In the previous chapter, we examined the small but numerous species of forest invertebrates. In terms of forest vertebrates, the situation is the opposite: the species are large, but they are not as numerous as invertebrates.

Vertebratic animals have an internal supporting structure called a skeleton. They can be divided into homeothermic and poikilothermic animals depending on how they regulate their body temperature. Homeothermic or warm-blooded animals, such as birds and mammals, retain a stable body temperature. In contrast, the body temperature of poikilothermic or cold-blooded animals, such as reptiles and amphibians, changes depending to the temperature of their surroudning environment. 

Many mammals and birds have their own territories. A territory is an area that is inhabited and defended by an individual or a group of organisms. Mammals and birds use their territories to search for food and to reproduce. Other individuals or herds of the same species are kept away from the territory. Because of these territories, only a limited amount of individuals can live in one forest. This is why forest vertebrates are less numerous than forest invertebrates.


The brambling announces its territory by singing.

Large species need territories, because they make sure that the individuals receive enough food to sustain themselves. Because of their large size, large invertebrates require a lot of food to maintain their body temperature, to grow, and to reproduce.

BIRDS

Group	Structure	Diet	Species	Other
Passerines: insectivores	thin beaks	insects	willow warbler, pied flycatcher	migrating birds
Passerines: seed-eaters	sturdy beaks	insects during the summer, otherwise seeds	chaffinch, crossbill	some species overwinter
Tits	thin beaks	insects and seeds	great tit	visit the bird feeder during the winter
Owls	thick plumage, tearing beaks	small rodents and birds	boreal owl, northern eagle owl	migrate when necessary
Hawks	tearing beaks	mammals and birds	sparrowhawk	fast predators
Woodpeckers	stiff tails, strong beaks	insects and seeds	great spotted woodpecker, black woodpecker	some species can visit the bird feeder

MAMMALS

Group	Structure	Diet	Species	Other
Insectivores	small teeth	insects and worms	shrew, mole	spend the winter under snow
Deer	hooves	plant parts	moose, white-tailed deer, reindeer	many species are hunted
Rodents	small size, chisel-like teeth	plant parts	bank vole, wood mouse, squirrel	large changes in population sizes
Predators	suited for preying and hunting	other animals	pine marten, wolf, bear, lynx	some are omnivores