Beavers, like many mammals, communicate with chemical signals. In scent marking, beavers actually build a mound of mud on which to place their scent. First they dive down to the bottom of their pond, dig up an armful of mud with their front feet and swim to shore with the mud held against their chest. Walking on to the shore on its two front legs, the beaver deposits this mud next to the water. Beaver scent mounds can be quite small, or as high as three feet or more, depending on how many loads of mud they contain. The beaver straddles this pile of mud and applies castoreum from its castor glands, or anal gland secretions, or both. The purpose of building a mound is to elevate the odor (helps with scent dispersal), to intensify the odor by putting it on a moist substrate, and to protect it from flooding when the pond level fluctuates. Beavers build most of their scent mounds in the spring, when young beavers are dispersing and claiming new ponds, but I have found several fresh ones this fall, including the one in the photograph. (Click on photo to enlarge.)
Like the majority of songbirds, American goldfinches use their nest only once — to raise one brood — and do not return to it after their young have fledged. This time of year, when leaves have fallen off of shrubs and trees, is a great time to try and locate where birds you saw all summer nested. Just as each species of bird has its own song, each species of bird builds a nest unlike those of other species. By noting the habitat in which it’s built, the material with which it was built, and the dimensions of a nest, it is often possible to determine the species of bird that constructed it. Female American goldfinches build a very neat nest composed of plant fibers, and line it with the down of cattails or thistles. The walls are quite thick, making it quite durable – the nest in the photograph even withstood the wind and rain that Irene delivered this fall. While it’s fun to hunt for nests, bear in mind that you need a federal permit to collect them.