Prothonotary Warbler - Photo Stan Lupo

The 2021 PROW season at the northern end of Alum Creek Lake near Kilbourne had its unique moments. I use my extra wide 12-foot Old Town canoe to maintain and monitor 45 nestboxes and nestjars along a one-mile stretch of the lake’s shoreline.  

All nest structures are mounted on five-foot-lengths of 1-1/4-inch PVC water pipe. Hose clamps hold the nestjars and boxes six or more feet above summer water level in order for nests to be above the highest recorded flood levels at Alum Creek Lake. In late summer, all structures are pulled off their steel anchor pipes to be stored in my basement until early March the following spring. All is done to avoid damaging ice flows that are quite common during each winter.

Prothonotary Warbler (Photo Mike Maier)
Prothonotary Warbler at a nestjar.

On March 9 and 10, I reinstalled 14 nest structures throughout the most northern portion of the project. I wore my hip boots and waded through the mud of the exposed lake bottom. The lake was still at winter pool at 885 feet above sea level and it was fun watching all sorts of wildlife as I returned the potential nest sites to their pipes. It was too early to see Tree Swallows and prothonotaries, so I was not disappointed.     

As the calendar days continued to add up, I was becoming weaker until a medical team installed a pacemaker in my chest on March 27. The heart’s pacemaker came with a medical directive for me to limit the use of my left arm and not lift anything that weighed more than 25 pounds for the next six weeks. That disallowed the use of my fifty-pound canoe until mid-May and the project still had 31 nest structures to install.     

The project was rescued after Craig Flockerzie organized six other staff members from Delaware Preservation Parks to meet on April 6 and 11 to finish installations before the prothonotaries were to arrive. We hiked the horse trail above the lake to access the lakeshore below where pipes awaited their nestjars and boxes.     

By May 27, the lake had risen to 886.1 feet to make it possible to check all 45 nest sites with my canoe, and everything turned out to be better than expected. The golden swamp warblers had eight active nests, seven with eggs and one nest with five-day-old nestlings.

Tree Swallows - Photo Rodney Campbell

Tree Swallows had 17 active nests, eight of which had nestlings, and House Wrens had launched their season with nine nests, five of which had young.

Since Tree Swallows dive to drive off egg piercing wrens, in recent years, I started to locate nest structures with 1-1/8 inch entrances further from the western shore than the swallows’ structures which have 1-3/8-inch entrances. The structures are paired five yards apart. I reason that swallows will inadvertently protect the swamp warblers’ homes as they protect their own from the wrens. When warblers return to their nests, they glide below, then soar up to their home’s entrance and the swallows seem not to be concerned, etc.

A “golden swamp warbler” lands at its nestjar’s entrance.

As I reviewed the season’s recorded data, I focused on my first visit where eight prothonotary nests were active with eggs or young. All eight nests matured to successfully fledge descendants. Six of the warbler nests had been paired with active swallow nests which may have endorsed the management plan. Most surprising were two successful swamp warbler nests that became paired with active House Wren nests that held hatching eggs on May 27. Researchers have found that once wrens have nests with days invested in incubation, and more advanced nests with nestlings, their behavior changes and they become more accepting of other species in their neighborhood. It could be that the wrens become so busy with being responsible parents that they don’t have enough time to spear the eggs of others.     

So how did the project’s residents do? The Prothonotary Warblers attempted 16 successful nests after 19 attempts with eggs for a rate of 84.2%. House Wrens caused the three nest failures by evicting prothonotary eggs.     

Prothonotary Warblers had active nests with eggs and young from the earliest first egg on May 5, to the last fledging event on August 6, for a 94-day active nest season. Two nest structures produced two families each.      

The warblers laid 78 eggs, 72 (92.3%) hatched, and all nestlings fledged for a 92.3% success rate for the eggs, and 100% rate for the hatchlings.     

The project’s Tree Swallows had 20 successful nests after 23 attempts for an 87.0% success rate. Two nest failures appeared to be abandoned nests and the third failure had no visible explanation. The swallows laid 106 eggs, 84 (79.2%) hatched and all fledged. So, the swallow parents did a great job of fledging 100% of their hatchlings.   

House Wren at Magee Marsh (Photo Tom Sheley)
House Wren, the “super bird”

Tree Swallows occupied their nests with eggs and young from April 24 to July 20 to make an 88-day active nest season. Three boxes raised two families each.      

I call House Wrens “super bird,” or “the boss of the brush lands,” and they produced 27 successful nests after 28 attempts for a 96.4% rate. The one failed nest appeared to be abandoned after two eggs were laid. Wrens laid 152 eggs, 147 (96.7%) hatched, and 146 (96.1%)fledged. After eggs hatched, 99.3% grew to fledge as the parent wrens lived up to their “super bird” title.     

Four boxes or jars raised two families each during the 122-day House Wren Season that ran from May 6 to September 4.     

As I do every year, I removed the project’s nest structures from their pipes and after leaning them up against my garage at home for five or more days in an effort to give spiders and insects a chance to escape, I moved them into my basement for storage. It took three trips, one per day, on August 14, 15, and 16 to retrieve all but five boxes that held wren families. I collected the last five boxes on September 4 to bring “my season” to a close.

Conserve on!