By Alex Harper
Billions of birds in their wintering grounds in South and Central America, Mexico, or the Sonoran Desert are fattening up and biding their energy. In sync with the seasons are waterfowl, shorebirds, raptors, hummingbirds, songbirds and more. Like the plants and insects, these birds register the increasing sunlight and cascades of hormonal changes prepare them for a seasonal movement that we call migration. Many of them will pass through Nevada in the coming months to take advantage of landscapes suitable for breeding and raising young.
On March 1, Southern Nevada receives about eleven hours and twenty-six minutes of direct daylight. This is about an hour more of total daylight compared to that on February 1, and about an hour and forty minutes more than on January 1. On the last day of March, we receive about twelve and a half hours of daylight. The increased daylight in the northern hemisphere brings increased warmth. The additional light and heat give plants additional energy to photosynthesize and kickstarts the processes of putting out new leaves and flowers. Insect activity follows and ramps up. Insects begin pollinating or laying eggs, and insect-eating birds arrive from warmer climates to take advantage. Plants, insects, birds and the rest of the living world operate within the same systems of light and temperature.
March offers a preview for what’s in store for April and May. Although March may have days that feel like spring, there are days that potentially can be reclaimed by winter. For many songbirds, it may be too energetically taxing to risk flying northwards into our region. It could even be fatal if an intense cold snap occurred. A few land birds manage to successfully navigate the temperamental month of March, seemingly adapted to cope with the unpredictability.
Some birds do begin to move into the lower valleys of Southern Nevada as March progresses. Short-distance migrants like Yellow-headed Blackbirds and cowbirds, which are sometimes coming from marshes and agricultural areas of Southern Arizona or northern Mexico, are some of the first to arrive. You may find or hear these birds at familiar parks, especially any with stands of wetland vegetation or large lawns.
Other birds on their way through Nevada in March are swallows. These strong flyers are diurnal migrants; unlike songbirds, they have the advantage of being able to hunt as they migrate. Swallows are specialists at catching flying insects on the wing. Tree, Violet-green, Barn, Northern Rough-winged and Cliff Swallows may be seen cruising low and purposefully northward through open desert or stopping to feed and drink anywhere with surface water. Some of the Northern Rough-winged and Cliff Swallows may end their spring journey in Las Vegas or Henderson, as some create nests under bridges at locations like Arroyo-Grande Park or Pittman Wash.
Along the Colorado River or Clark County Wetlands Park, the Lucy’s Warbler begins to trickle in. These small, gray warblers seek out stands of mesquite tress, joining the assemblage of overwintering Yellow-rumped and Orange-crowned Warblers. The Lucy’s Warbler winters as close by as the Mexican state of Sinaloa. This means that the distance that they needed to traverse to get to Southern Nevada is far less than that of comparatively sized warblers wintering deeper into Mexico, and helps explain why we see these warblers arrive well before the others.
Other birds are departing our region. The wintering duck numbers begin to thin out at the popular birding sites in the region. Geese and ducks are well-adapted to finding food in winter but are often driven by accessible waterbodies for roosting or foraging. With lakes and ponds thawing out to the north, they will largely begin departing the region for the wetlands of the Great Basin and prairies of the west, the taiga belt of Canada or Alaska, or even the tundra of the Arctic.
Close to your home, you may be observing flurries of breeding behavior from resident doves, hummingbirds and songbirds. The birds that live their entire life cycles in the same region breed well before some birds have begun migratory journeys that can be hundreds or thousands of miles in duration. These residents are our Anna’s Hummingbirds, Verdins and Northern Mockingbirds. It’s possible that by late March you may see fledged hummingbirds or some songbirds sitting on eggs.
Like every year, month or week, no day is the same when observing birds. Each species has its own unique life history. As you get outside in March, you’ll be able to observe behavior changes amongst species and individuals. Tune in to these subtle changes and watch for the trickle of incoming spring migrants. And come April the dam breaks and the flycatchers, vireos, warblers, orioles, and tanagers begin to pour in.