last update July 7, 2000
Four of the eight sample plots, San Felipe Wash, Barrel Springs, QuarryWash and PaloVerde Wash, demonstrated both high species composition and high totalnumber ofindividuals sighted. The cornmon denominator between all four sites is theexistance oflarge size trees and/or shrubs and patches of fairly dense vegetationcover. The desertwillow (Chilopsis linearis) trees of San Felipe Wash, the mesquitetrees (Prosopisglandulosa) of Barrel Springs, the ironwood trees (Olneyatesota) of Quarry Wash and thepalo verde trees (Cercidium floridum) of Palo Verde Wash allprovide food, nesting sites,perching sites and protection from predators for a large number of birds.Subsequently.both density and diversity of bird species in these four sites isrelatively high.
Three of the other four sites, Poleline Road, Gas Dome Road and ShellReef, all have verylittle vegetation cover leading to a lack of food and nesting sitesrequired to support even aminimal bird population. The last site, Holmes Camp, falls between thesetwo groups ofextremes due to the existance of a mature windbreak of exotic tamarisktrees providingsome food and protection for birds. This lack of vegetation leads to theextremely low birddensity and low diversity found in these four sites.
The high density and diversity descriptions of San Felipe Wash and BarrelSprings inrelation to the other sample sites demonstrates that these two habitattypes, desert washwoodland and mesquite dune, are the most productive bird habitats withinOcotillo WellsState Vehicular Recreation Area. This can also be seen by reviewing thespecific speciesfound on these two sites. Three warbler species, Townsend's warbler,yellow warbler andthe yellow-rumped warbler are definite migrants that were observed as theywere passingthrough Ocotillo Wells SVRA. These species were only seen in these twohabitats.Several other species, the black-headed grosbeak, hooded oriole and Weid'screstedflycatcher are not typical desert species but were also observed at thesetwo sites, in allprobability because of the heavy vegetation cover. The vegetation coverfound at these twosites not only provides for resident desert bird species, but supportsboth migrant andcasual visitor species such as the Townsend's warbler and the hoodedoriole respectively.
RECOMENDATIONS
Information collected during this project strongly emphasizes theimportance of vegetationin the presence or absence of birds in a desert environment. The 4 siteswith a largetree/shrub vegetation cover, had more species, more individuals sighted,higher density andgreater diversity than the 4 sites with much less vegetation cover. Thesehigh vegetationcover habitats include desert willow woodland (San Felipe Wash), MesquiteDune (BarrelSprings), ironwood woodland (Quarry Wash) and palo verde woodland (PaloVerdeWash). Of these 4 sites, San Felipe Creek and Barrel Springs appear to bethe mostproductive, each with a density ranging from 2 to over 10 times greaterthan the other 6sites. These two sites are also the locations where migrant and casualvisitor species wereobserved, demonstrating the importance of these habitats on a much largerscale thanOcotillo Wells SVRA.
Of these productive habitats, the most susceptible to damage and habitat loss from OHV activity is the mesquite mound system because of its small, compact size and desirability by OHV riders. Barrel Springs is already protected through much of the habitat being fenced into 4 protected areas. However, there are several other mesquite mound habitats located within Ocotillo Wells SVRA that are not currently protected. These other mesquite mound areas are also very productive habitats which have the ability to support a high density bird population. It is strongly recommended that the remaining mesquite mound habitats be protected through fencing much the same way Barrel Springs has been. Such protection will prevent the loss of one of the most productive habitats within the boundaries of Ocotillo Wells SVRA and help ensure the maintenance of a thriving bird fauna, not only at Ocotillo Wells SVRA but on a regional or even higher level.