When I was a youngster, my grandfather would periodically tell me that, “children are to be seen but not heard.” Unfortunately for my grandfather, the concept never took root, and being heard was practiced with gusto. Similarly, shorebirds are all about being heard on the tundra, but only seen on their terms. Many species prefer a strategy of short-term exposure, just enough to make themselves known to competitors for territory, but not enough to draw the attention of would-be predators. While we have been out on the Yukon Delta National Wildlife Refuge, we have heard shorebirds singing from high and low while we survey for them in this vast land.
A male Rock Sandpiper in full ground display on lichen tundra. Yukon National Wildlife Refuge.
For most of the birds, there is a fine line between the need to advertise their locations to secure a territory and the potential for showing too much of themselves. Shorebirds use a variety of tactics to advertise robustly, then quickly vanish into their surroundings. They use superb colors and patterns of their plumage to meld with the tundra vegetation, but can also alter their calls and songs for the appropriate situations: subtle low calls for cautious moments or full-on raucous song when needed. Rock Sandpipers are a good example of this “be heard, but only seen when needed” approach. The species prefers to nest in lichen dominated tundra and their plumage has all of the colors and smudgy patterns of a mixed lichen landscape, allowing for intensely effective camouflage. When the advertising is needed and the airways are clear of predators, the show is on for male Rock Sandpipers bent on maintaining territorial boundaries. The stocky little sandpipers stand high, sing from the gut, and really let the world know who is boss of lichen-land by raising a wing so the bright white feathers can be seen for…well, hundreds of yards anyway. These impressive shows help ensure that the eggs being laid by a mate only have one father.
A male Rock Sandpiper singing from the air. With no trees, tundra-nesting shorebirds need to use flight displays to advertise their presence.
Lichen tundra is the preferred nesting habitat for Rock Sandpipers. Other shorebirds do well here too, including Whimbrel, Western Sandpiper, and Pacific Golden Plover.
For the wider audience, aerial displays are needed and Rock Sandpipers get airborne, patrolling the space above their nesting areas with short rapid wingbeats, rolling out their song, using the wind to help them stay aloft. The display goes on for many minutes, and when done, the birds drop rapidly to the ground and nearly vanish back into the patterned tundra.
A Whimbrel on lichen tundra on the outskirts of Bethel, Alaska. These birds can emit low flute-like calls that float out on the tundra without giving the bird’s location away. In essence, a pair can hide in plain sight while communicating with this shorebird form of ventriloquism.
As we have travelled across the Yukon Delta rapidly surveying plots of tundra, one side assignment has been to help define the distribution of Short-billed Dowitchers and to determine if any of the multitudes of Long-billed Dowitchers might be nesting on the refuge. The Pacific subspecies of the Short-billed Dowitcher (Limnodromus griseus caurinus) looks very similar to its Long-billed cousin. Without a very close encounter or good photographs to study, confusing the two is very easy to do. Luckily for us, the calls and songs of the two species are distinct, and we have relied on voice to help understand their distribution across the refuge. The Long-billed Dowitchers have been encountered along the coast, while the breeding Short-billed have been found at more inland areas of the refuge.
We found the Long-billed Dowitchers in good numbers along the coast, sometimes in flocks of more than one hundred, most likely migrating to points north like the Arctic National Wildlife Refuge.
Subtle plumage differences between long and short-billed include the angle of the black line extending from the bill to the eye, the extent of white on the belly, the orange vs salmon hues of the breast, the shape of the pattern on wing coverts, and exceptional bill length for female Long-billed Dowitchers. These differences can all help lead to visual identification of the birds.
This Short-billed Dowitcher uses its superb camouflage to hide, but calls to alert all in hearing range that “this turf is taken.” We found the Short-billed variety mostly in pairs, exhibiting high flying flight displays on interior plots well away from the coast.
Another strategy we have seen practiced by shorebirds to protect nests and eggs from the eyes of predators, is to be outwardly visible and overtly aggressive to any would-be egg eaters. One species, the Black Turnstone, has impressed us at being bold and brash in defense of nest and territory. Anything but subtle, the male’s deep black plumage can be seen from a long way off, belying the take-no-prisoners attitude of these tough little birds.
A male Black Turnstone near his nest on high alert for any gull or jaeger who might enter the no-fly zone wrapped like an invisible halo around its nest.
A Black Turnstone nest shaped from coastal grasses of the Yukon Delta.
When a predatory bird crosses the line of tolerance established by a pair, the male Black Turnstone begins a staccato, rapid-fire call that sounds a bit like a miniature machinegun. The small compact bird then launches into the air, continuing the call while zeroing in on the threat. The uniquely wedge-shaped bill that has been flipping stones all winter is now a honed lance, perfect for jabbing into the soft parts of passing gulls.
A Glaucous Gull, one of the larger gulls in the world, is looking back in fear and taking evasive action as a Black Turnstone rockets in to make a point.
And ouch! The Black Turnstone makes contact. His eggs will be safe from this gull.
So as we wrap up our brief but productive time here in southwestern Alaska, we are grateful to have experienced the wide variety of calls and magnificent displays of the shorebirds we have been studying. Our three rapid assessment crews have surveyed more than three hundred locations in the last two weeks. The data we have generated have, in part, been attributed to the songs and calls that the shorebirds have been making, allowing us to understand how many of each species are out there and what sorts of habitats they need for nesting. This biologist will do all that he can to make sure that the amazing stories of these birds will be seen and also heard, so that more people can appreciate them and help protect and manage the habitats the birds depend upon throughout migration.
Middle and South Delta shorebird crews.