Natural History Journal

As a group, mammals are surprisingly diverse.  While all mammals breathe air, have fur or hair, and give birth to live young, they vary significantly in their habitats and modes of transportation.  While most walk or hop while moving about on land, some fly and others swim, some spending most or all of their lives in water!  While some of these aquatic mammals spend a good deal of time on land at the water's edge, like seals and sea lions, other mammals, such as whales and dolphins, never leave the marine environment they were exquisitely designed to inhabit. With 840 miles of coastline (ranking third in the nation behind Alaska and Florida), it is perhaps not surprising that marine mammals make up a significant portion of California's wildlife. Let's explore the variety of mammals that may be seen along California's beautiful coast and within its offshore waters. Sea Otter, Elkhorn Slough Sea Otters, the most aquatic members of the weasel family, only rarely come asho...

Mammals are among the most exciting types of wildlife to see, but also some of the most difficult.  Far less numerous than birds and often exhibiting secretive or nocturnal habits, many groups of mammals are rarely encountered in the wild.  Observant naturalists are far more likely to encounter signs of a mammal's presence than the mammal itself, the most obvious of which are tracks, scat and fur.  But more subtle clues may be discovered as well, such as dens, nests, burrows or bedding areas, as well as evidence of feeding, like chewed bark, twigs or pinecones.  All of these are forms of mammal "sign" and are good indicators that the mammal which left the sign is or has recently been present in the area.   I like to think of mammal signs as similar to bird songs and calls : proof of a species' presence in the area, and valuable for research purposes, even when I'm unable to get a look at the animal itself! Sure, seeing the animals is always more exciting, ...

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...