Delaware Wildlife Area Report: 2015

Leonardsburg Marsh

I maintain 63 bluebird nestboxes at three locations on the Delaware Wildlife Area (DWA), a public hunting area managed by the Ohio Division of Wildlife in Delaware County, Ohio. Boxes are managed to avoid hunting seasons by storing boxes and their baffles at my home during hunting seasons and reinstalling them to stand on their poles between March 15 and September 1 each year. All but a few of the boxes are placed to attract nesting Tree Swallows and no Eastern Bluebirds attempted to nest in any of the boxes in 2015. All totaled, the boxes raised 235 Tree Swallows and 24 House Wrens.

I report on all locations below, and then I will propose a possible hypothesis to explain a disturbing downturn of survival rates for swallow hatchlings.

The Panhandle Road Grid (PRG) consists of 30 nestboxes evenly spaced at 25 yards apart in six rows of 7, 6, 6, 5, 4, and two boxes, respectively. An additional pair of boxes is located across the road from the grid but joins the grid’s boxes in my data book to make a total of 32 boxes. The PRG’s Tree Swallows attempted 39 nests and 33 (84.6%) nests successfully fledged 124 young for an average of 3.76 fledglings per successful nest. The field with the grid is managed as grassland, an excellent habitat for pheasants and swallows.

The Leonardsburg Road Grid (LRG) is a perfectly square grid of five rows of five boxes each, making the grid “as long as a football field on a side.” Swallows attempted 33 nests and 27 became successful for an 81.8% success rate. The grid’s boxes fledged 104 swallows for an average yield of 3.85 swallows per successful nest.

Leonardsburg Marsh
This March 22, 2013 photo shows the first row of nestboxes in the Leonardsburg Road Grid after the vegetation had been brush hogged. The grid was too wet for pre-season maintenance in 2015.

During the 2015 season, the water level in the grid was the highest ever with posts for only six of 25 boxes remaining above standing water. I needed hip boots to monitor in water knee-deep in places. My presence occasionally flushed Woodcocks in open areas, but in most of the grid, cattails grew to be six to eight feet tall. I used my pocket knife to easily snip cattails so swallows had clear fly paths to their entrance holes.

Before European trapping markets arrived in the New World prior to the seventeenth century, Tree Swallows nested in cavities in dead trees flooded by beaver dams, well above any cattails. As I waded through this year’s flooded grid, I enjoyed learning and thinking of the ancient past that favored Tree Swallows.

Six nestboxes stood along the ditch at the Green Tree Marsh where old Leonardsburg Road passes over the flood levee as you travel east. The marsh’s flooded woodland is where bird watchers go to have a sure chance of seeing Red-headed Woodpeckers. Red-bellied Woodpeckers can also be sighted at the marsh and both species will rob nests of other birds to feed on eggs and nestlings. Woodpeckers are my prime suspects for low swallow production at the marsh. Tree Swallows attempted six nests and only three were successful fledging an average of 2.33 per successful nest. A lone, battle-scarred nestling showed wounds on its crown, but nonetheless, it ultimately fledged with both eyes.

All four House Wren nest attempts fledged all 24 hatchlings for an average of six per nest. Wrens fill their nest chambers with sticks that encase tunnels leading to their nest cups. Bulky wren nests will block most woodpeckers’ beaks and barbed tongues from spearing eggs and nestlings. One of the six boxes at the marsh is really a “nestjar” made of four-inch PVC drainpipe. It has an experimental entrance made from a plumber’s fitting that sticks out 1-1/2 inches to deter woodpeckers. Wrens have no trouble nesting in these special boxes as I also have four other such nestjars at other locations that also produce wrens.

Ironically, both Tree Swallows and House Wrens occupied nestboxes on the wildlife area with eggs or nestlings for periods of 89 days; swallows from May 3 through July 30, and wrens from May 19 to August 15.
The Panhandle Road Grid served as an educational resource on June 24, 2015 when flood waters closed roads in Delaware State Park along the west side of Delaware Lake. I was teaching my annual course, “Bluebird Trail Management,” to talented and gifted middle school students attending OWjL (pronounced “Owl”) Academic Camp at Ohio Wesleyan University. I teach one class per week for three weeks in June, and we take field trips to Delaware State Park on Tuesdays, Wednesdays and Thursdays to experience life cycles of Eastern Bluebirds, Tree Swallows, and House Wrens that inhabit the 166 nestboxes there. The course is very hands-on and every camper gets to add a leg band to a nestling under my close direction.

Ten campers, ages 12 and 13, including eight girls and two boys, followed their instructor into the grid’s waist-high, wet grass to visit nine nestboxes to experience the nesting cycle of Tree Swallows. We banded three nestlings from two nests to complete the banding experience for every camper. We extracted one dead nestling from a nest with two live siblings. We counted three new eggs laid in a new nest built on top an old, successful nest, and we found a nest with two new hatchlings squirming among three eggs.

I cautioned the campers not to touch one nestbox since it had a bloody entrance hole left by a swallow’s bloody foot. I explained that such a sight is a sign of avian pox, a disease not passed to humans, but we took no chances. I also extracted nine-day-old nestlings to show their healed head wounds inflicted by an unknown avian aggressor.

Visiting nine nestboxes within a 45-minute visit was made possible by the grid’s nestboxes being spaced 25 yards apart. While learning of swallow nest life, the campers were also impressed by the aerial feeders swooping overhead. It was a good time in the wildlife area.

An Ominous Trend

Dead Tree Swallow Nestling
Dead Tree Swallow Nestling

I will use 11 years of data from the Panhandle Road Grid to state a concern of mine. By the time swallow eggs hatch, their habitats should be stable enough with food items to enable nine of every ten hatchlings to grow to fledge. This has been an observation of mine for all nestbox species since the beginning of my 48 years of bluebirding. I established the PRG in 2005, and its prairie habitat is one of the most constant of my trails and grids.
Between 2005 and 2010, the percent of hatchlings growing to fledge, starting with 2005, were 89.4%, 94.5%, 91.7%, 95.1%, 92.8%, and 91.4%, respectively. For the last five years, starting with 2011, the values have dropped to 73.9%, 83.8%, 81.4%, 66.4% and 71.3%, respectively. Finding dead siblings that died in stages due to food shortages is quite a strong message; it says that there had been a shortage of flying insects to support the diets of Tree Swallow nestlings.

When I communicate my observation of a five-year decline of hatchling success to anyone who wants to listen, I then ask, “How long has California had its drought?” The answer is five years. Then I state that the Pacific Ocean is heating up to throw the Jet Stream off its path, and new weather patterns are failing to deliver rain clouds to California. The Jet Stream continues north until it cools and dips down into the Midwest to deliver erratic weather that could be killing some insect species during, and after, their hibernation. My Tree Swallows are paying the price along with other creatures that rely on Mother Earth for their survival.

Happy climate change everyone!

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