The group does not follow a leader nor does each individual bird tract the location of all others. The impulsive movement of but a few individuals, reverberates through the flock and thousands of birds react instantaneously as a single entity. Scientists have unraveled part of the story but much still lies shrouded in mystery.
Great Salt Lake is a staging area where a large portion of the world’s population of Wilson’s Phalaropes forage on insects storing energy reserves as they migrate to their wintering grounds. Every year hundreds of thousands of Wilson’s Phalaropes scatter widely across western Canada and northern United States to nest. In a rare role reversal, the larger brighter rusty, white and black female lays the eggs, then splits leaving the less colorful male behind to incubate and then brood the chicks. Often, off she flies to attract another mate and initiate a second clutch. A few of these nine-inch in length phalaropes will nest in the grass/sedge wetlands of Great Salt Lake.
After nesting, about one third of the world’s population of Wilson’s Phalaropes funnel to Great Salt Lake like grains in a giant hourglass. Fall migration on Great Salt Lake is a drama as millions of shorebirds make passage through on their annual route south to wintering grounds. Wilson’s Phalaropes are in the vanguard of this massive hemispheric movement with females arriving in mid-June, followed a couple weeks later by the males and lastly the juveniles. Here they feast and fatten often doubling their weight primarily on the abundance of brine flies, midges, and other invertebrates.
Phalaropes famously spin in circles while jabbing at food vortexed to the surface by the rapid paddling of their flange-toed feet. But they are equally adept at foraging in shallow water and Wilson’s is the only phalaropes that regularly forage on bare mudflats. Movement is animated with constant walking often with jerky motion while scanning for prey. Each individual invertebrate is very small and many must be caught and consumed as energetically efficient as possible. Capture usually takes only quick jab but sometimes requires a rapid shaking of the head and bill to dislodge.
They rise in large groups from the lake so obese they can scarcely fly and with a perpetual flapping of their wings, hour after hour after hour cross over the equator flying 5000 miles in 54 hours to reach their destination. This epic non-stop journey usually ends somewhere in Argentina, Bolivia, Peru, or Chile at scattered inland saline lakes. As the phalarope ends its long journey, flight elevation decreases as they glide down from the sky and with a final rapid fluttering of the wings settles onto the water’s surface weighting 40% less than when they started. The pathway of the adults is thought to follow a Grand Circle looping southward over the Pacific Ocean in fall and overland northward in spring. The young follow a more land based route with more frequent stops.
Here they will remain, south of the equator until the hand of spring turns the hour glass over and they head north once again.