114th CBC West Indies/Bermuda Regional Summary

By Robert L. Norton

There were 17 Christmas Bird Counts this season; Bermuda, four from the Bahamas, two in the Dominican Republic, one from Haiti, four from Puerto Rico, three from the US Virgin Islands and two from the British Virgin Islands.  The hope is that Jamaica and Cuba will return in future seasons with three or more counts.

High species count honors go to Cabo Rojo, Puerto Rico with 119 followed by New Providence, Nassau, Bahamas with 118. Highest participant total goes to St. John, US Virgin Islands with 48 birders and Cabo Rojo with 47 counting birds.  Abaco, Bahamas had the greatest number of birds counted per party/hour with 9.25 (74 species and eight birders) while St. John’s 48 birders found only 53 species. The average ratio of the six highest performers was 2.29 species per hour by about 27 birders yielding 62 species. Historically, St. John had around 74 species per year with fewer participants.

At Bermuda, there is a long historical CBC record and a gold mine of data. The island offers a control of sorts for resident species compared to the tropical count circles farther south. Using Audubon’s powerful database, any CBC participant can research and plot trends of species from island groups across decades of counts. The database can now show the benefit of hours of counting birds in the region and can be compare against each other. All other things being equal, and they rarely are, trends of resident species can be compared inter-annually as well as inter-island. I present here a gross analogy of trends of Eurasian Collared-Dove, an exotic, to the indigenous Common Ground-Dove between island groups. These results can illustrate the trends of potential negative impact by an exotic species on a resident and competitive species.

Figure 1. 1980-2013 period of record of Eurasian Collared-Dove in Puerto Rico.

Figure 2. 1980-2013 period of record of Eurasian Collared-Dove in the Bahamas.

Figure 3. 1980-2013 period of record for Common Ground-Dove for Puerto Rico.

Figure 4. 1980-2013 period of record for Common Ground-Dove for the Bahamas.

Figure 5. 1980-2012 period of record for Common Ground-Dove at Bermuda.

It seems clear that Common Ground-Dove populations have been slipping from about 1990 when Eurasian Collared-Doves were making advancements in the Bahamas and Puerto Rico versus Bermuda where collared-doves are scarce if not absent and ground-dove populations seem to be stable. 

Other strictly population trends (absent of competitive introduced species) may not be as clear when we look at a common migrant and winter resident, Northern Parula. Northern Parulas counted per party-hour at St. John have clearly fallen since about 1990, yet fluctuated greatly while appearing to increase slightly in Puerto Rico during the same timefram. The effort at Bermuda shows a moderate increase as does Puerto Rico. The decline in the later seasons of the St. John CBC trend may suggest a redeployment of birders to more appropriate habitat rather than assuming an otherwise unequal competitive influence.

Figure 6. 1980-2013 period of record for Northern Parula at Puerto Rico.

Figure 7. 1980-2013 period of record for Northern Parula in US Virgin Islands.

Figure 8.  1980-2012 period of record for Northern Parula at Bermuda.

In the case of another migrant/local resident warbler, Yellow Warbler, these trends suggest a higher winter residency east and south of the Bahamas the Puerto Rican Bank.

Figure 9. 1980-2012 period of record for Yellow Warbler in the Bahamas.

Figure 10. 1980-2012 period of record for Yellow Warbler at Puerto Rico.

Figure 11. 1980-2012 period of record for Yellow Warbler in US Virgin Islands.

CBCs in the West Indies are as popular as ever and even expanding when resources are available. There is great potential for the data collected over the half century, in some places, to be used for conservation and better understanding of the environment we all share. These exciting data could not be possible without the selfless dedication to this enduring citizen science effort by people like you. Thank you.