Bad crown days

With so many other birds in their breeding finery, who could blame the Gambel's White-crowned Sparrows for feeling a little self-conscious? Their crowns are full of pinfeathers now, but those skunk-skin caps should be sleek and gorgeous again by the time they reach their nesting grounds in the Great White North. —SW

Off duty

A Mexican Spotted Owl snoozes in an oak in Scheelite Canyon. —SW

Golden spurs

The Golden Columbines (Aquilegia chrysantha) are just beginning to bloom in upper Miller Canyon, but this beauty was blooming in mid-March among palms and organ pipe cacti in a canyon on Rancho Los Baños, about 60 miles south of Douglas in northeastern Sonora. —SW

Caterpillars on the march

Southwestern tent caterpillars (Malacosoma incurvum) are maturing and dropping out of the trees along the San Pedro River, providing a boon for northbound migrants. As Tom likes to say, these fuzzy eating machines are nature's way of turning cottonwood leaves into warblers. As unpleasant as it can be to have creepy crawlers and their poop raining down on you on a bird walk, it's peculiarly satisfying to watch a tiny Wilson's Warbler slamming a python-sized caterpillar against the ground to subdue and tenderize it before squishing out the good parts like toothpaste from a fur-covered tube.

Not everyone is as appreciative of southwestern tent caterpillars as we and the migrating birds are, though. When they emerge in spring and start stripping the cottonwoods and willows of their tender new leaves, some people freak out. We've gotten panicked calls asking why someone isn't doing something to halt the destruction before the caterpillars kill the trees. Well, the trees are in danger, but it's not from the caterpillars. The defoliation happens every spring, and healthy trees can recover quickly once the cats stop eating and go into the pupal stage. Stressed trees whose water supply is being sapped away may not be able to recover, though, and the annual caterpillar invasion may push more and more trees beyond the point of no return as more and more residential wells drain the aquifers that feed the San Pedro River. —SW

An Earth Day treat

The week of Earth Day is a great time to be birding in southeastern Arizona, but White-eared Hummingbird isn't on the list of anticipated delights. On Earth Day, this studly male was putting on a show for visitors to Beatty's Guest Ranch in Miller Canyon. He's about three weeks early, but based on his use of the same perches this is the same male that I videoed last summer.

Though you can't see the brilliant green and violet from this angle, it's currently his most flattering angle. From the front he's got a pinfeather sticking out of his crown like a tiny unicorn's horn—a bit goofy looking. —SW

Ballroom dancers of the mudflats

American Avocets at Whitewater Draw Wildlife Area on March 13, before the playa lake dried completely. Migrating pairs renew their bonds with an elaborate courtship ritual, the grand finale of which is a graceful side-by-side pirouette with the male's bill laid gently across the female's neck and his wing across her back. —SW