Bahia Lomas, Tierra del Fuego is home to the single largest population of wintering red knots. Along a 30-40 mile stretch of coastline, there once were more than 50,000 knots.
This tally came from the ground-breaking surveys of Guy Morrison and Ken Ross who put most of South America’s shorebird hotspots on the map when they surveyed the continent’s coastline in small planes during the 1980s.
Now the population of knots at Bahia Lomas is somewhere between 10 and 12 thousand.
Flyway-wide, the population experienced a crash following the overharvest of horseshoe crabs in the Delaware Bay in the late 1990s.
Despite the 75% decline, these diminished flocks are still an impressive sight to see.
Joining the knots are tens of thousands of Hudsonian godwit and white-rumped sandpiper.
At high tide the birds feed in flocks at the water’s edge along a narrow remainder of tidal flats.
They frequently erupt into the sky as a whole, murmurating with the best of them.
They resettle again shortly, perhaps a bit further down the tide line when the threat, or shadow of one (say, a peregrine), has passed.
As the tide begins to fall the birds spread themselves out to feed more earnestly. Now they seem more relaxed, or at least more focused on a task. All of them with their bodies angled forward, head down, bills knitting the sediment, searching for prey.
The knots specialize on bivalves in general and at Bahia Lomas on one in particular — Darina solenoides — A thin-shelled clam with the incredible ability to scud itself around shallow water when necessary and to spryly dive out of sight into the sand when under threat.
The godwits feed on polychaete worms while the white-rumped sandpiper seems to have a more diverse palate. They feed not only on tidal flats, but also in the salt marsh that fringes the bay. The marsh is composed entirely of salt wort (Sarcocornia).
As the birds feed, the tide recedes. The exposed mud and sand at low tide can extend up to 4.5 miles from shoreline to waters edge.
These incomparably vast feeding areas appear to be the primary distinguishing feature of this place, a result of a nine-meter tidal range that sucks the bay dry at low tide.
Another characteristic feature is wind. Tierra del Fuego might be one of the windiest places on earth.
“I think of them as birds of wind” wrote Peter Matthiessen, in his book devoted to shorebirds titled The Wind Birds.
“The restlessness of shorebirds, their kinship with the distance and swift seasons, the wistful signal of their voices along the coastlines of the world make them, for me, the most affecting of wild creatures”
–Peter Matthiessen
For me, wind does not seem to be a particular attraction to the birds, rather it seems irrelevant to them.
They appear at ease no matter the wind speed….unlike those of us tasked with roving the flats to survey the birds.
It’s what’s under the bird’s feet that matters – the flats.
The tidal flats are composed of sand in places, while mud dominates in others. The muddy areas are cleft with uncrossable crevasses of branching tidal channels.
In other regions of the bay, the coast is a bit rockier and the flats are composed of a mosaic of dense mussel beds (another food of red knots), rock, mud and sand.
In January 2018, our team from Canada and the United States joined Chilean colleagues at Bahia Lomas for a project that will create critical habitat maps for several species of migratory and resident shorebirds that depend on the bay.
Top row: Ross Wood, Stu Mackenzie (Bird Studies Canada), Carmen Espoz (Universidad Santo Tomás), Larry Niles, Joe Smith (Conserve Wildlife Foundation of NJ), Yann Rochepault, Christophe Buiden
Bottom row: Antonio Larrera, Rick Lathrop (Rutgers University), Stephanie Feigan (Conserve Wildlife Foundation of NJ), Amanda Dey.
The project is part of a broader effort by our team to develop habitat maps for key stopover and wintering sites for shorebirds throughout the Western Hemisphere.
There was a time when the most critical information gap was simply knowing where shorebirds were at different parts of their annual cycle. Thanks to the work of many people, at this stage, we know where the birds are.
The next step is understanding why a particular site is important by examining the factors that determine the distribution of feeding and roosting shorebirds within the site.
This more granular knowledge improves our ability to manage important shorebird areas by identifying where critical habitats may be threatened by existing and emerging threats.
Our collaborator, Carmen Espoz from the Centro Bahia Lomas and the Universidad Santo Tomás has extensive data sets on sediment composition and invertebrate distribution that will be linked with satellite imagery and shorebirds surveys. Bringing it all together will allow us to ultimately create species-specific habitat maps for shorebirds and their prey.
It is still a marvel that, of all the potential places across North and South America that these birds could have selected as a homeland, red knots have chosen this single bay at the end of the earth.
Mile-for-mile Bahia Lomas is still the biggest red knot population in the world. 10,000 knots roving a 30 mile coastline for 6 months of the year.
The wintering red knot population in Brazil is now larger, at about 15,000 birds, but they spread themselves thinly across a much larger coastline that spans 500 miles.
This means that Bahia Lomas is the last place of spectacle, where you can see 8,000 Wind Birds wheeling in a single flock.
The conservation efforts of many people throughout the flyway are to ensure that this waning spectacle endures.
Thousands of miles away, decades of research still point to Delaware Bay as a life-cycle lynch pin for this population.
A bird that is unable to achieve adequate fat reserves during spring stopover in the Delaware Bay due to a scanty supply of horseshoe crab eggs is less likely to nest and furthermore less likely to survive than a bird that makes proper weight.
The best way to ensure that the red knot population at Bahia Lomas recovers is to first recover the population of horseshoe crabs in the Delaware Bay.
And yet, continued conservation and stewardship at Bahia Lomas is also necessary to ensure that this unique place continues to be hospitable for shorebirds.
Learn more about the work being done at the Bahia Lomas Center:
