If you have finches you will need a hospital cage! Believe me I learnt the hard way by not having one.
My attitude with finches is, invariably, at various times they will get sick. If we are forever rushing to the vets the hobby is going to cost a fortune.
I use the Hospital Cage as the first step in trying to save a sick finch. If they die they die but if you can save them it gives you a buzz and at little cost to your pocket.
When finches are sick their body temperature of 40 degrees Celsius (104 degrees Fahrenheit) drops quickly. A Hospital Cage will assist in restoring the finches body temperature otherwise the finch will use all its energy to puff him or herself up attempting to retain their own body temperature.
Such cages can be purchased from retail outlets, however they are expensive. The alternative is to purchase one from a local Aviculture Club at a more reasonable price or better still make your own like I did as shown in the photograph.
The wood is 12mm chipboard approximately 32cm wide, by 22cm deep and 37cm high. There are two 40-watt lamps in the bottom section. I use a blue and clear coloured bulb. The blue one is good during the night as the clear bulb keeps them in too much light. You can buy these cheap from your local hardware shop along with the electrical wire that you can purchase by the meter.
It is quite easy to assemble but check that you abide by local electrical requirements. I built mine for about $23.00 Australian dollars. I have not painted it yet. An open square wire tray that I cover with a sheet of paper separates the bottom and top bird section.
The cage heats up quickly and I have placed a thermometer on the middle of the back wall. When the cage has heated up sufficiently you can turn off one of the lamps keeping the top section at a comfortable temperature.
If you find 40-watt bulbs are not sufficient to obtain the desired temperature you can experiment with a slightly higher wattage. Make sure you have this SORTED OUT well before you ever use the cage.
Whilst in the Hospital Cage I supply a 50ml beaker of water with Spark Electrovet and some seed.
When the bird recovers I place it in a quarantine holding cage for at least 4 weeks until I am satisfied they are right to be returned to the aviary. I have saved many a Gouldian using my Hospital Cage otherwise they would have surely perished.
Make sure the cage is cleaned with disinfectant after use! Good luck...