The difference between the specialist and a generalist is that a specialist is a species with a narrow niche and a generalist is a species with a much boarder niche.
The specialist species can only survive on fairly limited diets. Specialist thrive when conditions are just right. They fulfill a niche and are very affective with competing with other organisms. They have good mechanisms for coping with “known” risks, but if there living conditions change they are likely to go extinct. Specialist examples include the koala which lives almost entirely eucalyptus filling a niche that is toxic to most animals. Another specialist species is the orchid mantis this is a colorful mantis with limbs that resemble leaves and thrives only on orchids in the tropics.
The Tuatara is a reptile like species found in offshore islands of New Zealand and consume mostly insects. Panda is a specialist species because over 95 percent of its diet consists of bamboo.
The sword-billed hummingbird is considered a specialist because it has a beak longer than its body. It has co-evolved due to flowers having very long corollas. The long beak allows for them to get food. An environment with more competition breeds more specialist. Rainforests have huge diversity and competition, and there for many specialist species.
Generalist are species with a much broader niches. They are able to thrive in a wide variety of environmental conditions and feed on a variety of different foods. A great example of a generalist would be the cockroach which survive in most climates and only need water/moisture and some sort of food source. The raccoon is a generalist because it has a natural range that includes most of north and central America, and it is omnivorous, eating berries, insects, eggs, and small animals.
The rat which is found everywhere in the world but the Arctic, will eat anything to suffice their appetites. The horseshoe crab has a wide diet on the floor of the sea bed and tolerates wide range of water temperature. They can survive in low oxygen waters and out of water for extended periods of time. This species is over 360 million years old.
The coyote is a generalist as well. They have a wide distribution throughout North America, Mexico and into Central America. They are a very versatile especially in their ability to exploit human modified environments. Elimination of wolves may also have assisted coyote expansion. Coyotes utilize almost all available habitats including prairie, forest, desert, mountain, and tropical eco systems. There ability to exploit human resources allows them to occupy urban areas. Coyotes are predators that eat a verity of foods ranging from fruit and insects to large ungulates and live stock.
The whitetail deer are the oldest living deer species do to their flexibility. They can survive in many different environments such as the woods, dry or swampy or grass plains.