Being from deep in the tropics, my wife grew up in the warm and typically humid world of the Yucatan, Mexico. In a country where the days are long and sunny and the seasons less well defined than our own here in coastal northern California, she thrives. So, when our long damp nights give themselves over to the progressively longer and sunnier days of spring, she blooms. Nothing in nature triggers her “spring blossom” and slams the cold door shut on winter better than the rich and liquid “bubbling, chortle-like” song from a male Tree Swallow!
Perched right outside our window, this sharply dressed chap sits with his mate in full view on a small wooden nest box and proclaims SPRING HAS ARRIVED! We placed their low-income housing there some five years ago. He announces his triumphant return with all of the exuberance of a thrilled friend returning from a most exciting trip to a far away land. This bird, crisply bi-colored in iridescent bottle-blue feathering above and immaculate cotton-white underparts will delight not only the inquisitive observer but more importantly the female Tree Swallow. He pours forth a song that only she can truly understand. However, I too feel that I have a pretty good idea of where this bird is “coming from”.
Physically, it could be coming from the Caribbean Panama where it may have spent the winter dipping and cavorting amongst the multitude of oceangoing vessels that wait their turn to “stair-step” up and over the locks, crossing the isthmus to the mighty Pacific. Perhaps it may have arrived from the mosquito laden, Flamingo rich wetlands that crown the north coast of the Yucatan peninsula where tens of thousands of these long distance migrants glean for us billions of winged hypodermic needles from the humid sky. Another possibility is that it may have wintered with small numbers of its fellow swallows in the vast wetlands of California’s great central valley, snapping up myriad winged morsels amongst the multitudes of Cranes, Geese and Swans.
Emotionally, it’s coming from a place of demand. To survive and to pass on its DNA, it demands much. An abundant source of food (exclusively flying insects), a proximity to water, a protected nesting site, a place to raise a family, the safety that comes in numbers, the fellow swallows with which it will hawk insects and most importantly, a mate, are all here.
Early in the spring, I have seen a newly returning Tree Swallow pair approaching the Bolinas Lagoon from the south. At the lofty altitude of perhaps a thousand feet, they vocalize and one can almost imagine the sheer excitement they must be feeling as their long, arduous and annual trip is at long last, ending. HOME AT LAST! Passing over Stinson Beach’s Sea Drift they voice their flight plan as they quickly swoop toward me from “migration altitude”. Without a moments hesitation, they drop rapidly over Kent Island calling wildly and smartly landing squarely on their humble abode. It’s as if this lichen encrusted box is not only the precious quest of their far flung journey but seemingly the first thing they had perched on since lifting off from a predawn rest stop somewhere in Sacramento, Los Banos or Monterey. They return year after year to the same nesting spot to raise three or four young.
In addition to the Tree Swallow, West Marin plays host to six other splendid species of swallows, five of which also nest here. Only the Bank Swallow graces our space as a rare migrant but does not breed here. In the western hemisphere they spend the winter as far south as northern Chile and central Argentina. Globally, the Bank Swallow, (known in the “Old World” as the Sand Martin) ranges widely. Small numbers of these small brown and white birds, sporting snappy blackish breast bands nest in communal sand or clay cliff banks in coastal San Mateo county.
California’s other “brown Swallow”, the Northern Rough-winged Swallow nests singularly or in small groups in appropriate habitat. That desired domain can be found on the Bolinas Beach at the end of Wharf Road in the clay cliffs that dominate the sand scape. To find the nests, look for the silver dollar sized holes that look as if they were carefully drilled directly into the vertical face. Snapping up insects not only in the sky but from as little as a few inches off the warm sand, one can hear, if listened for carefully, the actual snap of the birds mandibles as it gathers its nourishment. This species winters as far south as Panama.
Perhaps the most colorful and certainly the most diminutive species is that of the Violet-green Swallow. This is a truly western bird with a range that extends from the west coast, east to the eastern Rockies, north to central Alaska and as far south as Costa Rica. Violet-green’s share the same taste for “home design” as does the Tree Swallow and the Purple Martin. That is, they are a cavity nester, meaning that they raise their young inside, most typically, dead snags where old abandon Woodpecker nests can be used. Alder stumps, and tall fir snags make fine dwellings for this well tailored creature. The snowy white of the birds underparts wrap up and around the birds flanks and face making identification possible even at great distances. The crown is a soft moss green color contrasting with the rich “Robin Hood” green back. Separating the head from the back is a thin crisp necklace of violet that is repeated over the entire rump, making this one of the most exquisite looking birds anywhere!
The least numerous and most sought after species is a giant cloaked in a glossy robe of deep royal purple. Its name is therefor appropriate. The Purple Martin arrives in our area in May after having flown here from its winter haunts in South America where it occurs east of the Andes and south to northern Argentina. Typically, this avian gift draws ones attention by its remarkably loud, rich and liquid calls. This swallow is often encountered hawking larger flying insects over the warm and sunny sands at the tip of Sea Drift spit. Find yourself at the mouth of the Bolinas Lagoon and like natural clockwork, you can almost guarantee a summer time sighting of a Purple Martin. Listen for its strong “bubbling” call between 4:00 and 6:00 PM and look up!
Interestingly, it, (as well as all of the other species of swallows) are not above foraging for insects on foot. This is rather comical to watch as all swallows have very short legs and must run very fast to capture the insects that are at ground level. I have witnessed five species together engaging in this novel act. Martins nest in small colony’s in very lofty, inaccessible Douglas Fir snags high atop Inverness Ridge.
Perhaps the most familiar swallow species is that of the Barn Swallow. This truly cosmopolitan bird occurs over most of the earth including the Americas, Europe, Asia, Africa, Australia as well as most of the worlds oceanic islands. These long winged and powerful fliers winter from as far south as Tierra del Fuego at the southern-most tip of South America and have even been recorded from the Falkland Islands, Argentina! Best known for their deeply forked “swallow tail” the Barn Swallow make themselves at home, on and around our homes. They create an open “cup” nest, composed of mud and spare bits of grass and straw. Upon completion, they line the interior with a soft comforter of feathers harvested from the sky. In flight, swallows will snag, let go and repeatedly snag again and again, an airborne feather. One wonders whether they simply do it for the nest lining or if there is a playful component to this unique behavior.
Barn Swallows nest singularly and most typically upon a beam that is situated beneath an eve. This nesting habit has endeared them to the countless as it brings an intimate and wonderful nature experience up close and into our world. For others it actually becomes a bit of a nuisance. Some folk are annoyed by the fact that these birds “take over” a site that comes into conflict with their own “site”. With droppings splattered on the walls, the sometime startling activity and the rerouting that some feel obligated to make when the nest is adjacent to a frequently used door, can all add up to “too much to take”. Sadly and all too often, many will blast the nest with a garden hose to discourage this annoying behavior. This clash of cultures leads me to my next and final species.
By far the most abundant swallow that calls West Marin its summer home is the Cliff Swallow. Often referred to as the “Mud Swallow” by some aggrieved home owners, this communal species painstakingly creates the spherical mud dwellings that one often encounters under bridges, freeway over passes or most notoriously under the eves of houses. Each year after having undergone the arduous journey from as far south as northern Argentina and northern Chili, these 22 gram swallows arrive in our area by about the first of April and immediately go to work constructing their “Pueblo style adobe condos”. A great place to witness this firsthand is near the end of Wharf Road in Bolinas. Several of the homes that stand on tall pilings over the mudflat, have these nests both under their eves and or in the beams and struts below their floors. Currently there are about 120 pairs of these voracious insectivores busy as bees laying the yearly foundation for a bustling, yet temporary, community. Scooping up mouth fulls of mud from either the puddles at the side of the road or from the lagoons mud flats, they quickly fly back to their nests and lay down hundreds of mud “beads”. This creates the grapefruit sized orb that will house 3 to 4 chicks.
Some time ago, the local and well known naturalist and author, Jules Evens wrote an article regarding the impact that these swallows, (and all swallows for that matter) have on keeping our flying insect numbers in check. He pointed out a few facts that have “weighty” ramifications. Lets take a look at a few numbers. According to The Cornell Lab of Ornithology, Cliff Swallows weigh between 19 and 34 grams. The average weight is at about 22 grams, or as much as what 9 pennies weigh. A Cliff Swallow needs to consume a quarter of its weight per day to sustain itself or 5 1/2 grams of high protein flying insects. Therefor our Wharf Road colony of 120 pairs, (240 individuals) consume 1,320 grams or 2.91 pounds of insects each and every day. Once the Swallows arrive in early April, complete construction on their nests, lay eggs and then brood them around 60 days have elapsed. That means that by the end of May the Wharf Road colony has now consumed some 174.6 pounds of insects. Young start to hatch around June 1st and then fledge or leave the nest, and the care of their parents by around August 1st. The colony has now increased to 720 individuals and so has the consumption. So, our Wharf Road colony, in one breeding season consumes over 523 pounds of flying insects!
For those who turn the garden hose on these nests, (hence the title of this piece) PLEASE think twice about what you are doing. While these Swallows may splatter your walls and windows with droppings and construct “muddy, unsightly and dirty” nests, there are several things to lessen the mess. You can always wash the walls below them, clean the windows whenever you want and even get rid of the nests after they have successfully fledged their young by about the beginning of August. The mud comes off and they will rebuild next year. If you really can’t deal with the birds, certain folks have successfully kept them away by hanging a fine mesh net across the under surface of the eves. Consider an alternative. When it is summer evening weather and the BBQ is fired up, sizzling with skewers of veggies, and the smell of roasted chicken with rosemary wafts across the neighborhood, wouldn’t you rather be relaxing and laughing with friends instead of swatting hungry mosquito’s? I mean really! Who wants to be spilling Cabernet on their cool new Hawaii shirt while running back and forth between the safety of your kitchen and the “hostile wilds?” On one hand you have carefree warm summer nights, on the other you are a human pin cushion being sucked dry by 523 pounds of blood thirsty insects. To me, the choice is clear.
Keith Hansen, May 2009