Hurricane Fifi and the 1974 Autumn Migration in El Salvador

Abstract

-In the autumn of 1974 the migration pattern in El Salvador had several unusual features, too many to have been merely coincidental: 1) delayed arrival of certain early migrants whose appearance overlapped with that of later migrants; 2) unprecedented numbers of a few species; 3) the appearance of several rarely seen or previously unreported species; 4) extension of winter ranges of a few species which was maintained for several years after. These events were closely associated with Hurricane Fifi (17-20 September) and to a lesser extent with Hurricane Carmen (1-6 September). I attribute the unusual features of the 1974 migration to Hurricane Fifi (possibly augmented by Carmen) after comparison of routes and schedules of early migrants with the route, dates, wind directions, and velocities of Fifi. I suggest that other hurricanes have affected and will affect migration through Middle America but that serious disruptions are probably rare and unpredictable. In the course of my 10 years of netting and banding birds in El Salvador, Central America, the fall of 1974 was exceptional for the early migration pattern and for the arrival of several uncommon and previously unreported species. These events aroused my interest but I did not note their conjuncture with Hurricane Fifi until almost three years later. Then in 1977, I encountered an unprecedented wave of Canada Warblers (Wilsonia canadensis) and learned that Hurricane Anita had crossed the Gulf of Mexico shortly before. Storms are known to affect bird movements. Hurricanes moving northward along North America's eastern seaboard force south-bound migrants and sea birds far inland (Pettingill 1970:271). Lowery (1946: 192) and Mayhew (1949:403) described instances of birds caught in hurricanes. Bagg (1967:87-121) showed how severe storms over the North Atlantic brought spectacular numbers of Eurasian Lapwings (Vanellus vanellus) to North America in 1927 and 1966. Raffaele and Roby (1977:338-342) credited the 1960 Hurricane Donna with introducing the Lesser Antillean Bullfinch (Loxigilla noctis) into the Virgin Islands. Fisk (1979:226) associated 1969 Hurricane Gerda with an exceptional wave of migrants at her banding station in south Florida. I propose that Hurricane Fifi was responsible for the unusual features of the 1974 fall migration in El Salvador and that such storms can and do affect migration patterns in Middle America. METHODS AND SOURCES OF DATA From my field notes and netting records I selected data which show the unusual nature of the 1974 migration. For comparison I summarized relevant information for other years as given by my notes and the literature. My field notes extend from 1966, my netting records from 1969. I have operated banding stations for about one month a quarter, each station for 12-14 days, using 1520 nets. One station at Cerro Verde (13050'N, 89038'W; 2,000 m elevation) has been used regularly once a quarter; the others were used less regularly and for only two to four years. Since 1969 I have maintained one lowland station to complement Cerro Verde. Dickey and van Rossem (1938) provided almost all that is known about migrants in El Salvador before 1966. Van Rossem collected for 20 months in 1912 and 1925-27. His data were not strictly comparable to netting data but he was a dedicated observer who annotated richly his impressions of abundance. Of other visiting ornithologists, only Marshall (1943) added information pertinent to this paper. The U.S. National Oceanic and Atmospheric Administration provided general information on cyclonic storms, details of Hurricanes Carmen, Fifi, and Anita, and surface maps for the periods of these hurricanes. MIGRATION PATTERNS IN NORTHERN MIDDLE AMERICA Lack of band recoveries limits understanding of migration patterns in Middle America. Approximate routes can be inferred from pecies accounts in regional summaries, e.g. Miller et al. (1957), Paynter (1955), Russell (1964), Land (1970), and Monroe (1968). Knowledge of migration schedules is in g neral limited to earliest recorded dates in species accounts in Bent (1949, 1950, 1953, 1958, 1968), Russell (1964), Land (1970), and Monroe (1968); these dates may not represent normal arrival dates.