Our Beach Isn't Just for Frisbees!

Here's today's bird of the day:

Piping Plover (Charadrius melodius),
Waukegan Beach, Lake Co, IL 5/3/2014

This beauty is a Piping Plover (Charadrius melodius). They are rare annual migrants through the Chicago area, almost always on beaches along Lake Michigan, on their way either north to Lake Superior or northwest to the Missouri River. There is also a breeding population along the northern Atlantic coast of the US. This particular guy is probably from the Missouri River population, since he's not wearing any leg bands.

They prefer to nest in the sandy upper stretches of beaches, as well as on riverine sandbanks. Needless to say, nesting on beaches tends to bring them into conflict with people. Burger showed that human disturbance impacts where the birds tend to forage and how much time they spend watching out for predators. (1) (While we don't like to think of ourselves that way, any 2 oz. bird has to consider us to be potential predators.) As a result, Piping Plovers are listed as Endangered in Canada, and the US considers the Great Lakes population to be endangered as well, with the Missouri River and Atlantic populations considered threatened. (2)

While conflict with humans and the resulting habitat loss probably account for much of the original decline in Piping Plovers, these days nest predation appears to be an important factor in their continued decline. (3) This seems odd on the face of it -- why would predators play such a part now, when they've been around for as long as the plovers have been nesting?

That question brings us to the mesopredator release hypothesis, where the loss of top predators is said to allow a population increase of smaller carnivores. In the US, that would include skunks (Mephites sp.), Raccoons (Procyon lotor), and Virginia Opossums (Didelphis virginiana), all of which feed on bird's eggs when they can. This hypothesis has a good deal of experimental support, although the process appears to be controlled by more factors than first thought. (4,5,6,7) In the case of Piping Plovers, it might explain why erecting predator exclosures over Plover nests has actually allowed the birds to nest much more successfully (3) and led to increases in all three populations. The Great Lakes population in particular has increased from 39 birds in 1991 (8) to 126 breeding birds in 2008. (2) In 2009, a pair even attempted to nest in Illinois, not far from where I photographed this one. Those birds either abandoned their nest or were predated, but the eggs were taken to Michigan and hatched in an incubator. At least one of those birds has returned to breed in Michigan.

I love watching these little guys, and it's great knowing that they're coming back, so we should be seeing more of them in the future.

(1) Burger, J. (1994). The effect of human disturbance on foraging behavior and habitat use in piping plover (Charadrius melodus). Estuaries, 17(3), 695-701.

(2) http://www.fws.gov/midwest/endangered/pipingplover/index.html

(3) Rimmer, D. W., & Deblinger, R. D. (1990). Use of Predator Exclosures to Protect Piping Plover Nests (Utilización de cercados para proteger nidos de Charadrius melodus). Journal of Field Ornithology, 217-223.

(4) Schmidt, K. A. (2003). Nest predation and population declines in Illinois songbirds: a case for mesopredator effects. Conservation Biology, 17(4), 1141-1150.

(5) Elmhagen, B., & Rushton, S. P. (2007). Trophic control of mesopredators in terrestrial ecosystems: top‐down or bottom‐up?. Ecology Letters, 10(3), 197-206.

(6) Ritchie, E. G., & Johnson, C. N. (2009). Predator interactions, mesopredator release and biodiversity conservation. Ecology letters, 12(9), 982-998.

(7) Johnson, C. N., & VanDerWal, J. (2009). Evidence that dingoes limit abundance of a mesopredator in eastern Australian forests. Journal of Applied Ecology,46(3), 641-646.

(8) Haig, S. M., & Plissner, J. H. (1993). Distribution and abundance of Piping Plovers: results and implications of the 1991 international census. Condor, 145-156.