Bluebird Project at the Arboretum

from the August 2017 Friends of the Arboretum Newsletter
By Milt Noelken
In 2007, Hugh McCreery, Bob Buehler, John Martin and Sue Davidson, members of the Friends of the Arboretum Bird Committee at the Overland Park Arboretum & Botanical Gardens, initiated the Bluebird Project. The project, designed to enlarge the local eastern bluebird population, consists of three dozen specially designed nest boxes separated by distances large enough (100 yards) to minimize competition among the bluebirds for the boxes. Hugh and Bob worked with Boy Scouts on the assembly. The project involves monitoring the boxes and recording when nests were built, eggs laid and hatched, and when the baby birds fledged.  Also, the monitors take care of some predators, such as wasps and help maintain the boxes. Ron Falcon and I joined the project as monitors in 2007. Over the years other monitors were involved, including Judy Moecker, Trent Reed, Dan Johnson, Sue Bolan, David Sinzheimer, Herb Comstock, Charlie Loftus, Leon Smith, Susan Smith, Pamela Hon and Jim Johnson.
A bluebird nest box is shown here; it is made from red cedar. The entrance hole is 1⅜” wide and prevents larger birds from entering the nest box. On the front is a predator guard, called a Noel guard, made of ⅟2″ mesh hardware cloth. This keeps predators such as raccoons from reaching into the box. Attached to the post is a “Kingston” stovepipe predator guard that prevents snakes and other predators from climbing into the box. It has at its top ⅟4″ mesh hardware cloth. In relatively warm weather, bluebirds eat earthworms, snails, and insects: thus, they prefer large mowed areas because of the enhanced visibility of prey. During the winter, bluebirds that stay in the area eat various berries. Birds compete with their own species and with other species for nest boxes. I saw in one box a vacated chickadee nest topped by a vacated house sparrow nest and on top of that a house wren nest. There is a display of nests in the Environmental Education Visitors Center, including the three layers of nests from one box. The nest boxes at the Arboretum are used by bluebirds but also by tree swallows, black-capped chickadees, titmice, house wrens and house sparrows. Except for house sparrows, these birds are protected by the 1918 Migratory Bird Treaty Act, so we must let them occupy the boxes. Monitors learn to identify the nests and eggs of these birds. House sparrows are very aggressive toward other birds and would eventually crowd out the protected birds, so we remove their nests as soon as we detect them. Over the period 2007-2016, we have had 635 bluebirds, 185 tree swallows, 35 chickadees and 6 titmice fledge.
The brooding season for bluebirds begins in March, with the first eggs of the year typically found in late March or early April. In March there is an increasing amount of light, which stimulates the birds’ reproductive processes. Also, the soil warms and earthworms come to the surface, providing food. In our area, the brooding season ends in mid-August, when the last of the babies fledge. In some years, the brooding season ends early, due to especially hot weather when the nest box temperature gets higher than the optimum temperature of 95F for successful incubation of eggs. Bluebirds can have up to three clutches per year, with 3-5 eggs per clutch. Tree swallows lay their first eggs in mid-April into May and have 1 clutch per year (occasionally 2), with 4- 7 eggs per clutch, and black-capped chickadees lay their first eggs in early April into May, with 1 clutch of 6-8 eggs.
We keep detailed monitoring records in order to guide us in relocating some boxes, not used enough by bluebirds, in order to maximize bluebird nesting. We also send our data to the Cornell Laboratory of Ornithology, which has a continent-wide ongoing study aimed at determining the effects of habitat loss and climate change on bird populations.
For further information on bluebird projects I recommend the following references:
Cornell Lab of Ornithology  This is a very comprehensive resource that has
many links to detailed information about monitoring, construction of bluebird boxes, etc.
K-State Research and Extension (local center). A great source of information
about many topics, including birds.
The Bluebird Monitors Guide to Bluebirds and Other Small Cavity Nesters by Cynthia Berger, Keith Kridler
and Jack Griggs, HarperResource, 2001, ISBN 0-06-273743-0