efficiently requires more technical knowledge on the part of the seamstress. More than two dozen species of birds have been identified in Inuit clothing, including species of auk, cormorant, crow, eider duck, goose, guillemot, loon, ptarmigan, puffin, seagull, and swan. The toughest and most desirable skins came from diving birds. The Qikirtamiut of the Belcher Islands relied on eider duck as their primary clothing material, as there were no caribou on the islands. As a result, they developed an extensive knowledge of the technical properties of eider duck skins depending on the age, gender, and season of each bird. Skins were used according to the properties desired for the garment being made – the tougher skins of adult male ducks were used for hunter's garments, which required durability, while the more flexible skins of juvenile ducks were selected for children's clothing. The unique characteristics of the types of feathers on the body were also taken into account. The more flexible back skin of the duck would be used for parts that required flexibility, like the hood, while the more thickly feathered skin from the belly would be used for the parka body, where warmth was required. Other natural materials Polar bear was a major source of winter garments for Greenlandic Inuit in the 19th century. Like caribou fur, polar bear fur grows in dual layers, and is prized for its heat-trapping and water-resistant properties. The long guard hairs of dogs, wolves, and wolverines were preferred as trim for hoods and mittens. The fur of arctic foxes was sometimes also used for trim, and was suitable for hunting caps and the insides of socks. In some areas, women's clothing was made of fox hides, and it was used to keep the breasts warm during breastfeeding. Adult musk-ox hide is too heavy to be used for most clothing, but it was used for mittens as well as summer caps, as the long hairs kept mosquitoes away. It was also suitable as bedding. In places where larger animals were scarce, such as Alaska and Greenland, the skins of small animals like marmots and Arctic ground squirrels were sewn together to make parkas. These animals were also used to make decorative pieces. The skin of cetaceans like beluga whales and narwhals was sometimes used for boot soles. Whale sinew, especially from the narwhal, was prized as thread for its length and strength. Tusks from