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Vol. LXII, No. 17
August 20, 2010

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2010 Bluebird Count Down from Last 2 Years, Virus May Be Culprit

A bluebird nest in one of the birdhouses on NIH’s Bethesda campus

A bluebird nest in one of the birdhouses on NIH’s Bethesda campus

One of NIH’s most popular pest control projects— erecting birdhouses to attract mosquito-eating feathered tenants—lost a bit of ground this year, according to project leader Lynn Mueller, NIH landscape architect.

“Well, as expected, this past nesting season was not as good as hoped for,” he wrote in a July 29 email to the campus’s bird census enthusiasts. “The number of campus-fledged bluebirds was back down to the 2007 number after rising the past 2 years. I guess the West Nile virus is still running its course through [the bird] population. Other songbird fledging numbers were fine and even up for some. Our final count for 2010 [is in the sidebar below]. Thank you all very much.”

Mueller said another possibility for the decline “may be that our campus is becoming more urbanized with more open space being returned to wildflower meadow and ‘no-mow’ zones along the banks of our two creeks. We also slightly increased our acreage of reforestation in 2009.

2010 Feathered Friend Census

15 bluebirds fledged
39 chickadees
61 house wrens
23 barn swallows (parking garage nests)
9 tree swallows

History of Bluebirds Fledged (since record-keeping began at NIH)

2010 — 15
2009 — 20
2008 — 29
2007 — 14
2006 — 37
2005 — 36
2004 — 31
2003 — 16
2002 — 13

“Bluebirds enjoy more open areas where they can safely find insects,” he continued. “The increase of house wrens and chickadees may indicate this landscape change to more wooded. However, attracting these various species to nest and remain on campus has been a huge success in our eliminating pesticide applications, especially insecticides. No insecticides were sprayed on the campus during 2009 and none are planned to be applied this year.”

The novel (and virtually natural) approach to pest management began at NIH in February 2001 with 30 birdhouses, 3 roosting houses and a even a couple of bat houses installed around the Bethesda campus grounds in hopes of attracting a corps of winged workers to keep mosquito populations low.

By the next spring, a crew of volunteer bird counters had been enlisted to keep a record of the project’s success. Bluebirds became the best-known residents and the bluebird count grew steadily every year until 2007, when it dropped drastically. This year’s total of fledglings dropped similarly.

Over the next few months, Mueller said, he will make adjustments to the birdhouses and their locations in order to improve attractiveness to next year’s house hunters.

“There are actually two nesting seasons,” he explained. “The first begins in April and ends about early June. Some adult birds—possibly young from the previous year’s second season—will nest starting about mid-June. Usually all young will have fledged, or flown away, by the end of July. This second nesting season usually has a lower number of nests and fledged young. We’ll be ready again next March to hopefully attract more birds to stay and nest on the campus.”—

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