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Individual Highlight

Steep Decline of a Winter Resident Bird Community in Puerto Rico Needs Swift Action

Photo of There have been overall population declines in resident and migratory birds in the Gu�nica Biosphere Reserve in Puerto Rico. USDA Forest ServiceThere have been overall population declines in resident and migratory birds in the Gu�nica Biosphere Reserve in Puerto Rico. USDA Forest ServiceSnapshot : The migratory bird community inhabiting one of the Caribbean's most unadulterated and extensive remaining dry forests, the Gu�nica Biosphere Reserve in southwestern Puerto Rico, has been in a general decline over the past 40 years. Constant-effort mist netting now results in one-third fewer birds captured as compared to 20 years ago; specifically, 400 captures recently versus 1,200 two decades ago. It is critical that managers accelerate on-the-ground conservation for migratory forest birds, many of which are in steep decline, and support research that attempts to understand these declines, while increasing public awareness and outreach.

Principal Investigators(s) :
Arendt, PhD, Wayne J. 
Research Location : Southwestern Puerto Rico, dry forest within the Gu�nica Biosphere Reserve
Research Station : International Institute of Tropical Forestry (IITF)
Year : 2013
Highlight ID : 454


Population declines of Nearctic-Neotropical migratory birds may first become apparent on their wintering grounds where they spend up to nine months of their annual cycle. A long-term study by scientists at the Forest Service's International Institute of Tropical Forestry, which began in 1973 using constant-effort mist netting in dry forest in southwestern Puerto Rico, shows a collapse in both the abundance and diversity of wintering birds over the past 40 years, but especially during the past decade. Whereas the estimated abundance of all winter residents combined fluctuated around a common mean from 1990 to 2001, migrant numbers declined dramatically beginning in 2002. When a set of constant, linear trend, and piecewise regression models was compared, a negative linear decline was strongly supported, with local extirpation of the winter resident community predicted in 2025. Environmental factors play a key role in the population dynamics of Gu�nica's birds. Regional hurricanes, with their recent increase in occurrence and intensity, have devastating impacts on the entire avian community. However, understanding population regulation in long-distant migrants is difficult. If the declines on the wintering grounds shown in the study are widespread, the baseline for current research is greatly changed and the populations they may study are already much reduced.

Forest Service Partners

External Partners

  • Frank R. Thompson III, USDA Forest Service, Northern Research Station, 2012 ABNR, University of Missouri-Columbia, MO 65211
  • email:
  • John Faaborg� Division of Biological Sciences, 105 Tucker Hall, University of Missouri, Columbia, MO 65211, email:
  • Judith D. Toms� Eco-Logic Consulting, 3014 Craigowan Rd., Victoria, B.C. V9B 1M8, email:
  • Miguel Canals Mora � Depto. De Recursos Naturales y Ambientales, Bosque de Gu�nica, P.O. Box 1185, Gu�nica, PR 00653�1185, email:
  • William Andrew Cox� Department of Biology, 103 Allwine Hall, University of Nebraska-Omaha, Omaha, NE 68106, email:

Program Areas