Natural History Journal

Tree Swallows are, in my opinion, one of our most beautiful birds, with their pure white undersides and iridescent blue heads and backs.  As aerial insectivores that feed almost exclusively on flying insects, Tree Swallows are a great boon to have in the neighborhood.  Unfortunately, like many other aerial insectivores, their numbers are in decline .  As secondary cavity nesters, Tree Swallows' struggle for survival is exacerbated not only by a decline in the insects they feed on, but a lack of the natural cavities they require for nesting as well.  Secondary cavity nesters rely on nest cavities excavated by other species (usually woodpeckers), often in standing dead trees.  The widespread practice of removing such trees in recent decades has led to a sharp decline in available nesting sites.  And Tree Swallows aren't the only species that depend on these increasingly rare nesting sites.  Western Bluebirds, Ash-throated Flycatchers, House Wrens, White-...

In a state known for its incredible biodiversity , one county stands above the rest in terms of sheer number of species: San Diego County.  Tucked in the southwestern corner of California and bordered by two extremes - the Pacific Ocean to the west and the Colorado Desert to the east - San Diego county encompasses a wide range of habitats.  And within those diverse habitats live more species of wildlife than any other single county in the country.   On an early spring visit to San Diego county, we tallied up nearly 150 species of birds over the course of a couple of days as we made our way from quintessentially Californian chaparral-covered hills and sandy beaches, to arid desert scrubland and even out onto the open ocean. Yellow-crowned Night Heron As we wandered through salt marsh habitat at the Tijuana Slough National Wildlife Refuge, we were surprised by the abundance and prominence of Yellow-crowned Night Herons at this location.  These close relatives of o...

The other day, while exploring one of the remaining patches of wetlands around my county, I came across a furry little critter that was a complete surprise for me: an American Mink!  Contentedly going about his (or her) business at the edge of the wetland, staying under the dense cover of an old clump of willows, the mink slipped out of sight before I was able to get a photograph.  But this mink sighting got me thinking about other mammals I've encountered here in California's Central Valley, and as it turns out... there have been quite a few!   California Ground Squirrel: A common sight in the Valley, and an important part of the ecosystem! Though the Central Valley is no longer the land of wild abundance it once was (at least not in terms of wildlife), more species of mammals than one might imagine still manage to make their living on the fringes of urban and agricultural land up and down the valley.  National Wildlife Refuges provide much-needed havens for a ...