The warm, hazy days of mid-July to August invariably turn my mind to shorebirds, for this is the start of their southward migration.

Reports of several species have been sent in to the Maine Audubon Bird Alert since early July. Dunlins, short-billed dowitchers, black-bellied plovers, whimbrels, lesser yellowlegs, least and semipalmated sandpipers -these and others – have been spotted as they move through the state on their southbound route.

Because Maine is only a stopover for most of these birds, there is but a small window of opportunity to see them before they are gone. However, there are a few species of shorebirds that nest in Maine, providing many chances to see and appreciate them. Two of these birds are least terns and piping plovers.

Historically, there were sizeable populations of these two birds that nested along Maine’s coastline. But that was before the skins and feathers of these birds became fashionable for ladies’ wear in the early 20th century. As if this assault weren’t enough, increasing habitat loss and human intrusion over the years combined to drive the birds’ numbers to dangerously low levels-low enough to place them on the Maine Endangered Species list and the national Threatened Species list.

Maine Audubon’s first survey of least terns, in 1977, found 50-60 pairs in the state. A 1981 survey found only 10 pairs of piping plovers.

Something had to be done.

That something, for piping plovers, included protecting their nests on crowded sandy beaches. Maine Audubon biologists devised special structures called “exclosures” to surround the nest, allowing the birds to come and go as they please, while keeping just about everything else out.

This included humans, for biologists found that nests were destroyed inadvertently many times by beachgoers. This is because these birds are small and light-colored, and so blend into the sand perfectly. Even experienced bird watchers have failed to detect them at short range. In addition, their nests are nothing more than a scrape in the sand, perhaps lined with bits of shell.

Construction of the exclosures, intense monitoring, public outreach and education, and cooperation of landowners have allowed the plovers to slowly increase. In the period between 1996-2000, Audubon found approximately 60 pairs of these birds nesting on 19 beaches throughout the state.

Improving conditions for the terns was trickier, but a measure of success was eventually realized. The larger colonial nesting habitats of the terns were fenced off to keep people at bay, and biologists patrolled them nightly to deter predators such as foxes and skunks.

Thanks to efforts like these, we and future generations will be able to appreciate these birds for many years to come.

A postscript to last week’s column on loons: Since 1988, 178 dead loons have been turned in to Audubon, according to Ali Chaney, an Audubon biologist. The highest cause of mortality was lead poisoning. The second highest was blunt trauma caused by collisions with boats and other watercraft.

Chris Corio, a volunteer at Fields Pond Nature Center in Holden, can be reached at fieldspond@juno.com