National Park Service

Mediterranean Coast Network (MEDN)

Bird Monitoring

Song Sparrow at Channel Islands Nationa Park
Song Sparrow at Channel Islands National Park

Landbird Resource Briefs

Landbird Monitoring Reports

Landbird Protocol Documents

For more information contact: Paula Power

Importance/Issues

The California Channel Islands have been the focus of many studies looking at origin and differentiation, species composition and turnover among insular avifauna populations. Breeding land bird communities on the islands are depauperate when compared to those of the mainland. Of the approximately 160 species which breed along the southern California coast, only 44 breed in the park. Thirteen of those species have differentiated into eighteen endemic subspecies.

Landbird populations have been previously influenced by historic land management practices such as grazing and agriculture, and are currently responding to ecological changes due to the removal of non-native ungulates from the islands. For example, the Santa Barbara Island Song Sparrow (Melospiza melodia graminea) was driven to extinction by 1959 due to a combination of conversion of native habitat for agricultural purposes, habitat destruction by introduced rabbits (Oryctolagus cuniculus) and other grazing stock, and predation by feral cats (Felis catus).

These same land use practices on Santa Barbara Island have also reduced available breeding habitat for the Orange-crowned Warbler (Vermivora celata sordida), a neotropical migrant which, on Santa Barbara, nests only in the thick stands of Coreopsis scrub in the canyons. As the island recovers from the influences of past grazing, expansion of Coreopsis stands may be accompanied by an increase in breeding Orange-crowned Warblers.

Monitoring Efforts

Park researchers have been monitoring land bird populations on the Channel Islands since 1993.

  • Past methodology utilized line transects on the smaller islands (San Miguel, Anacapa, and Santa Barbara) and point count transects on larger Santa Rosa Island. Current methodology uses 226 randomly selected point count locations (33 on Santa Barbara, 8 on East Anacapa, 145 on Santa Rosa and 40 on San Miguel Island).
  • To correlate data using the different methodologies, previously monitored line transects and point counts were conducted simultaneously with the newly selected random sites for a period of three years. Monitoring of old sites were discontinued in 2009 on Santa Rosa Islands but continues on the smaller islands.
  • Surveyed are conducted during spring (March - June), with observers recording data on all birds seen or heard. Perpendicular distance to birds is also recorded, facilitating estimation of density via distance methods.

Monitoring Objectives

  • Determine the status and long-term trends in the distribution and abundance of breeding land birds

Management Implications

  • The number of species observed on each island and relative abundance of individual species on islands and in habitat types varies annually, due to interannual variation in migrant occurrence and land bird populations in general.
  • Species richness varies by habitat type, being highest in riparian, grassland, coastal sage scrub and chaparral habitat types.
  • Regression of landbird densities over time has provided trend results for a number of species. Several land bird species increased after cattle were removed from Santa Rosa Island. The program also detected ecological changes during the period of island fox (Urocyon littoralis) absence from the wild, due to captive breeding, on San Miguel and Santa Rosa Islands.
Western Gulls are a common breeder at Channel Islands National Park
Western Gulls are a common breeder at Channel Islands National Park

Seabird Resource Briefs

Seabird Monitor Reports

Seabird Protocol Documents

For more information contact: David Mazurkiewicz

Importance/Issues

Seabirds are becoming increasingly threatened at a faster rate globally than all other species-groups of birds. Oil or chemical pollution, changes in food availability and abundance, climate change, and human disturbance are just some of the threats facing seabirds today.

The Channel Islands are home to the largest seabird colonies in southern California, providing essential nesting and feeding grounds for 99% of seabirds in the region. The islands host half of the world's population of ashy storm-petrels and western gulls (Larus occidentalis) and 80% of the nation's breeding population of Xantus's murrelets (Synthliboramphus hypoleucus). In addition, the islands are home to the only major breeding population of California brown pelicans (Pelecanus occidentalis californicus) in the western United States.

Of the eleven species that nest at Channel Islands National Park, only six can be reasonably monitored – double-crested (Phalacrocorax auritus) and pelagic (Phalacrocorax pelagicus) cormorants, California brown pelicans, western gulls, Xantus' murrelets, and Cassin's auklets (Ptychoramphus aleuticus). Nest inaccessibility, nocturnal behavior and variable breeding sites prohibit monitoring of the other five species. The six selected species to be monitored are diverse and provide broad geographic coverage for the park's monitoring program.

Monitoring Efforts

For practical reasons, not all the recommended parameters are measured for each species.

  • Counts of incubating birds, pairs at nest sites, young at nest sites and number of nests are used to measure abundance.
  • Reproductive success is determined through counts of chicks and brood size.
  • Direct observation or dates based on the age of the young is used to estimate phenology.
  • Counts of individuals based on plumage and band sightings are used to determine the population age structure.

Monitoring Objectives

  • Detect changes in abundance and distribution of six breeding seabird species in the Channel Islands over time.
  • Where feasible, use productivity, survivorship, food habits and growth rates as indicators of change.

Management Implications

  • Following the removal of black rats from Anacapa Island, an increase in Xantus's murrelet breeding populations has been observed.
  • Though DDT continues to persist at levels higher than anticipated in several seabird populations, California brown pelican populations have successfully improved and have been delisted from Endangered status.
  • The removal of non-native plants, restoration of native vegetation and construction of "nest boxes" have improved nesting habitat for Xantus's murrelets and Cassin's auklets on Santa Barbara Island, as well as seabirds on Santa Cruz Island.
Last Updated: December 30, 2016 Contact Webmaster