For the last eighteen years, Dick Phillips has driven his truck from his home in eastern Delaware County to Delaware City where I join him to monitor a fifty-mile-long trail of roadside kestrel nestboxes found mostly in the northwest corner of Delaware County. Every nest has its story, and monitors only see, record and interpret a small fraction of events that make up the history of a family trying to take their eggs to fledging. Each family’s nesting cycle has its own chapters of survival over time, making monitoring fun, sometimes disappointing, but always intellectually stimulating. Nestbox No. 14 (K-14) that hangs from an electric pole along Claypool Road near where Morrow, Marion and Delaware Counties share a common border presented a most intriguing history that played out as the latest and last kestrel nest of the 2010 season.
Perhaps the first chapter of K-14’s story began on July 3, 2009 when Dick and I lowered the box to the ground and dug out its used nest after it had raised five sparrow hawks. We added clean white pine livestock bedding to the nest chamber before pulling the box back to its place on the utility pole, 12-feet above the ground.
After nestboxes are cleaned and refurbished, there is no reason to revisit them until the following spring. Kestrels on the other hand, will use nestboxes as roost-boxes when seeking shelter from harsh winter weather. Also, male falcons will use nestboxes as they adamantly hold on to their territories for as long as they can.
However, sometime after our last visit at K-14 in 2009, another species moved into the clean kestrel box as hundreds of individuals followed their queen. When we returned on March 24 for the first box check of the 2010 season, we could see from the road that something was obstructing the box’s entrance from the inside. I was apprehensive as I climbed up the ladder to the back of the box where I unhooked the lid and slowly lifted it to bring three honey bee combs into view. Thankfully, I heard no buzzing, and nothing flew around my head, so I quickly assessed that the situation was safe for me. I peered inside and found that all of the bees were dead. Most of their little bodies were piled on the bedding, but some were still clinging to their combs. The walls of beeswax resembled a mausoleum with its burial crypts exposed. It took me only minutes to dislodge the failed colony and return the nest chamber to its intended use, that of raising a kestrel family.
As we left the site, we discussed whether the previous summer’s drought had set the bees up for failure, or had our nestbox been too ventilated for them? Did drafts through the box’s three inch-wide entrance and six ventilation ports rob the colony of its energy during a very cold, snowy winter? I have a great respect for what honeybees do for our food supply, but their demise saved me from possible stings and an unplanned, hazardous exit from the ladder. Of course, the bees’ temporary claim prevented our continent’s smallest falcon from claiming the box for its own, and on March 24, 2010, four kestrel nests at other sites already held eggs.
Two weeks passed before we checked all of our project’s 18 boxes for a second round on April 7. We found 11 kestrel nests active with eggs as well as three grassy starling nests in other boxes, including K-14.
The third round of monitoring took place on April 21 and the kestrel season looked very promising with 16 nests holding eggs. As we approached K-14, a male kestrel flew from his perch on the electric wire strung over the nestbox. His slate-colored wings confirmed his sex, and his presence was encouraging, but six starling eggs occupied the nestbox. We did not disturb the starling’s grass nest but we always remove their eggs that are not protected by the Migratory Bird Act.
We also removed starling eggs from K-14 on the fourth and fifth monitoring rounds on May 6 and 23. The season was rolling along, but apparently, the male at K-14 had not won a mate. By May 23, we had attached leg bands to eight falcon families and one family had already fledged five. One kestrel nest had failed due to a raid by opportunistic starlings, but the K-birds had reclaimed it with four new brown eggs.
For the rest of the season, in order to add leg bands to falcon nestlings during their window of 13 – 24 days of nest life, our monitoring visits took place every seven days or so. By the time we revisited K-14 on June 5, young kestrels had fledged from six nestboxes and we had banded most of the other families. Nonetheless, K-14 held new hope on June 5. It was not surprising to find an empty starling nest since first-eggs of the alien species normally don’t appear after the first week in June, but the round nest cup had been reshaped into an oval to fit a kestrel’s body. A female falcon had done this renovation; our male had finally won a mate!
The female in K-14 turned out to be stubborn, or dedicated, or both, depending on your interpretation. During visits on June 13 and 30, she stayed on her nest, preventing me from counting her eggs. For someone addicted to recording accurate data, this was frustrating, but I was also encouraged to see that the nest was active with an attending parent with an upturned head, a threatening dark eye, and an opened beak. She was prepared to flip on her back to rake me with sharp talons if I did something stupid. Many times, late-nesters are young birds nesting for the first time and their skills have not been tempered with experience, but so far, this female had won my respect since her response to a Peeping Tom in her ceiling was quite typical for her species.
As we approached K-14 on July 14, we noticed an adult kestrel’s tail sticking up and moving about inside the nest chamber. We concluded that feeding or some other activity was in progress, so not wanting to disturb the parent bird, we traveled on to check two other boxes while planning to circle back later. Dick and I had been discussing the fact that sixteen kestrel nests had already produced 70 fledglings, a new yearly production record for the 18-year history of the project. But the day was not over and bad news was waiting ahead. After we found four eight-day-old nestlings in K-13, a second clutch for the season, we found four dead nestlings in K-16. The decomposed nestlings had been scheduled to fledge around Memorial Day. I followed proper procedure for the Bird Banding Laboratory and systematically extracted the remains to read and destroy their leg bands, made “systematic” because one nestling had lived long enough to fledge. As Dick and I discussed possible scenarios as to what happened to the family, including one that involved Peregrine Falcons, the kestrels’ larger cousin that has been a visible suspect in other failures during recent years, an excited kestrel-watcher arrived and told us that he had seen three kestrels, a set of parents with one offspring. After his announcement, we told him the bad news concerning the rest of the family, and at that point in the conversation, only one good explanation remained: West Nile Virus, a villain that wasn’t done yet.
When we returned to K-14 later that day, we found a very young family of five in the nest. Shell fragments littered the nest and one kestrel had just hatched. The new hatchling was a few days younger than its siblings, a natural occurrence since kestrel incubation usually starts after the next-to-last egg is laid, and new eggs appear every two days.
Ten days later, on July 24, we set out to band four nestlings in K-13, expected to be 18 days old. Instead, we found all of them dead, having died soon after our last visit. Again, West Nile Virus is the best guess since the box overlooks one of the deepest drainage ditches in the county. Adding to the evidence are three oval-shaped galvanized steel conduit pipes that are laid side-by-side to occupy ten feet that drains runoff under the road from one ditch to another. The damp, dark caverns look like perfect hideouts for mosquitoes that carry and spread WNV. The road is extra wide to accommodate the drainage system, and we installed K-13 there because the wider space makes parking safer along the narrow road. At the same location, I found a drain leading three feet underground to field tile that held standing water. All factors add up to make good habitat for mosquitoes and a good reason to move K-13 to a drier site. Also, I used “Google Earth” to measure the distance between both boxes that might have lost nestlings to WNV. The boxes are 0.55 miles apart. After finding the disaster in K-13, we found five healthy nestlings in K-14 that were too small to band.
At this point in the season, the media was reporting on large populations of mosquitoes that included trapped ones testing positive for WNV, along with forecasts for daily heat and humidity. The last falcon family had some issues to avoid or conquer. Even with a new production record for the project, we were rooting for the last family to fledge.
We banded K-14’s family on July 31. Without using a scale, we agreed that a female nestling felt under weight and we recorded a male nestling as a “runt.” The runt’s smaller size was due to his age and sex. He was two or three days younger than his siblings and male kestrels are ten to 30-percent smaller than females, a phenomenon common in the world of raptors. I enjoy telling grade school students that being a male hawk or owl is like sixth grade, when girls are larger than boys. Their reactions to this revelation are priceless.
As for the small, male kestrel, he was a possible survival ration if his siblings became stressed during a food shortage. Cainism, when siblings kill siblings, followed by cannibalism, has occurred several times in our kestrel boxes. Being lunch for your siblings can be part of nature’s plan to help some, but not all, fledge from the nest.
K-14’s earliest predicted fledge-date was August 11. We set out on August 15 hoping to find an empty nestbox. Instead, as we approached the site, a parent kestrel flew from the wire directly above K-14, and as we rolled by to park, we could see a young falcon sitting in the entrance, so we drove on. We suspected that the late bird was most likely the runt and we did not want him to fledge if he was not ready. During hot days of late summer, more of a nestling’s food energy is used for cooling, and growth slows as a result.
Three days passed before I decided to load my ladder into my hobby car, which has no passenger seat, and check on K-14. I was ready to accept anything as I climbed my ladder and lifted the lid to find the box empty, except for a thick layer of Cicada wings, lots of wings, so many that the nest chamber resembled a bag of potato chips. I swirled my fingers through the delicate debris to feel for bird remains and found none. All five falcons had made it out of the box and I think they have Cicadas to thank for it. The big, juicy insects probably supplied the “extra” moisture needed for cooling and growth during the hot and humid days of late summer. Cicada and grasshopper wings are common finds in our later nests but I have never seen as many wings as I found in K-14. The nestbox hangs next to a fallow field that is part of the Delaware Wildlife Area managed by the Ohio Division of Wildlife. The Whetstone River makes up the field’s western border. Kestrels can prey upon night crawlers, rodents, small birds, frogs, and large insects. For the last family of 2010, Cicadas could have been the difference between success and failure.
The Delaware County Kestrel Project’s 2010 season consisted of 19 nest attempts in 17 of 18 nestboxes. Two nests failed and 17 (89.5%) succeeded to add 76 American Kestrels to the environment. Ninety-six eggs were laid, 86 (89.6%) hatched, and 76 (79.2%) fledged. Using the same numbers, once hatched, 88.4% of nestlings fledged. Two nests fledged six, nine nests fledged five, three fledged four, two boxes fledged three each, and one box raised one after four siblings died. An average of 4.47 kestrels fledged per successful nest, and the most common family size was five raised. The season, from the first egg to the last fledgling, lasted 154 days from March 15 through August 15.
Perhaps the most important number is 637, the number of kestrels raised from efforts started in 1993 with working partnerships among the Delaware County Bird Club, the Delaware General Health District, Ohio Department of Transportation, and later, Consolidated Electric Cooperative.
Kestrels have responded to our conservation effort, an effort that is needed since Falco sparverius‘s population has been in decline since 1984. Conservation does work, and it is fun, even with its fair number of disappointments.