A further lesson in the biology, recovery of snowy plovers.

Byline: GUEST VIEWPOINT By David Lauten

I am writing in response to Patrick Roelle's Nov. 20 letter, "Plover math doesn't add up." I am the Oregon State University plover biologist who was quoted in the original news release. I have worked with the plovers since 1997.

While we did indeed find 236 nests in 2009, and each nest does require a male and a female plover, each individual plover has the ability to nest up to four times in a given year.

Therefore, 236 nests does not equate to 236 times two plovers.

It would be a rather remarkable biological feat for every nest to be successful - there is no population of any bird that suffers zero mortality of nests. Nests are prey items for numerous predators, eggs get eaten and nests are destroyed.

Thus plovers, typical of most birds, have the ability to renest multiple times within a single season.

Furthermore, it also would be a remarkable feat of any species to have 100 percent survival rates. Thus, just because 106 chicks survived to fledge (that is, survived to learn to fly at about 28 days old), not all 106 fledglings will survive over the winter and become breeding adults the next year.

In fact, on average, about 45 percent of the young birds return to Oregon to breed in the following year; thus, the average overwinter survival rate is about 45 percent. So we may predict that about 47 of those 106 plovers will survive over this winter.

Adult plovers also have a survival rate of less than 100 percent, as all species do. The survival rate for adults varies from year to year, and it is typically somewhere between 60 percent to 75 percent.

In 2009, there were approximately 150 to 175 breeding snowy plovers on the Oregon Coast, and those plovers had about 236 nests, or about 1.5 nests per adult - a fairly typical number. We can expect about 70 percent of those breeding plovers to return next year.

If someone has a good understanding of plover biology, one will see quickly that 236 nests does not equate to 472 adult plovers. Furthermore, adding 106 fledglings to this total of 472 adult plovers shows a total lack of understanding of population dynamics.

So we do not have 578 plovers on the Oregon Coast. We wish we did, but that number is just fanciful thinking.

The recovery goal for Recovery Unit 1 is 250 breeding plovers. If one has a good understanding of plover issues, one would know that Recovery Unit 1 is Oregon and Washington, and that the recovery goal is 200 breeding plovers for Oregon and 50 breeding plovers in Washington.

When intense plover monitoring began in the early 1990s, there were as few as 35 breeding plovers along the Oregon Coast. The number of breeding plovers is now 150 to 175 - only 25 to 50 plovers fewer than recovery goals.

Oregon has a lot to be proud of. Ours is one of the few recovery units that is very close to our recovery goals, and our management actions have been successful at increasing plover populations.

David Lauten of the Oregon Natural Heritage Information Center at Oregon State University is a plover biologist.