Wintering Peregrine Falcons (Falco peregrinus) on South Padre Island, Texas

• Main Author: Juergens, Paul W.
• Other Authors: Baccus, John, Manning, Richard, Simpson, Thomas
• Language: English
• Published: 2020
• Subjects: Migration; Peregrine falcon; Falcons; South Padre Island; Falco peregrinus; peregrine falcon
• Online Access: https://digital.library.txstate.edu/handle/10877/10518

The Lower Laguna Madre Region of the Lower Texas coast is an important wintering area for a variety of birds many of which migrate from more northern latitudes. I studied Peregrine Falcons on South Padre Island (SPI), Texas, during winter 2001-2002 and 2002-2003. I captured falcons using standard falconry techniques and banded them with U. S. Fish and Wildlife Service aluminum leg bands. I captured 21 and 16 falcons in 2001-2002 and 2002-2003, respectively, and fitted 13 (2001-2002) and 6 (2002-2003) falcons with tail mounted radio transmitters to identify individuals throughout each winter. I analyzed mark-recapture data using the Jolly - Seber method, which provided an estimate of 6 to 9 falcons (x̄ = 7.05, SE= 0.42) on SPI in 2001-2002 and 7 to 14 individuals (x̄ = 8.9, SE= 1.2) in 2002-2003. The majority of falcons wintering on SPI were females with no detectable difference in number of adults or juveniles. In 2001-2002, falcons frequented the wind - tidal flat more than other habitats on SPI. In 2002-2003, more falcons frequented the vegetated barrier flat on the leeward side of the fore-island dune ridge. This switch in habitat may be in response to a greater prey base at more fresh water pools within the vegetated barrier flat than in 2001-2002, however, the wind-tidal flat still was important to falcons in 2002-2003. Within year site fidelity was common in falcons during both winters. In 2007-2003, 3 of 4 falcons returning to the island were faithful to certain areas on SPI within 2. 7 km of last encounter sites of the previous winter. The majority of prey eaten by peregrines consisted of shorebirds, primarily gulls (Larus sp.), which winter on SPI. I conducted a summer survey in 2002 and was unable to confirm the presence of any Peregrine Falcons on SPI between 19 May and 4 August. Biology