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Nocturnal Bird Migration In Mexico: First Records From Marine Radar

By Jack Clinton Eitniear

The La Mata - La Ventosa Wind Farm in Oaxaca, Mexico is a collaborative effort between Mexico Valley Electric and Walmart of Mexico.
A recent paper in Ornitologia Neotropical by Sergio A. Cabrera-Cruz, Todd J. Mabee, & Rafael Villegas Patraca describes the migration of Nearctic-Neotropical birds along the Pacific side of the Isthmus of Tehuantepec in Oaxaca, Mexico.
Millions of Nearctic-Neotropical migrant birds fly over Mexico during their migratory journeys to their wintering grounds, creating high concentrations of migrating birds in different regions of the country. The Atlantic side of the Isthmus of Tehuantepec is known as an important stopover site and corridor for birds migrating to Central and South America, but few studies have been conducted on the Pacific side until recently, when interest has been awakened because of the potential of that area for wind energy development.

In this paper the authors studied bird migration with an X-band marine radar during 21 nights from 15 October–8 November 2010 on the Pacific side of the Isthmus of Tehuantepec in Oaxaca. They estimated a mean Migratory Traffic Rate (MTR) of 79.9 targets/km/h (mean nightly range = 25.3–158 targets/km/h), with a typical pattern of migratory activity through the night, peaking around midnight and decreasing thereafter. Mean flight direction was seasonally appropriate for fall migration (i.e., southeast). Mean flight altitude was 523.5 m above ground level (range of nightly means = 402–755 m a.g.l.).

Wind-energy development has recently increased within the Isthmus, generating the need for information on the characteristics of bird migration in the area. This paper provides the first published results about nocturnal bird migration in the region, information undoubtedly valuable for avian risk assessments.

Attached File  ON 24(4)299-309.pdf   1.22MB   1735 downloads

Membership information for the Neotropical Ornithological Society can be obtained by contacting: jce(at)cstbinc.org