i 9 6 WET FOREST COMMUNITIES 



Farther north the blackburnian warbler nests here. The tree stratum 

 of primeval conditions usually included the pine marten {Maries 

 americana Tur.). It lives in trees in dark coniferous forests. Merriam 

 (142) says that it nests in a hollow tree or log, rarely on the ground. 

 It preys upon partridges, rabbits, squirrels, chipmunks, mice, shrews, 

 birds' eggs, young birds, and frogs and toads. It disappears when 

 civilized man settles the country. The marten's close relative, the fisher 

 (Marks pennanti Erx.), is said to be the wildest of all wild animals. It 

 is somewhat similar (21, 22, 162) to the marten in habits. 



c) The pine-birch transition girdle (Station 54; Table XL VI). — This 

 succeeds the tamaracks and contains a few old trees of this species. The 

 pools are all dry in summer, though they may contain water in spring. 

 The subterranean stratum has not been investigated. 



The ground stratum includes the frogs of the tamarack formation 

 (Hyla pickeringii) . Insects, spiders, centipedes, and snails, which belong 

 chiefly to mesophytic forest, are more numerous than in the tamarack 

 stage. Nesting of the ruffed grouse likewise indicates that the swamp 

 stage is past. The field and shrub strata likewise include more of the 

 mesophytic forest animals than the true tamarack stage. 



The tree stratum has not been studied. The trees are white pine, 

 yellow birch, and an occasional maple. Felt (137) records no insect 

 common to these two trees. There are several common to the white 

 pine and tamarack (larch lappet, engraver beetle, etc.). Pines have 

 many borers and few leaf-feeders. Each borer usually prefers a certain 

 part, as the trunk, limbs, or growing shoots; some, as the white-pine 

 weevil (Piss odes strobi Peck) (161), attack young pines. Felt records 

 about 25 injurious insects common to birches and maples in general 

 and one or two which occur only on yellow birch. The great crested 

 flycatcher nests in holes in dead limbs; the wood pewee nests on 

 horizontal limbs, and the red-eyed vireo builds a nest in trees from 

 5 to 40 ft. from the ground. Dead birches form suitable nesting- 

 places for woodpeckers. The Canada porcupine (142) which we have 

 noted in the ground stratum is a good climber and feeds largely in 

 the trees, which it often girdles. 



d) The geographic relations of the animals. — Most of the non-aquatic 

 animals of the swamps are commonly said to belong to species common 

 farther north where conifers dominate. However, our lists and the 

 unpublished work of Messrs. Wolcott and Gerhard do not bear out this 

 conclusion. Some of the species of these swamps doubtless formerly 

 occurred among the hemlocks of Southern Michigan. 



