Thursday, March 17, 2011

Reconstructing Habitat for the Vaux's Swift


Bull, E.  2003.  Use of Nest Boxes by Vaux's Swifts.  Journal of Field Ornithology.  74-4:394-400.

Logging has diminished the amount of old growth forests over the past 100 years.  For many years now, forestry companies have replanted trees in areas which have been logged, and clear cuts are only clear for a few years until saplings take root and replace them.  However, despite this reforestation effort, much habitat is still lost because may species require either large, old growth trees, or the additional habitats provided by an old growth forest.

One example of such species, is the Vaux’s Swift.  This species of bird has a summer breading range from northern California, through Oregon, Washington and into the interior of British Columbia, from the coast into southern Alberta, northern Idaho and western Montana.  Vaux’s swift nest in deep, hollow cavities which form in old growth trees which have become infected by heart-rot fungi (Bull 2003).  Heart-rot fungi invade the heartwood (inner wood of the tree), and decays it to a point of collapse, forming a hollow cavity.

Because of logging practices, many trees do not live long enough anymore in order to develop heartwood, and subsequently become infected by heart-rot.  Most forests are secondary or even tertiary forests, which are not old enough to have developed hollow cavities.  In addition, dead hollow trees are cleared away during logging, so these have diminished also.

In an effort to re-establish nesting sites for Vaux’s swifts, Evelyn Bull began constructing artificial hollows out of pine (Bull 2003).  She used 2.4 cm by 30 cm (1x12 for all of you carpenters or Americans out there) planks of pine to create a square shaft 28 cm wide and 3.5 m long.  These were hung on trees at a height between 10 and 15 meters, in three different forest types: late-seral stands of Grand Fir (the swifts natural habitat), harvested stands of Grand Fir, and mature stands of Ponderosa Pine and Douglas Fir.  99 boxes were constructed and distributed approximately evenly throughout the three forest types.

Over the four year period, 30 nest boxes were used by Vaux’s Swifts, with a total of 51 nest attempts and a 53% success rating.  Percentage of boxes used over time changed, with the first year having all ten boxes used in the late-seral Grand Fir stand.  Over the four year study the percentage shifted to most boxes being used in the pine and harvested stands, rather than the late-seral Grand Fir stands.  Bull suggests this is because the swifts will nest in other habitats, but needed to discover nest sites available in habitats other than the late-seral Grand Fir stands.

This study has provided a number of key highlights in Vaux’s Swift restoration efforts.  First, it is possible for swifts to exist in habitats other than old growth forests.  It seems they only require old growth forests for the nesting habitat, and if alternate nesting sites are available, the swifts can nest in 2˚ or 3˚ forests.  Second, the study provides examples of nesting sites, their construction and placement, all steps which are easily replicatable.

Words:  500

3 comments:

  1. This is a perfect example about how monitoring can be very informative! Finding out that Vaux Swifts will nest in secondary or tertiary forests will no doubt aid in their recovery. Putting out nest boxes seems like a relatively easy way for us to help this species recover. I hope researchers continue these types of longer term monitoring because finding this type of information will no doubt improve conservation efforts in the future.

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  2. Logging affects such a vast amount of species,especially those living in old growth forests. This study demonstrates how important it is to lessen logging in these areas. I thought the nest boxes were a great idea! Since there was long-term monitoring conducted on Vaux Swifts, the nest boxes were able to be placed at a suitable height and depth which likely increased the usage and success of the boxes. It was interesting, and helpful to the conservation of the species, to discover that they can also successfully nest in secondary and tertiary forests. Hopefully, this information will also help other similar bird species that require nesting habitat in old growth forests.

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  3. This type of situation is always so interesting to me, how logging companies attempt to play their part in restoring the environment, but it will never count for much if they are destroying a specific type of habitat that will take many years to restore. This study is great though. When time plays a big factor in reversing damage that humans have caused, it’s so useful to find alternative methods in the mean time. And as Sarah already mentioned, this type of study can really help with attempts at providing alternate nesting sites for other bird species that are suffering from habitat loss.

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