Despite its relatively small size and urban location, Ruskin Park provides a good number of different habitats.

The ornamental pond supports a surprisingly large number of bird species; mallards, coots and moorhens regularly breed there. Since the 1990s more and more Canada geese have been arriving; for several years one pair has had the pond to themselves. Greylag geese, Egyptian geese, tufted ducks and grey heron are occasional visitors. A male shoveller, recognisable by its long broad bill, has been spotted making the pond its home for a couple of weeks before flying off, presumably feeling lonely. For a while a terrapin used to live in the pond, and could be seen basking in the sun; it had probably been dumped there by its owner when it got too big for a tank. The water can become clouded by an excess of algae and of bread thrown in for the ducks . There may be a few fish, but any frog spawn that is laid is eaten by the ducks. Large numbers of pigeons tend to congregate around the pond because of the bread people feed to the ducks and nuts to the squirrels. In 2010 overhanging tree branches were cut back to prevent pigeons perching on branches and fouling the water below. This was partially successful, but they are resilient birds and find new perches. Bread is not a suitable or natural food for ducks; despite generations of parents taking children to feed the ducks it should be avoided. Please do not feed the ducks, as the pond is capable of sustaining its inhabitants.

The wildlife pond, beside the tennis courts alongside the railway line, is already starting to attract mallards and Canada geese. The banking along the back of the pond was planted by volunteers with wild flowers. Volunteers also planted some sapling trees along the railway boundary behind the banking and to the side towards the tennis courts. The pond provides an excellent wetland habitat for amphibians, particularly the common toad, and other species associated with standing water habitats like water-borne insects and dragonflies.

Robins, blue tits, great tits and, especially in winter, long-tailed tits can be seen in the trees and shrubs across the lawn and flower beds from the pergola towards the stable block. The path from the main pond towards the portico and Denmark Hill gate is known as Lonely Walk and is also a good area to view various birds amongst the shrubs. Greenfinches can be heard chattering high up in the trees, and sometimes in winter a mistle thrush can be heard singing from the very top of a tree. Nuthatches regularly nest in the park. In the trees nearer the pergola and old bowling green one can hear song thrushes and willow warblers. Green woodpeckers are in the area and can be heard regularly, and occasionally seen, in the park. There have also been sightings of a great spotted woodpecker, normally seen in woodland areas or the trees opposite the tennis courts. The loud squawking of the brilliant green rose-ringed parakeets that are colonising London’s parks is now becoming a familiar sound.

On the sports field in winter flocks of gulls can be seen, puddling for worms. They are mostly black-headed gulls, but common gulls and lesser black-backed gulls have also been seen. Song thrushes also use the field to seek their food and kestrels sometimes hunt over the park. Crows have become numerous and bold, and will watch the grey squirrels burying nuts so as to dig them up when the squirrel leaves. The grey squirrels are very common in Ruskin Park and have become rather tame, sometimes running up your leg to get a nut out your hand, although they can still give a nasty nip at times if fed by hand. The profusion of food given to the squirrels, and to the birds on the pond, has unfortunately caused the population of rats living around the pond to increase. Foxes also take advantage of the food supply, although they mainly visit the park at night. They have been seen on occasions at dawn in the streets beside the park and in daylight in the park and local back gardens.