Eastern bluebirds are now common in central Virginia due in large part to the building of nest box trails specifically for them. We had almost lost these cavity nesters by mid twentieth century. Primary causes were loss of habitat as large farming tracts were turned over to development coupled by competition for natural nesting cavities in trees by non-native species (house sparrows and starlings). Efforts to return the species to our area began in the 1980s, Prominent in this effort was Bob Hammond, retired veterinarian, who built and monitored more than 300 bluebird nest boxes throughout the CHO/ Albmarle area. His trail thrived for more than 25 years but by 2007, after Bob had retired from active duty, nesting productivity was much diminished and many of his sites badly in need of refurbishing. In response, that same year, the RMN established a new project specifically aimed at restoring and maintaining the then officially named “Bob Hammond Bluebird Trail”.
Today this program is one of the most popular citizen science projects in the Rivanna Chapter. The Hammond trail now consists of 30 sites including parks, schools, hospitals, golf courses, farms and roadways. In 2013, 2233 native cavity nesters fledged out of the 362 nest boxes on the trail. The vast majority of these fledglings ( 79%) were bluebirds, fourteen percent were tree swallows, the remainder an assortment of chickadees, titmice and house wrens. It was a very productive season as measured by the number of eggs developing into fledging birds at eighty four percent. This data was sent on to the Virginia Bluebird Society. Thirty four dedicated volunteers monitored these boxes of which twenty three were RMN members.
The bluebird monitor’s season starts in February as nest boxes are cleaned out in anticipation of the arrival of breeding pairs into the area. Nest building begins usually in late March at which time the monitor begins weekly visits to his/her designated site . From this time on until sometime in August when the season winds down, the monitor carefully records all nesting activity in each box, which species visit, how many eggs are laid, how many hatch and how many hatchlings fledge. Each nesting sequence takes approximately 6.5 weeks to complete. Here in Central Virginia bluebird pairs usually have two and sometimes three nestings a year. Throughout the season, the monitor is alert to any signs of predation and responds by installing the proper guard and/or relocating the endangered box.
The importance of selecting suitable boxes, with appropriate mounts for nesting success was dramatically reinforced in a recent study by RMN monitor Mary Tillman. Mary measured productivity at two similar sites, each with 12 nest boxes. Site A had been fitted for many years with small, poorly ventilated boxes, mounted on fences posts lacking predator guards, Nest boxes at Site B were of a newer model, with good ventilation and well-shaded by overhanging roofs. These were mounted on metal poles with both snake baffles and wire mesh raccoon/cat guards. Although there were more nesting attempts at Site A (24) than at Site B (15), nesting productivity at site B was much greater (65 fledgings or 88%) compared to that of site A (27 fledgings or 25%).
Hopefully the Bob Hammond Trail and others like it, with their dedicated monitors, will continue to keep the common Eastern Bluebird common here and everywhere for the years to come.
–From Rivanna Master Naturalist volunteer Ann Dunn, who is also the Albemarle County coordinator for the Virginia Bluebird Society’s nest box monitoring program. Ann Dunn and RMN volunteer Mary Tillman recently led an Advanced Training session on bluebird monitoring for our chapter.