The commonest problem you’ll encounter amongst birds is aggression. In a large aviary where individuals can find personal space and escape to the far corners of the enclosure, you have a better chance of getting the balance right, even with a mixed flock of birds. In smaller setups you will need to have some extra ‘cooling down’ cages for aggressors (or their victims). Some species are pretty incompatible, and many others become aggressive when hormones boil over in the breeding season.
Canaries in the breeding season sometimes enter into bouts of competitive singing, even if they are being kept in separate cages. Although this can be pleasant to the human ear, a constant song-based faceoff between the birds can cause them stress, and it’s best to move one of the competitors out of earshot, if possible. If the songsters are housed together in an aviary, there’s little you can do. The confrontation may end in a scuffle, or one of the birds may grow so exhausted that he retreats to a quiet corner. Keep an eye on any such development, to make sure the ‘loser’ doesn’t fall ill.
Hens sometimes lay eggs when there has been no mating. It is mating and nesting that require the specific stimulation of courtship and bonding, not egg-laying per se. If a hen lays eggs without a cock bird, they will of course be infertile. The eggs will often be laid in the food tray - the nearest thing to a nest that the hen can find.
Hot or Cold
A bird with drooping wings and open beak is probably over-heated. Make sure there’s shade available in your cage setup, if the bird is outside. Indoors, you could move the cage to a cooler room; but that room will have to be bird-safe. A hot bird is not usually in any danger, and if it’s a consequence of hot weather he will simply spend more time than usual sitting and panting. You should still be watchful, though, as panting behaviour in your birds could indicate a disease and should be referred to the Finch Health section of this guide.
A fluffed-up bird could, again, indicate illness; but your finch may simply be cold. If there’s anything you can do to safely heat up the environment, do so. A cover over the cage at night will help.
The feet of a Canary can be a clue to its health
Owners whose pet canaries or Zebra finches perch on their fingers learn to recognise the normal temperature of their pets’ feet. If the bird is hotter or colder than usual, they can tell by the foot temperature. This is a useful gauge, a starting point for further investigation - i.e. is the hot or cold down to the ambient temperature, or are there other signs that could indicate the onset of illness?
It sometimes happens that a cock finch enters the breeding season earlier than the hen. In this situation the female will not be receptive, and the frustrated male will begin chasing, or even attacking her. If this happens the pair will need to be temporarily separated.
A tired bird might not be ill - he might just not be getting a good uninterrupted night’s sleep. If there are lights on in the house, or security lights interrupting outdoor slumber, the finches will not be happy. They need an uninterrupted rest from dusk until dawn, all year round.
Some cock finches become over-zealous in defending their nests while the hen is incubating the eggs. Given enough space, other finches will soon learn to keep away. In a smaller cage, this is an untenable situation, and is one of the reasons why finches are generally kept in breeding pairs.