Florian Boyd has beautiful photos from his hikes around Southern California's inland deserts and mountains.
He's got a picture of native fan palms here, which are vital to many bird and mammal species. For instance, the Hooded Oriole, which nests in its fronds, takes shelter there for the insulation; the air within the dead fronds that hang down can be ten to fifteen degrees Fahrenheit lower than surrounding air. In deserts that have several 100+ days every year, that's a big help. Though their traditional range is the desert of far southern California (and thus, so is the range of that oriole), they've been planted extensively as landscaping trees. When I lived in Fremont, in the San Francisco Bay Area, our neighbors had a fan palm too tall to trim dead fronds from, and Hooded Orioles, far to the north of their historic habitat, set up a nest, and frequently raided our hummingbird feeders.
If you've got fan palms and have the option to let the dead fronds stay, please do -- Habitat's a precious thing.
(Don't miss the rosy boa.)