For eight nesting seasons I have spied on Prothonotary Warbler (PROW) families in nest tubes, nestboxes, and PVC nest jars at four different locations in Delaware County, Ohio. For the last five seasons, all my efforts to help these “yellow swamp warblers” have taken place at the most northern portion of Alum Creek Lake south of Kilbourne. Three divisions of the Ohio Department of Resources patrol the area and the U.S. Army Corps of Engineers manages the water level at their dam nine miles to the south.
Along the northern and western lake shores visible from Hogback Road, 41 water and gas pipes have been salvaged to stand five feet above the lake bottom all year long, and from mid-April through August, the pipes support five feet long tubular sleeves made of 1-1/4-inch PVC conduit, and the sleeves slide over the pipes and are held in place by stainless steel hose clamps. The sleeves support nest chambers above known flood levels to welcome four avian species. Most of my 41 nest structures are arranged in pairs with at least five yards between them. One nest chamber of each pair has a 1-1/8 inch wide entrance hole that points toward the shore for warblers, and the other jar or box has a 1-3/8 inch entrance that points east toward the lake for swallows. Swallows cannot enter a 1-1/8″ hole, and protective swallows are known to defend their nests out to fifteen yards and inadvertently also protect nesting neighbors that pose no threat to them. In other words, I expect Tree Swallows to protect their warbler neighbors by driving away egg-piercing House Wrens and woodpeckers, while warning all birds in the vicinity of marauding hawks. That is my management plan.
I launch my management plan when I take nest structures from my basement and reinstall them to their pipes in mid-April. Each year since 1976, Alum Creek’s pool level is managed at 885 feet above sea level from October through March. During spring and summer, the lake’s pool is managed at 888 feet, allowing my canoe to easily reach each pair of pipes. Nonetheless, in 2012, Mother Nature failed to deliver enough rain in early April for the lake to rise three feet to its summer pool level, leaving the northern lake bottom exposed and dry when it was time for me to reinstall my nestboxes and jars.
On April 16, I loaded my canoe with its cargo and paddled the valley’s original channel south where I parked it on many beaches made of exposed sediment deposited since the lake’s creation. I had to carry the project’s PVC sleeves and nest chambers to their ultimate destinations many yards away, but all went well during a long, tiresome day. The following day, I did not need my canoe to install structures along the northern shore. I climbed across the guardrail at Hogback Road and carried my cargo across the dry lake bottom. It was May 7 before rains had added enough water to fill the ancient valley with a pristine lake for the nesting passerines and Osprey.
I began monitoring my boxes and jars on May 12, the first of a dozen trips to record nest histories, including four forays to add leg bands to seven warbler families. On days when I checked all nests, I used a kayak paddle to propel my Old Town Stillwater canoe for a two mile round trip. I prefer to use a kayak paddle instead of a traditional canoe paddle since a double-bladed paddle challenges both sides of my body equally, something to consider when you’re well into your sixth decade of life.
Three Successful Species and One No-show
Carolina Chickadees did not attempt to nest in 2012 even though the project produced two chickadee families in 2011. Nonetheless, House Wrens laid 32 eggs in five nests and 29 eggs (90.6%) hatched and 27 (84.4%) grew to fledge. Once eggs hatched, 93.1% fledged.
Tree Swallows nested in all nest chambers equipped with 1-3/8″ entrances. Eighteen of 20 nest attempts were successful after 94 eggs were laid, 85 (90.4%) hatched, and 78 (83%) fledged. Once eggs hatched, 91.8% grew to fly from their nest chambers.
The target species had the worst luck during the season. After twelve nest attempts where eggs were laid, only seven nests (58.3%) produced young Prothonotary Warblers. Warblers laid 54 eggs, 38 (70.4%) hatched, and 34 (63%) fledged. Using the same numbers, once eggs hatched, 89.5% fledged wearing numbered leg bands.
Of the five prothonotary nests that failed, one failure was my fault and what happened sickened me. My canoe sliced an unseen, submerged log that caused the vessel to “slap” the nest jar’s pipe and sleeve, shattering four eggs. I plan to install collision guards before the 2013 season.
A House Wren punctured and evicted four warbler eggs and deposited sticks as its calling card.
All of the last three warbler nests failed since they stood alone to face an unknown predator. Their guardian Tree Swallow neighbors had left the area with their new families. On July 2, I counted four hatchling prothonotaries in one nest and two other warbler nests held eggs. I expected to find hatchlings and nestlings on my next visit on July 8, but instead, I found empty nests. Even though I have no proof, I have a suspect: Red-bellied Woodpeckers.
During the years that I raised PROW’s in the Green Tree Marsh on the Delaware Wildlife Area, I had suspected woodpeckers for surgically removing eggs or young from warbler nests without leaving a trace of evidence. I had read eyewitness accounts of woodpeckers removing and eating bluebird hatchlings, and I have also listened to other accounts of red-bellies raiding Cliff Swallow nests to feast on nestlings. I own a 520-volume set of The Birds of North America, and No. 518 (Red-headed Woodpecker) and No. 500 (Red-bellied Woodpecker) document both species eating nestlings. Red-bellies have been observed feeding upon more than five species of young birds, including Carolina Chickadees, House Wrens, and two species of woodpeckers. A Red-belly’s tongue can spear a target 1-1/2 inch from the tip of its bill, and I have used a study skin at the Ohio Wesleyan Zoology Museum to show that a red-belly’s head and neck can easily stick inside a 1-1/8″ entrance. Designing a nest chamber acceptable to prothonotaries that excludes woodpeckers remains an important objective.
What Ricky Racoon Can’t Do
I never had proof that a raccoon can’t climb my project’s PVC sleeves until the end of the 2012 season when the prolonged drought lowered Alum Creek Lake enough to allow a wet and muddy raccoon to walk to a pipe and sleeve that supported an active House Wren nest. Ricky’s muddy tracks showed that the raccoon had anchored its hind feet to the hose clamp near the bottom of the PVC sleeve, but was unable to overcome the slipperiness of the situation for a climb.
By July 30, all sleeves and nest chambers were back in my basement waiting for another season to be launched.
Warbler on to 2013!