Landbird Monitoring in the Southern Plains, Sonoran Desert, and Chihuahuan Desert
Landbirds are one of many natural resources monitored by the National Park Service (NPS) Division of Inventory & Monitoring (I&M). Landbirds are considered good indicators of ecosystem health for many reasons. In NPS units of the American Southwest, three I&M networks monitor landbirds using the scientific protocol described here.
Landbirds are a conspicuous component of many ecosystems. Because they have high body temperatures, rapid metabolisms, occupy high trophic levels, and can respond quickly to changes in resource conditions, landbirds are considered good indicators of ecosystem health. In addition, landbirds are highly detectable relative to other vertebrates, and they can be efficiently surveyed with the use of several standardized methods.
Landbirds are also protected under the legal mandates of the Endangered Species Act (1973) and Migratory Bird Treaty Act. Monitoring changes in landbird population and community parameters can be an important component of any comprehensive, long-term monitoring program.
For these reasons and because they are specifically identified in the management objectives of many network parks, the National Park Service’s Southern Plains, Sonoran Desert, and Chihuahuan Desert Inventory and Monitoring Networks have chosen landbirds as a focus for long-term natural resources monitoring. To gain operational efficiencies and improve the spatial and thematic scope of our results, the three networks conduct monitoring in an integrated, collaborative fashion, in partnership with the Rocky Mountain Bird Observatory.
Specific, measurable objectives for landbirds monitoring are:
To estimate the proportion of points occupied for most species in most parks. Occupancy is a measure of presence or absence of a species in space. This measure, when evaluated across time, indicates changes in the distribution of a species.
To estimate parameters related to community dynamics—particularly species richness and composition, which are essential to understanding the effects of changing landscapes and management practices on native biodiversity. Using community-level estimators is an efficient means of obtaining meaningful landbird data within our operational constraints.
To estimate density of the most common species using the point-transect distance-sampling method at fixed points. Where assumptions are met, density estimates can provide a robust and widely accepted method for estimating bird abundance. For larger parks, we will likely be able to estimate density for only the most common species, due to time and other constraints on field efforts.
The researchers developed an aerial survey method specifically for counting sea otters and estimating abundance and distribution. Aerial surveys were conducted annually.
From vessels and from the shore, the researchers observed thousands of sea otter foraging dives and recorded information on foraging success and efficiency based on prey numbers, types and sizes obtained, and time expended.
Benthic invertebrates, such as clams, urchins, crabs, and snails, were collected by divers, measured, and returned to the seafloor. This study compared the fauna of intertidal and subtidal habitats before and after their re-occupation by sea otters.
Products, Scope, and Schedule
Network-scale status and trends reports and park-specific landbird resource briefs are produced annually. Appropriate assessments of potential trends requires several years of data, so early reports focus on current status and species composition. The scale of inference of each report is the individual park.
Information on bird communities and natural history is also communicated through live presentations, updated bird checklists and other written summaries, and podcasts and other media produced and distributed through the network websites and the Science of the American Southwest website (www.nps.gov/swscience).
The protocol and standard operating procedures for the Sonoran Desert Network were approved in December 2008. The protocol is currently being revised to incorporate Southern Plains and Chihuahuan Desert Network parks. A database and supporting documentation that meet NPS and FGDC standards are complete and available. Final data from 2007–2008 are available from the NPS DataStore. Data from 2009 and on are available from the Rocky Mountain Bird Observatory (http://rmbo.org/v3/avian/ExploretheData.aspx).
Parks where landbirds monitoring is being implemented
Inventory and Monitoring Network
Big Bend NP
Carlsbad Caverns NP
Fort Davis NHS
Guadalupe Mountains NP
White Sands NM
Alibates Flint Quarries NM
Bent’s Old Fort NHS
Capulin Volcano NM
Fort Union NM
Fort Larned NHS
Gila Cliff Dwellings NM
Lake Meredith NRA
Lyndon B. Johnson NHP
Sand Creek Massacre NHS
Washita Battlefield NHS
Casa Grande Ruins NM
Fort Bowie NHS
Organ Pipe Cactus NM
Montezuma Castle NM
NHP = National Historical Park; NHS = National Historic Site; NM = National Monument; NMem = National Memorial; NP = National Park; NRA = National Recreation Area
Robert E. Bennetts, Southern Plains Network firstname.lastname@example.org, (719) 846-4663