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Distribution & Abundance Maps for 1997
1997 Puerto Rican Acknowledgements

1997 Puerto Rican Breeding Bird Survey
Results and Summary
by Keith L. Pardieck* and Bruce G. Peterjohn*

The Puerto Rican Breeding Bird Survey (PRBBS) is a long-term avian monitoring program that was begun in 1997 with the purpose of monitoring the status and trends of Puerto Rican breeding bird populations over time.  The survey consists of 8-kilometer (5-mile) routes randomly located along local roads.  There are currently 29 routes dispersed among the three major ecological life zones (dry, moist, and wet) of Puerto Rico (Ewel and Whitmore 1973) (Figure 1), although we intend to establish an additional 15 routes in the near future.  Stops are located at 0.8 km (0.5 mi.) intervals along these routes (totaling 11 stops), where the observer records every bird seen or heard within 0.4 km (0.25 mi.) during a five minute period.  Routes are run once per year between 15 April and 15 May.  Requirements for participation are the availability of suitable transportation to complete a survey and the ability to identify all breeding birds in the area by sight and sound.

The inaugural year of the PRBBS was met with considerable enthusiasm.  Fifteen individuals volunteered to survey 26 routes.  Of those 26 routes, six were aborted due to scheduling conflicts.  However, two-thirds (20) of the routes were successfully completed and the data submitted to the BBS office. A total of 4893 individuals was detected, representing 68 bird species or 50% of the breeding bird species likely to be found in Puerto Rico (Raffaele 1989).  Among the 68 species were 56 native species (including 11 endemics and 2 endangered subspecies), 7 introduced species, and 2 breeding migrants (Table 1).  Mean species richness and mean total individuals were highest for routes in the dry life zone and both measures demonstrated an inverse relationship with the moisture gradient;  mean species richness (and mean total individuals) for routes in the dry (N=3), moist (N=6), and wet (N=11) life zones were 29.3 (306 ind/rte), 28.3 (264.7 ind/rte), and 20.0 (217 ind/rte), respectively.  Not surprisingly, the lowest species richness (10) occurred on route 001 in the wet life zone while the maximum species richness (35) occurred on route 036 in the dry life zone.  These findings are similar to those of Kepler and Kepler (1970) who reported that avian diversity and density were higher in Guánica Forest, a dry zone forest, than in the Luquillo Experimental Forest, a moist zone forest.

With one notable exception, the twenty most abundant species detected were native permanent residents.  The Black-whiskered Vireo, a breeding migrant that winters in South America, was the third most abundant species.  The Bananaquit topped the list with 825 individuals while the Gray Kingbird was second with 361 individuals.  The Orange-cheeked Waxbill was the most common introduced species and the twenty-first most abundant species.  The five most abundant species in the dry life zone were, in descending order, the Greater Antillean Grackle, Cattle Egret, Bananaquit, Adelaide's Warbler, and Gray Kingbird.  The five most abundant species in the moist and wet life zones were identical, though the rank order differed slightly between the two zones.  In the moist zone the five most abundant species, in descending order, were the Bananaquit, Gray Kingbird, Black-whiskered Vireo, Scaly-naped Pigeon, and Puerto Rican Bullfinch;  in the wet zone the only difference in the top five species order was the Gray Kingbird which dropped from the second to the fifth most abundant species.

As mentioned earlier, the PRBBS is designed to monitor long-term bird population trends.  It may take five years or longer before enough data has been collected to calculate meaningful population trends.  Until that time, we will provide annual PRBBS summaries and periodically provide 2-year population changes.  The 2-year changes provide some insight into bird population dynamics but tend to be highly variable and should be used with considerable caution.  Also at the end of the 1998 PRBBS field season, assuming adequate funding and technical support, we will begin developing species distribution and abundance maps and make them available on the Internet.

Finally, we are always looking for skilled observers to participate in the PRBBS.  If you are interested in conducting a survey between April 15 and May 15 or would just like more information about the program, please contact one of our island coordinators or our office directly.

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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