Even though there are many species, few of them are abundant. For example, only a few mating pairs of Eurasian Teal, tufted ducks, Mallards and Red Shank are found here. The Lapwing is more common. In addition, a pair of the rare Coot have sometimes nested here. The Mute Swan has also tried its luck at Lake Ulvenvatnet, the only place in Hordaland where it has attempted to nest. Some people maintain that rare birds like the Spotted Crake and Little Grebe also have once nested here. One of Hordaland's largest colonies of nesting sand swallows was previously found at a sand pit at Ulven. But after the sand pit was dug out the swallows disappeared along with the sand.
Lake Ulvenvatnet is more important as a migration locality than as a nesting place. In late autumn several tens of Snipe can be seen resting on the marshes by the lake. The rare Jack Snipe is more common here than any other place in Hordaland. But, this species will never be very common, given its behaviour. Sometimes it is so reluctant to move that it gets trampled on.
There is a high production of midges and other insects at Lake Ulvenvatnet , but this is rarely a nuisance for hikers. The insects tend to fly high - as can be measured by the swallows hunting them intensely at dusk. Several unusual species of dragonfly have also been found, as well as some that probably have never been described. Lake Ulvenvatnet is fertile, with vegetation all along the water's edge. There is a thick belt of reeds in the middle of the north side of the lake, and this is where the birds prefer to sleep. Food is found other places. The birds get their most important nourishment from wherever the extensive aquatic plants water horsetail, beaked sedge and great bulrush grow.
The bird life has adapted to living in the proximity of a military practice area, but the terns that nest on an islet in the north end of the lake are better able to steer clear of the noise. Neither did the barn swallows seem to be especially keen when their night's sleep was disrupted by cannon fire at the Ulven camp. By the way, one fat carp leaping in the water can sometimes have the same affect on nocturnal peace.
