Regional Gardening Reports :: National Gardening Association

In the Garden:
April, 2009
Regional Report

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Building an inviting, safe, and attractive bluebird house is an art AND a science.

Building a Better Bluebird House

There are birdhouses that leak, rot, and tempt unwanted guests. And there are birdhouses that stay dry inside, intact, and thwart intruders. For more than a decade of observing bluebirds and 4 years of striving to build the perfect bluebird house, Keith Snyder has watched birds and their houses come and go.

"The first time I saw a bluebird was here -- at the Morris Arboretum -- 11 years ago," he said. Back then, a few standard bluebird houses stood on the Arboretum's farmland, a stone's throw north of Philadelphia's Chestnut Hill. Not much special attention was given the songbirds though.

Today Keith and Bloomfield Farm Horticulture Section Leader Anne Brennan are in the midst of their own bluebird and wood duck support projects. Though Keith is the Fleet Operations and Procurement Management, late in winter his shop turns from vehicle repair to a bluebird and wood duck house construction zone. He borrows a special saw, rigs up work tables, and cuts and assembles yellow pine scraps into rectangles and squares.

Though his birdhouse is based on the Audubon Society's box, every season he customizes to improve its design and function. To stop leaks at the wood joints, his roof overhangs 2 inches in front, 1 inch in the back and is covered with vinyl siding. He cuts the wooden sides with narrow air vents at the top.

A birdhouse floor is usually quick to crack, warp, and rot from the birds' nesting. For longevity and structure, Keith cuts a square of grey composite material for the bottom. Then he saws off the corners to allow drainage and ventilation. He forms a three-sided wire mesh screen to fit in the bottom to let blowfly maggots fall through rather than stay in the nest.

He's devised a predator guard attached to the entrance that's too thick to allow cat or raccoon paws to reach inside for nestlings. There's a piece of plastic mesh tacked inside under the entrance, giving birds a place to grip when they climb out.

All this thoughtful design and work is for naught if the nestlings don't survive. So he, Anne, and Louise Clark are determined to monitor nests regularly. Once a week is the goal. Anne created a spreadsheet to keep track of all 47 tagged and numbered bluebird houses. Columns include Year Built and Placed; Area (on their grid); Box #; Date and What's Done; Notes; Next Action Planned. The most common Note: "cleaned out house sparrow nest," Anne said.

Keith keeps a close eye on one particular box along the bike path every day "for sparrows peeking out." He has a personal attachment; after he removed house sparrow and feathery tree swallow nests, two bluebirds moved in. Cleaning house means opening one side of the box and removing used or old nests -- after the fledglings have flown. For easy access, Keith devised a screw-in brass closure -- an L-hook to turn to secure or open the side.

"The monitoring is a teaching tool in itself," Keith explained. "We've found downy woodpeckers wintering inside. Anne's looking for patterns. "We want to see which areas the bluebirds prefer and put more houses there...Everything's in place if someone wants to do a research project."

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