During its nesting season, the marbled murrelet, known affectionately among bird watchers as a “strange, mysterious little seabird,” lays a single egg in the thick mosses that grow on the branches of British Columbia’s old-growth forest canopy. With some of those forests under threat from logging, the small black-and-brown mottled seabird is considered threatened, too. The marbled murrelet is among a growing number of migratory species animals facing a perilous future, a new UN report found. …A report by a United Nations conservation group released Monday on the state of the world’s migratory species found the threats to these animals, ranging from fish to birds to butterflies, are greater than ever. …Along with habitat loss, other human-caused impacts such as over-exploitation, pollution and climate change are making it harder for migratory species to survive, the report found.