Sunday, June 5, 2022. During the 2021 breeding season, the Lawrence Peregrines did not lay eggs in the Ayer Mill Clock Tower nest box. Many individuals and small groups diligently and regularly scanned the skies and mill buildings in the local area, but with no success. During February and March, 2022, the Peregrines were seen many times, but provided absolutely no actionable clues on the whereabouts of their new nest ledge location. We could sense they were nearby, but just didn’t know where.
In March, the male was regularly seen perched on the old smokestack just past the north end of the Casey Bridge and on the west side of the Pacific Mills complex, near the corner of Amesbury and Canal Streets. Most of the time, it was facing the Merrimack River. This image on the left, shows the male lifting off in flight, heading SW, late afternoon on March 16,2022.
Many mornings, the male was perched in the upper zone of the smokestack, facing south or southeast, and soaking in the morning sun. The departure flight patterns, altitudes, and directions were quite a mix and never really provided firm clues. This image was captured on March 23, 2022, and likely before the female had selected the exact nest ledge location for laying eggs.
From time to time, the female was seen perched on the faded green weathervane atop the Ayer Mill Clock Tower. This was a fascinating scene to observe as her reaction made it clear that it was not the local male but rather a very unwelcome interloper passing through the neighborhood. She went into full territorial defense mode, rolling over on her back, and using her outstretched talons to send a very clear message! This image was captured on April 5, 2022. At this point the female may have not yet laid eggs. Our biggest challenge was where to look next to find the nest!
Bridges have played a significant role in the national peregrine falcon recovery, consistently supporting more than 30% of the known population.
In Virginia, two researchers from the Center for Conservation Biology, conducted 166 surveys of bridges in coastal Virginia using a call-broadcast protocol. Broadcast calls were extremely effective in eliciting a response from falcons with nearly 60% and 100% of falcons responding within five and 30 seconds of call initiation respectively.
The ten-minute, call-back protocol includes a series of advertisement and courtship calls interspersed with silent listening periods. Response rates measured from detection trials were 83% during the breeding season overall with a peak of 100% during the courtship period.
Occupied bridges supported more potential nest sites, were longer and higher and were embedded within landscapes with more foraging habitat compared to unoccupied bridges. The current practice of installing nest boxes or trays has resulted in higher breeding success and reproductive output.
The flight image above shows the female responding to one of our call broadcast surveys performed along the east side of the Casey Bridge. After two successful surveys, we had almost full confirmation in regard to the highly probable nest ledge location.
Citation: Watts, B. D. and M. U. Watts. 2017. Investigation of breeding peregrine falcons on bridges. The Center for Conservation Biology. Technical Report Series, CCBTR-17-01. College of William and Mary & Virginia Commonwealth University, Williamsburg, VA. 38 pp.
On Sunday afternoon, June 5, 2022, we launched a kayak into the Merrimack River on the upriver and south side of the Casey Bridge. The Joseph W. Casey Bridge runs north/south over the Merrimack River. From the south, access to the bridge is from Parker Street, and from the north, access to the bridge is from Amesbury Street. On kayak approach to one of the large bridge archways, the unseen female started defense cacking vocalizations, and flew off downriver. While scanning the ledges up and under the west side of the bridge, the two peregrine chicks came into view……HOOORAY! Best guess on age is around 34-35 days old, and likely days away from the first one being ready to fledge.
Looking back, and making a number of probability calculations, it looks like the eggs were laid first week in April, hatched first week in May, and the first chick fledged late this past week. These estimates fall within all of the normal breeding season sequence and timing for Peregrine Falcons in Eastern Massachusetts!
Click on any image to enlarge!