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Distribution & Abundance Maps for 2001

2001 Puerto Rican Breeding Bird Survey
Results and Summary

NTRODUCTION: Island bird communities are particularly susceptible to catastrophic declines due to their small population sizes and the fact that the species are often narrowly adapted to the specific conditions of their limited range (Temple 1985).  Since the 1600s, 93 percent of the bird species and subspecies that have become extinct were island natives (King 1980).  Moreover, Collar and Andrew (1988) estimate that approximately 46 percent of threatened bird species are island inhabitants.  For these reasons, the International Council for Bird Preservation identified the long-term monitoring of endemic island species as a conservation priority (Johnson 1988).  However, few such programs exist for the majority of the avian species endemic to the Caribbean basin over a decade later.

Puerto Rico, in particular, harbors numerous endemic and native avian species whose populations are not being monitored on an island-wide scale.  Out of 141 breeding bird species found in Puerto Rico (Raffaele 1989), 16 are single-island endemics while another 15 species are endemic to the Caribbean basin (AOU 1998).  Yet only about 13% of the species found in Puerto Rico benefit from any type of long-term island-wide monitoring program.  Moreover, the species that are being monitored consist primarily of game birds (Rivera-Milan 1993) and threatened or endangered species (D. Ramos, Puerto Rico Department of Natural and Environmental Resources, Pers. Commun.), leaving the majority of the avian species, including two-thirds of the endemics, outside of an existing monitoring framework.  Thus, in 1997, in cooperation with the Puerto Rico Department of Natural and Environmental Resources, we established the Puerto Rican Breeding Bird Survey (PRBBS) to monitor the long-term status and trends of Puerto Rican bird populations.  This information will allow bird population changes to be identified, and declines reversed through further research and management actions, before populations reach critically low levels.

METHODS: The PRBBS consists of 44, 8-kilometer (5-mile) roadside routes randomly located across the island.  Stops are located at 0.8-kilometer (0.5-mile) intervals for a total of 11 stops per route.  At each stop, a skilled observer conducts a 5-minute point count recording every bird heard or seen within a 400-meter (0.25-mile) radius.  Surveys begin at local sunrise and take approximately 2 hours to complete.  Routes are run once per year between 15 April and 15 May.

RESULTS & DISCUSSION: In 2001, six participants sampled 27 of the 44 established PRBBS routes.  Of the sampled routes, 15 are located in the wet life zone, 5 in the moist zone, and 7 in the dry zone (Ewel and Wetmore 1973).  A total of 5472 individuals were detected representing 70 species and one unidentified hummingbird (Table 1).  Of the 70 species, 13 are endemic to Puerto Rico, 11 are endemic to the Caribbean basin, 4 are breeding residents (i.e. they breed in Puerto Rico but winter elsewhere), 7 are exotic, and 1 is an endangered sub-species (Table 1).

The 10 most abundant species were, in descending order, the Bananaquit, Greater Antillean Grackle, Black-whiskered Vireo, Gray Kingbird, Puerto Rican Bullfinch, Scaly-naped Pigeon, Adelaide's Warbler, Black-faced Grassquit, Common Ground-Dove, and Zenaida Dove, while the two most widespread species were the Bananaquit and Gray Kingbird which were both detected on all 27 routes.  The most abundant exotic species was the Rock Dove (52).

However, species abundance (Table 2) and species richness differs between life zones

Table 2. Relative abundance of species per life zone in descending order.

Wet Life Zone	Moist Life Zone	Dry Life Zone
Bananaquit	Black-whiskered Vireo	Greater Antillean Grackl
Black-whiskered Vireo	Bananaquit	Gray Kingbird
Scaly-naped Pigeon	Gray Kingbird	Adelaide's Warbler
Gray Kingbird	Puerto Rican Bullfinch	Common Ground-Dove
Puerto Rican Bullfinch	Adelaide's Warbler	White-winged Dove
Pearly-eyed Thrasher	Zenaida Dove	Cattle Egret
Black-faced Grassquit	Greater Antillean Grackle	Bananaquit
Puerto Rican Woodpecker	Puerto Rican Vireo	Black-faced Grassquit
Puerto Rican Spindalis	Common Ground-Dove	Northern Mockingbird
Puerto Rican Tanager	Black-faced Grassquit	Zenaida Dove

On both the dry and moist life zones routes, an average of 28 species were detected, while on average only 22 species were detected on the wet life zone routes.  Also the average number of individuals detected per route increases as the life zone becomes drier (Table 3).  Thus, the island habitats (coastal and mid-elevation sites) under the heaviest development pressures also harbor the most bird species and individuals, suggesting that continued development should follow sound conservation practices in order to preserve the island's unique habitats and associated avifauna.

Table 3. Mean species abundance and richness per life zone

	Wet (n=14)	Moist (n=5)	Dry (n=7)
Mean individuals/route	162	247	272
Mean species richness	22	28	28

To participate, please contact one of the following individuals:

Enrique Hernandez Prieto Univ. of Puerto Rico CUH Station 100, 908th Rd. Humacao, PR 00791-4300 787-850-9388 x9145 en-hernandez@hotmail.com

Jose Colon P.O. Box 1656 Ciales, PR 00638-1656 787-834-0934

Keith Pardieck USGS-PWR 12100 Beech Forest Rd. Laurel, MD 20708-4038 301-497-5843 Keith_Pardieck@usgs.gov

 

ACKNOWLEDGMENTS: We would like to thank Enriquez Hernandez Prieto and Jose Colon for coordinating PRBBS activities on the island, as well as, the 2001 PRBBS participants Shelby Birch, Jose Colon, Sergio Colon Lopez, and Adrianne Tossas.  We also are indebted to Kinard Boone and Alan Hedin for developing the figures.

REFERENCES:

American Ornithologist's Union.  1998.  Check-list of North American Birds.  7^th edition.  American Ornithologist's Union, Washington, D.C.

Collar, N.J. and P. Andrew.  1988.  Birds to watch: the ICBP world checklist of  threatened birds.  Int. Council Bird Preserv. Tech. Pub. 8.  Cambridge.

Ewel, J.J. and J.L. Whitmore.  1973.  The ecological life zones of Puerto Rico and the U.S. Virgin Islands.  USDA Forest Service Research Paper ITF-18, Institute of Tropical Forestry, Rio Piedras, Puerto Rico.

Johnson, T.H.  1988.  Biodiversity and conservation in the Caribbean:  profiles of selected islands.  Int. Council Bird Preserv. Monograph No. 1.  Cambridge.

King, W.B.  1980.  Ecological basis of extinctions in birds.  Acta XVII Congr. Int. Ornith. 905-911.

Peterjohn, B.  1994.  The North American Breeding Bird Survey.  Birding 26:386-399.

Raffaele, Herbert A.  1989.  A guide to the birds of Puerto Rico and the Virgin Islands.  Princeton University Press, New Jersey.

Rivera-Milan, F.F.  1993.  Standardization of roadside counts of columbids in Puerto Rico and on Vieques Island.  USDI, National Biological Survey Resource Publication 197.  Washington, D.C.

Temple, S.A.  1985.  Why endemic island birds are so vulnerable to extinction, Pp. 3-6 in S.A. Temple, ed.  Bird Conservation 2.  Int. Council Bird Preserv., U.S. Section.  The   University of Wisconsin Press, Madison, WI.

 

 

 

U.S. Department of the Interior | U.S. Geological Survey
Patuxent Wildlife Research Center Laurel, MD, USA 20708-4038
http://www.pwrc.usgs.gov/bbs
Operations Contact: Keith Pardieck, email: Keith_Pardieck@usgs.gov
Analyses Contact: John Sauer, email: John_Sauer@usgs.gov
Last Modified: 10/31/01
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