Friday, August 10, 2007

PS 72-107: Mechanical habitat restoration improves demographic performance of Florida scrub-jays (Aphelocoma coerulescens)

Gregory R. Schrott, Michelle Dent, and Reed Bowman. Archbold Biological Station

The Florida Scrub-Jay (FSJ) is a Threatened bird species endemic to xeric oak scrubs in Florida. They inhabit areas with vegetation <2m and bare sand, generally occurring 4 - 20 years post-fire. Prescribed fire is necessary for maintaining FSJ habitat, and fire suppression can result in growth of fire-resistant vegetation of height and density unfavorable to long-term persistence of FSJs. The FSJ population on Avon Park Air Force Range declined from 90 groups in 1993 to 52 in 2007. The majority of these birds occur on a central sand ridge. In 1999 scrub restoration involving clearance of pines and prescribed fires occurred in the southern part of the ridge. In 2002, nearby areas were restored with hydro-axing to fell trees >~3m, followed by prescribed fire. This also was implemented in the northern part of the ridge; however some of this area could not be treated because of unexploded ordnance. In the south ridge, the number of FSJ territories decreased from 17 in 1993 to 7 in April 1998, and then increased to 15 by 2007. Territories shifted to areas where restoration efforts had been concentrated. In 2002 the treated and untreated portions of the north ridge each contained 11 territories. By 2007 the number of territories in treated areas had increased to 15, but declined to 5 in the untreated areas. Differences between these populations were mostly due to higher adult survivorship in treated areas rather than juvenile survivorship, immigration, or emigration. While fire is necessary for FSJ habitat management, much oak scrub in Florida is overgrown with fire-resistant woody vegetation that degrades FSJ habitat quality and makes prescribed burning more difficult. In such cases, more intensive restoration efforts through the mechanical removal of taller trees followed by fire could be beneficial to the persistence of FSJ populations.

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