PRINCIPAL INVESTIGATOR: Barbara Kus, San Diego Field Station

BACKGROUND AND JUSTIFICATION: Protection and management of endangered birds is a primary focus of resource managers and state and federal wildlife agencies. However, many species or groups of species lacking formal listing status are also of conservation concern in that they exhibit population declines which, if continued, will likely place the species at risk of extinction. Neotropical migratory birds, or birds that breed in temperate regions and winter at tropical latitudes, are one such group. Long-term data from the North American Breeding Bird Survey (BBS) and other sources suggest that many neotropical migratory species are declining, prompting action by governmental, non-governmental and private organizations to develop coordinated monitoring and research of neotropical birds. Central to these efforts is the goal of preventing future listings through an ability to detect, identify the causes of, and reverse declines in species before they reach critically low numbers, at which point the potential for recovery is limited.

"MAPS", or Monitoring Avian Productivity and Survivorship, is a coordinated program to provide long-term data on landbird species throughout North America. MAPS is distinguished from other monitoring programs such as the BBS in that in addition to an index of population size, it provides critical demographic information necessary for developing and testing hypotheses explaining population trends. Modeled after the British Trust for Ornithology’s Integrated Population Monitoring Programme, and operated by the Institute for Bird Populations (IBP), MAPS is an integrated program of standardized, constant-effort mist-netting and banding of breeding birds at a network of stations spanning the continent. Capture-recapture analysis of banded birds provides data on sex- and age-specific annual survivorship and recruitment, while ratios of adults to juveniles captured yield an estimate of annual productivity. These data allow determination of the stage(s) of the life cycle at which population limitation is occurring, which in turn provides a guide for investigation of potential causal factors. For example, reduced productivity suggests that population decline may be the result of factors on the breeding grounds reducing nesting or fledging success, while reduced adult survival suggest that factors other than those influencing nesting success may be operating. Given the wide range of possible explanations for declines in neotropical migrants, including loss and degradation of breeding habitats, deforestation of tropical wintering habitats, mortality during migration, cowbird parasitism, and predation, it is essential that research be directed towards factors most likely to account for a particular species’ decline based upon the demography of that species.

This study plan describes a continuing project started in 1995 before the P.I. joined USGS-BRD, in which three MAPS stations were established at Camp Pendleton, California. Camp Pendleton, at 125,000 acres, is the largest undeveloped tract of land remaining in coastal southern California, and supports large contiguous blocks of habitats representative of the region. This, coupled with Base security and a natural resource policy to maintain native habitats makes Camp Pendleton an ideal location for long-term monitoring. At the time the MAPS stations were established, they were the first in San Diego County, adding to the only two other MAPS stations operating in the coastal ecoregion south of Monterey. Data collected at these stations contribute not only to IBP’s continent-wide monitoring program, but also provide resource agencies such as the U.S. Fish and Wildlife Service and Department of Fish and Game, as well as Camp Pendleton natural resource managers, with information on trends in local bird populations under their combined stewardship. This ability of MAPS to serve as an "early warning" system allows for the fine-tuning of local and regional conservation efforts in a manner that directs management attention in an efficient and timely manner to the species in need of it.

OBJECTIVES: The objectives of this study are to provide annual indices and estimates of adult population size, post-fledging productivity, adult survivorship, and recruitment into the adult population for select species in southern California. It is the goal of Camp Pendleton to fund this project for a minimum of 10 years.

STUDY AREA: We will operate three MAPS stations at Marine Corps Base Camp Pendleton in San Diego County, California. Two of the stations are in riparian habitat, one on the lower reach of the Santa Margarita River, and the other on De Luz Creek. The third station is located in an oak woodland near Case Springs in a mountainous region of the Base. The Case Springs station will be operated for a total of five years, through 1999; the two riparian stations will be operated throughout the entire study period.