Monday, October 29, 2012

Rooting for the underdog: eastern bluebirds

Imagine you live inside of a tree.  Your hunger forces you down to the ground where you glean ants and worms out of the grass.  Upon returning to your tree you find a strange bird comfortably occupying your home.  Its time to move. 

An eastern bluebird in its preferred open-woodland habitat

This has happened again and again to the eastern bluebird, which live in small holes in trees.  The non native European starling and house sparrow (both intoduced to the Americas after the Columbian exchange) pose a serious threat to the bluebirds: starlings (another 'cavity-nesting' bird) enter bluebird cavities and evict the occupants while house sparrows kill bluebirds and/or destroy bluebird eggs.  Its a rough world for the adorable bluebird, which are also negatively affected by severe winters and loss of habitat. 

The bluebird has been subject to an extremely dynamic and turbulent history in North America. See here for a nice synthesis of their history.  To sum it up, due to loss of habitat, land conversion, and the introduction of non native birds (European starling and house sparrow), the bluebird population crashed around the middle of the 20th century.  Their numbers were so low that by the 1960's birders and scientists feared that bluebirds may actually become extinct.  A widespread, grass-roots movement to save the bluebird ignited a new interest in their plight, research for their conservation and the spread of bluebird boxes across the country.       

Bluebird boxes?  Yes, there is something that you can do to help the bluebird! 

To mimic the tree cavities that bluebirds find so comfortable, scientists, conservationists, nature enthusiasts, birders and school children have built and errected small wooden homes for the bluebirds, A.K.A., bluebird boxes.  These easy to build boxes provide bluebirds with a safe place to make a nest and bring up their babies. European starlings are too big to fit through the door hole which means that the bluebird family is safe from unwanted squatters and killers.        

A bluebird on a bluebird box.  A bluebird's door hole must be precisely sized (1.5 inch) to allow bluebirds to enter while keeping out unwanted European starlings.   

This type of human mitigation has truly paid off; bluebird populations have responded to the wide-spread use of bluebird boxes.  Their numbers are up, but still not as high as they were before humans severely impacted them with starlings, sparrows and sprawl.  Choosing to erect a bluebird house is still a fun and worthwhile endevour - one that directly helps wild animals survive in the face of serious human-induced obstacles.  You can see working bluebird boxes in the meadows at the Pound Ridge Land Conservancy's Clark Preserve and the Westchester County's Ward-Pound Ridge Reservation

If you want to build or buy a bluebird box you should consult the many websites dedicated to bluebirds to understand their specific habitat and ecological requirements.  Here are a few websites:

Bluebirds forever
From the USDA
Bluebird box info and building plans

A bluebird sitting on a bluebird box.  This picture shows how a bluebird box can be mounted onto a piece of metal. 

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