Reprinted from: Purple Martin Update 8(1): 28-29
James R. Hill, III
Purple Martin Conservation Association
Dr. Thomas B. Dellinger
PO Box 380163
Both of us are federally-licensed bird banders and band hundreds of Purple Martins annually. Because of this close involvement with the species, we were curious to know how many banded martins had been recovered south of the U.S. border, and where and when these recoveries had occurred.
To answer these questions, we asked the Bird Banding Lab in Laurel, Maryland, for a computer printout of all known martin recoveries. The list they sent, current to November 9th, 1994, contained information on 1149 banded Purple Martins that had been recovered during the past 73 years. Surprisingly, only 21 of these were from areas south of the United States' border. The map and accompanying table summarize these. As you can see, there have been 10 recoveries in Brazil, three in Colombia, one in Venezuela, three in Bolivia, three in Central America, and one in Mexico.
As interesting as the locations of band recoveries, are the areas where there are no band recoveries. There are no recoveries in Cuba, the Greater Antilles, the Yucatan, Guatemala, Belize, Costa Rica, Panama, Guyana, or Paraguay. These are all areas that martins migrate through, or in the case of Paraguay, to. Most amazing to us, though, are the locations of the Brazilian recoveries. Only one of the ten Brazilian recoveries is from the southern state of São Paulo, where, up til now, martins have been assumed to be most abundant in winter, and where they are known to form gigantic nocturnal roosts in the town squares (numbering 25,000 to 250,000 birds). This is also an area of high human abundance (increasing the odds of band encounter). In contrast, 8 of the other 9 Brazilian recoveries are from along the Amazon River and its tributaries, where the human population is comparatively low. This suggests that, even though the Purple Martin appears to be quite abundant in the agricultural state of São Paulo, it must be substantially more so along the Amazon River in northern Brazil, during this, the southern summer.
Other things of interest can be found in these data. Note that birds #15, 16, and 17, which were all recovered near each other in Bolivia, were also banded near each other in Iowa, Illinois, and Michigan. Is this a coincidence, or do birds from one area of the breeding grounds migrate to the same region of the wintering grounds?
Migration Routes Revealed
The recovery locations of birds #19, 21, and 22 seem to suggest that western martins use the western coastal route of Mexico and Central America on their southward journeys. In contrast, birds #18 and 20, which were eastern martins, seem to be using the eastern coastal route on their way south through Central America. Did these later two birds cross the Gulf of Mexico from the Gulf coast, or did they go around through Texas? And finally, bird #23, banded in Maryland, was migrating southward through the Florida peninsula, suggesting that some east coast martins travel to South America via the Caribbean Island route.
Bird #13, banded near Duncanville, Texas, made the 2950 mile journey to Paipa, Colombia, in just 65 days (or less), arriving there by at least the 21st of August, a date when martins at the northern limit of their breeding range are just peaking in numbers at their premigratory roosts. At the other extreme, bird #22 from Oregon was still in Arizona on the late date of November 4th. And finally, bird #23, banded in Maryland, was migrating southward through the Florida peninsula on October 2nd. Note that bird #1, banded in Virginia, was recovered in Brazil on a March 20th, a date when some adult martins would have already been back in Virginia. Similarly, bird #10 was still in Brazil on the 22nd of April, just one or two weeks before others of its kind would have arrived back in Alberta.
Tom's Three South American Recoveries
Birds #7, 8, and 13 were all banded in or near Duncanville, Texas, by author, Tom Dellinger, and were later recovered in South America. Bird #7 was recovered in Manaus, Brazil, by a World Wildlife Fund employee; bird #8 in Caceres, Brazil, by a 9-year-old boy; and bird #13 in Paipa, Colombia, by a hotel operator. We hope that the information in this article will inspire all landlords to keep their eyes open for leg bands on their martins.
Copyright 1997 by Purple Martin Conservation Association. All Rights Reserved.
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