anymore - I know, and have found it exceptionally useful - so I just do it!

Measurements for a current clutch of Society eggs laid by a young first-season hen


  • First column = (2) clutch number for season, (15) year, (7) total clutches over hen's breeding life TO DATE. Older hens may have a number as such: 2.15.18 - see the last number? That represents ALL clutches over the breeding lifetime of that particular hen.
  • Second column = Date egg was laid
  • Third column = Egg length in millimeters
  • Fourth column = Egg weight in grams



In my aviary the breeding season begins for all Australian species and Societies in the Fall. The season typically runs until Mid to late March and occasionally early April depending on how long it takes for each clutch to fledge and wean. That means that parts of a "season" for each hen may be split up between 2014 and 2015 (example).

The "season" column indicates ALL clutches laid in a single calendar year including remnants from the end part of the previous Fall breeding season and the beginning parts of a new Fall breeding season resulting, in most cases, in a total of 6 clutches per "Season".

When I see "3" in that first column, it tells me the hen should not be bred again until the next Fall season. If she lays 3 clutches before the end of the year and a "6" is entered in that column, she will not be bred again until the NEXT Fall season - regardless of time in between. That's my self-imposed restriction to keep my hens healthy.

I consider ANY clutch laid - regardless of hatch status - to be a clutch and it's entered as such in that record. Once she hits a 6, she's not bred until the NEXT Fall season.

In addition, my hens are never allowed more than 3 clutches per season and are often pulled down after 2 or even 1 clutch if I see something I don't like. That could be ratty or messy feathers, messy droppings, missing feathers, an overly amorous or aggressive mate, or unusually large or small eggs that may mean calcium processing issues. Sometimes I pull them down because I'M done, not necessarily for any other reason! Breeding season is a lot of work!

To each his own, but in MY aviary I'm about QUALITY...NOT QUANTITY!!! I will not sacrifice the health or quality of my birds for any reason! This careful husbandry leads to healthier adults, rare illness in the aviary, and more robust chicks - even if it means fewer of them per season! ~k