|6/26/2013 11:26:00 AM|
Life on the Beach -
by Don ReimerFledgling birds are appearing in lots of places. Baby woodpeckers, titmice and sparrows now join their parents at my feeders. Juvenile Chickadees and American Robins are close to gaining their independence. By June 18, the occupants of the Ovenbird nest I wrote about earlier in the month had vacated their temporary dwelling place to seek a summer livelihood in the woods.
But what about those birds that nest on the ground in open spaces such as beaches and shorefronts? I am thinking species-ifically of the endangered Piping Plover. What natural adaptations do they employ to maximize breeding success and boost their chances for survival in increasingly crowded and contested beach environments?
Let's start with the plover's cryptic gray coloration that matches the general color palette of dry beach sand. Dark markings on the head and neck add to their overall subterfuge. While standing motionless along the beach line, adult plovers are hard to detect.
That briefly explains the adult plover's situation. Exposed to hazards and predation, hatchlings face other challenges. All shorebird chicks are precocial. They are cloaked in downy feathers, are entirely mobile and able to forage for themselves shortly after hatching. Strong legs enable the flightless chicks to scurry away from approaching danger.
If you have observed newly hatched domestic chickens, you have witnessed this same phenomenon. Much like chicken eggs, shorebird eggs are relatively large for the size of the small bird. Both sexes share the incubation duties for about 27-28 days. This extended incubation period provides ample time for the chicks to develop and mature inside the egg. After hatching, the parents brood the young plovers at night for about two weeks to compensate for their low body metabolism.
Ground-nesting species do not build extensive, high-profile nest structures. Why advertise your presence? For the Piping Plover, a simple scrape in the sand that is lined with shell fragments, pebbles and locally available materials such as mosses and lichen makes a suitable nest. Random strips of dried seaweed and sticks help to further disguise the site.
Look closely at the beach photos taken at Reid State Park on June 10, one of a handful of Maine sites where Piping Plovers still nest. Several acres of the upper beach were roped and posted to inform visitors of the endangered plovers' presence. As I moved a bit closer, one of the adult plovers skittered to a higher zone of sand and whistled a warning message to its three chicks. I detected movements across the sand as the fuzzy chicks scrambled toward the sheltering adult.
Nuzzling their way beneath the parent's skirt of belly feathers, the orange legs of the chicks still protruded. This helps to explain why shorebirds limit their clutch sizes to 3 to 4 eggs - due to their small body size, the parents could never incubate or brood more than four chicks at a time.
One bold little chick emerged, staring into its parent's face. After a period of five minutes, the adult bird stood and proceeded toward a patch of beach grass. With a two-noted whistle, she summoned her wards and they collectively left my sight. Good luck to all of them. They will need it.
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