“You probably expect me to give you bad news about the bluebird boxes,” Bill said as he started his presentation to almost 35 Central New Mexico Audubon Thursday Birders. “However, every year is different – not necessarily good or bad.”
He passed out a page with graphs of fledge numbers and inches of precipitation for the 12 years he has been keeping data. “You’ll see that surprisingly, there is not much correlation between precipitation and nest success – even though the numbers for both are low this year.”
Bill started maintaining boxes and keeping data in 1999 with 25 boxes. He added 5 boxes the next year. By 2002 he had 40 boxes, and by 2007 there were 47. That number has remained static since then. “Of course,” he explains, “not every box is occupied every year.” The boxes are scattered throughout the ranch and he checks each one weekly.
Until last year, the number of fledglings has always been over 100. Last year, with one of the higher rainfall totals, the number went from 181 (2009) to 74. This year it was 68.
He reports his data to Cornell University’s Lab of Ornithology’s NestWatch, one of their citizen science projects. While they accept data on nests of all types, Cornell Lab staff have identified 24 Focal Species, based on “many factors including migratory status, nest type, range and tolerance to disturbance.” Western Bluebirds, which make up 99% of the birds using his boxes, are one of the Focal Species. Mountain Bluebirds, also a species of focus, originally made up 50% of the nests; however, over time, that has diminished to almost none.
“Two of the nest boxes this year were occupied by Juniper Titmouse parents – a first,” Bill said.
The number of second broods is dependent upon the available food supply. This year, with drought conditions, there was a paucity of insects and berries, so only one pair attempted a second nest. Unfortunately, the chicks hatched on a day of extreme heat and they didn’t survive.
Bill explained that the bluebirds are early nesters and when they are finished with the box, it will often be occupied by an Ash-throated Flycatcher pair. “In fact,” one of our group said, “the flycatchers will often assist in feeding bluebird chicks to hasten their growth – and to stake a claim on a box.”
The boxes are often used for roosting during the winter. Following the minus 20 degree weather, Bill found five dead birds huddled in the bottom of boxes.While we listened to him share information on the bluebirds, we were treated to the buzzing wings of four species of hummingbirds: Calliope, Rufous, Black-chinned and Broad-tailed. A pair of Juniper Titmice flew in for seed in the tray feeder behind him, while the calls and songs of Lesser Goldfinches, Black-headed Grosbeaks and Western Scrub Jays serenaded us as these birds busied themselves in the junipers and piñon pines around his property.
By late morning we were ready to move down the road to Bonnie’s house for a potluck lunch and to enjoy the myriad of birds that danced in and out of the trees and visited her many feeders.
It was a delightful and educational day.