Saddle-billed Stork Ephippiorhynchus senegalensis Scientific name definitions
Version: 2.0 — Published June 25, 2021
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Movements and Migration
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Most accounts on the species have considered it to be sedentary with nomadic behavior, yet no data on movement exist. There is no evidence of long-distance migration, but it is clear from some literature and thousands of records spanning more than a century that seasonal movements and congregations of large groups do occur in some years (JG, unpublished data). The four largest recorded gatherings – 100 at Lake Turkana, Kenya (70), 85 and 58 in Zakouma National Park, Chad (34, Wetlands International, unpublished data) , and 84 along the Luangwa River, Zambia (71) – were during the dry season in the respective regions. In northern Central African Republic it is more abundant in the dry season (33, 32), and in Cameroon's Waza-Logone floodplain records of adults are only from December–April, when water levels are lowest (72). Aerial surveys of Liuwa Plain National Park in Zambia in two consecutive years, the first following a drought and the second following a normal rainy season, found twice as many storks in normal conditions than during the drought (African Parks Zambia, unpublished data), suggesting that during the drought year many storks dispersed elsewhere temporarily.
With this evidence, it obvious that seasonal movements of this stork are determined by precipitation and water levels. Research on the Marabou Stork (Leptoptilos crumeniferus) and the Wood Stork (Mycteria americana) has found low seasonal rainfall and water levels is related to reproductive success because these concentrate aquatic prey and allow for more successful foraging (73, 74, 75). Thus, it is likely similar processes contribute to seasonal movements of the Saddle-billed Stork, which may occur at lower densities during the rains and then seek out low water levels in the dry season. Seasonal aerial surveys would greatly improve the knowledge of this, as would a telemetry study.
Dispersal and Site Fidelity
As no research has addressed any aspect of spatial ecology of the species, information on dispersal is largely lacking. However, several records of hatch-year juveniles far from any known population have shed light on dispersal ability. In August 1975 and 1978, Newby (76) observed juveniles following heavy storms at Arada in the Ouadi Rimé-Ouadi Achim Faunal Reserve in Chad. While these extralimital occurrences were attributed to the weather events that apparently blew the storks into the desert, they demonstrate potential dispersal distance given the closest known breeding site is over 500 km away. There are also two records of juveniles on the Nazinga Game Ranch in Burkina Faso, which is roughly 175 km from the closest known breeding site in Mole National Park (28). While these anecdotes provide some information about dispersal, mark-resight of nestlings or telemetry research will help better quantify aspects of movement upon independence. Other examples of knowledge gaps in this regard include: how long juveniles remain in their natal territories; to what extent dispersing juveniles use unprotected habitat; and the length of the dispersal period.
Information is lacking on breeding site fidelity of adults.
Timing and Routes of Migration
Control and Physiology of Migration