Alternate-plumage Black-bellied Plover. Photo Bob Boekelheide
Homage to Black-bellied Plovers
by Bob Boekelheide
March 2022
The “Big Three” shorebird species found in Dungeness Bay during winter are Black-bellied Plovers, Sanderlings, and Dunlins. Without fail, these three species comprise the highest shorebird numbers during our Sequim-Dungeness Christmas Bird Count (SDCBC). There are smatterings of other shorebird species in winter such as Black Turnstones and Killdeers, but nothing as reliable or as numerous as the Big Three.
Christmas Bird Count data for Black-bellied Plovers show that we usually average over 300 Black-bellied Plovers on a typical SDCBC (Fig. 1). In reality, their numbers range far and wide. For example, the count in 2010 had only 46 plovers, but a year later in 2011 the count was 707 plovers. Why so different? We hold our CBC in mid-December, when daytime tides unfortunately stay high all day long and usually no mudflats are visible. When there are no mudflats, plovers move inland to feed at pastures and harvested fields. We do our best to search the fields and pastures, but sometimes we just don’t find the plovers. Other times their flocks might get counted more than once as they fly back and forth during the day, which could explain the sky-high counts as well. It’s not a perfect world when counting birds.
During these counts, we often hear Black-bellied Plovers before we see them. BB Plovers have a lovely mournful flight call with three slurred notes descending and rising in a minor key, kind of a “Pee-oo-EE.” It is one of the most distinctive sounds of Dungeness Bay.
Between 2014 and 2018, OPAS volunteers also counted birds at Three Crabs as part of the Three Crabs Estuarine Restoration Project, coordinated by the North Olympic Salmon Coalition and WA Dept of Fish and Wildlife. During this study, OPAS volunteers observed birds at Three Crabs three times each month for five years, tallying all the shorebirds we could find on the mudflats and beaches.
Our data showed that Black-bellied Plover is the most ubiquitous of all shorebird species in Dungeness Bay, occurring year-round on 90 percent of our 151 surveys. Black-bellied Plovers ended up being present more than Dunlin, Sanderlings, and even locally-nesting Killdeer, which mostly migrate south in winter.
Black-bellied Plovers might be the heart and soul of Dungeness Bay’s winter shorebird flocks, but their highest numbers actually occur during spring and fall migration, also revealed by the Three Crabs Bird Study (Fig. 2). Peak spring migration occurs in April and peak fall migration occurs in August. Our highest count ever during the Three Crabs study occurred on 8/13/18, when we tallied 219 plovers. The average count was 75.2 plovers per survey for the entire five years.
What’s the big attraction for Black-bellied Plovers in Dungeness Bay? Food. One of Black-bellied Plovers’ favorite prey items is polychaete worms, which they hunt on the mudflats. It’s not uncommon to see a plover yank up a big polychaete, then get chased across the mudflats by a gull trying to steal the worm. With those big eyes, plovers also hunt the mudflats at night. Their hunting style is to walk a few steps, pause and look, walk a few more steps, then pause and look again, very different from the rapid pecking of sandpipers or the deep probing of dowitchers.
In winter, Black-bellied Plovers in Dungeness Bay do not have black bellies, a conundrum that often confuses beginning birders. Shouldn’t Black-bellied Plovers have black bellies? The “basic,” or non-breeding plumage of Black-bellied Plovers, along with the juvenal plumage, is plain brownish-gray, without a black belly (see photo).
Basic-plumage Black-bellied Plover. Photo: Bob Boekelheide
Many if not all of the Black-bellied Plovers that stay in Dungeness Bay in June and July do not have black bellies. These are pre-breeders, only one year old. Black-bellied Plovers do not breed until their second year, staying in their basic plumage through their first summer. Some one-year-olds migrate north, but many do not, staying here in Dungeness Bay.
After Black-bellied Plovers molt into their breeding plumage (aka “alternate plumage”), they are among the most spectacular birds on the mudflats (see photo). They start this molt during March, so now is the time to look for the start of black bellies on the Black-bellied Plovers. By April and May the breeding birds are striking in their blacks and whites, particularly adult males.
Alternate-plumage Black-bellied Plover. Photo Bob Boekelheide
Along with Sanderlings and Dunlin, Black-bellied Plovers are a cosmopolitan species known as a “Holarctic breeder.” This means that they nest all the way around the northern hemisphere, as far north as the northern limits of tundra. They nest from the North Slope of Alaska through northern Canada, then all across northern Russia. Their winter distribution is even more extensive – just about any suitable mudflat or bay in middle and tropical latitudes around the Americas, Europe, Africa, Asia, and Australia might have Black-bellied Plovers in winter. The British call them “Grey Plovers,” which might be consistent with their basic plumage, but hardly respectful of their flashy alternate plumage.
Like many shorebirds, Black-bellied plovers waste no time with their nesting duties. After migrating to the Arctic, the males quickly create nest scrapes, likely to attract females. Females arrive, pair with males within a week or two, then lay four beautifully-camouflaged eggs, colored like the lichens found in their nesting material.
The combined mass of the four eggs equals about 16 percent of the female’s body mass, a big energy investment for a bird that just migrated thousands of miles. Each egg develops over about a week inside the female, then the female lays the four eggs over about 36-hour intervals. Adults don’t start continuously incubating the eggs until the last egg is laid, so the chicks hatch fairly synchronously. Both sexes incubate -- some studies showed that males actually incubated more than females. The eggs start to hatch after an incubation period as short as 23-24 days.
The chicks all hatch within a day or two, then within another day they’re out of the nest walking around the tundra. The chicks find their own food, mostly insect larvae, while they’re guided and protected by their parents. The chicks grow very quickly, becoming independent from their parents within only three to four weeks. Then the adults take off, leaving the juveniles behind to fend for themselves.
Did I mention it all happens very quickly? If all goes as planned, adults might only spend a couple months at their nesting areas, before quickly migrating south once again to spend the winter at places like Dungeness Bay.
The next three months, March through May, are intense spring migration months. Shorebirds move north very quickly, spending just a few days at each rest-over spot to fuel up for the next leg of their journey. The best places to see migrating shorebirds in Dungeness Bay are at Three Crabs beach, Dungeness Landing County Park, or walking out Dungeness Spit. Plan your shorebird viewing around incoming and outgoing tides at 2 to 5 feet, when the tides are neither too high nor too low. The viewing can be spectacular if you hit the right tide, with flocks of feeding shorebirds spread out around you, one of the greatest spectacles of nature.
Many of the interesting facts about Black-bellied Plovers in this story came from Birds of the World, an on-line resource available through Cornell Lab of Ornithology. I highly recommend that all bird aficionados subscribe to Birds of the World, both for the information and to support the Lab of Ornithology.