Reno -- On the windswept desert of northern Nevada, spring in one tiny town has been welcomed for years with a festival to a celebrated group of visitors - migrating loons. Perilously clumsy on land but graceful and sleek in water, the large birds with a haunting call used to descend on Walker Lake by the hundreds to gorge on a fishy feast of small tui chub before continuing their journey to who knows where. Not this year, and the reason is Walker Lake itself. Its water quality and levels have declined and along with them the rich bounty of...